Faculty Profiles - UEDA Hiroshi

Papers - UEDA Hiroshi

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医薬用タンパク質の超電導高勾配磁気分離装置の開発 Reviewed

植田浩史, 柁川一弘, 上岡泰晴, 我妻洸, 淵野修一郎, 古瀬充穂, 飯塚倫尋, 中村秀一

低温工学 49 ( 1 ) 25 - 34 2014.1

Spatial and Temporal Behavior of Magnetic Field Distribution Due to Shielding Current in HTS Coil for Cyclotron Application Reviewed International journal

Hiroshi Ueda, Mitsuhiro Fukuda, Kichiji Hatanaka, Tao Wang, Atsushi Ishiyama, So Noguchi

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 ( 3 ) 4100805 2013.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

We intend to develop and obtain a compact, high-efficiency and high-performance cyclotron using the high-temperature superconducting (HTS) magnet technology. In cyclotron applications, a high-accuracy magnetic field distribution with an isochronous field and an azimuthally varying field is spatially and temporally required for an HTS coil. In coils wound with HTS tapes, large shielding currents are induced in the HTS tape by the radial component of the magnetic field. The magnetic field generated by the shielding current affects the magnetic field distribution in the cyclotron application in the following issues: (1) field reduction by the shielding current, (2) accuracy of the field distribution, (3) temporal stability of the time-dependent shielding currents, and (4) field repeatability after charge and discharge repetitions. These effects are very critical in cyclotron applications. We developed a novel numerical simulation based on the finite element method, boundary integral equation, and fast multipole method. We investigated the spatial and temporal behavior of the magnetic field attributed to the shielding current in the HTS coil for the HTS cyclotron application.

DOI： 10.1109/TASC.2012.2234813

HTS magnet to polarize ultra cold neutrons

K. Hatanaka, M. Fukuda, N. Hamatani, K. Kamakura, T. Saito, H. Ueda, T. Yorita, Y. Yasuda, T. Kawaguchi

3522 - 3524 2013.6

Conceptual Design of Next Generation HTS Cyclotron Reviewed International journal

Hiroshi Ueda, Mitsuhiro Fukuda, Kichiji Hatanaka, Tao Wang, Xudong Wang, Atsushi Ishiyama, So Noguchi, Shigeo Nagaya, Naoji Kashima, Nobuyuki Miyahara

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 ( 3 ) 4100205 2013.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

In recent years, the quality of high-temperature superconducting (HTS) tapes has been improving rapidly, becoming available in sufficient quantity and length, and can be applied to devices for power systems and industrial applications. Therefore, we are carrying out a feasibility study on the application of HTS coil to a medical accelerator system for particle cancer therapy, and designing a new HTS cyclotron that is to be compact, highly efficient, is able to extract high-energy beam and consume less power. In this paper, we report our effort to develop a conceptual magnetic design of a "next generation HTS cyclotron" using high-temperature superconducting technology.

DOI： 10.1109/TASC.2012.2232955

Numerical simulation of screening current distribution in HTS tape of high field magnet Reviewed

Ryusei Itoh, Yuki Oga, So Noguchi, Hajime Igarashi, Hiroshi Ueda

Physica C: Superconductivity and its Applications 484 300 - 304 2013.1

Language：English Publishing type：Research paper (scientific journal)

In recent years, properties of high temperature superconducting (HTS) tapes, especially in-field performance and mechanical strength, have been continuously improved. The HTS tapes have been widely used for high field (&gt
20 T) magnet researches and there are several technical challenges including field attenuation of an HTS magnet by screening currents induced within the HTS tapes. Several publications reported that the screening currents, induced by penetration of self magnetic fields into HTS tapes within an HTS magnet, weakened a field constant of the HTS magnet. The result may demonstrate that the screening current changes an overall current density distribution in HTS tapes and, as a consequence, the generated magnetic field. Therefore, it is necessary to investigate the screening current distribution in an HTS tape. This paper reports numerical simulation of the screening current distribution in an HTS tape of high field magnets using 2D finite element method with the E-J characteristic of the HTS tape taken into account. Self magnetic field distribution and its orientation to the HTS tape are also considered to compute critical currents and locally generated electric fields, two key components to figure out the distribution of screening currents.

