MISC - KIM Seokbeom

Experimental study of an equivalent circuit model considering the path of all strands in an AC current-carrying Litz wires

高田隆一, 井上良太, 植田浩史, KIM SeokBeom

電気学会全国大会講演論文集(CD-ROM)   2024   2024

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Development of REBCO coil system for Skeleton Cyclotron (Spring 2024): Numerical analysis on transient electromagnetic force behavior in 1/2 scale demonstration REBCO coil system

植田浩史, 山下葵, 廣田悠力, 南前俊介, 井上良太, KIM SeokBeom, 野口聡, 渡部智則, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   107th   2024

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Numerical analysis on transient electromagnetic force behavior in REBCO coil system for Skeleton Cyclotron

植田浩史, 山下葵, 廣田悠力, 南前俊介, 井上良太, KIM Seok Beom, 野口聡, 渡部智則, 福田光宏, 石山敦士

電気学会研究会資料(Web)   ( MC-24-016-025/ASC-24-016-025 )   2024

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A Study on the Structural Design for Large Capacity Litz Wires

井上良太, 高田隆一, 植田浩史, KIM SeokBeom

電気学会全国大会講演論文集(CD-ROM)   2024   2024

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Measurement of magnetic properties of ferrite and dust cores at liquid nitrogen temperature

井上良太, 白石智也, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   107th   2024

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「スケルトン・サイクロトロン」用REBCOコイルシステムの開発（2023年秋）－ 1/2スケール実証用REBCOコイルシステムの機械特性評価 －

植田 浩史,山下 葵,小前 諒太,井上 良太,金 錫範,野口 聡,渡部 智則,吉田 潤,西島 元,福田 光宏,熊谷 塁,石山 敦士

低温工学・超電導学会講演概要集 106 128   2023.12

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ジシクロペンタジエン樹脂で含侵した伝導冷却用REBCOコイルの伝熱特性および超電導特性評価

塩﨑琉登, 薦田遥暉, 高田隆一, 井上良太, 植田浩史, 金錫範

2023年度(第74回)電気・情報関連学会中国支部連合大会   2023.10

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高温超電導コイルを用いたMRI装置の励磁波形の違いによる遮蔽電流磁場への影響

今井拓弥,島尚徳,青木一馬,井上良太,植田浩史,金錫範

2023年度（第74回）電気・情報関連学会中国支部連合大会   2023.10

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伝導冷却下におけるパルス通電法を用いた 低温超電導線材の臨界電流評価

錦織敏志, 尾上凜空, 坂本知也, 井上良太, 植田浩史, 金錫範, 菊池章弘, 飯嶋安男

2023年度(第74回)電気・情報関連学会中国支部連合大会   2023.10

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Investigation of resonance circuit topologies for a large-capacity wireless power transmission system using HTS coils

井上良太, 岩本貴大, 薦田遥暉, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   105th   2023

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Development of REBCO coil system for Skeleton Cyclotron (Spring 2023): (Part 4) Strain estimation of 1/2 scale demonstration REBCO coil system

植田浩史, 山下葵, 小前諒太, 井上良太, KIM SeokBeom, 石山敦士, 熊谷塁, 野口聡, 渡部智則, 吉田潤, 福田光宏, 西島元

低温工学・超電導学会講演概要集   105th   2023

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Investigating of the measurement accuracy of the contact resistance in NI REBCO coil by LFAC method

井上良太, 宮本康平, 小林大剛, 植田浩史, KIM SeokBeom, 野口聡

低温工学・超電導学会講演概要集   103rd   2022

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Electric power transmission characteristics in the WPT system for railway vehicle using the non-circular HTS coils

井上良太, 井上雄太, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   103rd   2022

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Development of REBCO coil system for Skeleton Cyclotron (Part 4): Evaluation of screening current and electromagnetic stress in real-scale coil system

植田浩史, 仲井悠貴, 井上良太, KIM SeokBeom, 石山敦士, 野口聡, 渡部智則, 長屋重夫, 福田光宏, 鷲尾方一, 東達也

低温工学・超電導学会講演概要集   103rd   2022

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AC transport current loss characteristics of locally degraded REBCO wire in kHz band

薦田遥暉, 松尾大樹, 井上雄太, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Three-dimensional electromagnetic field analysis for the magnetic levitation transport systems using HTS bulk

高田隆一, 植木駿斗, 木庭駿, 前田裕貴, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Study on the bending characteristic of the critical current of condution - cooled flexible Nb₃Al superconducting wires

尾上凜空, 坂本知也, 福田響, 井上良太, 植田浩史, KIM SeokBeom, 菊池章弘, 飯嶋安男

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Study on the transmitting and receiving coil structure for a high-capacity wireless power transmission system using superconducting and copper coils

岩本貴大, 松尾大樹, 井上雄太, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Measurement of AC magnetization loss in twisted REBCO wires for high temperature superconducting assemble conductor

大橋千波也, 原田亮, 井上良太, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Measurement of screening-current-induced field in non-circular non-insulated high-temperature superconducting coil applying a local magnetic field

山下葵, 仲井悠貴, 小前諒太, KIM SeokBeom, 井上良太, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   73rd   2022

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Study on the structure of HIS coil for high energy density and low AC loss in wireless power transmission system

井上良太, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   101st   2021

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Study on the turn-to-turn contact resistance measurement of no-insulation HTS coils

宮本康平, 小林大剛, 井上良太, 植田浩史, KIM SeokBeom, 野口聡

低温工学・超電導学会講演概要集   101st   2021

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Study on the frequency dependence of transport AC loss characteristics in MgB₂ superconducting wire

松尾大樹, 坂本知也, 福田響, 井上雄太, 井上良太, 植田浩史, KIM SeokBeom, 田中秀樹

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Study to improve the transient stability of no-insulation HTS coil by copper tape and metal ring

佐藤大輝, 小林大剛, 宮本康平, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Study on the critical property and AC current loss of very small diameter and flexible Nb₃Al superconducting wires

福田響, 木村諒, 井上良太, 植田浩史, KIM SeokBeom, 菊池章弘, 飯嶋安男

低温工学・超電導学会講演概要集   101st   2021

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Numerical evaluation on screening-current-induced stress in REBCO pancake coil during charging and discharging processes

内藤敬介, 井上良太, KIM SeokBeom, 植田浩史

低温工学・超電導学会講演概要集   101st   2021

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Development of REBCO coil system for Skeleton Cyclotron (Part 3): Numerical Analysis on Mechanical strength of YOROI-reinforced and non-insulated non-circular REBCO pancake coil

仲井悠貴, 三宅雄大, 井上良太, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   101st   2021

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Study on the evaluation of critical current of low temperature superconducting wires under the conduction cooling

坂本知也, 福田響, 井上良太, 植田浩史, KIM SeokBeom, 菊池章弘, 飯嶋安男

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Basic study on the shape design of a single plate magnetic tester used at low temperature to evaluate the magnetic properties of high Tc superconductors

三宅洋輔, 久米一輝, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Study on the basic shape of a gradient coil for compact finger MRI composed of high temperature superconducting magnets

青木一馬, 井上雄太, 大澤慶博, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Measurement of AC magnetization loss in horizontally and vertically arranged REBCO high temperature superconducting wires

原田亮, 内藤敬介, 井上良太, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   72nd   2021

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Turn-to-turn contact resistance measurement of non-insulated high temperature superconducting coil by AC current

小林大剛, 宮本康平, 西川大亮, 井上良太, 植田浩史, KIM SeokBeom, 野口聡

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Dynamic characteristics of 3-D superconducting actuator with the HTS bulk as the mover based on driving current waveform

木庭駿, 前田裕貴, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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The ultra-fine Nb₃Al monofilament strands and round cables

菊池章弘, 飯嶋安男, 平田和人, 二森茂樹, 西島元, 北口仁, 瀧川博幸, 土谷悦子, 山本優, 河野雅俊, 木村基良, 今仁順也, 永松純, 大坪正人, 一瀬中, 大内徳人, 有本靖, WANG Xudong, ZONG Zanguo, 土屋清澄, 青木和之, 川井正徳, KIM SeokBeom, 植田浩史, 井上良太, 木原工, 中村武恒

低温工学・超電導学会講演概要集   100th   2020

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Numerical evaluation on Reinforced Structure for Noncircular No-Insulation REBCO coil

三宅雄大, 仲井悠貴, 井上良太, KIM Seokbeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   100th   2020

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Fundamental study to improve the magnetic field characteristics of HTS bulk magnet for compact NMR device

佐々木晟人, 河村康平, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Measurement of critical properties of newly developed very small diameter and flexible Nb₃Al superconducting wires

福田響, 木村諒, 井上良太, 植田浩史, KIM SeokBeom, 菊池章弘, 飯嶋安男

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Study on Reinforcement Structure of Non-Circular High Temperature Superconducting Coil for Cyclotron Application

仲井悠貴, 三宅雄大, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 福田光宏, 石山敦士

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Fundamental shape design of high temperature superconducting magnet considering wire consumption for compact MRI

井上雄太, 大澤慶博, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Numerical evaluation on stress and strain of high-field REBCO pancake coil in consideration of winding, cooling and excitation processes

植田浩史, 徳永佳祐, 内藤敬介, 井上良太, KIM SeokBeom

低温工学・超電導学会講演概要集   100th   2020

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Measurement of the critical properties of very small diameter and flexible Nb₃Al wires for the conduction-cooled superconducting applications

木村諒, 福田響, 井上良太, 植田浩史, KIM SeokBeom, 菊池章弘, 飯嶋安男

低温工学・超電導学会講演概要集   100th   2020

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Study on the turn-to-turn contact resistance measurement of no-insulation HTS coils with repeated liquid nitrogen cooling

宮本康平, 小林大剛, 西川大亮, 井上良太, 植田浩史, KIM SeokBeom, 野口聡

低温工学・超電導学会講演概要集   100th   2020

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Numerical evaluation on coupling and screening currents in HTS coils wound with REBCO bundle conductor

植田浩史, 徳永佳祐, 内藤敬介, 井上良太, KIM SeokBeom

低温工学・超電導学会講演概要集   100th   2020

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Study on the fundamental shape of HTS magnet for compact MRI using a distributed genetic algorithm

大澤慶博, 井上雄太, 廣瀬瞭, 井上良太, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   100th   2020

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Development of magnetic filters for high gradient magnetic separation of medical proteins

KIM UiYeong, 森優輝, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Study on operating conditions considering thermal stability of a wireless power transmission system for railway vehicles using HTS coils

井上良太, 植田浩史, KIM SeokBeom, 津田理

低温工学・超電導学会講演概要集   100th   2020

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Study on Reinforcement Structure against Thermal Stress in Non Circular Coil for Cyclotron Applications

三宅雄大, 仲井悠貴, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 福田光宏, 石山敦士

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Magnetic property measurements of material for carbon steel pipes by using small-sized single sheet tester

SONG Chaeeun, 久米一輝, 井上良太, 植田浩史, KIM SeokBeom, 廿日出好

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Study on the thermal stability of non-insulated HIS coil with a metal ring on the outermost layer

西川大亮, 小林大剛, 宮本康平, 井上良太, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   100th   2020

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Numerical Evaluation on Reinforcement against Thermal and Electromagnetic stress in High Field No-Insulation REBCO coil

徳永佳祐, 内藤敬介, 井上良太, KIM SeokBeom, 植田浩史

低温工学・超電導学会講演概要集   100th   2020

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Power transmission characteristics of a wireless power transmission system using HTS coils in commercial frequency

高宮裕志, 井上良太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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Numerical Evaluation on Distribution of Non-uniform Electromagnetic Stress due to Screening Current in HTS Coils

内藤敬介, 徳永佳祐, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   71st   2020

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核医学治療用高温超電導スケルトン・サイクロトロンの開発(2)―実証用高温超電導小型マルチコイルシステムの設計―

野口聡, 植田浩史, 粟津佑太, KIM SeokBeom, 渡部智則, 長屋重夫, 吉田潤, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   98th   78   2019.5

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核医学治療用高温超電導スケルトン・サイクロトロンの開発(4)―実証用高温超電導小型マルチコイルシステムの機械特性解析―

粟津佑太, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 吉田潤, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   98th   80   2019.5

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核医学治療用高温超電導スケルトン・サイクロトロンの開発(3)―実証用高温超電導小型マルチコイルシステムの遮蔽電流解析―

植田浩史, 粟津佑太, KIM SeokBeom, 野口聡, 渡部智則, 長屋重夫, 吉田潤, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   98th   79   2019.5

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小型NMR/MRI装置用高温超電導コイルの形状設計に関する基礎研究

大澤慶博, 石井翔己, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   70th   2019

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サイクロトロン用高温超電導マグネットの巻線精度が発生磁場に及ぼす影響

三宅雄大, 粟津佑太, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 吉田潤, 福田光宏, 石山敦士

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   70th   2019

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REBCOコイル励消磁時の遮蔽電流に起因する電磁力解析

細谷野里香, 徳永佳祐, 盛川瑛亮, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   70th   2019

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Development of Medical Protein Screening System using High Gradient Magnetic Separation

植田浩史, KIM SeokBeom

Annual Report of the Okayama Foundation for Science and Technology   ( 28 )   2019

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完全非接触でのSQUID式超音波ガイド波検査技術の開発-その1-

横内祐紀, 東雄貴, 窪田章吾, 寺若友博, 植田浩史, KIM S.B., 廿日出好

応用物理学会春季学術講演会講演予稿集(CD-ROM)   66th   2019

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次世代医療用スケルトンサイクロトロンに用いる高温超電導コイルシステムの電磁力解析

粟津佑太, KIM SeokBeom, 植田浩史, 野口聡, 渡部智則, 長屋重夫, 吉田潤, 福田光宏, 石山敦士

低温工学・超電導学会講演概要集   97th   88   2018.11

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無絶縁REBCOマグネットのターン間接触抵抗の測定方法

野口聡, 野口聡, 立田貴裕, 植田浩史, KIM Seokbeom, 石山敦士

低温工学・超電導学会講演概要集   97th   98   2018.11

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高強度小型多機能スケルトンサイクロトロンの開発―遮蔽電流磁場解析―

粟津佑太, KIM SeokBeom, 植田浩史, 野口聡, 石山敦士, 渡部智則, 長屋重夫, 吉田潤, 鶴留武尚, 高橋伸明, 三上行雄, 福田光宏

低温工学・超電導学会講演概要集   96th   78   2018.5

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2G HTS magnet with smart insulation method

Seok-Beom Kim, Young-Sik Jo, Hyung-Wook Kim, Seog-Whan Kim, Doohun Kim, Rock-Kil Ko, Dong-Woo Ha, Heui Joo Park, Ho Min Kim, Dong-Gyun Ahn, Jung-Pyo Hong, Jin Hur

IEEE Transactions on Applied Superconductivity   28 ( 3 )   547 - 563   2018.4

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This paper proposes an advanced method to satisfy both the stability and charging/discharging time constant requirements of second generation high-temperature superconductor (2G HTS) magnets. This novel method entails installing metal–insulator transition (MIT) material between the turns of the 2G HTS magnets. The MIT material acts as an insulator when the temperature is lower than a certain value. Above this temperature, the MIT material becomes a conductor. This transition can be used as a switch between the turns of the 2G HTS magnets. We refer to this temperature-dependent smart switch as “smart insulation.” Considering the operating temperature, we selected V2 O3 as the material for smart insulation. We have experimentally verified that the advantages of both the insulation magnet (in the superconducting state) and no-insulation magnet (during quenching) can be simultaneously realized.

DOI： 10.1109/TASC.2017.2779491

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Current bypassing and transient stability in a partially insulated HTS coil

SeokBeom Kim, Haruyoshi Okusa, Kentaro Tami, Hiroshi Ueda

IEEE Transactions on Applied Superconductivity   28 ( 3 )   4603105 - 4603105   2018.4

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The no-insulation (NI) winding technique to improve the transient stability of high-temperature superconducting (HTS) magnets has been studied and a cowinding method using a metallic tape was tested. Normally, the operating current in NI HTS coils is bypassed into the transverse direction due to the normal region generated within the coils. Therefore, a method that controls such current bypassing into the turn-to-turn direction of NI HTS coils was investigated as a means to regulate the effective number of turns. In this study, we experimentally investigated the characteristics of current bypassing in the transverse direction within a test coil wound with a GdBCO tape. First, to find an optimized heater location, a 20-turn HTS pancake with two partial insulation shapes was prepared and tested experimentally. The current bypassing characteristics in the normal region created by heaters (strain gauges) were studied while varying the number of heaters, heater positions, and the amount of heating at liquid nitrogen temperature. Using both short and long heating periods, we found that we could effectively control the number of turns (coil inductance) via long-duration heating.

DOI： 10.1109/TASC.2017.2787108

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Development of HTS Bulk NMR Relaxometry with Ring-Shaped Iron

Seokbeom Kim, Susumu Fukada, Ryota Nomura, Hiroshi Ueda

IEEE Transactions on Applied Superconductivity   28 ( 3 )   4301505 - 4301505   2018.4

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The compact NMR magnets consisted of the stacked higherature superconducting (HTS) GdBCO bulk annuli trapped by field cooling (FC) method have been developed. The target values of strength and homogeneity of magnetic field for proposed NMR relaxometry are 1.5 T and 150 ppm/cm3, respectively, at liquid nitrogen temperature. Since last year, we have been developing a hardware and software to detect the NMR signals by ourselves. Therefore, we needed to determine the final structure of HTS bulk magnet to be used in the NMR relaxometry. We can obtain the trapped magnetic field over 1.5 T at 77.4 K experimentally. However, it is still difficult to obtain the magnetic field homogeneity under 150 ppm/cm3 experimentally, due to their different superconducting properties. Therefore, in this study, four types of HTS bulk magnets to determine the final structure of compact NMR relaxometry were designed and their field properties including the degraded HTS bulk were investigated using three-dimensional finite-element method analysis. The field properties of 10-stacked HTS bulk magnets with the ring-shaped irons for field compensation and the degraded HTS bulk were investigated experimentally.

DOI： 10.1109/TASC.2017.2785260

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2G HTS Magnet With Smart Insulation Method Reviewed

Young-Sik Jo, Hyung-Wook Kim, Seog-Whan Kim, Doohun Kim, Rock-Kil Ko, Dong-Woo Ha, Heui Joo Park, Ho Min Kim, Dong-Gyun Ahn, Jung-Pyo Hong, Jin Hur, Seok-Beom Kim

IEEE Transactions on Applied Superconductivity   28 ( 3 )   1 - 4   2018.4

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This paper proposes an advanced method to satisfy both the stability and charging/discharging time constant requirements of second generation high-temperature superconductor (2G HTS) magnets. This novel method entails installing metal–insulator transition (MIT) material between the turns of the 2G HTS magnets. The MIT material acts as an insulator when the temperature is lower than a certain value. Above this temperature, the MIT material becomes a conductor. This transition can be used as a switch between the turns of the 2G HTS magnets. We refer to this temperature-dependent smart switch as “smart insulation.” Considering the operating temperature, we selected V2 O3 as the material for smart insulation. We have experimentally verified that the advantages of both the insulation magnet (in the superconducting state) and no-insulation magnet (during quenching) can be simultaneously realized.

DOI： 10.1109/tasc.2017.2779491

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An Extended Thin Approximation Method to Simulate Screening Current Induced in REBCO Coils Reviewed

So Noguchi, Seungyong Hahn, Hiroshi Ueda, SeokBeom Kim, Atsushi Ishiyama

IEEE Transactions on Magnetics   54 ( 3 )   1 - 4   2018.3

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Superconducting magnets wound with second-generation high-temperature superconductors, i.e., REBa2Cu3O7-x (REBCO, RE = Rare Earth) tapes, are desired to apply high magnetic field nuclear magnetic resonance, MRI, and accelerators. However, a major problem for practical application is an undesirable irregular magnetic field caused by screening currents induced in REBCO tapes. To investigate the screening current-induced magnetic field, a few simulation methods have been proposed. One of the effective simulation methods employs a finite-element method with a thin approximation method. Although the thin approximation method was developed to simulate eddy currents in magnetic steel sheets, and it is not applicable to REBCO tapes carrying a transport current. Therefore, the thin approximation method is extended to simulate screening currents in REBCO tapes considering a carrying transport current. To show the validity of the proposed extended thin approximation method, the screening currents of an REBCO magnet are computed, and the results are compared with the measurement and simulation results of the conventional thin approximation method. The more accurate solution is available by using the proposed methods.

