掲載種別：研究論文（学術雑誌）  

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掲載種別：研究論文（国際会議プロシーディングス）  

LiteBIRD is a JAXA-led strategic large-class satellite mission designed to
measure the polarization of the cosmic microwave background and Galactic
foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020s.
The scientific payload includes three telescopes which are called the low-,
mid-, and high-frequency telescopes each with their own receiver that covers a
portion of the mission's frequency range. The low frequency telescope will map
synchrotron radiation from the Galactic foreground and the cosmic microwave
background. We discuss the design, fabrication, and characterization of the
low-frequency focal plane modules for low-frequency telescope, which has a
total bandwidth ranging from 34 to 161 GHz. There will be a total of 4
different pixel types with 8 overlapping bands to cover the full frequency
range. These modules are housed in a single low-frequency focal plane unit
which provides thermal isolation, mechanical support, and radiative baffling
for the detectors. The module design implements multi-chroic lenslet-coupled
sinuous antenna arrays coupled to transition edge sensor bolometers read out
with frequency-domain mulitplexing. While this technology has strong heritage
in ground-based cosmic microwave background experiments, the broad frequency
coverage, low optical loading conditions, and the high cosmic ray background of
the space environment require further development of this technology to be
suitable for LiteBIRD. In these proceedings, we discuss the optical and
bolometeric characterization of a triplexing prototype pixel with bands
centered on 78, 100, and 140 GHz.

DOI： 10.1117/12.2630574

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arXiv

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その他リンク： http://arxiv.org/pdf/2209.09864v1

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

The data from the Planck and Herschel space observatories revealed that the cosmic rays at L2 orbit can have a significant impact on the performance of scientific instruments. In this paper, we present our simulation results of such impacts on SAFARI/SPICA, a far-infrared spectrometer equipped with transition-edge sensors (TESs). These TESs are fabricated on SiN membranes and suspended by long and thin SiN legs that thermally isolate them from the surrounding silicon structure (wafer). Cosmic rays that pass through this surrounding structure deposit a portion of their energy, leading to temperature fluctuations in the wafer. These temperature fluctuations are sensed by the TES detectors as an effective bath temperature and result in additional noise. To simulate the impact, we generate a 2D model of the wafer and the suspended TESs in COMSOL 5.4. This 2D model is bombarded with 128 randomly generated cosmic rays according to the observed energy distributions at L2. Subsequently, the temperature fluctuations at different points on the wafer are estimated. Our results show that these thermal fluctuations, as well as the calculated additional TES noise caused by them, depend strongly on the heat-sink design of the wafer. We study the impact of the different heat sink designs on the noise profile of the system. Later, these results are compared to the SAFARI instrument noise requirements.

DOI： 10.1007/s10909-022-02815-8

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掲載種別：研究論文（学術雑誌）  

Feedhorn- and orthomode transducer- (OMT) coupled transition edge sensor (TES) bolometers have been designed and micro-fabricated to meet the optical specifications of the LiteBIRD high frequency telescope (HFT) focal plane. We discuss the design and optical characterization of two LiteBIRD HFT detector types: dual-polarization, dual-frequency-band pixels with 195/280 GHz and 235/337 GHz band centers. Results show well-matched passbands between orthogonal polarization channels and frequency centers within 3% of the design values. The optical efficiency of each frequency channel is conservatively reported to be within the range 0.64- 0.72, determined from the response to a cryogenic, temperature-controlled thermal source. These values are in good agreement with expectations and either exceed or are within 10% of the values used in the LiteBIRD sensitivity forecast. Lastly, we report a measurement of loss in Nb/SiNx/Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature.

DOI： 10.1007/S10909-022-02808-7

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

LiteBIRD is a space-borne experiment dedicated to detecting large-scale B-mode anisotropies of the linear polarization of the cosmic microwave background (CMB) predicted by the theory of inflation. It is planned to be launched in the late 2020s to the second Lagrangean point of the Sun-Earth system and map the sky in 15 frequency bands using thousands of transition edge sensor bolometers. LiteBIRD will be exposed to the cosmic-ray radiation throughout its lifetime, which may lead to the degradation of the scientific performance. Energy deposition by cosmic rays upon the focal plane bolometer detectors is considered a serious source of systematic effects. For a quantitative assessment of the effect, we present the result of Geant4 simulations to estimate the energy deposited by cosmic rays into the focal plane. We simulated different cosmic-ray components using CAD-based spacecraft models. We derive the spatial and energy distribution of the particles in the focal plane.

DOI： 10.1117/12.2629759

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掲載種別：研究論文（国際会議プロシーディングス）  

The BISOU (Balloon Interferometer for Spectral Observations of the Universe) project studies the viability and prospects of a balloon-borne spectrometer, pathfinder of a future space mission dedicated to the measurements of the CMB spectral distortions, while consolidating the instrumental concept and improving the readiness of some of its key sub-systems. A balloon concept based on a Fourier Transform Spectrometer, covering a spectral range from about 90 GHz to 2 THz, adapted from previous mission proposals such as PIXIE and FOSSIL, is being studied and modelled. Taking into account the requirements and conditions of balloon flights (i.e. residual atmosphere, observation strategy for instance), we present here the instrument concept together with the results of the CNES phase 0 study, evaluating the sensitivity to some of its potential observables. For instance, we forecast a detection of the CMB Compton y-distortion monopole with a signal-To-noise ratio of at least 5.