DOI： 10.1016/j.physc.2012.03.040

Quench Detection and Protection of Cryocooler-Cooled YBCO Pancake Coil for SMES Reviewed International journal

Hiroshi Ueda, Atsushi Ishiyama, Kazuki Muromachi, Takahiro Suzuki, Koji Shikimachi, Naoki Hirano, Shigeo Nagaya

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 ( 3 ) 4702804 2012.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

In this paper, we focus on the quench detection and protection of a cryocooler-cooled pancake coil for SMES wound with a YBCO bundle conductor composed of laminated electrically insulated YBCO-coated conductors. Because the normal-zone propagation velocity is much slower in a high-temperature superconducting (HTS) coil than in a low-temperature superconducting (LTS) coil, the detection of the non-recovering normal zone using a voltage signal is quite difficult. Quench detection is considered to be more difficult during SMES operation because of the noise of the converter or other equipment. Therefore, a quench must be detected using some other method. In the previous paper, we showed that a quench in the coil could be detected by observing the transposition of the current in the bundle conductor caused by local normal transition. In this paper, based on this quench detection method, we investigate the transposition of current and the thermal behavior during the quench detection and the dumping of the stored energy by an external resistance in coils wound with a YBCO laminated bundle conductor for SMES and determine the appropriate stabilizer thickness of the YBCO-coated conductors.

DOI： 10.1109/TASC.2011.2174578

Transport and emittance study for 18 GHz superconducting-ECR ion source at RCNP Reviewed

T. Yorita, K. Hatanaka, M. Fukuda, H. Ueda, M. Kibayashi, S. Morinobu, A. Tamii

REVIEW OF SCIENTIFIC INSTRUMENTS 83 ( 2 ) 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

As the upgrade program of the azimuthally varying field (AVF) cyclotron is at the cyclotron facility of the RCNP, Osaka University for the improvement of the quality, stability, and intensity of accelerated beams, an 18 GHz superconducting (SC) ECR ion source has been installed to increase beam currents and to extend the variety of ions, especially for highly charged heavy ions which can be accelerated by RCNP AVF cyclotron. The production development of several ions such as B, O, N, Ne, Ar, Ni, Kr, and Xe has been performed by Yorita et al. [Rev. Sci. instrum. 79, 02A311(2008); 81, 02A332 (2010)]. Further studies for the beam transport have been done in order to improve the beam current more for injection of cyclotron. The effect of field leakage of AVF main coil is not negligible and additional steering magnet has been installed and then beam transmission has been improved. The emittance monitor has also been developed for the purpose of investigating correlation between emittance of beam from ECR ion sources and injection efficiency. The monitor consists with :BPM82 with rotating wire for fast measurement for efficient study. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3671748]

DOI： 10.1063/1.3671748

Developments of hts magnets

Kichiji Hatanaka, Mitsuhiro Fukuda, Nobuhiko Izumi, Takane Saito, Hiroshi Ueda, Tetsuhiko Yorita, Yuusuke Yasuda, Keita Kamakura, Noriaki Hamatani, Takeo Kawaguchi

IPAC 2012 - International Particle Accelerator Conference 2012 1095 - 1097 2012

Language：English Publishing type：Research paper (international conference proceedings)

We have been developing mgnets utilizing hightemperature superconducting (HTS) wiresfor a decade. We have investigated the performance of HTS wires excited by alternatingcurrents as well as direct currents. A scanning magnet was designed, fabricated, and testedfor its suitability as a beam scanner. After successful cooling tests, the magnetperformance was investigated in AC mode. The magnet was operated at frequencies of 10- 20Hzand 20K. The power loss dissipated in the coils was measured and compared with the modelcalculations. In order to check feasibilities of pulse magnet using HTS wire, we havefabricated a super-ferric dipole magnet to be operated by lumping currents. Preliminaryperformance is described. Copyright © 2012 by IEEE.