DOI： 10.1109/tmag.2017.2752083

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高温超電導コイルの巻線内電磁力解析

植田浩史, 徳永佳祐, 盛川瑛亮, 小泉智暉, KIM SeokBeom

低温工学・超電導学会講演概要集   97th   2018

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単板磁気試験器を用いた電磁鋼板の2Hコイル法による磁界強度測定法の検討

太田葵, 藤本賢哉, 大原慎也, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   69th   2018

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REBCOコイルの遮蔽電流に起因する巻線内電磁力解析

徳永佳祐, 盛川瑛亮, 小泉智暉, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   69th   2018

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500MHz LTS/REBCO NMRにおける遮蔽電流磁場解析による磁場均一度評価

盛川瑛亮, 徳永佳祐, 小泉智暉, KIM SeokBeom, 植田浩史, 柳澤吉紀

低温工学・超電導学会講演概要集   97th   2018

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高温超電導コイルの小型化とインダクタンス制御に関する研究

西川大亮, 立田貴裕, 大草晴義, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   69th   2018

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500MHz LTS/REBCO NMRの遮蔽電流磁場解析

盛川瑛亮, 小泉智暉, KIM SeokBeom, 植田浩史, 濱田衞, 柳澤吉紀, 前田秀明

低温工学・超電導学会講演概要集   96th   2018

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医薬用タンパク質の高勾配磁気分離用磁性フィルターの断面形状設計

安部拓郎, 窪田幹久, 森優輝, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   69th   2018

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Numerical Simulation on coupling current in HTS coil wound with multifilamentary HTS tape

植田浩史, 小泉智暉, 盛川瑛亮, KIM SeokBeom

電気学会研究会資料   ( MC-18-001-023/ASC-18-001-023 )   2018

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Study on the Rotation Properties and the Design Issue of Non-Contact Rotating System Using HTS Bulks and Permanent Magnets

R. Okamura, S. B. Kim, Y. Ozaki, H. Ueda

Journal of Physics: Conference Series   871 ( 1 )   702 - 709   2017.7

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In previous study, non-contact rotating system consisting of the ring-shaped high temperature superconducting (HTS) bulks, ring-shaped permanent magnets (PMs) and stator coil was proposed. In this system, HTS bulks were magnetized by PMs and PMs were levitated with strong restoring force. In our previous study, we have constructed the rotating system with the ring-shaped HTS bulks with ID 20 mm, OD 60 mm, and 15-mm thickness. However, since these bulks costs too much, we switched to use HTS bulks with ID 20 mm, OD 60 mm, and 5-mm-thickness to miniaturize the system. However, this system have potential to fail the radial stability of rotating shaft. Therefore, we focused on the rotating and the radial restoring force in terms of the stability of the rotating shaft in the rotating system with 5-mm thickness HTS bulks.

DOI： 10.1088/1742-6596/871/1/012096

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Fundamental study on the magnetic field control method using multiple HTS coils for Magnetic Drug Delivery System

R. Hirano, S. B. Kim, T. Nakagawa, Y. Tomisaka, H. Ueda

Journal of Physics: Conference Series   871 ( 1 )   969 - 976   2017.7

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The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is very important issue in MDDS. In this application, the strength of magnetic field and gradient required to MDDS devices are 54 mT and 5.5 T/m, respectively. We proposed the new magnetic force control system that consists of the multiple racetrack HTS magnets. We can control the magnetic field gradient along the longitudinal direction by the arrangement of the multiple racetrack HTS magnets and operating current of each magnet. When the racetrack HTS magnets were used, the critical current was reduced by the self-magnetic field. Therefore, the shape design of HTS magnet to reduce the magnet field into the surface of HTS tapes was required. Therefore, the electromagnetic analysis based on finite element method (FEM) was carried out to design and optimize the shape of multiple racetrack HTS magnet. We were able to suppress the reduction of critical current by placing the magnetic substance at upper and lower side of the HTS magnets. It was confirmed that obtained maximum values of magnetic field strength and field gradient were 33 mT and 0.18 T/m, respectively.

DOI： 10.1088/1742-6596/871/1/012104

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Numerical study to obtain the improved field homogeneity of HTS bulk magnet with enlarged inner diameter for compact NMR

S. Fukada, S. B. Kim, T. Nakagawa, R. Nomura, H. Ueda

Journal of Physics: Conference Series   871 ( 1 )   1488 - 1495   2017.7

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The strength and homogeneity of the magnetic field required for NMR relaxometry device are 1.5 T and 150 ppm/cm3 respectively. It is relatively easy to generate the trapped magnetic field over 1.5 T at 77.4 K using the stacked HTS bulks, and 150 ppm/cm3 field homogeneity was obtained using the fabricated field compensation methods on HTS bulks magnet with 20 mm inner diameter. However, it is still hard to obtain 150 ppm/cm3 field homogeneity without field compensation methods. In this paper, in order to improve the trapped magnetic field homogeneity, the HTS bulk magnet with enlarged inner diameter was proposed and studied as the functions of size and shape of HTS bulk. The analytical study based on FEM was carried out to optimize the shape of HTS bulk magnet with enlarged inner diameter.

DOI： 10.1088/1742-6596/871/1/012088

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Improvement in Stability and Operating Characteristics of HTS Coil Using MIT Material Reviewed

Hyung-Wook Kim, Jin Hur, Seog-Whan Kim, Seok-Beom Kim, Rock-Kil Ko, Dong-Woo Ha, Ho Min Kim, Jin-Hong Joo, Young-Sik Jo

IEEE Transactions on Applied Superconductivity   27 ( 4 )   1 - 4   2017.6

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This paper proposes a new method of achieving electrical stability and controllability of a high-temperature superconductor (HTS) coil. The proposed method applied a material with a metal-insulator transition (MIT) property to the turn-to-turn resistance of an HTS coil. As a result, the turn-to-turn resistance remained at the insulator level in the normal state, thus removing delay during charging and discharging. During transient state, the turn-to-turn resistance dropped to the metal level, and current bypass occurs similar to that in a noinsulation coil, thus preventing the coil from burning out. The validity of the MIT characteristic and the proposed method were verified through experiments.

DOI： 10.1109/tasc.2017.2655262

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Fast Computation Method of Magnetic Field Homogeneity for NMR/MRI REBCO Pancake Coils

Ryosuke Miyao, Hajime Igarashi, SeokBeom Kim, So Noguchi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   27 ( 4 )   610 - 616   2017.6

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Recently, multiple-stacked pancake coils wound with rare-earth barium copper oxide (REBCO) tapes are expected to apply for nuclear magnetic resonance (NMR)/MRI magnets. Since REBCO tapes are very expensive, REBCO magnets should be optimally designed so as to minimize the winding volume. Surely, a highly homogeneous magnetic field is also required for NMR/MRI magnets. To achieve the accurate homogeneity of REBCO magnets, it is necessary to compute the contribution of all REBCO layers one by one, because currents carry over very thin area compared with a whole magnet cross section. However, NMR/MRI magnets generating high-magnetic field usually consist of multiple-stacked REBCO pancake coils, and each pancake coil has > 300 turns. To evaluate the field homogeneity contributed by every REBCO layer, therefore, it is necessary to repeatedly compute more than ten thousand times as one magnet shape. In a conventional optimization algorithm, it is necessary to iterate more than one million times for the optimal design of an NMR or MRI magnet. Such an iterative computation is not realistic. Based on the backgrounds, we present a fast computation method using the shift operator of spherical harmonics. In addition, to confirm the validity of the proposed method, it was applied to the shape optimization of 1.5-T MRI magnet. In this paper, the optimization result and computation time are also shown.

DOI： 10.1109/TASC.2016.2637937

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液体窒素冷却の小型NMR用高温超伝導バルクマグネットの開発

金 錫範

低温工学   52 ( 1 )   11 - 17   2017

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DOI： 10.2221/jcsj.52.11

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Development of HTS bulk magnets for compact NMR devices cooled by liquid nitrogen

52 ( 1 )   11 - 17   2017

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DOI： 10.2221/jcsj.52.11

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サイクロトロン応用のための高温超電導マグネットの発生磁場精度評価

粟津佑太, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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銅メッキ付きマルチフィラメント化REBCO線材の電流分布解析

盛川瑛亮, 小泉智暉, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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高温超電導バルク体による積層構造小型NMR装置用マグネットの試料測定空間拡張に関する基礎研究

乙倉孝輔, 深田進, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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無絶縁高温超電導コイルを想定した高温超電導線材間の電気的接触抵抗の圧力依存性に関する研究

立田貴裕, 大草晴義, 民健太郎, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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鉄リングによる超電導マグネットの磁場補正に関する研究

有岡直紀, 野村亮太, 富坂良和, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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マルチフィラメント高温超電導線材で巻線された高温超電導コイルの遮蔽電流解析

植田浩史, 小泉智暉, 盛川瑛亮, KIM SeokBeom

低温工学・超電導学会講演概要集   95th   2017

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三次元超電導アクチュエータの床・壁走行間の高温超電導バルク体移動子の動的特性に関する研究

山崎尊雄, 平塚祐介, 中嶋淳夫, 植田浩史, KIM SeokBeom

低温工学・超電導学会講演概要集   95th   2017

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医療用タンパク質の高勾配磁気分離用磁性フィルターの周囲の磁性粒子の挙動解析

森優輝, 窪田幹久, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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単板磁気試験器を用いた電磁鋼板の磁気特性測定方法に関する研究

藤本賢哉, 中川拓弥, 大原慎也, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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小型NMR装置用のハルバッハ配列永久磁石の磁場均一度向上に関する研究

美濃孝明, 野村亮太, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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連結高温超電導バルク体移動子を用いた三次元アクチュエータの動的特性に関する研究

中嶋淳夫, 平塚祐介, 山崎尊雄, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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小型NMR relaxometry装置用の高温超電導マグネットの形状に関する基礎研究

石井翔己, 菅生圭登, 喜来雅人, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   68th   2017

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Study of the Dynamic Properties of HTS Bulk Movers for Traveling Along Vertical Walls as a Three-Dimensional Actuator

S. B. Kim, M. Sawae, S. Ozasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 4 )   2016.6

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We have been investigating three-dimensional actuators using bulk high-temperature superconductors (HTS) as transportation devices that move in free space. The large flux-pinning force of HTS allows motion without contact, even when the levitation force is not aligned against gravity, which could make them useful in clean or dangerous environments, such as clean rooms for semiconductor fabrication or in tunnels containing flammable gas. An actuator prototype, consisting of an HTS bulk with trapped magnetic field as a mover and a two-dimensional array of electromagnets as a stator, has been developed. In a previous study, the dynamic characteristics for traveling over floors were examined. In this study, horizontal, vertical, and oblique motions along vertical walls have been investigated. Movement characteristics have been studied for HTS bulks of two diameters and related to measurements of the axial components of their trapped magnetic fields. Maximum vertical displacements of 5.80 and 11.5 mm were achieved for HTS bulks of 60- and 46-mm outer diameters, respectively.

DOI： 10.1109/TASC.2016.2535665

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Study on the Magnetic Field Homogeneity of HTS Bulk Magnets Including the Degraded HTS Bulk for Developing the Compact NMR Relaxometry

S. B. Kim, K. Hojo, D. Miyazawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 4 )   2016.6

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We have been studying the compact magnet for NMR device that consists of a stacked high-temperature superconducting (HTS) GdBCO bulk annuli trapped by a field cooling method. It was difficult to trap the uniform magnetic field above 4.7 T (200-MHz-class NMR magnet) and field homogeneity under 0.01 ppm/cm(3) at liquid nitrogen temperature (77.4 K) because of the low Jc-B characteristics of present HTS bulks. On the other hand, the strength and homogeneity of the magnetic field required for NMR relaxometry device are 1.5 T and 150 ppm/cm(3), respectively. Therefore, we have been investigating the development of the compact magnet for NMR relaxometry device. In our previous work, we obtained the trapped magnetic field over 1.5 T at 77.4 K using the stacked HTS bulk magnet with 80-mm height, and 150-ppm/cm(3) field homogeneity was obtained using the fabricated field compensation methods. However, the asymmetric problem of the magnetic field uniformity occurs by the different superconducting characteristics of HTS bulks when we produce the compact NMR magnet by stacking a large number of HTS bulks. Therefore, in this study, the field homogeneity of HTS bulk magnet by the arrangement of the degraded HTS bulk was investigated using 3-D FEM analysis. We examined the effects of the stacking position of degraded HTS bulk using various Jc-B characteristics.

DOI： 10.1109/TASC.2016.2521381

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Development of Non-Contact Levitated Rotating Machine Using HTS Bulks and Permanent Magnets

S. B. Kim, K. Nakamura

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 4 )   2016.6

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We have studied a non-contact magnetic levitation system using ring-shaped high-temperature superconducting (HTS) bulks and ring-shaped permanent magnets (PMs). Because the HTS bulks were magnetized by PMs fixed between the HTS bulks, this PMs levitated with strong restoring force. We used a stator coil to rotate the iron shaft combined with PMs. In order to rotate the shaft stable, restoring the force of radial direction is very important. Therefore, the ring-shaped PMs magnetized in the radial direction were fitted to the shaft. In this rotating system, we focused on two parameters, i.e., the rotation and the control. In the rotation, we measured the maximum rotating speed and the axial vibration due to the rotating speed. The three types of stator coils were designed by electromagnetic analysis, and these stators were tested experimentally.

DOI： 10.1109/TASC.2016.2518021

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Dynamic Characteristics of a 3-D Superconducting Actuator With Arranged Permanent Magnets and Electromagnets

S. B. Kim, S. Ozasa, M. Sawae

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 4 )   2016.6

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High-temperature superconductor (HTS) bulks can trap high magnetic fields due to strong flux pinning. We have been investigating 3-D superconducting actuators using HTS bulks for transportation applications. The actuator consists of an HTS bulk as a mover and 2-D arranged electromagnets (EMs) as a stator. However, many EMs and power supplies would be needed to produce a 3-D actuator with a large moving area; therefore, a new type of 3-D actuator based on a 2-D array of permanent magnets (PMs) in combination with a small number of EMs was designed and tested. In this new type of actuator, the speed control of the HTS bulk mover is very important to develop a reliable noncontact transportation device. In this paper, the dynamic movement characteristics of the HTS bulk mover in the new type of actuator were experimentally investigated as a function of the gap distance between PMs and the drive current patterns.

DOI： 10.1109/TASC.2016.2536440

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Shape Optimization of the Stacked HTS Double Pancake Coils for Compact NMR Relaxometry Operated in Persistent Current Mode

S. B. Kim, R. Saito, M. Takahashi, Y. J. Park, M. H. Lee, Y. K. Oh, S. Noguchi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 4 )   2016.6

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The low temperature superconducting (LTS) coils are used in NMR devices, and liquid helium is used for their cooling. It is possible to reduce the operating costs by manufacturing the superconducting magnet that is consisted of the high temperature superconducting (HTS) coil using liquid nitrogen cooling. We have been developing the NMR relaxometry devices using the HTS double pancake coils and operated in the persistent current mode at liquid nitrogen temperature. The required strength and homogeneity of the magnetic field of proposed NMR relaxometry devices are 1.5 T and 150 ppm/cm(3), respectively. To achieve the target field strength of 1.5 T, it is necessary to increase the numbers of pancake coils and winding turns of each coil, and the large operating current is required as much as possible. In this paper, I-c - B properties of HTS wire and superconducting joint are measured to determine the operating current (load line) for the proposed NMR relaxometry devices. Moreover, 3-D finite-element-model-based analysis was carried out to design the stacked HTS magnets for compact NMR relaxometry with downsizing and low cost.

DOI： 10.1109/TASC.2016.2518487

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(50T・500A/mm²・5GPa)‐REBCO超電導コイルシステムの開発

石山敦士, 我妻洸, 齋藤隆, 野口聡, 植田浩史, KIM SeokBeom, 渡部智則, 長屋重夫

低温工学・超電導学会講演概要集   93rd   114   2016.5

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Electrical Characteristic Analysis According to Contact Resistance Between Turns of HTS Coil

Hyung-Wook Kim, Jin Hur, Seog-Whan Kim, Dong-Woo Ha, Rock-Kil Ko, Jung-Pyo Hong, Ji Hyung Kim, Ho Min Kim, Jin-Hong Joo, Seok-Beom Kim, Young-Sik Jo

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   26 ( 3 )   2016.4

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This paper presents our analysis of the output characteristics of a high-temperature superconductor (HTS) coil depending on the turn-to-turn contact resistance. Important design factors were investigated by taking into account the turn-toturn contact resistance based on the analysis results. Analyses were performed on five self-fabricated coil models with different turn-to-turn contact resistances. To consider only the turn-to-turn contact resistance, we used a first-generation HTS BSCCO wire with simpler architecture and mechanical properties than the second-generation HTS wire. From this study, it was confirmed by experiment that as the turn-to-turn contact resistance decreases, the electrical stability increases but the output efficiency decreases compared with the input.

DOI： 10.1109/TASC.2016.2540162

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Study on the magnetic field homogeneity of stacked HTS bulk magnets including the deteriorated HTS bulk by crack for compact NMR relaxometry

K. Hojo, S. B. Kim, D. Miyazawa, R. Nomura, S. Fukada

PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015)   81   166 - 169   2016

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We have been studying the compact magnet for NMR device that consists of a stacked high temperature superconducting (HTS) GdBCO bulk annuli trapped by a field cooling (FC) method. It was difficult to trap the uniform magnetic field above 4.7 T ( 200 MHz-class NMR magnet) and field homogeneity under 0.01 ppm/cm(3) at liquid nitrogen temperature (77.4 K) because of the low Jc-B characteristics of present HTS bulks. On the other hand, the strength and homogeneity of the magnetic field required for NMR relaxometry device are 1.5 T and 150 ppm/cm(3) respectively. Therefore, we have been investigating the development of the compact magnet for NMR relaxometry device. In our previous study, we obtained the trapped magnetic field over 1.5 T at 77.4 K using the stacked HTS bulk magnet with 80 mm height, and 150 ppm/cm(3) field homogeneity was obtained using the fabricated field compensation methods on inner diameter of 20 mm HTS bulk magnet. However, it is expected that the asymmetric problem of the magnetic field uniformity will be occurred by the crack in the HTS bulks with long-term operation. Therefore, in this study, the field homogeneity of HTS bulk magnet by the arrangement of the HTS bulk with crack was investigated using 3-D FEM analysis. We examined the effects of the stacking position of HTS bulk with the crack and the allowable range of degradation of HTS bulk to achieve the target field homogeneity of 150 ppm/cm(3). (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2016.04.042

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小型NMR用高温超電導バルクマグネットの挿入コイルによる磁場均一度向上に関する研究

山本雅彦, 深田進, 北条勝也, 野村亮太, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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医療用タンパク質の高勾配磁気分離装置用磁性フィルターの開発に関する基礎検討

窪田幹久, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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ハルバッハ配列永久磁石を用いた小型NMR用マグネットの磁場校正用磁石による磁場均一度向上に関する研究

大原慎也, 北条勝也, 野村亮太, 深田進, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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非接触型超電導回転機の回転数向上のための固定子コイル設計に関する基礎研究

小崎裕介, 岡村亮太, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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複数の高温超電導レーストラックコイルを用いたMDDS用マグネット開発のための基礎研究

富坂良和, 平野亮磨, 中川拓弥, KIM Seokbeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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無絶縁高温超電導コイルの熱擾乱に対する過渡安定性向上とコイルの小型化に関する研究

大草晴義, 民健太郎, 金本太石, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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REBCO超電導コイルの線材内電流分布解析

小泉智暉, 植田浩史, KIM SeokBeom

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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3次元超電導アクチュエータの連続回転動作に伴う捕捉磁場減衰特性と移動子の動的特性

平塚祐介, 山崎尊雄, KIM SeokBeom, 植田浩史

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM)   67th   2016

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Electromagnetic Analysis on Magnetic Field and Current Distribution in High Temperature Superconducting Thin Tape in Coil Winding Reviewed

Hiroshi Ueda, SeokBeom Kim, So Noguchi, Atsushi Ishiyama, Hiroshi Miyazaki, Sadanori Iwai, Taizo Tosaka, Shunji Nomura, Tsutomu Kurusu, Shinichi Urayama, Hidenao Fukuyama

2016 IEEE CONFERENCE ON ELECTROMAGNETIC FIELD COMPUTATION (CEFC)   2016

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High temperature superconducting (HTS) wires are high aspect ratio cross-section tapes. Therefore, the applications of HTS tapes lead to various problems such as AC loss, nonuniform current, and screening current. In practice, we must investigate the detail of current distribution in HTS tapes using the electromagnetic analysis technique dealing with high aspect ratio tape and nonlinearity of superconductor. We developed the numerical simulation code of electromagnetic field analysis in HTS tape using a finite element method (FEM) and fast multipole method (FMM).

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Study on the Shape Optimization of the HTS Bulk Magnets With Active Compensation for Compact NMR Relaxometry Magnets

S. Kim, D. Ishizuka, H. Kitamura, D. Miyazawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   4602404 - 4602404   2015.6

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Compact NMR magnets consisted of the stacked HTS bulk annuli trapped by a field cooling (FC) method have been suggested and developed. The strength and homogeneity of the magnetic field required for the NMR relaxometry device are 1.5 T and 150 ppm/cm(3) respectively, and these values are much lower than the conventional NMR device. It is relatively easy to generate a magnetic field over 1.5 T at 77.4 K using the stacked HTS bulk annuli, but it is still hard to obtain 150 ppm/cm(3) field homogeneity with the conventional superconducting magnet (SCM) as the magnetizing magnets. In this paper, to improve the trapped magnetic field homogeneity and to obtain the enlarged sample space of HTS bulk magnet for compact NMR relaxometry, the HTS bulk magnet with 10 mm gap length in the center region of HTS bulk magnet (we call it " split coil-shaped HTS bulks") were proposed and studied as the functions of size and shape of HTS bulk. It was studied using 3D FEM based electromagnetic analysis. The improved field homogeneity was obtained by using hybrid models consisted with the HTS bulk and attached small size HTS coil.