DOI： 10.1117/12.2630136

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP Publishing Ltd  

Systematic effects arising from cosmic rays have been shown to be a significant threat to space telescopes using high-sensitivity bolometers. The LiteBIRD space mission aims to measure the polarised Cosmic Microwave Background with unprecedented sensitivity, but its positioning in space will also render it susceptible to cosmic ray effects. We present an end-to-end simulator for evaluating the expected scale of cosmic ray effects on the LiteBIRD space mission, which we demonstrate on a subset of detectors on the 166 GHz band of the Low Frequency Telescope. The simulator couples the expected proton flux at L2 with a model of the thermal response of the LFT focal plane and the electrothermal response of its superconducting detectors, producing time-ordered data which is projected into simulated sky maps and subsequent angular power spectra.

DOI： 10.1088/1475-7516/2021/09/013

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arXiv

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その他リンク： http://arxiv.org/pdf/2107.00473v1

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 mu K-arcmin with a typical angular resolution of 0.5 degrees at 100 GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes.

DOI： 10.1117/12.2563050

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

LiteBIRD is a proposed JAXA satellite mission to measure the CMB B-mode polarization with unprecedented sensitivity ( r 0.001). To achieve this goal, 4676 stateof-the-art TES bolometers will observe the whole sky for 3 years from L2. These detectors, as well as the SQUID readout, are extremely susceptible to EMI and other instrumental disturbances, e.g., static magnetic field and vibration. As a result, careful analysis of the interference between the detector system and the rest of the telescope instruments is essential. This study is particularly important during the early phase of the project, in order to address potential problems before the final assembly of the whole instrument. We report our plan for the preparation of a cryogenic testbed to study the interaction between the detectors and other subsystems, especially a polarization modulator unit consisting of a magnetically rotating half-wave plate. We also present the requirements, current status and preliminary results.

DOI： 10.1007/s10909-020-02359-9

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arXiv

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その他リンク： http://arxiv.org/pdf/1911.11902v1

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

Recent developments of transition-edge sensors (TESs), based on extensive experience in ground-based experiments, have been making the sensor techniques mature enough for their application on future satellite cosmic microwave background (CMB) polarization experiments. LiteBIRD is in the most advanced phase among such future satellites, targeting its launch in Japanese Fiscal Year 2027 (2027FY) with JAXA's H3 rocket. It will accommodate more than 4000 TESs in focal planes of reflective low-frequency and refractive medium-and-high-frequency telescopes in order to detect a signature imprinted on the CMB by the primordial gravitational waves predicted in cosmic inflation. The total wide frequency coverage between 34 and 448 GHz enables us to extract such weak spiral polarization patterns through the precise subtraction of our Galaxy's foreground emission by using spectral differences among CMB and foreground signals. Telescopes are cooled down to 5 K for suppressing thermal noise and contain polarization modulators with transmissive half-wave plates at individual apertures for separating sky polarization signals from artificial polarization and for mitigating from instrumental 1/f noise. Passive cooling by using V-grooves supports active cooling with mechanical coolers as well as adiabatic demagnetization refrigerators. Sky observations from the second Sun-Earth Lagrangian point, L2, are planned for 3 years. An international collaboration between Japan, the USA, Canada, and Europe is sharing various roles. In May 2019, the Institute of Space and Astronautical Science, JAXA, selected LiteBIRD as the strategic large mission No. 2.

DOI： 10.1007/s10909-019-02329-w

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

We introduce the 'Joule stepping' technique, whereupon a constantly biased bolometer has its bias voltage modified by a small additional step. We demonstrate this technique using a composite NTD semiconductor bolometer and a pulsing device that sends an extra step in voltage. We demonstrate the results of the technique over a range of bias voltages at 100, 200 and 300 mK. Joule stepping allows us to directly measure long thermal tails with low amplitudes in the response of the global thermal architecture of bolometers and could be a useful tool to quickly and easily calibrate the thermal time response of individual bolometric detectors or channels. We also show that the derivative of the Joule step is equivalent to the bolometer response to a delta-pulse (or Joule pulse), which allows for greater understanding of transient behaviour with a better signal-to-noise ratio than pulsing alone can provide. Finally, we compare Joule step pulses with pulses produced by alpha particles, finding a good agreement between their fast decay constants, but a discrepancy between their thermal decay constants.