Evaluation of Positional Stability in Active Magnetic Levitation Using Spherical HTS Bulk for Inertial Nuclear Fusion Reviewed

Tao Wang, Hiroshi Ueda, Koh Agatsuma, Atsushi Ishiyama

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 1579 - 1583 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Fuel supply is a fundamental issue in application of inertial nuclear fusion. To address this issue, we propose the use of an HTS superconductor capsule containing nuclear fuel, which can levitate in a magnetic field. During magnetic levitation, positional stability is important because it affects levitation accuracy to the focal point of giant lasers. We have developed a numerical simulation program based on a 3-D hybrid finite element and boundary element method to evaluate positional stability during magnetic levitation. Moreover, we have optimally designed and constructed a multi-coil system wherein spherical HTS bulk of 5 mm diameter can levitate stably. Finally, we have conducted the experiments for the evaluation of magnetic levitation, and compared the results with our simulation.

DOI： 10.1109/TASC.2010.2098383

Current Margin Against the Fault Current in REBCO Coated Conductors Reviewed

Atsusi Ishiyama, Hiroshi Momotari, Xudong Wang, Michio Arai, Hiroshi Ueda, Masayoshi Ohya, Kazuya Ohmatsu, Noboru Fujiwara

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 3033 - 3036 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

The application of yttrium barium copper oxide (YBCO) coated conductors in power cables is anticipated. In practical applications, high-temperature superconducting (HTS) cables can be subjected to short-circuit fault current and are expected to operate for over 30 years. In order to safeguard the current margin of YBCO coated conductors against fault current, we carried out preliminary experiments on overcurrent characteristics using an HTS model cable. Meanwhile, we performed numerical simulations to clarify the electromagnetic and thermal behaviors of the HTS model cable. In this study, we numerically simulated the fault current waveform in each YBCO coated conductor that constitutes an entire cable. We then carried out experiments focusing on the current-voltage (I - V) characteristics and the current margin without causing critical current (I(c)) degradation against the fault current by varying the amplitude of the waveform obtained numerically. Furthermore, we repeatedly applied the fault current to a YBCO coated conductor to experimentally investigate the I(c) degradation caused by iterative fault current.

DOI： 10.1109/TASC.2010.2086413

Degradation of YBCO Coated Conductors Due to an Over-Current Pulse Reviewed

Atsushi Ishiyama, Michio Arai, Hiroshi Momotari, Xudong Wang, Hiroshi Ueda, Takashi Saito, Yuji Aoki, Masashi Yagi, Takato Machi, Noboru Fujiwara

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 3025 - 3028 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

YBCO coated conductors are candidate materials for future electric power devices such as transmission cables, transformers, and fault current limiters. In practical applications, YBCO coated conductors are subject to short-circuit fault currents greater than the operating current. These fault currents cause heat generation, resulting in degradation of the characteristics of YBCO coated conductors. It is therefore necessary to identify the maximum temperatures under which YBCO coated conductors can operate without suffering degradation. To date, we have carried out preliminary experiments on the degradation of YBCO coated conductors due to an over-current pulse. We also focused on the relationship between increases in temperature and Ic degradation. In this study, we prepared YBCO coated conductors fabricated by TFA-MOD method. We also carried out over-current tests to investigate the Ic degradation and performed numerical simulations on thermal stress to estimate the stress and strain acting on the YBCO layer.