DOI： 10.1109/TASC.2014.2374337

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The Study to Improve the Field Homogeneity of the NMR Relaxometry Magnets Using the Packaged HTS Bulks With Various Iron Rings

S. B. Kim, H. Kitamura, D. Ishizuka, D. Miyazawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   4602204 - 4602204   2015.6

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The compact magnet for NMR device that consists of a stacked high temperature superconducting (HTS) Gd-Ba-Cu-O bulk annuli was trapped by a field cooling method. However, it was difficult to trap the uniform magnetic field above 4.7 T (200 MHz-class NMR magnet) and field homogeneity under 0.01 ppm/cm3 at liquid nitrogen temperature (77.4 K) because of the low Jc-B characteristics of present HTS bulks. On the other hand, the strength and homogeneity of the magnetic field required for NMR relaxometry device are 1.5 T and 150 ppm/cm3 respectively. It is easily to generate the trapped magnetic field over 1.5 T at 77.4 K using the stacked HTS bulks, but it is still hard to obtain 150 ppm/cm3 field homogeneity with the conventional superconducting magnet (SCM) as the magnetizing magnets. Therefore, we have studied the compensation methods to improve the field homogeneity. In this paper, we proposed the packaged HTS bulk magnet consisted of HTS bulks annuli and various iron rings as the field compensation, and investigated it in analysis and experiment.

DOI： 10.1109/TASC.2014.2372896

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Study on the Dynamic Stability of 3-D Superconducting Actuator by Various Typed HTS Bulk Movers

S. Kim, H. Nakano, S. Ozasa, M. Sawae

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   3601104 - 3601104   2015.6

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High-temperature superconductor (HTS) material can trap high magnetic fields due to its strong flux pinning force. Herein, based on our belief that such a device would be useful as a transporter in clean rooms where silicon wafers are manufactured, we report on the development of a three-dimensional (3-D) superconducting actuator using HTS bulk material in a noncontact transportation device that will move freely in 3-D space. The proposed actuator consists of a trapped HTS, which provides the mover, along with two-dimensionally arranged copper-wound iron-core electromagnets that form the stator. The current and the polarity of each electromagnet can be individually controlled via the power supply. In our previous experiments, a singlecomponent mover was observed to overshoot during operation, which led us to conclude that a more powerful levitation force was needed. In this study, single-component HTS movers (inner diameters of 46 and 60 mm) and multicomponent HTS movers were used to increase the levitation force and dynamic stability.

DOI： 10.1109/TASC.2015.2393055

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Study of Magnetomotive Force Control Type Superconducting Magnet Using BSCCO HTS Wire

Hyung-Wook Kim, Young-Sik Jo, Seog-Whan Kim, Rock-Kil Ko, Dong-Woo Ha, Ho Min Kim, Jin-Hong Joo, Hyung-Jin Kim, Seok-Beom Kim, Jin Hur

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   4600804 - 4600804   2015.6

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In this study, a method for controlling the magnetomotive force using the current bypass of no-insulation magnets was developed, and the characteristics of 1G high-temperature superconductivity (HTS) no-insulation magnets were elucidated through experiments. The experiments were performed using a magnet designed with bismuth strontium calcium copper oxide HTS wires. Film-type heaters were used to control the MMF. The analysis of the experimental results was carried out in conjunction with an analysis using finite elements method.

DOI： 10.1109/TASC.2014.2365549

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Development of Magnetic Field Control System Using HTS Bulk for ON/OFF Field Switching and Magnetic Field Amplification

S. B. Kim, T. Abe, I. Eritate, M. Takahashi, S. Shima, A. Nakashima

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   4603104 - 4603104   2015.6

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High magnetic fields are used in many branches of modern medicine. So, the techniques for magnetic field concentration are very important, and the novel electromagnets and trapped HTS bulk magnets have been fabricated and used in the cell culture and the bulk magnetic drug delivery system. In general, although superconducting magnet can generate high magnetic fields, ON/OFF magnetic switching is impossible because of its large inductance. Therefore, not only the generating of magnetic field but also controlling of magnetic field including ON/OFF switching are very important issues. So, we have been studied the control methods of magnetic field using HTS bulks. In this study, the magnetic field control system consisted of the various shaped HTS bulks and magnetic sources were proposed to achieve the ON/OFF field control and field amplification. The shape of HTS bulk to develop the magnetic control system was optimized by FEM based on analysis, and the abilities of its field switching and amplification were confirmed by experiments. We found that the HTS bulk with slit did control the applied magnetic field, and amplified magnetic fields were obtained at slit parts of HTS bulks.

DOI： 10.1109/TASC.2014.2379946

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Development of Magnetic Field Control System Using HTS Bulks and HTS Coil for MDDS

S. B. Kim, I. Eritate, T. Abe, M. Takahashi, S. Shima, A. Nakashima

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   4602704 - 4602704   2015.6

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Magnetic drug delivery system (MDDS) is a key technology effects in the medical applications, and also the magnetic force control is a very important issue in MDDS. In general, the high magnetic field along the axial direction and high magnetic field gradient along the longitudinal direction are very useful for MDDS. So, we proposed the new magnetic force control system consists of superconducting magnet, high temperature superconductors (HTS) bulks or tapes and irons. In this system, the shielding currents in HTS bulks and tapes due to the diamagnetism of the superconductor generate the magnetic field with same direction of external magnetic field, and we can control the magnetic field gradient along the longitudinal direction by the arrangement of the superconductors and irons. In this study, the stacked GdBCO tapes were used in experiments and electromagnetic analysis based on finite-element method was carried out to optimize the arrangement of the superconductors and the irons. It was confirmed the control of magnetic field gradient along the longitudinal direction was possible by arranging the HTS bulks, tapes and irons on the superconducting magnet. In analysis, the magnetic field of 164.6 mT and field gradient of 1.89 T/m were obtained.

DOI： 10.1109/TASC.2014.2376992

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The Levitation Characteristics of the Noncontact Rotating System Using HTS Bulks Trapped by Permanent Magnets

S. B. Kim, Y. Fujii, K. Nakamura, M. Takahashi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   25 ( 3 )   3600904 - 3600904   2015.6

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We have studied a noncontact magnetic levitation system using the ring-shaped high-temperature superconducting (HTS) bulks and ring-shaped permanent magnets (PMs). Because HTS bulks were magnetized by PMs fixed between the HTS bulks, these PMs levitated with strong restoring force. We used the stator coil to rotate the iron shaft that was combined with PMs. In order to rotate the shaft stable, a restoring force of the radial direction was important. Thus, we placed ring-shaped PMs that magnetized in the radial direction with the inner part of the HTS bulks. In this rotating system, we focused on two parameters, the rotation and the control. In the rotation, we measured the maximum rotational speed and the axial vibration caused by increasing of rotational speed. In the control, we measured slippage from the convergence position when rotated by 60 degrees. In addition, we compared the slippage by changing the conditions.

DOI： 10.1109/TASC.2014.2383411

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Numerical study to obtain the improved field homogeneity and enlarged inner diameter of HTS bulk magnet for compact NMR

D. Miyazawa, S. B. Kim, H. Kitamura, D. Ishizuka, K. Hojo

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   245 - 248   2015

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We have been studying the compact magnet for NMR device that consists of a stacked high temperature superconducting (HTS) GdBCO bulk annuli. We can generate the trapped magnetic field over 1.5 T at 77.4 K and 150 ppm/cm(3) on inner diameter of 20 mm HTS bulks using field compensation methods. However, it is necessary to enlarge the inner diameter of the HTS bulk magnet because the diameter of commercial NMR probe is larger than 20 mm. In this paper, we studied an optimal shape of the stacked HTS bulk magnet to obtain the enlarged inner diameter using 3-D FEM based analysis. We was able to enlarge the inner diameter of the HTS bulk magnet from 20 mm to 34 mm remaining magnetic field strength of 1.5 T and magnetic field homogeneity of 666 ppm/cm(3) by proposed passive field compensation method. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.135

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Current bypassing properties by thermal switch for PCS application on NMR/MRI HTS magnets

S. B. Kim, M. Takahashi, R. Saito, Y. J. Park, M. W. Lee, Y. K. Oh, H. S. Ann

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   149 - 152   2015

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We develop the compact NMR/MRI device using high temperature superconducting (HTS) wires with the persistent current mode operating. So, the joint techniques between 2G wires are very important issue and many studies have been carried out. Recently, the K.JOINS, Inc. has developed successfully the high performance superconducting joints between 2G wires by partial melting diffusion and oxygenation annealing process [1]. In this study, the current bypassing properties in a loop-shaped 2G wire are measured experimentally to develop the permanent current switch (PSC). The current bypassing properties of loop-shaped test coil wound with 2G wire (GdBCO) are evaluated by measured the self-magnetic field due to bypassed current by Hall sensors. The strain gauge was used as heater for persistent current switch, and thermal properties against various thermal inputs were investigated experimentally. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.088

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Magnetic-Thrust Flexible Electrode with Integrated Preamplifier for Neural Recording

Toshihiko Noda, Yoshiya Matsuzaka, SeokBeom Kim, Hiroaki Takehara, Kiyotaka Sasagawa, Takashi Tokuda, Hajime Mushiake, Hiroshi Onodera, Jun Ohta

SENSORS AND MATERIALS   27 ( 11 )   1079 - 1089   2015

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Flexible electrodes for use in recording neural activity were fabricated in this study, and their use was demonstrated. By using the mechanical force generated by a magnetic field, an electrode can be inserted into a tissue, and the position of the electrode can be controlled. The position and insertion path of the electrode can be controlled accurately with a high degree of freedom. No stiffener materials are required for the insertion process. A headstage amplifier, which is indispensable for low-noise recording, was hybrid-integrated with a flexible electrode. A miniaturized main amplifier that served as a second-stage amplifier was also fabricated. The magnetic controllability of the fabricated electrode was demonstrated using a phantom of a tissue. An in vivo experiment was also performed for the functional validation of the recording function. Local field potentials were recorded successfully as a result of the experiment.

DOI： 10.18494/SAM.2015.1145

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Development of field control method and basic design of HTS magnet for MDDS

A. Nakashima, S. B. Kim, I. Eritate, T. Abe, S. Shima, M. Takahashi, N. Sanada

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   237 - 240   2015

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The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications. We proposed the new magnetic force control system that consists of superconducting magnet, high temperature superconductors (HTS) tapes and iron blocks. In this study, it was confirmed that the control of magnetic field gradient was possible by arranging the HTS tapes and iron blocks on the superconducting magnet. In addition, the multiple racetrack HTS magnets were proposed in order to generate the high field gradient along the longitudinal direction. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.132

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The study on the shape of 2-D stator with electromagnets and permanent magnets for 3-D superconducting actuator

S. Ozasa, S. B. Kim, H. Nakano, M. Sawae, H. Kobayashi

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   257 - 260   2015

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The electric device applications of a high temperature superconducting (HTS) bulk magnet having stable levitation and suspension properties due to their strong flux pinning force have been proposed and developed. We have been investigating the three-dimensional (3-D) superconducting actuator using HTS bulk to develop a non-contact transportation device.
Probably, the cost of the manufactory will be increased to install the 2-D arranged electromagnets (EM) in a large area because many EMs are needed to cover the area. Therefore, we have been trying to find the method for reducing the number of EMs. In this study, all the EMs except for rotation were replaced in the 2-D arranged permanent magnets (PM), and gap length between PMs were experimentally investigated to improve the dynamic behavior of the mover and to reduce the cost of the manufacturing. As a result, we have succeeded in conveyance of the bulk and reduce the convergence time and maximum overshoot. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.141

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The Dynamic Characteristics on the Wall Traveling of the HTS Bulk Superconducting Actuator

M. Sawae, S. B. Kim, S. Ozasa, H. Nakano, H. Kobayashi

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   249 - 252   2015

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The electric device applications of a high temperature superconducting (HTS) bulk having stable levitation and suspension properties due to their strong flux pinning force have been proposed and developed. We have been investigating the three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and moves in free space. It is expected that our proposed 3-D superconducting actuator to be useful as a transporter used in clean room which manufactures the silicon wafer where dislikes mechanical contact and dust. Proposed the actuator consists of a field-cooled HTS bulk for mover and two-dimensional arranged multiple electromagnets as a stator. In our previous study, the dynamic characteristics on the floor traveling of the HTS bulk mover had been studied. Therefore in this study, a system for the wall traveling was proposed to use the limited space effectively. It is expected that the wall traveling system is very useful to apply the transporter used in the tunnels which flammable gas may be produced. In this paper, the optimal angle between electromagnets located at floor and wall for moving to the wall traveling from the floor traveling was investigated experimentally. The position displacement on the rotating of the HTS bulk during the wall traveling was measured. As a result, the bulk with initial gap of 2 mm could move to the wall traveling from the floor traveling. Also, the position displacement on the height direction during the rotating of the HTS bulk was 18 mm from the initial position because of its gravity, but it was possible to rotate by changing the pattern NSNS of the trapped magnetic field in near the initial position. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.138

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Development of the current bypassing methods into the transverse direction in non-insulation HTS coils

K. Tanaka, S. B. Kim, H. Ikoma, D. Kanemoto

Proceedings of the 27th International Symposium on Superconductivity (ISS 2014)   65   229 - 232   2015

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In the case of motors and generators, the benefits of using high temperature superconducting (HTS) coils can be represented by the reduction of 50% in both losses and sizes compared to conventional machines. However, it is hard to establish quench detection and protection devices for the HTS coils applied to the rotors of motors and generators. So, the stability of the coils is lower than for the quiescent coils applied to NMR, MRI and so on. Therefore, it is important to improve the self-protection ability of HTS coils. We have studied the methods to improve the self-protection ability of HTS coils by removing the layer-to-layer insulation and inserting metal tape instead of the electrical insulation. The operating current in the non-insulated HTS coil was bypassed into the transverse direction by the generated normal region because of their electrical contact among the winding. In this study, we examined the method to control the current bypassing on layer-to-layer for controlling the inductance of the non-insulated HTS coil. The current bypassing properties on non-insulated HTS coil wound with 2G wires will be discussed. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.phpro.2015.05.129

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The fundamental study to control the magnetic field for MDDS using shielding currents of HTS tapes and bulks

B. Kim, I. Eritate, T. Abe, S. Shima, M. Takahashi

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   506   27 - 32   2014.11

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The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is a very important issue in MDDS. In general, the high magnetic field along the axial direction and high magnetic field gradient along the longitudinal direction are very useful for MDDS. So, we proposed the new magnetic force control system that consists of superconducting magnet, high temperature superconductors (HTS) bulks or tapes and ferromagnetic substances. In this new system, the shielding currents in HTS bulks and tapes due to diamagnetism of the superconductor generate the magnetic field with same direction of external magnetic field, and we can control the magnetic field gradient along the longitudinal direction by the arrangement of the HTS bulks, tapes and ferromagnetic substances. In this study, the stacked GdBCO tapes without stabilizer were used in experiments and electromagnetic analysis based on finite element method (FEM) was carried out to optimize the arrangement of the superconductors and the irons. It was confirmed that the control of magnetic field gradient along the longitudinal direction was possible by arranging the HTS bulks, tapes and irons on the superconducting magnet and then it was possible to obtain a magnetic field higher than the external field. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2014.08.001

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Study on the Remagnetization Process to Improve the Field Homogeneity of the Stacked HTS Bulk Magnets

S. B. Kim, N. Hayashi, H. Kitamura, I. Eritate

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   24 ( 3 )   4301405 - 4301405   2014.6

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The compact NMR magnets consisting of stacked HTS bulk annuli trapped by a field cooling (FC) method have been developed. However, it is difficult to trap a uniform magnetic field above 4.7 T (200 MHz-class NMR magnet) and field homogeneity under 0.01 ppm/cm(3) at liquid nitrogen temperature (77.4 K) because of the low Jc-B characteristics of present HTS bulk magnets. On the other hand, the strength and homogeneity of the magnetic field required for the NMR relaxometry device are 1.5 T and 150 pprn/cm(3) respectively; these values are much lower than the conventional NMR device. It is relatively easy to generate a magnetic field over 1.5 T at 77.4 K using the stacked HTS bulk annuli, but it is still hard to obtain 150 pprn/cm(3) field homogeneity with the conventional superconducting magnet (SCM) as the magnetizing magnets. In this paper, we proposed that the homogeneity had been improved by utilizing the remagnetization process.

DOI： 10.1109/TASC.2013.2290591

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Development of the Noncontact Rotating System Using Combined Ring-Shaped HTS Bulks and Permanent Magnets

S. B. Kim, T. Ikegami, Y. Fujii, M. Takahashi, H. Onodera

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   24 ( 3 )   6800105 - 6800105   2014.6

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In this study, the noncontact magnetic levitation system using combined high temperature superconducting (HTS) hulk annuli and ring-shaped permanent magnet (PM) was proposed. In the suggested levitation system, the HTS bulk annuli were magnetized by ring-shaped PMs fixed between the HTS bulk annuli, so there was no more need to apply source for magnetization. In this paper, the levitation forces on the radial and axial directions were measured using 1 PM + 2 bulks (1 unit) and 2 PM + 3 bulks systems to study the optimization of levitation system. To improve the levitation property of proposed levitation system, the shape of PM and materials of the rotor shaft were studied experimentally.

DOI： 10.1109/TASC.2013.2284021

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Study on the Electrical Contact Resistance Properties With Various Winding Torques for Noninsulated HTS Coils

S. B. Kim, H. Kajikawa, H. Ikoma, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   24 ( 3 )   4600405 - 4600405   2014.6

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In the case of motors and generators, the benefits of using high-temperature superconducting (HTS) coils can be represented by the reduction of 50% in both losses and sizes compared to conventional machines. However, it is hard to establish quench detection and protection devices for the HTS coils applied to the rotors of motors and generators. Therefore, the stability of the coils is lower than for the quiescent coils applied to NMR, MRI, and so on. Therefore, it is important to improve the self-protection ability of HTS coils. We have studied the methods to improve the self-protection ability of HTS coils by removing the turn-to-turn insulation and inserting metal tape instead of the electrical insulation. When the coils are energized, there are voltages generated by sweep rate of the current (di/dt) and inductance of the coil. Because noninsulated HTS coils have electrical contacts along the transverse direction, a bypass current is generated along the transverse direction and noninsulated HTS coils have a risk of Joule heating in the stabilizer and metal substrate. Furthermore, the electrical contact resistance of noninsulated HTS coils was changed by a winding torque. In this paper, we measured the electrical contact resistance along the transverse direction with various winding torques for noninsulated HTS coils.

DOI： 10.1109/TASC.2013.2283103

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Passive Shimming by Eliminating Spherical Harmonics Coefficients of all Magnetic Field Components Generated by Correction Iron Pieces

So Noguchi, SeokBeom Kim, Seungyong Hahn, Yukikazu Iwasa

IEEE TRANSACTIONS ON MAGNETICS   50 ( 2 )   7014904 - 7014904   2014.2

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When a magnet generating highly homogeneous magnetic field is designed, a shimming is required. The shimming is usually performed so that the magnetic field only in the axis direction is compensated by iron pieces and/or coils. The compensation is commonly achieved by eliminating the coefficients of the spherical harmonics expansion of the magnetic field generated by the main magnet. Some papers showed the coefficients of the spherical harmonics expansion in only the z-direction for passive shimming. However, recently some magnets generate a magnetic field tilted from the z-axis, such as a magic-angle-spinning nuclear magnetic resonance/MRI. It is, therefore, necessary to eliminate the coefficients of the spherical harmonics expansion in the x- and y-direction.

DOI： 10.1109/TMAG.2013.2276736

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The dynamic characteristics of 3-D superconducting actuator using the magnetized HTS bulk by sandwiched electromagnets

H. Nakano, S. B. Kim, S. Ozasa, M. Sawae

PROCEEDINGS OF THE 26TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2013)   58   294 - 297   2014

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The electric device applications of a high temperature superconducting (HTS) bulk, having stable levitation and suspension properties due to their strong flux pinning force, have been proposed and developed. We have been investigating the three-dimensional (3-D) superconducting actuator using HTS bulk to develop a non-contact transportation device. In our previous works, the overshooting of the HTS bulk mover magnetized by 2-D arranged electromagnets were observed. Therefore, the new magnetization method using sandwiched electromagnets was purposed in order to solve the overshooting problems of HTS bulk mover. In this paper, the dynamic stabilities on the rotating and horizontal moving of the HTS bulk mover magnetized by sandwiched electromagnets was investigated experimentally, and the maximum moving displacements and convergence times during the overshooting state were reduced by proposed magnetization method with small magnetizing current. (C) 2014 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2014.09.073

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Numerical study on split coil-shaped HTS bulks to improve the field homogeneity for compact NMR relaxometry magnets

D. Ishizuka, S. B. Kim, N. Hayashi, H. Kitamura, D. Miyazawa

PROCEEDINGS OF THE 26TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2013)   58   290 - 293   2014

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We have been developing a new compact NMR magnet using stacked HTS bulks. In this paper, in order to improve the trapped magnetic field homogeneity and to obtain the enlarged sample space of HTS bulk magnet for compact NMR relaxometry, the HTS bulk magnet with 10 mm gap length in the center region of HTS bulk magnet (we call it split coil-shaped THS bulks) were proposed and studied as the functions of size and shape of HTS bulk using 3D FEM based electromagnetic analysis. The improved field homogeneity was obtained using notch coil shaped HTS bulk configuration and the field compensation by attached the coil instated of the bulks. (C) 2014 The Authors.Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2014.09.072

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The study to improve the field homogeneity of the HTS bulk magnets for NMR Relaxometry device by passive compensation methods

H. Kitamura, S. B. Kim, N. Hayashi, D. Ishizuka, D. Miyazawa

PROCEEDINGS OF THE 26TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2013)   58   298 - 301   2014

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In this paper, the compensation method to obtain the high field homogeneity (150 ppm/cm(3)) of compact NMR magnet was studied analytically. In order to improve the trapped magnetic field homogeneity of HTS bulk magnet, we used the packaged HTS bulk magnet consisted of HTS bulks annuli and 3 iron rings for field compensation. We could confirm that the target homogeneity of trapped magnetic field of HTS bulk magnet was achieved by the proposed passive compensation method. (C) 2014 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2014.09.074

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The levitation characteristics of the magnetic substances using trapped HTS bulk annuli with various magnetic field distributions

S. B. Kim, T. Ikegami, J. Matsunaga, Y. Fujii, H. Onodera

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   494   270 - 275   2013.11

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We have been investigating the levitation system without any mechanical contact which is composed of a field-cooled ring-shaped high temperature superconducting (HTS) bulks [1]. In this proposed levitation system, the trapped magnetic field distributions of stacked HTS bulk are very important. In this paper, the spherical solenoid magnet composed of seven solenoid coils with different inner and outer diameters was designed and fabricated as a new magnetic source. The fabricated spherical solenoid magnet can easily make a homogeneous and various magnetic field distributions in inner space of stacked HTS bulk annuli by controlling the emerging currents of each coil. By using this spherical solenoid magnet, we tried to make a large magnetic field gradient in inner space of HTS bulk annuli, and it is very important on the levitation of magnetic substances. In order to improve the levitation properties of magnetic substances with various sizes, the external fields were reapplied to the initially trapped HTS bulk magnets. We could generate a large magnetic field gradient along the axial direction in inner space of HTS bulk annuli, and obtain the improved levitation height of samples by the proposed reapplied field method. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2013.05.020

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Experimental and Analytical Studies on Non-Uniformity Properties of HTS Bulk Annuli for High Magnetic Performance Applications

S. B. Kim, Y. Yano, N. Hayashi, Jin-Hong Joo

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   23 ( 3 )   4602804   2013.6

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In designing and manufacturing of a new type of compact nuclear magnetic resonance/magnetic resonance imaging magnet, which consists of a stacked high-temperature superconducting (HTS) bulk annuli, the spatial homogeneity and the temporal stability of the trapped magnetic fields are the key issues. On the other hand, there is an asymmetry problem for superconducting properties including the critical current density along the axial (thickness) direction in HTS bulks due to its manufacturing process using a seed crystal located at the top surface. Therefore, in this study, we find the nonuniformity of the critical current density of the HTS bulk along the axial direction, which probably comes from the quench-melt-growth process using a seed crystal. The measured axial positions of the maximum magnetic field were slightly shifted to the bottom direction lower than the axial center position. The critical current density and/or superconducting properties of HTS bulks are probably decreased in proportion to the distance from a seed crystal. Therefore, the superconducting properties along the thickness direction in the HTS bulk were represented as a variable J(c) - B and electrical conductivity.

DOI： 10.1109/TASC.2013.2250331

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The Transient Stability of HTS Coils With and Without the Insulation and With the Insulation Being Replaced by Brass Tape

Seok Beom Kim, Takeshi Kaneko, Hiromu Kajikawa, Jin Hong Joo, Jeong-Min Jo, Young-Jae Han, Hyun-Seung Jeong

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   23 ( 3 )   7100204   2013.6

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In the case of motors and generators, the benefits of using high-temperature superconducting (HTS) coils could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. However, it is hard to establish the quench detection and protection devices for the HTS coils applied to the rotors of motors and generators. Therefore, the stability of the coils is lower than the quiescent coils applied to NMR, MRI, and so on. Therefore, it is important to improve the self-protection ability of HTS coils. We have been developing a novel self-protection method, which removes the insulation turn-turn winding and inserts various metal tapes instead of the insulation. In our previous research, the higher self-protection ability for the thermal disturbances in the HTS coils removed the insulation and inserted Cu tape has been proved. This paper presents the results of an experimental study for the quench current using the insulated, the noninsulated, and the Brass tape inserted HTS coils in liquid nitrogen and background magnetic fields. Also, the measured quench currents of each coil will be discussed.

DOI： 10.1109/TASC.2012.2234492

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Study on optimization of YBCO thin film stack for compact NMR magnets

S. B. Kim, T. Kimoto, S. Hahn, Y. Iwasa, J. Voccio, M. Tomita

Physica C: Superconductivity and its Applications   484   295 - 299   2013.1

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A compact high temperature superconducting (HTS) magnet, which consists of a stack of 500 HTS thin film annuli, was constructed and tested. Each thin film annulus, manufactured by the AMSC using the Rolling Assisted Bi-axially Textured Substrate (RABiTS) method, has a square cross-section of 40 mm × 40 mm with a thickness of 80 m. It has a 25-mm center hole created by machining. This paper reports a study on the anisotropic Jc issue due to the rolling procedure of the Ni substrate direction and its impact on field homogeneity. Also, three different stacking methods with rotation angles of 22.5°, 90°, and 0° against the rolling direction have been tested to study their impacts on strength, spatial homogeneity, and temporal stability of trapped fields. Finally, the 500-annulus magnet was tested at 21 K under a cryogen-free environment using a GM cryocooler. The spatial field homogeneity and temporal stability were measured at 21 K and compared with those obtained in a bath of liquid nitrogen at 77 K.

DOI： 10.1016/j.physc.2012.02.042

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The study on improving the self-protection ability of HTS coils by removing the insulation and lamination of the various metal tapes

S. B. Kim, T. Kaneko, A. Saito, H. Kajikawa, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   484   310 - 315   2013.1

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The high temperature superconducting (HTS) coils have very low normal zone propagation velocity (NZPV) and complicated quench behaviors. Because of these reasons, it is difficult to expect the self-protection. In this paper, two methods are suggested to improve the self-protection ability of HTS coils. One is to remove the insulation between turn-turn winding in HTS coils to enhance the thermal and electrical contacts along transverse direction and to increase the whole thermal stability of them. The other is Cu or Brass tapes are wound with HTS tape wire instead of the insulation to improve the thermal, electrical and mechanical stability of the HTS coils. To clarify the quench behaviors of the suggested coils, the normal zone propagation properties of the fabricated non-insulated HTS pancake coils were shown by measured voltage and temperature traces during the quench as a function of the operating temperature. And the characteristics of the normal transition and amount of the shared current to adjacent layers were quantitatively measured by a Hall sensor located at the center of HTS coils to measure the change of the self-magnetic field by operating current. The current sharing behaviors in the non-insulated HTS coil and the coil with Cu tape inserted were observed. The minimum quench energy (MQE) of the HTS coil with Cu tape inserted was the largest in the tested coils. It means that the HTS coil with Cu tape inserted had the highest transient stability against the thermal disturbances among the tested coils and the improvement of self protection abilities was proved. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2012.03.064

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Study on the characteristics of magnetic levitation for permanent magnets and ferromagnetic materials with various sizes using stacked HTS bulk annuli

S. B. Kim, J. Matsunaga, A. Doi, T. Ikegami, H. Onodera

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   484   316 - 320   2013.1

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We achieved stable levitation of cylindrical permanent magnets and irons using stacked ring-shaped high temperature superconducting (HTS) bulks with 20 mm ID, 60 mm OD and 50 mm height, and those were magnetized by field cooling method. The levitation characteristics of permanent magnets and iron samples located in the inner space of that levitation system were investigated experimentally. Iron samples with needle-shape and smaller than 1 mm diameter could not levitate stably. However, we found that the high strength of magnetized field was not necessary to levitate small needle-shaped irons. In order to levitate them, we need a uniform magnetic field in radial direction, so, a spherical solenoid magnet that can easily make a homogeneous magnetic field in inner space of HTS bulk annuli was developed. The spherical solenoid magnet, composed of seven solenoid coils with different inner and outer diameters, was designed by an electromagnetic analysis and fabricated. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2012.02.030

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The levitation characteristics of ferromagnetic materials by ring-shaped HTS bulks with two trapped field distributions

S. B. Kim, J. Matsunaga, Y. Fujii, H. Onodera

IEEE Transactions on Applied Superconductivity   23 ( 3 )   4603204   2013

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Stable levitation of cylindrical iron and permanent magnet (PM) samples of various sizes has been achieved by using high temperature superconducting (HTS) bulk annuli which were magnetized by field cooling (FC) method. In this paper, we examined the forces acting on iron and PM samples levitating in the inner space of HTS bulk annuli. The levitation forces of the 3 stacked HTS bulk system (3 bulks system) have been compared withthe 2 stacked HTS bulk system (2 bulks system) having a gap between the bulks. In our experiments, the levitation force increases with increasing the magnetization field strength, the strength of magnetic flux density of PM, and the sample size. The levitation force of the 2 bulks system was better than the 3 bulks system, and we found that the levitation force using the field in magnetized HTS bulk systems strongly depends on the strength of the magnetic flux density of the sample and the magnetic field gradient in the levitating space. © 2002-2011 IEEE.

DOI： 10.1109/TASC.2013.2242513

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The improved transient stabilities of HTS coils by removing the insulation and inserting the metal tapes

S. B. Kim, H. Kajikawa, H. Ikoma, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

PROCEEDINGS OF THE 25TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS2012)   45   249 - 252   2013

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NMR/MRI magnets have a protection device to prevent the damages due to a quench. On the other hand, the protection device design of HTS coils or magnets are very difficult because it has a very low normal zone propagation velocity (NZPV) and complicate behaviors of quench. We have studied the methods to improve the self-protection ability of HTS coils by removing the turn-to-turn insulation and inserting the metal tape instead of insulation. In this paper, the improved transient stabilities and self-protection abilities of HTS coils by removing the insulation and inserting metal tapes will be presented by minimum quench energy (MQE). (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2013.05.014

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Numerical and Experimental Study to Fabricate the New Type Compact NMR Device Using Stacked HTS Bulks

S. B. Kim, T. Kimoto, Y. Yano, S. Hahn, Y. Iwasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   22 ( 3 )   4302004 - 4302004   2012.6

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In fabrication of a compact NMR (Nuclear Magnetic Resonance) magnet which consists of a stacked HTS (High Temperature Superconducting) bulk annuli, generally there are three key issues: spatial homogeneity, temporal stability, strength of trapped magnetic fields. This paper presents a study on the effects of axial gap length between stacked HTS bulks on the three key issues of a bulk HTS magnet for compact HTS NMR applications. The HTS bulk magnet of which the ID and OD are 20 and 60 mm respectively has a 50 and 80 mm heights depending on the axial gap lengths between HTS bulks. The gap length between each HTS bulk varied from 0 mm to 10 mm and were used as parameters to optimize, analytically as well as experimentally, the overall field homogeneity of the HTS bulk magnet. The optimized axial gap length was obtained by analytical results, and the better magnetic field homogeneity and temporal stability of trapped magnetic field were achieved by lower magnetization field. The improved spatial homogeneity and strength of generated magnetic field by a new compact NMR magnet will be presented.

DOI： 10.1109/TASC.2011.2182170

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The Characteristics of the Normal-Zone Propagation of the HTS Coils With Inserted Cu Tape Instead of Electrical Insulation

S. B. Kim, A. Saito, T. Kaneko, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   22 ( 3 )   4701504 - 4701504   2012.6

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In the case of motors and generators, the benefits of using superconductors could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. The high temperature superconducting (HTS) coils wound with HTS conductors have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the conductors have a low thermal conductivity and large specific heat. According to these reasons, in case of HTS coils and magnets, it is difficult to expect the self-protection like as low temperature superconducting (LTS) coils. In this paper, we suggest a method which inserts the Cu tape between turn-turn winding in the HTS coil instead of electrical insulation to improve the self-protection ability of HTS coils. Because the thermal and electrical contacts along the transverse direction are enhanced by inserted Cu tape instead of insulator and the whole thermal stability of HTS coils would be increased. To clarify the quench behavior of this suggested coil, we investigate the normal-zone propagation properties of the fabricated HTS pancake coils wound with 2G conductor and Cu tape under the cryocooled operation using GM cryocooler. The effects of inserted Cu tape and the improved the self-protection ability for the suggested HTS coil will be discussed.

DOI： 10.1109/TASC.2011.2174559

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A Study on Characteristics of the Trapped Magnetic Field for HTS Bulk Superconducting Actuator Operated in AC

S. B. Kim, Y. Uwani, J. H. Joo, R. Kawamoto

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   22 ( 3 )   4700304 - 4700304   2012.6

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The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contact transportation device which moves freely in space. In our previous work, the unstable movement characteristics of HTS bulk were observed under DC operation, and the AC control system was proposed in order to solve these problems. In this paper, the horizontal movement and the field decay characteristics as a function of the gap length between electromagnet and HTS bulk and the frequency of driving current were investigated experimentally.

DOI： 10.1109/TASC.2011.2181472

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The normal-zone propagation properties of the non-insulated HTS coil in cryocooled operation

S. B. Kim, A. Saitou, J. H. Joo, T. Kadota

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   471 ( 21-22 )   1428 - 1431   2011.11

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High temperature superconducting (HTS) coils wound with HTS wires have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the wires have a high thermal stability and large specific heat. According to these reasons, in case of FITS coils and magnets, it is difficult to expect the self-protection like low temperature superconducting (LTS) coils.
In this paper, we suggest a method which can remove the insulation among turn-to-turn in the coil to improve the self-protection property of HTS coils. Because the thermal and electrical contacts along transverse direction are enhanced by no turn-to-turn insulation, the whole thermal stability of HTS coils begins to increase. Furthermore, although a quench occurs in the coil, it is possible to realize a self-protection of HTS coil because the current path of the coil is modified in order to avoid quenching. To confirm a quantitative evaluation for quench behavior of the suggested coil, we carried out the measurements with the coils having variety types of turn-to-turn insulation. The experimental results and the self-protection ability about the tested coils will be presented. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.209

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The characteristics of spatial homogeneity and strength of magnetic field for compact NMR magnets using stacked HTS bulks with various gap lengths

S. B. Kim, T. Kimoto, M. Imai, Y. Yano, J. H. Joo, S. Hahn, Y. Iwasa, M. Tomita

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   471 ( 21-22 )   1454 - 1458   2011.11

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A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an high temperature superconducting (HTS) bulk. In design of a compact NMR magnet which consists of the stacked HTS bulk annuli, the issues of strength, spatial homogeneity and temporal stability by trapped magnetic fields are very important. This paper presents a study on the effects of magnetization field strength and gap length between stacked bulks for the compact HTS bulk NMR applications. Four-stacked HTS bulk magnet with ID 20 mm and OD 60 mm was prepared to investigate the optimized configuration. The thickness of each HTS bulk is 5 mm, and the gap lengths from 0 mm to 10 mm were used as parameters in analysis and experiment, respectively. Four-stacked HTS bulk magnets with various gap lengths were tested at two different background magnetic fields of 0.5 T and 2 T at 77 K. The optimized axial gap length was found out by analytical results, and the better magnetic field homogeneity and temporal decay property of trapped magnetic field were obtained by lower magnetization field in this experiments. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.215

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The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

S. B. Kim, Y. Uwani, J. H. Joo, R. Kawamoto, Y. S. Jo

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   471 ( 21-22 )   1479 - 1482   2011.11

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The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HIS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HIS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.220

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Simulation of Magnetic Fluid to Develop the Magnetic Chromatography for Magnetic Particle Separation

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON MAGNETICS   47 ( 10 )   3947 - 3950   2011.10

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A magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation. Recently, its performance has been enhanced using a superconducting magnet. The superconducting magnet can generate a high magnetic field and its strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the fine particles. However, its numerical simulation is difficult, since the scale of the fine magnetic particles in fluid is much different from the scale of the superconducting magnet generating the strong magnetic field. In order to accurately simulate the magnetic separation, it is necessary to develop the simulation code dealing with the multiscale. The performance of the developed magnetic chromatography is evaluated by the developed simulation tool, and it is clarified that it is unsuitable for magnetic particle separation. Therefore, a magnetic chromatography is newly designed and its performance is evaluated by the developed simulation tool.

DOI： 10.1109/TMAG.2011.2158989

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Study on Optimized Configuration of Stacked HTS Bulk Annuli for Compact NMR Application

S. B. Kim, M. Imai, R. Takano, J. H. Joo, S. Hahn

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   21 ( 3 )   2080 - 2083   2011.6

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In design and manufacture of a compact NMR (nuclear magnetic resonance) magnet which consists of a stack of high temperature superconducting (HTS) bulk annuli, spatial homogeneity and temporal stability of trapped magnetic fields are key issues. This paper presents a study on optimized configuration of stacked HTS bulk annuli for the compact NMR application. A three-stack bulk magnet was designed and tested at two different temperatures of 20 and 77 K, and two different background fields of 3 and 5 T. The test results were compared with analytic results to verify the validity of the calculation. Then, various optimized patterns were investigated numerically to find out an optimized stack pattern of HTS bulk annuli in a given condition. The results prove that with the proposed optimized method trapped field strength as well as its homogeneity of a bulk-annulus stack can be improved.

DOI： 10.1109/TASC.2010.2089590

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Investigation on Novel Magnetic Chromatography With Ferromagnetic Nano-Wires for Ion Separation

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   21 ( 3 )   2068 - 2071   2011.6

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Magnetic chromatography is a very useful system for ion and/or fine magnetic particle separation due to strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the ions and fine particles. It is, however, difficult to separate the ions or the magnetic particles using the developed magnetic chromatography. It makes the strong magnetic field gradients in the flow channel, but the alternate direction of the gradient is not suitable for magnetic separation. Therefore, we have newly designed a novel magnetic column with ferromagnetic nano-wires. In this paper, the new magnetic column is presented, and the magnetic field and its gradients in the flow channel are investigated.

DOI： 10.1109/TASC.2010.2090857

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Field Performance of an Optimized Stack of YBCO Square "Annuli" for a Compact NMR Magnet

Seungyong Hahn, John Voccio, Stephane Bermond, Dong-Keun Park, Juan Bascunan, Seok-Beom Kim, Tomita Masaru, Yukikazu Iwasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   21 ( 3 )   1632 - 1635   2011.6

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The spatial field homogeneity and time stability of a trapped field generated by a stack of YBCO square plates with a center hole (square "annuli") was investigated. By optimizing stacking of magnetized square annuli, we aim to construct a compact NMR magnet. The stacked magnet consists of 750 thin YBCO plates, each 40-mm square and 80-mu m thick with a 25-mm bore, and has a empty set10 mm room-temperature access for NMR measurement. To improve spatial field homogeneity of the 750-plate stack (YP750) a three-step optimization was performed: 1) statistical selection of best plates from supply plates; 2) field homogeneity measurement of multi-plate modules; and 3) optimal assembly of the modules to maximize field homogeneity. In this paper, we present analytical and experimental results of field homogeneity and temporal stability at 77 K, performed on YP750 and those of a hybrid stack, YPB750, in which two YBCO bulk annuli, each empty set46 mm and 16-mm thick with a 25-mm bore, are added to YP750, one at the top and the other at the bottom.

DOI： 10.1109/TASC.2010.2103920

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The Dynamic Characteristics of the HTS Bulk Superconducting Actuator Driven With AC Electromagnets

S. B. Kim, D. Inoue, J. H. Joo, Y. Uwani

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   21 ( 3 )   1519 - 1522   2011.6

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Electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties due to their strong flux pinning force, has been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device that moves freely in space. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in a clean room where silicon wafers which dislike mechanical contact and dust are manufactured. The proposed actuator consists of an HTS bulk (trapped magnetic field by field cooling method) magnet for the mover and two-dimensional arranged multi-pole electromagnets as the stator. Up to now, the electromagnets consisted with ironed cores and copper coils were used as a stator, and each electromagnet was individually controlled using DC supplies. The movement of HTS bulk (mover) was not smooth because of the DC control. In this paper, the new electromagnets driven with AC control were proposed to improve the moving characteristics of the bulks. The characteristics of horizontal movement by newly proposed system will be presented.