DOI： 10.1109/TASC.2010.2092396

Quench Behavior and Protection in Cryocooler-Cooled YBCO Pancake Coil for SMES Reviewed

Atsushi Ishiyama, Hiroshi Ueda, Yoshiaki Aoki, Koji Shikimachi, Naoki Hirano, Shigeo Nagaya

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 2398 - 2401 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

The thermal behavior of a high-temperature superconducting (HTS) coil is significantly different from that of low-temperature superconducting (LTS) coil because it has a greater volumetric heat capacity at the temperature required for practical use. Therefore, the possibility of quench in HTS coils is much lower than that in LTS coils. In the application of the YBCO coil to Superconducting Magnetic Energy Storage (SMES) system, electrical charging and discharging are repeated; therefore, the superconducting characteristics of the YBCO coated conductor may deteriorate as a result of cyclic subjection to tensile strain. To enhance the reliability and safety of HTS coil, protection scheme assuming a quench is also required for HTS coil. In this study, we focus on the coil wound with YBCO laminated bundle (parallel) conductor supposing SMES application and investigate the characteristics of normal-zone propagation and the thermal behavior within the coil during a quench by using a newly developed computer code based on the finite element method and an equivalent circuit. And we also propose a quench detection method using observation of nonuniform current in YBCO laminated bundle conductor and discuss the validity of the detection method comparing with conventional quench-voltage detection.

DOI： 10.1109/TASC.2010.2093491

Over-Current Characteristics of 275-kV Class YBCO Power Cable

Atsushi Ishiyama, Xudong Wang, Hiroshi Ueda, Toshikuni Uryu, Masashi Yagi, Noboru Fujiwara

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 1017 - 1020 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

In Japan, a project for the development of a 275-kV class YBCO power cable started in 2008. High-temperature superconducting (HTS) power cables typically consist of a copper former, an HTS conductor layer, an electrical insulation layer, an HTS shield layer, and a copper shield layer. In practical applications, the 275-kV class transmission line may be subjected to short-circuit fault currents such as 63 kA(rms) for a duration of 0.6 s. Therefore, in order to ensure the stability and demonstrate the feasibility of the cable, it is important to estimate the current distribution and temperature increase under the fault condition. We designed the copper former, copper shield layer, and copper plating of the YBCO coated conductor carefully so as to fulfill the requirements of practical applications. In this study, we carried out over-current experiments on a 2-m long YBCO model cable and performed numerical simulations by a computer program developed using the finite element method (FEM) and an electric circuit model. We investigated the electromagnetic and thermal behaviors of the cable under fault conditions from the experimental and simulation results.

DOI： 10.1109/TASC.2010.2085413

Development of high-quality intense proton beam at the rcnp cyclotron facility Reviewed

M. Fukuda, K. Hatanaka, T. Yorita, H. Yamamoto, T. Saito, H. Ueda, H. Tamura, M. Kibayashi, K. Nagayama, Y. Yasuda, S. Morinobu, S. Kurashima

IPAC 2011 - 2nd International Particle Accelerator Conference 2694 - 2696 2011

Publishing type：Research paper (international conference proceedings)

An upgrade program for increase of beam intensity and improvement of beam quality is in progress at the cyclotron facility of Research Center for Nuclear Physics(RCNP). A 2.45 GHz ECR proton source was modified to increase 392 MeV proton beam intensity. Rated output power of a microwave power supply was increased from 200 W to 2 kW. A water-cooled waveguide system for high power microwave transfer is being installed for the proton source. A 15 keV proton beam with intensity of 0.6 mA was stably produced for output microwave power of 200 W. Emittance of 50 to 100 mm-mrad was obtained for 0.05 to 0.1 mA proton beams in the LEBT system. Beam transmission, defined by the ratio of the beam intensity between a Faraday cup placed in the axial injection beam line and an inflector electrode of the AVF cyclotron, was improved from 25 % for a 0.07 mA proton beam to more than 90 % for 0.03 mA, which indicated that the beam transmission was limited by the acceptance of the axial injection beam line. A new active gradient corrector is being designed for horizontal beam focusing in the extraction region of the AVF cyclotron and for reducing a beam loss at the vacuum chamber in the extraction region. An asymmetric dee voltage distribution at an acceleration gap is being analyzed for improvement of a flat-top acceleration system of the AVF cyclotron. Copyright © 2011 by IPAC'11/EPS-AG.