DOI： 10.1109/TASC.2010.2090446

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Development of a Numerical Simulation Method for the Magnetic Separation of Magnetic Particles

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON MAGNETICS   47 ( 5 )   898 - 901   2011.5

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Magnetic separation is a very useful tool in medicine manufacturing and sludge disposal, and we have developed the magnetic chromatography system, which separates the magnetic particles or the ions from fluid due to its strong magnetic field gradients in the very small flow channel. There are many fine ferromagnetic wires on the wall of the developed magnetic column. A superconducting magnet applies a strong magnetic field to the magnetic column, and fine ferromagnetic wires make strong magnetic field gradients. It was, however, impossible to accurately evaluate the performance of the developed magnetic column due to the absence of a good simulation method. In order to enhance the accuracy of the simulation, it is necessary to couple the fluid dynamics simulation with the magnetic field simulation. Therefore, we have developed a simulation code dealing with the fluid dynamics, solving Navier-Stokes, control volume, and magnetic field equations simultaneously, and compared the simulation result to the experimental one to verify the validity.

DOI： 10.1109/TMAG.2010.2072911

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超電導バルク体を用いたアクチュエータの開発

金錫範

超電導Web21   2011

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Stability of Toroidal SMES using YBCO Tapes for Simultaneous Quench of a few Coils

So Noguchi, Seok Beom Kim

APPLIED ELECTROMAGNETIC ENGINEERING FOR MAGNETIC, SUPERCONDUCTING AND NANOMATERIALS   670   3 - +   2011

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We have investigated the stability of 2.0 GJ toroidal HTS-SMES, which consists of 90 element coils wound from YBCO tape. If one or more element coils are quenched, the storage energy reduces due to change of the magnetic field distribution. A series of quench for some element coils may occur, when the energy of the quenched coil cannot be consumed adequately. The simultaneous quench of some element coil may cause the system down. Therefore, it is necessary to investigate the simultaneous quench properties.

DOI： 10.4028/www.scientific.net/MSF.670.3

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Numerical Study to Design the New Type Compact NMR Magnet Using HTS Bulk Annuli with High Magnetic Field Performances

S.B. Kim

Proceedings of 18th Conference on the Computation of Electromagnetic Fields   2011

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高温超電導バルク体を用いるNMR用マグネットの積層構造最適化に関する研究

金錫範, 今井 諒, 木本敬章, 矢野順一, 朱鎮弘

日本ＡＥＭ学会誌   19 ( 2 )   103 - 108   2011

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Characteristics of trapped magnetic fields in HTS bulk annuli with various axial spaces for compact NMR magnets

S. B. Kim, M. Imai, R. Takano, K. Kashima, S. Hahn

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470 ( 20 )   1740 - 1744   2010.11

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Recently, the performance of high-temperature superconducting (HTS) bulks such as a critical current density, size, and mechanical strength has been improved. In consequence, various applications with HIS bulks such as motors, bearings, and flywheels are being investigated by many research groups; Compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an HIS bulk more than 11.7 T. 500 MHz (1)H NMR frequency, has been developed. This new compact NMR magnet out of FITS bulks is far less expensive than those conventional NMR magnets and expected to be widely used in food and drug industry. In design and manufacture of those compact NMR magnets, the issues of spatial homogeneity and temporal stability of trapped magnetic fields in HTS bulk annuli are very important. In this paper, the characteristics of the trapped magnetic fields in a stack of assembled HIS bulk annuli were investigated with various axial spaces between HTS bulks, experimentally and analytically. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.197

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A study on electromagnetic and mechanical characteristics of the field coil in HTS motor

S. B. Kim, T. Kadota, J. H. Joo, H. Sano, S. Murase, S. H. Lee, J. P. Hong, H. M. Kim, Y. K. Kwon, Y. S. Jo

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470 ( 20 )   1756 - 1762   2010.11

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High temperature superconducting (HTS) motors electromagnetically consist of a rotator wound with HTS wires and an armature with conventional copper wires like Litz wire. The HTS rotor windings, as field coils, consist of a straight part and an end-ring part. Because a major rotation torque is induced by an interaction between magnetic fields and current-carrying conductors in the straight part, most of mechanical stresses in the motor occur at the straight part. An end-ring is placed in the edge of the straight part and used to connect to each adjacent straight-part coils. The magnetic fields by coil currents concentrate on the end-ring part, therefore, it is expected that the critical current of the entire coil, straight and end-ring, can be determined by the magnitude of the field in the end-ring. This paper deals with the overall J(c) degradation in the end-ring part by self-field generated from the coil. In addition to electromagnetic analyses, we have performed a numerical analysis in order to evaluate mechanical stresses in the straight part of field coil by armature reaction on steady-state operation. The analytical results will be presented in this paper. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.201

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The study on optimization issues for magnetic separation by magnetic chromatography

S. B. Kim, R. Iwamoto, K. Kataoka, S. Noguchi, H. Okada

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470 ( 20 )   1804 - 1807   2010.11

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The magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation because it has strong magnetic field gradients even in a very narrow flow channel. We have not only developed the magnetic chromatography system to separate the fine particles and ions, but also the numerical analysis code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this study, the simple experiments using a superconducting magnet with a large room-temperature-bore and a micro-scale magnetic column consisting of ferromagnetic wires were carried out to understand the ions separation. The cobalt chloride (CoCl(2)) and the nickel sulfate (NiSO(4)) were used as ions, and the magnetic field and length of magnetic column were used as a parameter in an experiment and an analysis. It can be expected that the ion mobility of a single and complex are quite different, and the ability of the separation will be improved by increasing the column length without external magnetic field. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.211

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Quench protection technique for HTS coils with electronic workbench

J. H. Joo, S. B. Kim, T. Kadota, H. Sano, S. Murase, H. M. Kim, Y. K. Kwon, Y. S. Jo

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470 ( 20 )   1874 - 1879   2010.11

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The stability and the protection of superconducting applications are very important issues. High temperature superconductor (HTS) is stable than low temperature superconductor (LTS). However, due to the high stability of HIS, HIS coils have complicate behaviors of normal transition - such as a recovery into the superconducting state or thermal runaway - which is determined by the magnitude of disturbance, coil size, the structure of winding wire and cooling condition. In this paper, we propose the quench protection system based on the active power method which can detect the quench by measuring the generating instantaneous active power in HTS coils. And the quench detection circuit adopted a software circuit by LabVIEW which was added a new quench protection technique to the circuit in order to improve its detection performance. Furthermore, it can monitor interior states of HIS coils with acquiring the only coil voltages in real time. To confirm the validity of the suggested technique, the experiments were performed with the hardware circuit for quench detection simultaneously. The experimental results are presented and discussed in this paper. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.226

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Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability

Seungyong Hahn, Seok Beom Kim, Min Cheol Ahn, John Voccio, Juan Bascunan, Yukikazu Iwasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   20 ( 3 )   1037 - 1040   2010.6

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This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40mm X 40 mm x 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed.

DOI： 10.1109/TASC.2010.2043832

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Development of Numerical Analysis Method for Magnetic Separation of Magnetic Particle and Ion With Magnetic Chromatography

So Noguchi, SeokBeom Kim, Katuhito Kataoka

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   20 ( 3 )   961 - 964   2010.6

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The magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the fine particles and ions. However, its numerical simulation is difficult, since the scale of the ions or fine particles in fluid is much different from the scale of the superconducting magnet generating the strong magnetic field. In order to accurately simulate the magnetic separation, it is necessary to develop the simulation code dealing with the multi-scale problem.

DOI： 10.1109/TASC.2009.2039928

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Study on Quench Protection Method With Regards to Normal Transition Behavior for HTS Coil

J. -H. Joo, H. Sano, T. Kadota, S. -B. Kim, S. Murase, Y. -K. Kwon, H. -M. Kim, Y. -S. Jo

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   20 ( 3 )   2027 - 2030   2010.6

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This paper presents the quench detection method with using normal transition behavior for HTS coil. If the HTS coil starts to propagate a normal zone by an initial quench, it will be recovered the superconducting state or runaway thermally. These behaviors were mainly determined by variety parameters like the magnitude of a disturbance, HTS coil size, the structure of winding wire and cooling condition. However, the first step of detection or protection for coils should be started from detecting the presence of a non-recovering normal zone. This paper classifies the initial quench behaviors of HTS wires or coils as a model of 3-type tendencies, and suggests suitable detection techniques for each tendency with using the end-to-end voltage of coil. In additional, this method is able to detect a quench without a decisive criterion used at other quench detection methods. In order to confirm the validity of the method, we used the HTS sample coil wound with YBCO tapes. This paper presents these results and the quench protection properties with fabricated detection method.

DOI： 10.1109/TASC.2010.2043238

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The Characteristics of the Normal Transition in the Longitudinal and Transverse Directions in Cryocooled YBCO Coils

S. -B. Kim, H. Sano, J. -H. Joo, T. Kadota, S. Murase, H. -M. Kim, Y. -S. Jo, Y. -K. Kwon

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   20 ( 3 )   2078 - 2082   2010.6

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Recently, the superconducting devices using cryogenic and superconducting technologies were widespread in the field of electric power. The 2G wires with YBCO superconducting layer, metal substrate and stabilizer layer are expected to be used in future superconducting applications, because it has high properties in high temperature and high magnetic fields. In order to operate safely at high transport currents, the thermal stability of the wounding wire should be addressed in terms of detection and protection against the quench. On the other hand, the understanding of the 3-dimensional normal zone expansion during a quench is very important to design the superconducting devices such as magnets and cables. This paper presents the results of an experimental study for normal zone propagation properties in the longitudinal and transverse directions using the pancake coil wound with 2G wires which have Cu and SUS stabilizers under the cryocooler cooling. And the minimum quench energy (MQE) of the pancake coils wound with two different kinds of stabilizers as functions of operating temperature and transport current will be described.

DOI： 10.1109/TASC.2010.2044652

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Development of numerical simulation method for magnetic separation of magnetic particles

So Noguchi, SeokBeom Kim

Digests of the 2010 14th Biennial IEEE Conference on Electromagnetic Field Computation, CEFC 2010   2010

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The magnetic separation is a very useful tool to manufacture medicine. We have developed the magnetic chromatography system, which separates the magnetic particles or the ions from fluid due to its strong magnetic field gradients in a very small flow channel. In order to simulate the magnetic separation, we developed the simulation code dealing with the multi-scale problem, and verified the results compared with the experimental ones. © 2010 IEEE.

DOI： 10.1109/CEFC.2010.5481745

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The effects of the shape of the 2-D arranged electromagnets on levitation performances of the 3-D superconducting actuator

OKUGAWA Keisuke, KIM SeokBeom, JOO JIN-HONG, INOUE Daiji, UWANI Youhei, MURASE Satoru

81   187 - 187   2009.11

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CiNii Article

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Development of compact NMR magnets with stacked HTS bulks and films

KIM S. B., TAKANO R., IMAI M., HAHN S. Y., IWASA Y., JOHN V.

81   114 - 114   2009.11

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CiNii Article

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Development of the compact NMR magnet using stacked HTS bulks

TAKANO Riki, IMAI Makoto, KIM SeokBeom

81   113 - 113   2009.11

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CiNii Article

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Characteristics of the magnetic field distribution on compact NMR magnets using cryocooled HTS bulks

S. B. Kim, R. Takano, T. Nakano, M. Imai, S. Y. Hahn

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   469 ( 15-20 )   1811 - 1815   2009.8

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Recently, the performance of high temperature superconducting (HTS) bulks such as critical current density, size, and mechanical strength has been improved rapidly. So. various applications using HTS bulks such as motors, bearings and flywheels have been investigated by many research groups. A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of the HTS bulk more than 11.7 T (500 MHz (1)H NMR frequency) has been developed.
This new compact NMR magnet out of HTS bulks is cost-effective compared with conventional NMR magnets and then expected to be widely used in food and drug industry. In design and manufacture of the compact NMR magnets, spatial field homogeneity of the large trapped magnetic field in HTS bulk annuli is a crucial issue because the behavior of a trapped field is highly non-linear and, as a result, a technique to improve the field homogeneity such as active/passive shimming now becomes more challenging compared with that of the conventional counterparts.
This paper presents the magnetic field distributions in single and three assembled HTS bulk annuli measured by a 3-axis and multi-arrayed Hall sensor under two different cryogenic environments: (I) in a bath of liquid nitrogen (LN(2)) and (2) dry cooling by a cryocooler. The spatial homogeneity changes with various operating temperatures were investigated and the effect of critical current density enhancement by lowering the operating temperature on the field homogeneity improvement was discussed in detail. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.05.161

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Effect of the hot pressing on the magnetic-field and temperature dependences of flux pinning for SiC-doped MgB2 tape

H. Kuwashima, N. Nanato, S. B. Kim, S. Murase, Y. Yamada, A. Nitta, K. Tachikawa, G. Nishijima, K. Watanabe

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   469 ( 15-20 )   1515 - 1518   2009.8

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To understand the effects of the hot pressing on the pinning behavior for the SiC doped MgB2 tape wire, magnetic field and temperature dependences on a critical current density J(c) and the pinning force have been studied. The MgB2 tapes were fabricated using an in situ powder-in-tube (PIT) method, the hot pressing process with nano-SiC powders and the carbon steel sheath. J(c) of the hot pressing processed wire is enhanced especially at low field compared with that of the no hot-pressed wire. It is suggested that the enhancement of J(c) is caused by the improvement of the MgB2 grain connectivity came from the hot pressing.
The pinning analysis using the pinning models of a surface pinning and a normal point pinning lead to that the scaled curve of the pinning force for the SiC-doped MgB2 tape with the hot pressing process showed anisotropy in a lower field. This result suggests that the pinning center of the hot pressing processed MgB2 wire forms into inequi-axial shape, which is different from that in the tape without the hot pressing having the equi-axial pinning center in our previous report. It was also found that the scaled pinning force of the SiC-doped MgB2 tape with the hot pressing is larger than the surface pinning model in a higher field. This suggests that the pinning force was enhanced by the hot pressing in a higher field. (C) 2009 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2009.05.231

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Characteristics of Magnetic Separation for Magnetic Particle and Ion by Magnetic Chromatography With Novel Magnetic Column

SeokBeom Kim, Yuichi Okimoto, Satoru Murase, So Noguchi, Hidehiko Okada

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   19 ( 3 )   2152 - 2156   2009.6

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The magnetic chromatography (MC) is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have not only developed the MC system to separate the fine particles and ions, we have also developed the numerical analysis computer code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this paper, we studied MC technology for magnetic particles and ion separations using micro-scale magnetic column with ferromagnetic wires experimentally. The influences of the strength of magnetic gradient, flow velocity and coefficient of viscosity of solvent were studied by the developed computer code.

DOI： 10.1109/TASC.2009.2019143

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Development of Quench Detection Method Based on Normal Transition Behaviors for HTS Coils

Jin-Hong Joo, Hayato Sano, Seok Beom Kim, Satoru Murase, Young Kil Kwon, Ho Min Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   19 ( 3 )   2415 - 2418   2009.6

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Recently, the superconducting devices using cryogenic and superconducting technologies were widespread in the field of electric powers. The quench protection is one of the important issues for safety operating of the superconducting devices, because the excessive joule heating brings about damage to the superconducting magnets when the quench occurs. However, if the HTS coil starts to transit normally by an initial quench, it will be recovered into the superconducting state or runaway thermally. These behaviors were mainly determined by the magnitude of a disturbance, HTS coil size, the structure of winding wire and cooling condition. Therefore, in order to detect the transition into the normal state at HTS coil more accurately, it needs to investigate these effects as parameters. This paper describes the electromagnetic and thermal behaviors of HTS during normal transition by the initial quench. The aim is the development of the quench detection method about HTS coil for 5 MW HTS motor after an initial quench. It adopted the hardware and the software that were able to estimate the quench by monitoring the voltage and temperature for the behavior between the thermal runaway and the recovery. This paper will be presented these results and the quench protection properties with fabricated detection method.

DOI： 10.1109/TASC.2009.2017695

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Quench and Normal Zone Propagation Characteristics of RHQT-Processed Nb3Al Wires Under Cryocooler-Cooling Conditions

Satoru Murase, M. Shimoyama, N. Nanato, S. B. Kim, G. Nishijima, K. Watanabe, A. Kikuchi, N. Banno, T. Takeuchi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   19 ( 3 )   2666 - 2669   2009.6

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The minimum quench energy (MQE) and normal zone propagation velocity (NZPV) of three kinds of Nb3Al superconductors fabricated by the rapid heating, quenching and transformation (RHQT) process were measured under various conditions of applied magnetic field (10-14 T), temperature (7-11 K), and transport current (80-95% of the critical current), while cooled by a cryocooler for developing the over 20-T class cryogen-free magnet. As a result, MQE values were related to the critical current density (J(c)); high MQE was obtained for low J(c). It is assumed that J(c) has a stronger influence on the MQE than specific heat, thermal conductivity, resistivity, and other parameters of the composite superconductor including the matrix and the stabilizer. NZPV was mainly proportional to the transport current density varying with applied field and temperature. The second contribution to NZPV is assumed to be heat capacity depending on the wire configuration.

DOI： 10.1109/TASC.2009.2018149

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Study on Trapped Field Characteristics of HTS Bulk Annuli With Iron Rings for Ferromagnetic Shimming of a Compact NMR Magnet

SeokBeom Kim, Toshiya Nakano, Riki Takano, Seung-yong Hahn

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   19 ( 3 )   2273 - 2276   2009.6

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Recently, the performance of high temperature superconducting (HTS) bulks such as critical current density, size, and mechanical strength has been improved rapidly. So, various applications with HTS bulks such as motors, bearings, and flywheels have been investigated by many research groups. A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after the technique to enhance maximum trapped field of the HTS bulk more than 11.74 T, a corresponding NMR frequency of 500 MHz, has been developed. This new compact NMR magnet out of HTS bulks is far less expensive than those conventional NMR magnets and expected to be widely used in food and drug industry. In design and manufacture of those compact NMR magnets, spatial field homogeneity of large trapped magnetic field in HTS bulk annuli is essential. This paper presents the magnetic field distribution in single and three assembled HTS bulk annuli, measured by a 3-axis hall sensor, and experimental results of its spatial homogeneity improvement by mounting an iron ring inside or outside of the HTS bulk annuli.

DOI： 10.1109/TASC.2009.2019083

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Investigation of separation phenomenon for ultra-fine particle by magnetic chromatography method (part III)

KATAOKA K., IWAMOTO R., KIM S. B., MURASE S., NOGUCHI S., OKADA H.

80   170 - 170   2009.5

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Transport characteristics of meander and bispiral types resistive fault current limiters

S. B. Kim, M. Nishimoto, J. H. Joo, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   468 ( 15-20 )   2059 - 2062   2008.9

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The resistive type fault current limiter based on YBCO thin film with high critical current density was proposed and developed because of its fast recovery characteristics. We have been developing a magnetic field measurement system with hall sensor to study the critical Current density distribution or magnetic properties of high-T-c superconductors such as thin film, tape conductor and coated conductors. In this study, the transport current distribution in straight line and U-corner region of meander type resistive fault current limiter using YBCO thin film was investigated experimentally. The both axial and radial self-magnetic field components according to the direct (DC) and alternating (AC) transport currents were measured by two-axis hall probe to estimate the current distribution. And also, the self-magnetic field at the corner of bispiral type fault current limiter was measured by two-axis hall probe with a high spatial resolution to compare with the meander type fault Current limiter. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2008.05.264

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J(c) anisotropy and pinning behaviors of the in-situ MgB2 wires with/without SiC addition

Hideyuki Kuwashima, Satoru Murase, Nozomu Nanato, Seok-Beom Kim, Yutaka Yamada, Akio Nitta, Kyoji Tachikawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   18 ( 2 )   1212 - 1215   2008.6

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In an attempt to understand the effects of SiC addition on the pinning behavior for the in-situ PIT MgB2 tape wire, field and temperature dependencies on critical current density, J(c) and the pinning force were studied by considering applied magnetic field direction for the rectangular-shaped wire. As a result, it was clarified that the SiC-doped wire has the equiaxial pinning center and the un-doped wire has the inequi-axial pining center. Taking the pinning scaling law into account, it is found that the SiG-doped MgB2 wire has two kinds of the pinning center and the dominant pinning center changes with temperature, that is, the pinning centers are the grain boundary and the precipitates at high and low temperatures, respectively. The un-doped MgB2 wire is assumed to have anisotropy of the pinning mechanism.

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Magnetic-field and temperature dependencies of flux pinning for SiC doped MgB_2 tape wire with hot pressing

KUWASHIMA H., NANATO N., KIM S. B., MURASE S., YAMADA Y., NITTA A., TACHIKAWA K., NISHIJIMA G., WATANABE K.

78   134 - 134   2008.5

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Fundamental studies for the application of quench protection systems based on an active power method for cryocooled LTS coils

Kazuya Takeuchi, Nozomu Nanato, Satoru Murase, SeokBeom Kim, Gen Nishijima, Kazuo Watanabe, Takao Takeuchi, Nobuya Banno, Akihiro Kikuchi

CRYOGENICS   48 ( 3-4 )   148 - 153   2008.3

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When the quenching occurs in a superconducting coil, excessive joule heating in normal area may damage the coil. It is necessary to detect quenching in the coil as soon as possible and discharge the magnetic energy stored in the coil. Therefore, we propose a superconducting coil protection system based on an active power method. The system is highly resistant to the noise and does not require cancel voltage taps, so it is useful for both AC and DC coils. We have presented the effectiveness of the system using some test coils cooled in LN2 or LHe. However, we have not discussed the effectiveness of the proposed system for helium-free cryocooled magnets, in which a larger temperature rise occurs after quenching than in liquid-cooled magnets. In this paper, we verify the effectiveness and practicality of the proposed system through coil protection tests for a cryocooled Nb3Al LTS coil. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cryogenics.2008.02.002

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Development of superconducting actuator for the contactless transporter

SeokBeom Kim, K. Kawakami, M. Nishimoto, Y. Okimoto, T.Nakano, S. Murase

International Conference on Electrical Machines and Systems (ICEMS2007)   1719 - 1722   2008

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Superconducting Coil Protection System by Active Power Method : Characteristic Improvement by Canceling Mutual Inductive Voltage

TAKEUCHI K., INOUE T., NANATO N., KIM S. B., MURASE S.

77   88 - 88   2007.11

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Thermal stability in the cryocooler cooling for RHQT processed Nb_3Al superconducting wires

SHIMOYAMA M., NANATO N., KIM S. B., MURASE S., NISHIJIMA G., WATANABE K., KIKUCHI A., BANNO N., TAKEUCHI T.

77   40 - 40   2007.11

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The defect detection in HTS films on third-harmonic voltage method using various inductive coils

S. B. Kim

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   702 - 706   2007.10

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We purposed and tested the contactless ac inductive method to estimate the critical current density of high temperature superconducting (HTS) films by detecting a third-harmonic voltage. In this study, a minimum diameter of the HTS film to estimate the correct critical current density was experimentally investigated using three miniature inductive coils with various sizes. It was clarified that the correct critical current density could be measured and estimated when the diameter of HTS films was about 1.2 times larger than outer diameter of each tested inductive coil. The accuracy of detection for micro-scale defects with various shapes in HTS films was studied using miniature inductive coils by the third-harmonic voltage method. And it was possible to detect the defects in HTS films by obtained the slope values of initial region at generated third-harmonic voltage traces. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.03.481

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Cap core design for high levitation force in a 3D superconducting actuator with HTS bulk

J. H. Joo, S. B. Kim, T. Inoue, A. Shimizu, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   420 - 425   2007.10

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We have been developing a 3D superconducting actuator with HTS (high temperature superconducting) bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension due to its strong pinning force. The performance of the actuator is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. For the sake of improving the levitation force, we proposed to attach a sliced iron sheet (we called this cap core) on the top surface of the core in each electromagnet. The proposed cap core was expected to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk of the electromagnets. We experimentally confirmed and measured the effect of the cap core. For the optimized design of the cap core, we calculated the spatial distribution of the magnetic field on the surface of the electromagnet using 3D FEM analysis for several cap cores and estimated the levitation force of the HTS bulk using the calculated result. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.05.029

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Development of 3-D superconducting actuator using HTS bulks based on eight-poles electromagnets

S. B. Kim, T. Inoue, A. Shimizu, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   1346 - 1351   2007.10

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We have been developing a three-dimensional (3-D) superconducting actuator with HTS bulk and electromagnets. Proposed 3-D superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. To realize the 3-D superconducting actuator with high performance, we have to investigate the shape-dependences of electromagnets and HTS bulk on levitating characteristics. In this study, we fabricated the individually controlled eight-polarities electromagnets and the two kinds of bolted joints cap cores to improve the control ability and levitation characteristics. And also, we prepared the disk-shaped and ring-shaped (with 20 rum inner diameter) HTS bulk with 60 mm diameter, and evaluated how magnetic field distribution influences the levitating characteristics as functions of levitation force and height. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.03.496

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The self-field loss on AC transport current for in situ PIT processed MgB2 superconducting tapes with carbides addition and the carbon steel sheath

T. Ohzawa, N. Nanato, S. B. Kim, S. Murase, D. Miyagi, N. Takahashi, Y. Yamada, A. Nitta, K. Tachikawa

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   798 - 801   2007.10

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The new in situ MgB2 tapes with/without SiC addition and the hot pressing process have been fabricated using the carbon steel sheath. The critical temperature (T-c), critical current density (J(c)) and the AC transport current loss of those tapes have been studied and discussed in various conditions. The MgB2 tapes with the carbon steel sheath that improved the core hardness and homogeneity, resulting in high J(c), and the SiC addition, and the hot pressing brought narrow T-c transition width. As the carbon steel has ferromagnetism, it affected the loss of the MgB2 tape. The large losses that were two to three orders of magnitude higher than Norris' theoretical curve were obtained. It was clarified that the main loss of the MgB2 tape was the hysteresis loss of the carbon steel sheath. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.04.266

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Development of quench protection system for HTS coils by active power method

N. Nanato, Y. Tsumiyama, S. B. Kim, S. Murase, K.-C. Seong, H. J. Kim

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   1281 - 1284   2007.10

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Recently, HTS coils have been developed for electric power apparatuses. In superconducting coils, local and excessive joule heating may give damage to the superconducting windings when a quench occurs and therefore it is essential that the quench is detected quickly and precisely so that the coils can be safely discharged. Resistive voltage measurement method is universally used for the quench detection, however, it is vulnerable to an electromagnetic noise which causes insufficient quench detection and at least needs a central voltage tap in windings. In a large superconducting coil, a lead-wire from the central voltage tap may cause a short-circuit when high voltage will be applied. In this paper, we present a quench protection system based on the active power method which detects a quench by measuring the instantaneous active power generated in a superconducting coil. The protection system based on this method is very strong against to the noise and no more needs a central voltage tap. The performance of system developed by us is confirmed by using test coil wound with Bi-2223 HTS tapes. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.02.047

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Development of magnetic chromatograph system for magnetic particle and ion separation with superconducting magnet

S. B. Kim, C. Nakada, S. Murase, H. Okada, T. Ohara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   1306 - 1310   2007.10

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The magnetic chromatograph (MC) system is one of the promising methods for ion separation because of its strong magnetic field gradients. We have been developing the MC system to separate the fine particles and ions, and have also developed the numerical analysis computer code based on fluid dynamics and electromagnetism to investigate the separating characteristics and optimization of MC system. We investigated MC technology for magnetic particles separation using superconducting magnet and micro-scale magnetic column with ferromagnetic wires experimentally. A channel height of magnetic column for ion separation was optimized by the developed computer code. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.04.305

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Fabrication and application of two-axis hall sensor array using ELO film bonding technology

Keishin Koh, Seok Beom Kim, Koji Hohkawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   17 ( 2 )   3773 - 3776   2007.6

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In this paper, we report a basic study on the development of a two-axis Hall sensor array using epitaxial lift-off (ELO) film bonding technology. We developed a novel Hall sensor array fabricated on a Si substrate that can directly measure axial and radial magnetic field components (Bx and Bz) simultaneously. We investigated conditions of basic fabrication process and fabricated a basic test device. We also estimated basic characteristics of the Hall sensor and measured the DC self-magnetic field profiles of a YBCO strip. The results clarified that the ELO film bonding technology is suitable for fabricating two-axis Hall sensor array.

DOI： 10.1109/TASC.2007.899041

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Three-directional FEM analyses of pre-bending effects for Nb3Sn composite wires

Satoru Murase, I. Okada, K. Kiyama, N. Nanato, S. B. Kim, H. Oguro, G. Nishijima, S. Awaji, K. Watanabe, M. Wake

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   17 ( 2 )   2676 - 2679   2007.6

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Pre-bending effects of Nb3Sn composite wires, enhancement in J(c) at the as-cooled condition and J(c) peak, J(cm), against applied tensile strain, are well known in especially Cu-Nb reinforced Cu stabilized Nb3Sn wire. In an attempt to understand the effects, three directional strain analyses using FEM were studied by considering thermally-induced residual strain due to temperature difference between the reaction temperature and the cryogenic temperatures including the pre-bending process at room temperature for three types of Nb3Sn composite wires. To evaluate effects of change in three directional strain, the von Mises strain was introduced. As a result, the minimum von Mises strain against the applied tensile strain corresponded to J(cm); low strain shows J(cm) enhancement by the pre-bending for Cu-Nb reinforced Nb3Sn wire. It was found that there is a direct correlation between the minimum von Mises strain and J(cm) related to the pre-bending.

DOI： 10.1109/TASC.2007.899597

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Characteristics of a 3-D HTS actuator with various shaped electromagnets

S. B. Kim, T. Inoue, A. Shimizu, J. H. Joo, S. Murase

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   17 ( 2 )   2327 - 2330   2007.6

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We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and move in free space. Proposed superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. The 2-D arranged electromagnets were individually controlled to move the HTS bulk. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in clean rooms where silicon wafers are manufactured. Wafers must be protected from contact with dust and other contamination. To realize the superconducting actuator with HTS bulks, the electromagnetic characteristics of HTS bulk, such as trapped field strength and patterns, should be clarified and the optimized controlling system is also required. Therefore, in this study, to construct the optimal 3-D actuator system, the fundamental characteristics of the levitation for HTS bulks with individually controlled four and eight-polarities electromagnets were investigated experimentally. And two kinds of cap cores attached the top of the core to improve the control ability of proposed actuator were fabricated and tested.

DOI： 10.1109/TASC.2007.898974

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Investigation of separation phenomenon for ultra-fine particle by magnetic chromatography method (part 2)

OKIMOTO Yuichi, KIM SeokBeom, MURASE Satoru, OKADA Hidehiko

76   88 - 88   2007.5

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Effects of SiC addition on temperature and magnetic-field dependences of flux pinning in MgB_2 tapes

KUWASHIMA H., KIM S. B., NANATO N., MURASE S., YAMADA Y., NITTA A., TACHIKAWA K.

76   36 - 36   2007.5

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Characteristics of a 3-D HTS actuator with various shaped electromagnets

KAWAKAMI Kouhei, KIM SeokBeom, NAKANO Toshiya, MURASE Satoru

76   83 - 83   2007.5

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Design of electromagnet for high levitation force in 3D superconducting actuator

Jin-Hong Joo, SeokBeom Kim, Kei Hitomi, Satoru Murase

Proceeding of International Conference on Electrical Machines and Systems, ICEMS 2007   1549 - 1552   2007

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We have been developing a new type of 3-D superconducting actuator using the strong pinning force of HTS (High Temperature Superconducting) bulk. The system includes HTS bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension, and its performance is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. To enhance the levitation force in the actuator, it is necessary to design the optimized geometry of the electromagnets. The target of the design is to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk over the electromagnets. For the optimized design of the electromagnets, we calculated the spatial distribution of the trapped magnetic field and the levitation force of the HTS bulk using 3-D FEM analysis that is adopted the critical state model.

DOI： 10.1109/ICEMS.2007.4412287

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The transport characteristics and the self-field distribution for high-Tc superconductor with neighboring magnetic materials

Jin-Hong Joo, Seok-Beom Kim, Satoru Murase

IEEJ Transactions on Power and Energy   127 ( 1 )   327 - 334   2007

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Many high-Tc superconducting (HTS) tape manufactures make an effort to improve the transport characteristics of HTS tapes. When AC or DC current flows in the HTS tape, AC or DC magnetic self-fields are induced around the conductor by the current and these self-fields affect on the AC loss and the critical current like the transport characteristics of HTS tapes. The spatial distribution and magnitude of the self-field are variable due to the neighboring materials on the HTS tape. In this paper, the relation between the transport characteristics and the self-field distribution of HTS tapes with paralleled ferromagnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) is experimentally investigated. The self-fields according to the DC and AC transport currents were measured by hall probe with axial and radial magnetic field components. The critical currents of HTS tapes with paralleled the Ni tape are slightly decreased and the transport current losses markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape showed more improved performance than those of single HTS tape. We explain these results using the change of the spatial distribution and magnitude of self-field on HTS tapes by the neighboring magnetic materials.

DOI： 10.1541/ieejpes.127.327

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冷凍機冷却低温超電導コイルへの有効電力法に基づくクエンチ保護システム適用に関する基礎的検討

竹内 和哉, 七戸 希, 村瀬 暁, 金 錫範, 西島 元, 渡辺 和雄, 竹内 孝夫, 伴野 信哉, 菊池 章弘

低温工学   42 ( 11 )   382 - 388   2007

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DOI： 10.2221/jcsj.42.382

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A pilot grogram to promote a venture business by undergraduate at Department of Electric and Electronic Engineering in Okayama University

KIM SeokBeom

The Papers of Technical Meeting on Frontiers in Education, IEE Japan   2006 ( 30 )   13 - 16   2006.12

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Superconducting Coil Protection System by Active Power Method

TAKEUCHI K., TSUMIYAMA Y., NANATO N., KIM S. B., MURASE S.

75   253 - 253   2006.11

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The shape dependences of HTS bulk and electromagnet on operating characteristics of 3-D superconducting actuator

INOUE T., KIM S. B., SHIMIZU A., MURASE S.

75   160 - 160   2006.11

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Investigation of separation phenomenon for ultra-fine particle by magnetic chromatography method (part1)

NAKADA Chiaki, KIM SeokBeom, MURASE Satoru, OKADA Hidehiko

75   268 - 268   2006.11

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Three-directional FEM analyses of pre-bending effects for Nb_3Sn composite wires

OKADA I., MURASE S., KIM S. B., NANATO N., AWAJI S., OGURO H., NISIJIMA G., WATANABE K., WAKE M.

75   266 - 266   2006.11

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The electromagnet design for 3-D superconducting actuator using HTS bulk

S. B. Kim, T. Inoue, A. Shimizu, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   445   1119 - 1122   2006.10

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We have been developing a three-dimensional (3-D) superconducting actuator consists of a field-cooled HTS bulk for mover and two-dimensional arranged multiple electromagnets as a stator. The HTS bulk is magnetically connected with electromagnets and it can be moved in 3-D directions and rotates without upper side electromagnets and spatial restrictions. The current and the polarity of each electromagnet were individually controlled by the switching power supply. In this paper, we experimentally investigated the effects of the shapes of HTS bulks (disk shape with/without inner hole) and electromagnets (4 and 8 polarities) in points of stabilities and forces of levitation. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2006.06.026

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Current density distributions of the meander type resistive fault current limiters

S. B. Kim, J. Watanabe, N. Nanato, S. Murase, O. B. Hyun

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   445   1069 - 1072   2006.10

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We have been developing a magnetic field measurement system with two-axis hall-probes to study the critical current density distribution or magnetic properties of high-T-c superconductors. In this study, the current distributions at corners of the meander type resistive fault current limiters were measured by hall probe with high spatial resolution. The both of axial and radial magnetic field components (B-x and B-z) according to the direct (DC) and alternating (AC) transport currents were measured by hall probe to estimate the current density distribution with high accuracy. And, it is confirmed that the measured radial components are very useful to estimate the current distribution. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2006.06.027

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Simple measurement of the AC transport current loss for HTS conductors using an active power detection method

N. Nanato, T. Ohzawa, S. Murase, S. B. Kim

CRYOGENICS   46 ( 9 )   672 - 675   2006.9

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Reducing AC loss in a superconducting apparatus is one of the most important issues, and the precise measurement and estimation of AC losses are essential to reduce them. The four-terminal method is universally used as an electric measurement method of AC losses for superconducting tapes and wires. In this method, noise and inductive voltage superposed on the terminal voltage of the superconductor are eliminated by a lock-in amplifier and cancel coil, respectively, and then measurement of very small resistive voltage is achieved. However, using this conventional method, a plurality of measuring instruments and apparatuses are needed, and therefore the measuring system becomes complicated and much time is consumed in the calibration process. In this paper, we present a simple and precise measurement system based on an active power detection method, which is proposed as a quench detection method. The proposed system consists of a small number of instruments and apparatus and is less susceptible to noise. Its usefulness is verified by comparing the proposed method and the conventional four-terminal method in measuring the AC transport current loss of a Bi2223/Ag tape. (C) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cryogenics.2006.04.001

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Effects of thermal hysteresis on residual resistance ratio of the Cu-stabilized Nb_3Sn superconducting wire

MURASE Satoru, KIYAMA Kazuyuki, OKADA Issei, NANATO Nozomu, KIM SeokBeom

2006 ( 16 )   1 - 4   2006.6

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Characteristics measurements of HTS tape with parallel HTS tapes

Jin-Hong Joo, Seog-Whan Kim, Kyu Jeong Song, Chan Park, Rock-Kil Ko, Ho-Sup Kim, Jung-Pyo Hong, SeokBeom Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   16 ( 2 )   119 - 122   2006.6

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Many high temperature superconducting (HTS) tape manufactures make an effort to reduce the transport current loss of HTS tapes. The knowledge of critical current and self-field in an HTS tape is very useful to compute the transport current losses. The spatial distribution and magnitude of self-field are variable due to the neighboring materials. In this paper, the critical currents and the transport current losses of BSCCO and YBCO tapes with paralleled magnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) are experimentally investigated to improve the AC loss properties. The critical currents of HTS tapes with paralleled Ni tape are slightly decreased and the transport current losses are markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape have not current carrying are more improved than single HTS tape.

DOI： 10.1109/TASC.2005.869674

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Self-field loss in AC transport current of Ni-sheathed MgB2 superconducting tapes

Satoru Murase, Toshiaki Ohzawa, Takashi Harada, Nozomu Nanato, Seok Beom Kim, Yutaka Yamada, Kyoji Tachikawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   16 ( 2 )   1403 - 1406   2006.6

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AC transport current loss (self field loss) of ex-situ-processed MgB2 superconducting tapes with Ni sheath was measured under different conditions of transport current value, transport current frequency, and temperature. Experimental results were compared with Norris' theoretical curves and previous measured losses of MgB2 tapes with CuNi and stainless-steel sheaths, which were larger than the theoretical ones and previous data. The loss vs. normalized transport current (transport current normalized by critical current) curves varied with temperature and the loss at 9 K was larger than that at 14 K. The measured loss approached Norris' curves in the high normalized transport current region. In order to gain insight into these origins, FEM analysis of magnetic flux concentration by Ni and estimations of hysteresis loss of ferromagnetic nickel-sheath and of homogeneity of the core were carried out. As a result, the hysteresis loss of Ni was very small based on the estimation and the loss, measurement of Ni. Main contributions to large loss are considered to be self-field enhancement due to magnetic flux concentration by the Ni-sheath and critical current density distribution of the MgB2 core caused by the inhomogeneity of critical current density and critical temperature.

DOI： 10.1109/TASC.2006.870448

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Thermal stability of copper ion-plating outer-stabilized Nb_3Al superconducting wire made by the transformation process in the cryocooler cooling

SHIMOYAMA M., MITSUHASHI T., KIYAMA K., MURASE S., KIM S. B., NANATO N., NISHIJIMA G., WATANABE K., KIKUCHI A., TAKEUCHI T.

74   228 - 228   2006.5

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Numerical analysis on magnetic chromatography for ultrafine particle and ion separation

KIM SeokBeom, NAKADA Chiaki, MURASE Satoru, OKADA Hidehiko

74   35 - 35   2006.5

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Transport current characteristics of HTS tape by neighboring magnetic materials (Part3)

HARADA T., JOO J. H., WATANABE J., INOUE T., NANATO N., MURASE S., KIM S. B.

73   144 - 144   2005.11

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Developments of two-axis hall sensor and magnetic field visualization system (Part1)

KIM S. B., WATANABE J., NANATO N., MURASE S., KOH K., HOHKAWA K.

73   142 - 142   2005.11

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Transport current characteristics of resistive fault current limiters by two-axis magnetic field measurement (part 2)

WATANABE J., NANATO N., MURASE S., HYUN O. B., KIM S. B.

73   143 - 143   2005.11

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FEM analysis of prebending effects for bronze-processed Nb_3Sn wires

KIYAMA K., NANATO N., KIM S. B., MURASE S., OGURO H., NISHIJIMA G., AWAJI S., WATANABE K.

73   45 - 45   2005.11

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Dependence of J_c estimation on coil form and measuring position in third harmonic voltage method

KIJIMA K., WATANABE J., NANATO N., MURASE S., KIM S. B.

73   92 - 92   2005.11

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Linear motion and rotation characteristics of YBCO bulk using exciting coils

S Okamura, A Shimizu, SB Kim, S Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   426   834 - 838   2005.10

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A superconducting actuator with multiple motions is proposed and experimentally investigated for the development of microelectrical machines. The disk-shaped YBCO bulk was located above the electromagnets and cooled down in the field-cooling method, which enabled the flux pinning. The YBCO bulk superconductor was driven in vertical, horizontal and/or self-rotation by PC-controlled coil currents using multiple electromagnets. The most suitable levitation stability was obtained when we used four electromagnets and NNSS trapped field type. It was confirmed that the levitation force and horizontal moving force strongly depended on the coil current and the air gap length, respectively. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2005.03.069

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The three-dimensional motion characteristics of superconducting actuator

SHIMIZU Akihiro, NANATO Nozomu, KIM SeokBeom, MURASE Satoru

2005 ( 22 )   19 - 24   2005.6

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Protection System for Superconducting Coil by Active Power Detection Method

TSUMIYAMA Yasukazu, FUJIWARA Kenji, NIWA Shinjiro, NANATO Nozomu, KIM SeokBeom, MURASE Satoru

2005 ( 22 )   81 - 84   2005.6

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Magnetic-field properties of high critical current density YBCO films deposited by TFA-MOD

SB Kim, S Murase, Y Yamada, T Araki, Hirabayashi, I

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   15 ( 2 )   2645 - 2648   2005.6

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The critical current density, J(c), of metal-organic deposition process using trifluoroacetates (TFA-MOD) based YBCO films was measured between 20 K and 77 K in magnetic fields up to 9.5 T as a function of the field direction. C-axis oriented YBCO films was deposited on LaAlO3 single crystalline substrates and also on CeO2 buffered IBAD (YSZ/Hastelloy) substrates by TFA-MOD method. The obtained Jc values at 77 K and 0 T were 7 and 1.7 MA/cm(2) for LaAlO3 and IBAD substrates, respectively. High Jc values over 10(5) A/cm(2) were maintained up to 4 T (B//c-axis) for the LaAlO3 substrate and up to 3 T (B//c-axis) for the CeO2 buffered IBAD substrate. These results imply that TFA-MOD with simple fabrication process is very promising for the practical YBCO coated conductor. And the dependences on temperature and angular of the Jc at various external magnetic fields for some different thicknesses YBCO films was reported.