Design of hts sector magnets for the rcnp new injector cyclotron

Kichiji Hatanaka, Mitsuhiro Fukuda, Tetsuhiko Yorita, Hiroshi Ueda, Hitoshi Tamura, Mitsuru Kibayashi, Keichi Nagayama, Yuusuke Yasuda, Takane Saito, Shunpei Morinobu, Nobuhiko Izumi, Takeo Kawaguchi

IPAC 2011 - 2nd International Particle Accelerator Conference 2460 - 2462 2011

Language：English Publishing type：Research paper (international conference proceedings)

The RCNP cyclotron cascade system consists of K140 AVF cyclotron and K400 ring cyclotron and is providing high quality beams for various experiments. There are increasing demands for high intensity beams and even to improve the quality. In order to increase the physics research opportunities, a new injector cyclotron is recently proposed, which has four separated sector magnets and two accelerating cavities. Sector magnets are designed to use High Temperature Superconducting (HTS) wire. At RCNP we have been developing magnets with HTS wires for a decade. In this paper, we will report recent results of developed HTS magnets and the design of sector magnets for the new injector SSC. Copyright © 2011 by IPAC'11/EPS-AG.

Degradation characteristics of YBCO coated conductors due to fault-current in power cable applications Reviewed

H. Kono, X. Wang, H. Ueda, A. Ishiyama, T. Saitoh, Y. Aoki, M. Yagi, S. Mukoyama, N. Fujiwara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1334 - 1337 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In high temperature superconductor applications used in electric power devices, YBCO coated conductors may be subjected to short-circuit fault-currents that are 10-30 times the normal operating current. These over-currents cause heat generation, resulting in 1, degradation of the YBCO coated conductor. Therefore, it is necessary to fully investigate the degradation characteristics of YBCO coated conductors. We previously conducted preliminary experiments on the degradation of YBCO sample tapes resulting from the over-current pulse drive.
In this study, we analyzed the waveform of fault-current that is supposed to flow into the YBCO coated conductor when a short-circuit fault occurs in a power cable application, by using a newly developed numerical simulation program. We also carried out experiments in which an over-current with the analyzed fault-current waveform was applied to two YBCO sample tapes. We then investigated the degradation characteristics, focusing on the amount of current permitted. Experimental results showed that both the sample tapes (initial I(c) = 118.6 A and 123.2 A) were degraded by applying an over-current with a peak value of 320 A. (C) 2010 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2010.05.106

Design and evaluation of 66 kV class RE-123 superconducting cable Reviewed

T. Minamino, M. Ohya, H. Yumura, T. Masuda, T. Nagaishi, Y. Shingai, X. Wang, H. Ueda, A. Ishiyama, N. Fujiwara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1576 - 1579 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In the new national project, as wire and cable development, Sumitomo Electric Industries, Ltd. (SEI) is trying to develop a 66 kV/5 kArms high temperature superconducting (HIS) cable with its own REBa(2)Ca(3)O(x) (RE-123, RE = rare earth element) coated conductors. In an actual power grid, an inflow of current higher than the normal rated power (fault-current) can occur. The maximum fault-current condition is set at 31.5 kArms for 2s for 66 kV-class transmission system in this project. Therefore, one of the technical targets in this project is to design the wires and cables to survive at this fault-current condition. As the first step, the prototype HIS cable was designed against the fault-current condition of 31.5 kArms for 2 s. The wires have copper plating as a stabilizer layer not to be damaged by over-currents. The designed HIS cable has a copper former and copper shield layers in parallel with the HIS conducting layers and HTS shield layers, respectively, to control the temperature rises in the cable core at fault-current conditions. As the second step, a sample HIS cable core was fabricated and fault-current tests were conducted to check its soundness. The temperature rises in the cable core were measured under various fault-current conditions. The critical current of the cable core was measured before and after the fault-current tests, and no deterioration in the critical current characteristics was observed. However, there was slight degradation of the n value. The investigation will be conducted, and the results will be fed back to designs of the RE-123 wires and cables. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.165

Computer simulation of fault current characteristics in 275 kV class YBCO power cable Reviewed

S. Sato, X. Wang, H. Ueda, A. Ishiyama, M. Yagi, S. Mukoyama, T. Saitoh, Y. Aoki, N. Fujiwara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1572 - 1575 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In japan, the development of a 275 kV class YBCO power cable was started in 2008 with the support of the New Energy and Industrial Technology Development Organization (NEDO). In the designing of 275 kV YBCO power cable, the thickness of insulator is required to be 26 mm. Thus, in order to design the 275 kV YBCO power cable, it is important to estimate the thermal diffusion through the electrical insulation layer for designing the high-voltage YBCO power cable. Furthermore, YBCO power cables might be subjected to short-circuit fault currents that are 10-30 times a normal operating current. Therefore, in order to ensure stability and feasibility of superconducting power cables, we need to investigate the thermal characteristics and current distribution in the cable in the normal and fault conditions. The objective of this study is to investigate the thermal characteristics and dielectric performance in 275 kV class power cables. We carried out experiments on dummy cables in a steady state to clarify the distribution of temperature. In order to estimate the thermal conductivity and the heat capacity of the insulation layer, we performed numerical simulations using a developed computer program on the basis of the 3D finite element method. We also measured a tans and permittivity of an insulation layer in order to investigate the dielectrical performance. (C) 2010 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2010.05.164

Numerical simulation on fault current condition in 66 kV class RE-123 superconducting cable Reviewed

X. Wang, H. Ueda, A. Ishiyama, M. Ohya, H. Yumura, N. Fujiwara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1580 - 1583 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The new Japanese national project of development of 66 kV/5 kA high-temperature superconducting (HIS) power cables has been started since 2008. In an AC power system, a fault current may flow in the event of a short circuit accident. The maximum fault current condition is defined to be 31.5 kA(rms) for duration of 2 s for 66 kV class transmission line in this project. Therefore, one of the technical targets in this project is to design the HIS power cable to survive at this fault current condition. The coated conductors have copper layer as a stabilizer not to be damaged by over-currents. The HIS cable has a copper former and copper shield layers in parallel with the HIS conductor layers and HIS shield layers, respectively, to control the temperature rises in the HIS cable at a fault accident. In this study, we simulated the maximum temperature rises in the HIS power cable at the fault current condition of 31.5 kA(rms) for 25 in order to design the copper stabilizer and copper shield layers by using a computer program we developed on the basis of 3D finite element method (FEM) and electrical circuit model. (C) 2010 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2010.05.166

Determination of stabilizer thickness for YBCO coated conductors based on coil protection Reviewed

Y. Kawai, A. Ishiyama, H. Ueda, S. Nagaya, K. Shikimachi, N. Hirano

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1865 - 1869 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The possibility of the occurrence of quench caused by mechanical disturbance in high-temperature superconductors (HTS's) is much lower than that in low-temperature superconductors. However, to enhance the reliability and safety of HTS coils, it is necessary to establish a stability criterion and a protection scheme on the basis of the assumption that the quench is caused by the failure in power supply, cooling systems, etc. In this study, we assume that the stored magnetic energy in the HTS coil is dissipated by an external resistance that acts as a quench protection. Under this assumption, we derive a function that examines the heat balance of quenching YBCO coil under an adiabatic condition and propose a criterion using the derived function to determine an appropriate stabilizer thickness of YBCO conductors. (C) 2010 Published by Elsevier B.V.

DOI： 10.1016/j.physc.2010.05.224

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