DOI： 10.1109/TASC.2005.847757

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Effects of Cu stabilizer configuration on thermal stability of Nb3Sn composite superconductors under cryocooling condition

K Watanabe, T Mitsuhashi, N Nanato, SB Kim, S Murase, G Nishijima, K Watanabe, K Miyoshi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   15 ( 2 )   3410 - 3413   2005.6

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It is known that current sharing effects of the stabilizer are limited in cryocooling conditions being different from poolboiling. Therefore we have studied stability under it, focusing on minimum quench energy (MQE) of Nb3Sn superconductors under various conditions of the applied magnetic field, temperature, and the transport current, for various volume fractions and configurations of Cu stabilizer. From the experimental results, the larger the external Cu volume fraction, the higher the MQE was obtained. All MQE data were summarized by only one line in characteristics of normalized MQE and normalized B (B/B-c2). The obtained MQE behavior was to be characterized by only one empirical equation. It is thought that the obtained formula is useful for a standard of designing the Nb3Sn superconductor and its coil under cryocooled condition.

DOI： 10.1109/TASC.2005.848946

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Empirical equation of MQE for Nb_3Sn wires under cryocooling

MITSUHASHII T., WATANABE K., MUASE S., KIM S. B., NANATO N., NISHIJIMA G., WATANABE K.

72   130 - 130   2005.5

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Measurement of AC transport current loss for HTS conductors by the active power detection method

OHZAWA T., MURASE S., KIM S. B., NANATO N.

72   2 - 2   2005.5

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Time-Frequency Visualization of AE Signal using Wavelet Transform for Precise Measurement and Estimation

NANATO Nozomu, MURASE Satoru, KIM SeokBeom

IEEJ Transactions on Fundamentals and Materials   125 ( 12 )   1069 - 1070   2005

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AE (Acoustic Emission) techniques are universally used for investigating and watching the deformation and crack of various materials because they enable the non-destructive and continuous measurement. However, it is not always easy to clarify the main cause or mechanism of AE signal generation by its analysis and an AE sensor is generally vulnerable to the noise, and therefore advanced measurement and estimation techniques of AE signal are needed. In this paper, the authors present time-frequency visualization of AE signal using the wavelet transform. The proposed method enables especially precise measurement of the frequency band and generation time of AE signal and gives a clue in advanced AE techniques.

DOI： 10.1541/ieejfms.125.1069

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Simple Measurement of the AC Transport Current Loss for HTS Conductors Using an Active Power Detection Method

NANATO Nozomu, OHZAWA Toshiaki, MURASE Satoru, KIM SeokBeom

Journal of the Cryogenic Society of Japan   40 ( 10 )   420 - 424   2005

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DOI： 10.2221/jcsj.40.420

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Development of the protection system of a superconducting coil based on the active power detection method

FUJIWARA Kenji, NANATO Nozomu, MURASE Satoru, KIM Seok Beom

71   56 - 56   2004.11

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Effect of thermal hysteresis on residual strain of Cu stabilizer for Cu/Nb_3Sn composite conductors

KIYAMA K., NANATO N., KIM S., MURASE S.

71   91 - 91   2004.11

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Pulsed field characteristics of trapped magentic fields for HTS Bulks

NOBUHIRA Atsushi, MURASE Satoru, KIM SeokBeom, NANATO Nozomu, OKAMURA Shingo, INOUE Takuya, MATSUMOTO Yasuaki

69   118 - 118   2003.12

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The effect of post-annealing process in NdGaO3 new seed layer for LPE

SB Kim, SI Yoo, Y Yamada

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   392   951 - 955   2003.10

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Novel porous NdGaO3 (NGO) thin film was fabricated as a new seed layer for liquid phase epitaxy growth of YBa2Cu3O7-delta. The microstructure and crystallization mechanism of NGO new seed layer due to post-annealing temperature were revealed by high resolution SEM. Amorphous NGO layers on LaAlO3 single crystalline substrate obtained by pulsed laser deposition method at room temperature and this layer shows the very porous and columnar structure. And this amorphous NGO layers were annealed at wide temperature range below 1300 degreesC in air. Amorphous NGO layer begins to crystallize by post-annealed at 750 degreesC and its orientation gets better with increased annealing temperature. The thickness of NGO layers decrease with increased annealing temperature above 500 degreesC and the well-oriented NGO layers were obtained between 900 and 1300 degreesC. The NGO layers annealed at above 1100 degreesC show very dense film. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0921-4534(03)00862-1

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Microstructure of Nd-Ga-O-3 new seed layer for LPE growth of YBCO film

S Kim, SI Yoo, Y Yamada

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   13 ( 2 )   2571 - 2574   2003.6

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The microstructure and crystallization mechanism of NdGaO3 (NGO) new seed layer for liquid phase epitaxy (LPE) growth of YBa2Cu3O7-delta (YBCO) were revealed using high resolution SEM and TEM. NGO layer deposited by PLD at room temperature shows that very porous and columnar structure and this layer indicated amorphous by x-ray analysis. Amorphous NGO layer was crystallized with good in-plane and out of plane orientations keeping columnar structure by simple post annealing process. Biaxially aligned YBCO thick films were successfully fabricated on oriented novel porous NGO new seed layer: Although many cracks were observed for normally LPE grown YBCO films on NGO(110) single crystalline substrate; it was crack-free formed on porous NGO(100) film.

DOI： 10.1109/TASC.2003.811851

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YBa2Cu3O7-delta deposition on Ni-Cr alloy tape by liquid phase epitaxy method

Y Yamada, T Suga, H Kurosaki, SB Kim, T Maeda, Y Yamada, Hirabayashi, I, Y Iijima, K Kakimoto, T Saitoh

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   378   971 - 974   2002.10

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Thick YBa2Cu3O7-delta (YBCO) films have been successfully formed by the liquid phase epitaxy (LPE) method on Ni-Cr alloy tape. A buffer layer of yttria stabilized zirconia and seed layer of YBCO were formed by the ion beam assisted deposition and by the pulsed laser deposition method, respectively. YBCO films have been grown from the solution of BaO-CuO-Ag-BaF2 at 820, 845 and 860 degreesC under low oxygen partial pressure of 2% to prevent the metallic substrate from reacting with the solution. Good YBCO films are obtained by the growth at 820 degreesC, and the best one shows high critical current density of 1.9 MA/cm(2). A cross-sectional observation by high resolution scanning electron microscopy shows neither reaction layer nor damaged region at the substrate[YBCO film interface. theta-2theta and pole figure X-ray diffraction of the seed layer and the YBCO LPE layer show that in-plane orientation distribution is highly improved by the LPE process. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(02)01579-4

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YBCO films formed on a Ni-base alloy tape by the low temperature Liquid phase epitaxy method

YAMADA Yasji, KIM S. B., SUGA T., YAMADA Yutaka, HIRABAYASHI I., IIJIMA Y., KAKIMOTO K., SAITOH T.

65   17 - 17   2001.11

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Superconducting properties of YBCO films formed by the low temperature Liquid phase epitaxy method

YAMADA Yasji, KIM S. B., SUGA T., YAMADA Yutaka, HIRABAYASHI I.

65   88 - 88   2001.11

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YBCO thin films on multilayers prepared by all-chemical solution deposition processing

H. Hiei, K. Yamagiwa, Y. Takahashi, S. B. Kim, Y. Yamada, J. Shibata, T. Hirayama, H. Ikuta, I. Hirabayashi, U. Mizutani

Physica C: Superconductivity and its Applications   357-360 ( 1 )   942 - 945   2001.9

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The chemical solution deposition (CSD) technique has been applied to prepare both YBa2Cu3O7-δ (YBCO) and buffer layers on a YSZ substrate. Y2O3 and CeO2 were employed as the buffer layers, and it was confirmed that they grew epitaxially by the CSD method. Cross-sectional transmission electron microscope observations revealed that Y2O3 grew up to the top of the film. Furthermore, the YBCO film on the Y2O3 or CeO2/Y2O3 layers were c-axis aligned and showed a good in-plane alignment. The transition temperature and the critical current density of the YBCO/Y2O3/YSZ multilayer were 89 K and 4 × 104 A/cm2 at 77 K, 0 T, respectively. © 2001 Elsevier Science B.V. All rights reserved.

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Critical current density and related microstructures of TFA-MOD YBCO coated conductors

Y Yamada, S Kim, T Araki, Y Takahashi, T Yuasa, H Kurosaki, Hirabayashi, I, Y Iijima, K Takeda

PHYSICA C   357   1007 - 1010   2001.8

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Metalorganic deposition process using trifluoroacetate (TFA-MOD) processed YBCO film on LaAlO3 and IBAD (YSZ/Hastelloy) substrate exhibited high critical current density, J(c), at 77.3 K. The obtained J(c) values at 0 T were 7 and 1.7 MA/cm(2) for LaAlO3 and CeO2 buffered IBAD, respectively. High J(c) values over 10(5) A/cm(2) were maintained up to 4 T (B parallel toc-axis) for the LaAlO3 substrate and up to 3 T (B parallel toc-axis) for the CeO2 buffered IBAD substrate. These results imply that TFA-MOD with simple fabrication process is very promising for the practical YBCO coated conductor. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(01)00471-3

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Superconducting properties of YBCO films formed by the Liquid phase epitaxy method

YAMADA Yasji, KIM S. B., SUGA T., YAMADA Yutaka, HIRABAYASHI I., IIJIMA Y., KAKIMOTO K., SAITOH T.

64   20 - 20   2001.5

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Lowering of LPE growth temperature for YBCO formation on metal tapes

SUGA T., YAMADA Y., KIM S. B., MAEDA T., YAMADA Y., HIRABAYASHI I., YOSHINO H., YAMAZAKI M., THANH T. D.

64   19 - 19   2001.5

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Low-temperature liquid-phase epitaxial growth of YBa_2Cu_3O<7-δ> on NiO-buffered textured-Ni tapes

MAEDA Toshihiko, KUROSAKI Haruhiko, SUGA Toshihiro, KIM SeokBeom, YAMADA Yasuji, WATANABE Tomonori, HIRABAYASHI Izumi

64   21 - 21   2001.5

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Fabrication of new seed layer for LPE growth of YBCO superconducting wires

KIM S. B., YAMADA Yasuji, SUGA T., MAEDA T., YAMADA Yutaka, WATANABE T., HIRABAYASHI I.

64   112 - 112   2001.5

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Fabrication of Gd123 films by TFA-MOD method on single crystalline substrates

IGUCHI Toshihiro, ARAKI Takeshi, KIM SeokBeom, YAMADA Yutaka, IKUTA Hiroshi, HIRABAYASHI Izumi, MIZUTANI Uichiro

64   176 - 176   2001.5

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Development of YBCO superconducting wire by metalorganic deposition using trifluoroacetate

YUASA T., YAMADA Yutaka, ARAKI T., KUROSAKI H., KIM S. B., SHIOHARA Y., HIRABAYASHI I., IIJIMA Y., SAITO T.

64   114 - 114   2001.5

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Fabrication of YBa2Cu3O7-x films on buffered metal tapes fired at low temperature by MOD method using trifluoroacetate salts

T Araki, Y Takahashi, K Yamagiwa, T Yuasa, Y Iijima, K Takeda, SB Kim, Y Yamada, Hirabayashi, I

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   11 ( 1 )   2869 - 2872   2001.3

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Metalorganic deposition (MOD) using trifluoroacetates is considered to be one of the most promising methods for coated conductors, because it enables us to obtain very high J(c) films with low-cost facilities. We have optimized various processing conditions in this method and successfully obtained critical current density (J(c)) of 4.1MA/cm(2) (77K, 0T) for the YBa2Cu3O7-x (YBCO) film of 1800 Angstrom in thickness on CeO2 buffered YSZ single crystal, which was fired at 800 degreesC. In the case of YBCO films on buffered metallic substrates, it is difficult to fabricate under the same deposition condition. Then low temperature heat treatment is required for deposition on metal substrate. On the other hand, such heat treatment also permits non-reacted BaF2 in fired film, that leads to low J(c) of the film. Therefore it is the key to fabricate YBCO film with entire reaction of BaF2 by the low temperature heat treatment. We have investigated chemical reactions in firing and established a firing profile to fabricate YBCO film even at 725 degreesC, With this profile, we can successfully fabricate the YBCO film at 725 degreesC on CeO2 buffered YSZ single crystal which has J(c) of 3.0MA/cm(2) and the YBCO film on CeO2 (sputtered) / YSZ (Ion-beam-assisted deposition: IBAD) buffered Ni based alloy (hastelloy) tape which has J(c) of 0.81MA/cm(2).

DOI： 10.1109/77.919661

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TYTBa2CU3O7-delta thick films grown on textured metal substrates by liquid-phase epitaxy process

T Maeda, SB Kim, T Suga, H Kurosaki, T Yuasa, Y Yamada, Y Yamada, H Yoshino, M Yamazaki, TD Thanh, T Watanabe, K Matsumoto, Hirabayashi, I

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   11 ( 1 )   2931 - 2934   2001.3

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Towards high-current wire application of high-temperature superconductors, YBa2Cu3O7-delta (YBCO) thick films are grown by means of a Liquid-phase epitaxy (LPE) process on a (001) surface of NiO single crystal and Laser-sputtered NiO buffer layer deposited on a (001) surface of SrTiO3 single crystal. NiO buffer layers can be rapidly formed on textured Ni tape by the recently developed "Surface-Oxidation-Epitaxy" (SOE) technique which is expected to be a low-cost production method of long metal substrates with highly-textured oxide buffer layer. LPE growth on SOE-buffered textured Ni tapes are also attempted. Moreover, we successfully prepared similar to0.1 m-long LPE-YBCO tapes on {120}&lt; 2(1) over bar 0 &gt; Ag-0.1 wt.% Cu alloy tape by using a specially designed LPE furnace equipped with a "reel-to-reel" attachment. BaF2-added BaO-CuO flux is used in this work, in which the growth temperature of YBCO is drastically lowered from usually used value of similar to 1000 degreesC down to 900-930 degreesC, While current transport performances of these LPE-YBCO films are still insufficient for high-current wire application, the present results show the high potential of this LPE process for long-length coated-conductor production.

DOI： 10.1109/77.919676

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Fabrication of NdGaO3 buffer layer on textured Ni tape for long length coated conductors

SB Kim, T Maeda, Y Yamada, T Suga, K Matsumoto, T Watanabe, Hirabayashi, I

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   11 ( 1 )   3317 - 3320   2001.3

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Biaxially aligned NdGaO3 (NGO) layers were successfully fabricated on the single crystalline substrates (STO, LAO and NiO/STO) and metalic substrate (NiO/Ni) by pulsed laser deposition (PLD) method and post-annealing process. And also, the good biaxial orientation YBa2Cu3O7.delta (YBCO) films on NGO layers were deposited by liquid phase epitaxy (LPE) method. From this work, it has been proved for the first time that NGO thin film can be used as a seed layer for the YBCO thick film deposition by LPE method. And it is clear that the NGO thin film growth process, where biaxially orientated films were deposited using PLD at room temperature followed by simple post-annealing process, is very effective for the uniform long length coated conductor production.

DOI： 10.1109/77.919772

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Long-length Y-Ba-Cu-O coated conductors produced by surface-oxidation epitaxy method

K Matsumoto, T Watanabe, T Tanigawa, T Maeda, S Kim, Hirabayashi, I

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   11 ( 1 )   3138 - 3141   2001.3

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A 50-m long, biaxially textured NiO buffer layer for epitaxial growth of YBa2Cu3O7-delta (YBCO) film has been fabricated on a long length cube-textured Ni tape using surface-oxidation epitaxy (SOE) technique. The thickness of NiO layer was arranged to be around 3 mum. The tape manufacturing speed was 15 m/h, The SOE-NiO layer was highly (100) oriented and the full width at half maximum from X-ray phi -scan for NiO(111) was varied from 13 to 19 degrees in the whole length. J(c) values exceeding 0.3 MA/cm(2) at 77K and self field have been obtained in short samples of YBCO films on NiO/Ni tapes, by using thin MgO cap layer with the thickness of about 100 nm, Crystal orientation control of YBCO coated conductors by SOE method is very effective even for the long length Ni tapes.

DOI： 10.1109/77.919728

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Fabrication of buffer layer for YBCO coated conductor on cube textured Ag substrate

T. Yuasa, H. Kurosaki, S. B. Kim, T. Maeda, K. Higashiyama, I. Hirabayashi

Physica C: Superconductivity and its Applications   357-360   934 - 937   2001

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In case of the cube textured (CUTE) Ag substrate, recrystallization process of as-rolled Ag substrate in various atmosphere changed surface flatness of the substrate. When the substrate was heated in a vacuum chamber with a oxygen partial pressure of less than 1 × 10-5 Torr at 600°C, the surface average roughness (Ra) of the substrate was less than 120 nm. Then the oxygen was introduced into the vacuum chamber to fabricate CeO2 buffer layer on the substrate by pulsed laser deposition. After the oxygen pressure reached to 50-150 mTorr, CeO2 layer was deposited on the CUTE Ag substrate immediately. By reducing the influence of oxygen to surface roughness of the substrate, Ra of the CeO2 buffered CUTE Ag substrate was 30 nm. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(01)00446-4

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Characterization of YBa2Cu3O7-δ films grown on NiO buffer layer by liquid-phase epitaxy process

Tomonori Watanabe, Kaname Matsumoto

Physica C: Superconductivity and its Applications   357-360   1042 - 1045   2001

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By means of a liquid-phase epitaxy (LPE) process, superconducting YBa2Cu3O7-δ (YBCO) thick film is grown on a biaxially textured NiO buffer layer which is pulsed-laser deposited on a (0 0 1) surface of SrTiO3 single crystal. Employment of BaF2-added Ba-Cu-O flux is found to be effective for LPE-YBCO growth because the growth temperature of YBCO is drastically lowered down to 900-920°C compared to the case of usually used simple Ba-Cu-O flux. This strongly suggests that the low-temperature LPE growth of YBCO on a NiO/Ni substrate is hopeful process for coated-conductor production. Superconductivity transition temperature (Tc) of the LPE-YBCO film is measured to be 91 K for onset and 87 K for a zero-resistance state. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(01)00528-7

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Fabrication of seed/buffer layers on metallic substrates for YBCO coated conductors

SeokBeom Kim, Toshihiko Maeda, Yasuji Yamada, Toshihiro Suga, Yutaka Yamada, Tomonori Watanabe, Kaname Matsumoto, Isumi Hirabayashi

Physica C: Superconductivity and its Applications   357-360   979 - 982   2001

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LaNiO3 (LNO) buffer layers with good c-axis orientation on SrTiO3 (STO), LaAlO3 (LAO), NiO/STO and SOE (NiO/Ni) tapes were successfully fabricated by the pulsed laser deposition (PLD) method. Biaxially aligned neodymium (NdGaO3, NGO) seed layers were successfully fabricated on the STO, LAO and LNO buffer layer by PLD method and post-annealing process. And also, the good biaxial orientation YBa2Cu3O7-δ (YBCO) films on NGO seed layers were deposited by liquid phase epitaxy (LPE) method. From this work, it has been proved for the first time that NGO thin film can be used as a seed layer for YBCO thick film deposition by the LPE method. This NGO thin film which is deposited by the PLD method at room temperature and post-annealed at 950°C for 5 h in air, is low cost and very effective for the coated conductor production by LPE. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(01)00464-6

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A study on stability criterion for cryocooler operating HTS coils

A. Ishiyama, S.B. Kim, K.H. Han

大韓電気学会論文誌（韓国）   2001

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DOI： 10.1109/77.920204

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Non-cuprate thin films as candidates of seed layer for liquid phase epitaxy process

Tadamasa Miura, Yasuji Yamada, Toshihiro Suga, Daxiang Huang, Seok Beom Kim, Toshihiko Maeda, Izumi Hirabayashi, Hiroshi Ikuta, Uichiro Mizutani

Physica C: Superconductivity and its Applications   357-360   983 - 986   2001

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As a seed layer for the liquid phase epitaxy (LPE) of YBa2Cu3O7-d (YBCO) we investigate non-cuprate thin film of Y-Ba-Fe-O deposited by pulsed laser deposition (PLD) method. The deposited film is highly oriented and it can be used as a seed layer at LPE temperatures below 980°C. PLD conditions for obtaining crystalline Y-Ba-Fe-O film is much wider than that for the seed layer of YBCO. LPE-grown YBCO film formed on the Y-Ba-Fe-O seed layer shows the same superconductive properties as that formed on the YBCO seed layer. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(01)00465-8

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Preparation of YBCO films on CeO2 buffered metallic substrates by the TFA-MOD method

Y. Takahashi, T. Araki, K. Yamagiwa, Yutaka Yamada, S. B. Kim, Y. Iijima, K. Takeda, I. Hirabayashi

Physica C: Superconductivity and its Applications   357-360   1003 - 1006   2001

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Biaxially aligned YBa2Cu3O7-y (YBCO) coated conductors on long metallic substrates are required for power applications. Recently trifluoroacetate-metal organic deposition (TFA-MOD) has been well-known as the most prospective method for the preparation of high Jc YBCO films and it has been applied on metallic substrates. We optimized the deposition condition of the CeO2 films on IBAD tapes and fabricated 10 cm class in-plane textured CeO2 buffered IBAD tapes by the PLD method. We prepared YBCO films on CeO2 buffered IBAD tapes by the TFA-MOD method. The YBCO films deposited on the buffered tapes were out of plane and in-plane aligned. The Jc value for short sample was 1.72 MA/cm2 at 77 K, 0 T. These results suggest that the CeO2 buffered IBAD tapes are feasible for the substrate for YBCO coated superconducting wire by the TFA-MOD method. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(01)00470-1

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Fabrication of buffer layers and seed layers on biaxially textured Ni tapes for YBCO superconducting wire

H. Kurosaki, T. Yuasa, T. Maeda, Y. Yamada, S. B. Kim, T. Watanabe, K. Wada, I. Hirabayashi

Physica C: Superconductivity and its Applications   357-360   938 - 941   2001

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We have deposited Y2O3 buffer layers by metal-organic chemical vapor deposition (MOCVD) on textured Ni tapes coated with biaxially aligned NiO(1 0 0) layers grown by surface oxidation epitaxy method. X-ray diffraction measurements showed that Y2O3 grew cube-on-cube on NiO layer, i.e. it has also biaxial orientation. With these Y2O3 layers, in-plane aligned YBa2Cu3O7-δ (YBCO) (0 0 1) thick films (∼3 μm in thickness) have been successfully grown by liquid phase epitaxy (LPE) method on the textured Ni tapes. YBCO seed layers, required in LPE process, had been also deposited by MOCVD. The LPE-grown YBCO thick films exhibit superconductivity transition temperature of Tc, onset = 90 K and Tc, zero = 65 K by four-probe transport measurement. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(01)00447-6

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Characterization of LPE-Grown YBCO on Textured Silver Tape

SUGA T., YAMADA Y., KIM S. B., MAEDA T., YAMADA Y., HIRABAYASHI I., YOSHINO H., YAMAZAKI M., THANH T. D.

63   176 - 176   2000.10

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Development of YBCO superconducting wire by metalorgnic deposition using trifluoroacetate : Characteristics of critical current density in magnetic field

KIM S. B., YAMADA Y., ARAKI T., TAKAHASHI Y., YUASA T., KUROSAKI H., IIJIMA Y, TAKEDA K., HIRABAYASHI I.

63   131 - 131   2000.10

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Characterization of YBa_2Cu_3O_<7-δ> Films grown on NiO by Liquid-Phase Epitaxy Process

MAEDA Toshihiko, KIM SeokBeom, SUGA Toshihiro, KUROSAKI Haruhiko, YUASA Toyotaka, YAMADA Yasuji, WATANABE Tomonori, WADA Katsunori, HIRABAYASHI Izumi

63   124 - 124   2000.10

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Fabrication of buffer and seed layers for LPE growth of YBCO thin film wires

KIM S. B., MAEDA T., YAMADA Yasuji, SUGA T., YAMADA Yutaka, WATANABE T., WADA K., HIRABAYASHI I.

63   178 - 178   2000.10

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Development of YBCO superconducting wire by metalorganic deposition using trifluoroacetate : CeO2 buffer layer for meta

YUASA Toyotaka, ARAKI Takeshi, TAKAHASHI Yasuo, KUROSAKI Haruhiko, KIM SeokBeom, IIJIMA Yasuhiro, TAKEDA Kaoru, HIRABAYASHI Izumi

63   130 - 130   2000.10

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Development of YBCO superconducting wire by metalorganic deposition using trifluoroacetate : heat treatment in lower temperature for fabrication of long wire on buffered metallic tapes

ARAKI Takeshi, YAMAGIWA Kastuya, TAKAHASHI Yasuo, KIM SeokBeom, YAMADA Yutaka, YUASA Toyotaka, KUROSAKI Haruhiko, SUZUKI Katsumi, HIRABAYASHI Izumi, IIJIMA Yasuhiro, TAKEDA Kaoru

63   129 - 129   2000.10

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Development of YBCO superconducting wire by metalorganic deposition using trifluoroacetate

YAMADA Yutaka, ARAKI Takeshi, TAKAHASHI Yasuo, KIM SeokBeom, YUASA Toyotaka, KUROSAKI Haruhiko, SHIOHARA Yu, HIRABAYASHI Izumi, IIJIMA Yasuhiro, TAKEDA Kaoru

63   128 - 128   2000.10

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Preparation of bi-axially aligned YBa2Cu3O7-delta film on CeO2-buffered MgO by chemical solution deposition

K Yamagiwa, H Hiei, Y Takahashi, SB Kim, K Matsumoto, H Ikuta, U Mizutani, Hirabayashi, I

PHYSICA C   334 ( 3-4 )   301 - 305   2000.6

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We have succeeded in preparing in-plane aligned YBa(2)Cu(3)Q(7-delta) (Y123) film by chemical solution deposition (CSD) processing on CeO2 (100)-buffered MgO (100) substrates. The CeO2 buffer film was deposited on MgO (100) single crystalline substrate by pulsed laser deposition (PLD). For CSD coating, a homogeneous coating solution having a molar ratio of Y:Ba:Cu = 1:2:3, was prepared by dissolving metal naphthenates in toluene. This solution was spin-coated both on the YSZ (100) and on the CeO2-buffered MgO (100) single crystalline substrates. The precursor films were calcined at 425 degrees C and fired at various temperatures under low oxygen partial pressure (pO(2)). All Y123 films showed strong (00n) peaks, which correspond to c-axis orientation perpendicular to the substrates and their a/b-axes were in-plane aligned. We confirmed that CeO2 buffer is usable for CSD processing. While the Y123 films on the YSZ reacted with the substrate forming BaZrO3 phase and did not show sufficient superconducting properties. The T-c,T-zero value of the Y123 film prepared on CeO2-buffered MgO substrate was 91.5 K and J(c) was 1.2 X 10(5) A/cm(2) at 77 K, 0 T. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(00)00185-4

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High critical current density YBa2Cu3O7-delta films on surface-oxidized metallic substrates

K Matsumoto, S Kim, K Yamagiwa, Y Koike, Hirabayashi, I, T Watanabe, N Uno, M Ikeda

PHYSICA C   335 ( 1-4 )   39 - 43   2000.6

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YBa2Cu3O7-delta (YBCO) films with high critical current density (J(c)) were fabricated on nickel tapes buffered with hi-axially textured NiO prepared by surface-oxidation epitaxy (SOE). The effects of oxide cap layers, such as YSZ, CeO2 and MgO, on the SOE-grown NiO were investigated to improve the superconducting properties of the YBCO films on NiO. By inserting a thin MgO cap layer between NiO layer and YBCO film, a J(c) of 3 X 10(5) A/cm(2) (77 K, 0 T) was achieved. This result indicates the potentiality of the SOE method. In this paper, the application of the NiO/Ni substrate to non-vacuum processings, such as metal-organic deposition (MOD) and liquid phase epitaxy (LPE) will be also introduced. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(00)00139-8

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Liquid-Phase Epitaxial Growth of YBa_2Cu_3O_<7-δ> Films on NiO Buffer Layer

MAEDA Toshihiko, SUGA Toshihiro, KOIKE Yoshihiro, KIM SeokBeom, YAMADA Yasuji, WATANABE Tomonori, MATSUMOTO Kaname, HIRABAYASHI Izumi

62   126 - 126   2000.5

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Continuous Fabrication of LPE-grown YBa_2Cu_3O_<7-d> Formed on Textured Silver

SUGA T., YAMADA Y., MIURA M., KIM S. B., MAEDA T., IKUTA H., MIZUTANI U., YOSHINO H., YAMAZAKI M., THANH T. D.

62   128 - 128   2000.5

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High critical current density YBa2Cu3O7-delta tapes prepared by the surface-oxidation epitaxy method

K Matsumoto, SB Kim, Hirabayashi, I, T Watanabe, N Uno, M Ikeda

PHYSICA C   330 ( 3-4 )   150 - 154   2000.3

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YBa2Cu3O7-delta (YBCO) films with high critical current density (J(c)) were successfully fabricated on nickel tapes buffered with epitaxial NiO. NiO was prepared on the textured nickel tape by the surface-oxidation epitaxy (SOE) method. We have reported so far a critical temperature (T-c) of 87 K and J(c) = 4-6 X 10(4) A/cm(2) (77 K, 0 T) for the YBCO films on NiO/Ni tapes. To enhance the superconducting properties of the YBCO films an the SOE-grown NiO, depositions of thin oxide cap layers such as YSZ, CeO2, and MgO on NiO were investigated. These oxide cap layers were epitaxially grown on NiO and provided the template for the epitaxial growth of YBCO films. Substantially improved data of T-c = 88 K and J(c)= 3 x 10(5) A/cm(2) (77 K, 0 T) and 1 x 10(4) A/cm(2) (77 K, H\\c, 4 T) were obtained for YBCO film on NiO, by using a MgO cap layer with a thickness of 50 nm. The method described in this paper is a simple way to produce long YBCO tape conductors with high-J(c) values. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(99)00622-X

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Direct observation of quench behavior in YBCO thin film

KIM S. B., TAKAHASHI Y., MATSUMOTO K., TAKAGI T., MACHI T., KOSHIZUKA N., ISHIYAMA A., HIRABAYASHI I.

60   133 - 133   1999.6

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In-plane alignment of YBa2Cu3O7-y films realized by CeO2 buffer layer on textured Ag{100}&lt; 001 &gt; tapes

Y Takahashi, K Matsumoto, SB Kim, Hirabayashi, I, H Akata, K Higashiyama

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   9 ( 2 )   2272 - 2275   1999.6

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Homogeneous in-plane aligned YBa2Cu3O7-y (YBCO) films on long metallic substrates are required for power applications. In order to establish in-plane aligned YBCO films, me have been studying Ag {100}&lt;001&gt; textured tapes buffered with a (001)-oriented CeO2 layer. The YBCO and CeO2 films were deposited by pulsed laser deposition (PLD). The CeO2 deposition rate was 900 Angstrom/min. The CeO2 films on Ag {100}&lt;001&gt; textured substrates were (100)-oriented and highly in-plane aligned. The YBCO films deposited by PLD on CeO2 buffered Ag substrates also have c-asis oriented and good in-plane alignment. T-c and J(c) values of the YBCO films were 81 K and 1x10(4) A/cm(2) at 77 K respectively.

DOI： 10.1109/77.784923

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Fabrication of in-plane aligned YBCO films on polycrystalline Ni tapes buffered with surface-oxidized NiO layers

K Matsumoto, SB Kim, JG Wen, Hirabayashi, I, T Watanabe, N Uno, M Ikeda

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   9 ( 2 )   1539 - 1542   1999.6

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Strongly in-plane aligned, c-axis oriented YBCO films were successfully grown on polycrystalline nickel tapes buffered with (100)-oriented NiO layers. The in-plane and out-of-plane alignments of the NiO layer were achieved by a surface-oxidation epitaxy (SOE) technique using a {100}&lt;001&gt; cube-textured nickel tape. The in-plane textures of NiO layers fabricated so far with the full width half maximum (FWHM) values of 11-13 degrees ale sufficient for the epitaxial growth of high-J(c) YBCO films. Pulsed laser deposited YBCO layers on the NiO/Ni tapes were not only c-axis oriented with respect to the tape surface, but also strongly in-plane aligned. The YBCO films on NiO/Ni tapes have a zero resistance T-c=87K and J(c)=10(4)-10(5)A/cm(2) at 77K.

DOI： 10.1109/77.784687

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Quench propagation properties in HTS pancake coil

S Shimizu, A Ishiyama, SB Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   9 ( 2 )   1077 - 1080   1999.6

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In this paper, we present the results of experiments and computer simulations to make clear the quench propagation properties in Bi-2223/Ag superconducting multifilament tape. We developed a computer code based on the two-dimensional finite element method (2-D FEM). Computed voltage and temperature traces during a quench agree well with the experimentally recorded voltage and temperature traces. Good agreement validates the computer code, making a useful tool in developing protection strategies for high-temperature superconducting (HTS) coils. Therefore, we simulate the quench process in a single pancake coil wound with Bi-2223/Ag superconducting multifilament tape with background magnetic filed up to 10 T at 20 K using the developed computer code. The quench propagation properties and stability in HTS coils are discussed and compare with those in low-temperature superconducting (LTS) coils.

DOI： 10.1109/77.783484

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Development of kA-class gas-cooled HTS current lead for superconducting fault current limiter

S Odaka, SB Kim, A Ishiyama, Y Sato, S Honjo, Y Iwata, S Shingo

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   9 ( 2 )   491 - 494   1999.6

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A current lead with kA capacity and small AC loss is being developed for use in superconducting current limiting devices cooled with liquid helium. A gas-cooled type current lead using Bi-based oxide superconducting bulk materials was examined to clarify the effects of the current lead geometry and the use of multiple current leads. This paper presents the results of experiments and numerical simulations based on the finite element method taking consideration of non-uniform transport current distribution among multiple current leads connected in parallel. The simulations are performed to investigate the relationship between the geometry of current leads and the amount of heat flow into a cryostat. In the simulations, the AC loss caused by both mutual and self-induced magnetic fields of multiple current leads is taken into account. The influence of AC loss, the joule heat generated by the contact resistance at joints of NbTi/CuNi multi-strand cables and the HTS bars, and the return passage for gas on the operating characteristics of the HTS current leads are evaluated.

DOI： 10.1109/77.783342

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In-plane alignment of YlCiOyy films realized by CeC&gt;2 buffer layer on textured Ag{100}&lt;001&gt; tapes

Yasuo Takahashi, Kaname Matsumoto, Seokbeom Kim, Izumi Hirabayashi

IEEE Transactions on Applied Superconductivity   9 ( 2 )   2272 - 2275   1999

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Homogeneous in-plane aligned YBa2Cu3O7_y (YBCO) films on long metallic substrates are required for power applications. In order to establish in-plane aligned YBCO films, we have been studying Ag {100}&lt
001&gt
textured tapes buffered with a (OOl)-oriented Ce(&gt
2 layer. The YBCO and CeO2 films were deposited by pulsed laser deposition (PLD). The CeO2 deposition rate was 900 A/min. The CeOj films on Ag {100}&lt
001&gt
textnred substrates were (lOO)-oriented and highly in-plane aligned. The YBCO films deposited by PLD on CeO2 buffered Ag substrates also have c-axis oriented and good in-plane alignment Tc and 3C values of the YBCO films were 81 K and IxlO4 A/cm2 at 77 K, respectively. © 1999 IEEE.

DOI： 10.1109/77.784923

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In-plane alignment of YlCiOyy films realized by CeC&gt;2 buffer layer on textured Ag{100}&lt;001&gt; tapes

Yasuo Takahashi, Kaname Matsumoto, Seokbeom Kim, Izumi Hirabayashi

IEEE Transactions on Applied Superconductivity   9 ( 2 )   2272 - 2275   1999

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Homogeneous in-plane aligned YBa2Cu3O7_y (YBCO) films on long metallic substrates are required for power applications. In order to establish in-plane aligned YBCO films, we have been studying Ag {100}&lt
001&gt
textured tapes buffered with a (OOl)-oriented Ce(&gt
2 layer. The YBCO and CeO2 films were deposited by pulsed laser deposition (PLD). The CeO2 deposition rate was 900 A/min. The CeOj films on Ag {100}&lt
001&gt
textnred substrates were (lOO)-oriented and highly in-plane aligned. The YBCO films deposited by PLD on CeO2 buffered Ag substrates also have c-axis oriented and good in-plane alignment Tc and 3C values of the YBCO films were 81 K and IxlO4 A/cm2 at 77 K, respectively. © 1999 IEEE.

DOI： 10.1109/77.784923

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Normal-Zone Propagation Properties in HTS Coil

SHIMIZU Satoshi, ISHIYAMA Atushi, KIM SeokBeom

59   99 - 99   1998.10

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Characteristics of normal-zone propagation in YBCO thin film

KIM SeokBeom, MATSUMOTO Kaname, TAKAHASHI Yasuo, ICHINO Yusuke, ISHIYAMA Atsushi, HIRABAYASHI Izumi

59   118 - 118   1998.10

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Transient stability characteristics of AC superconducting multi-strand cables

SUSA Tadahiro, SASAKI Mitsuyasu, KIM Seokbeom, ISHIYAMA Atsushi, YUMURA Hiroyasu, OHMATSU Kazuya, SATO Ken-ichi

58   196 - 196   1998.5

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The Estimation for Transient stability of AC Multi-strand Superconducting Cables

SASAKI Mitsuyasu, OHGITANI Kaneto, KIM Seobeom, ISHIYAMA Atsushi

1998 ( 7 )   43 - 48   1998.1

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Normal-zone propagation properties in Bi-2223/Ag superconducting multifilament tapes

KIM S. B.

Cryogenics   38   823 - 831   1998

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Normal transition characteristics of AC superconducting multi-strand cables

SASAKI Mitsuyasu, SUSA Tadahiro, OHGITANI Kaneto, KIM SeokBeom, ISHIYAMA Atsushi, YUMURA Hiroyasu, OHMATSU Kazuya, SATO Ken-ichi

57   224 - 224   1997.11

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Evaluation of Heat Flow in HTS Current Leads for AC Use

KIM Seokbeom, ODAKA Satoshi, ISHIYAMA Atsushi, HONJO Shoichi, IWATA Yoshihiro, SHINGOU Seizi

1997 ( 30 )   75 - 80   1997.7

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The Effect of Cu Located in CuNi Matrix for Transient Stability Analysis of AC Superconducting Multi-strand Cables

SASAKI Mitsuyasu, OHGITANI Kaneto, KIM Seokbeom, ISHIYAMA Atsushi

1997 ( 30 )   1 - 6   1997.7

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交流用高温超電導電流リードの熱侵入量形状依存性評価(1) : 戻りガスによる冷却の様子

金 錫範, 永塚 満, 石山 敦士, 本庄 昇一, 三木 剛, 岩田 良浩, 財満 英一, 新郷 征二

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   56   171 - 171   1997.5

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交流用高温超電導電流リードの熱侵入量形状依存性評価(2) : 複数本化の効果

小高 聡, 永塚 満, 金 錫範, 石山 敦士, 本庄 昇一, 三木 剛, 岩田 良浩, 財満 英一, 新郷 征二

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   56   172 - 172   1997.5

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高温超電導コイル内の常電導伝播シミュレーション(その1)

丹羽 祥仁, 金 錫範, 石山 敦士

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   55   237 - 237   1996.11

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Normal-Zone Propagation Properties in Bi-2223/Ag Superconducting Multifilamentaly Tapes

KIM S. B.

31 ( 7 )   379 - 390   1996

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Bi系銀シース多芯テープ導体の線間方向常電導伝播特性

金 錫範, 上野 豊, 石山 敦士, 岡田 秀彦, 野村 俊自, 引地 健雄

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   54   167 - 167   1995.11

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Bi系銀シース多芯テープ導体の常電導伝播速度測定

金 錫範, 石山 敦士, 岡田 秀彦, 野村 俊自, 引地 健雄

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   53   228 - 228   1995.5

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密巻超電導巻線の過渡安定性に関する数値実験

上野 豊, 鈴木 俊明, 金 錫範, 石山 敦士

低温工学・超電導学会講演概要集 = Meetings of Cryogenics and Superconductivity   53   209 - 209   1995.5

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Permissible Disturbance Energies in Filled and UnFilled High-Performance Superconducting Magnets

A. Ishiyama, S. B. Kim, T. Takahashi

IEEE Transactions on Magnetics   30 ( 4 )   2483 - 2486   1994

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In high-performance superconducting magnets, the winding is densely packed with conductor to enhance the overall current densities. In these magnets, void space, unoccupied by conductor, is more often than not, filled with substances such as epoxy resin. That is, the structural integrity achieved by the filler is generally considered to be more important than cooling which is provided by liquid helium permeating the unfilled void space in the winding. This paper presents numerical results of a three-dimentional finite element method analysis of the transient thermal behavior of both filled and unfilled high-performance superconducting magnets. The analysis focuses on the effect of copper to superconductor ratio and the position of disturbances, and the maximum permissible disturbance energy. © 1994 IEEE

DOI： 10.1109/20.305781

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