DOI： 10.1007/s10909-019-02302-7

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arXiv

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その他リンク： http://arxiv.org/pdf/1912.04276v1

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

We present the design and implementation of a thermal model, developed in COMSOL, aiming to probe the wafer-scale thermal response arising from realistic rates and energies of cosmic rays at L2 impacting the detector wafer of Athena X-IFU. The wafer thermal model is a four-layer 2D model, where two layers represent the constituent materials (Si bulk and Si3N4 membrane) and two layers represent the Au metallization layer's phonon and electron temperatures. We base the simulation geometry on the current specifications for the X-IFU detector wafer and simulate cosmic ray impacts using a simple power injection into the Si bulk. We measure the temperature at the point of the instrument's most central TES detector. By probing the response of the system and pulse characteristics as a function of the thermal input energy and location, we reconstruct cosmic ray pulses in Python. By utilizing this code, along with the results of the GEANT4 simulations produced for X-IFU, we produce realistic time-ordered data (TOD) of the temperature seen by the central TES, which we use to simulate the degradation of the energy resolution of the instrument in space-like conditions on this wafer. We find a degradation to the energy resolution of 7 keV X-rays of approximate to 0.04 eV. By modifying wafer parameters and comparing the simulated TOD, this study is a valuable tool for probing design changes on the thermal background seen by the detectors.

DOI： 10.1007/s10909-020-02380-y

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arXiv

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その他リンク： http://arxiv.org/pdf/2001.11646v1

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER/PLENUM PUBLISHERS  

For the future satellite mission at the second sun-earth Lagrangian point (L2), we need to mitigate phonon propagation created by cosmic rays to superconducting detectors. We simulate phonon propagation in silicon substrate and show that putting a metal layer on the substrate or making hole in the substrate reduces the propagation. We also show a function which shows the response of a TES bolometer on a substrate. To validate these theoretical expectations, we make irradiation tests using two types of superconducting detectors: transition edge sensor bolometers and kinetic inductance detectors. From the tests, we show that putting metal can reduce correlations between detectors and number of hit events from charged particles.

DOI： 10.1007/s10909-020-02393-7

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掲載種別：研究論文（学術雑誌）  

The X-ray Integral Field Unit (X-IFU) will operate an array of more than 3000 Transition Edge Sensor pixels at 90 mK with an unprecedented energy resolution of 2.5 eV at 7 keV. In space, primary cosmic rays and secondary particles produced in the instrument structure will continuously deposit energy on the detector wafer and induce fluctuations on the pixels’ thermal bath. We have investigated through simulations of the X-IFU readout chain how these fluctuations eventually influence the energy measurement of X-ray photons. Realistic timelines of thermal bath fluctuations at different positions in the array are generated as a function of a thermal model and the expected distribution of the deposited energy of the charged particles. These are then used to model the TES response to these thermal perturbations and their influence on the onboard energy reconstruction process. Overall, we show that with adequate heatsinking, the main energy resolution degradation effect remains minimal and within the associated resolution allocation of 0.2 eV. We further study how a dedicated triggering algorithm could be put in place to flag the rarer large thermal events.

DOI： 10.1007/s10909-019-02330-3

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掲載種別：研究論文（学術雑誌）  

The Polarized Instrument for Long-wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon-borne experiment that aims to measure the polarized emission of thermal dust at a wavelength of 240 µm (1.2 THz). A first PILOT flight of the experiment took place from Timmins, Ontario, Canada, in September 2015 and a second flight took place from Alice Springs, Australia in April 2017. In this paper, we present the inflight performance of the instrument. Here we concentrate on the instrument performance as measured during the second flight, but refer to the performance observed during the first flight, if it was significantly different. We present a short description of the instrument and the flights. We measure the time constants of the detectors using the decay of the observed signal during flight following high energy particle impacts (glitches) and switching off the instrument’s internal calibration source. We use these time constants to deconvolve the timelines and analyze the optical quality of the instrument as measured on planets. We then analyze the structure and polarization of the instrumental background. We measure the detector response flat field and its time variations using the signal from the residual atmosphere and from the internal calibration source. Finally, we analyze the spectral and temporal properties of the detector noise. The inflight performance is found to be satisfactory and globally in line with expectations from ground calibrations. We conclude by assessing the expected inflight sensitivity of the instrument in light of the measured inflight performance.

DOI： 10.1007/s10686-019-09648-6

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記述言語：英語   掲載種別：学位論文（博士）  

We have studied the effect of cosmic rays in detectors using a composite NTD germanium bolometer at low temperatures and an alpha particle source as a generic source of pulses. We have characterised this bolometer, finding that its pulse shape is due to a combination of its impulse response function (the sum of two double exponentials), and position-dependent effects arising from thermalisation of ballistic phonons into thermal phonons in its absorber. We have derived a scheme for describing the pulse shape in this bolometer, comparing a generic mathematical pulse shape with a second description based on thermal physics. We find that ballistic phonon thermalisation, followed by thermal diffusion, play a significant role in the pulse shape, along with electro-thermal coupling and temperature-dependent electrical effects. We have modelled the pulses, finding that their behaviour can be reproduced accounting for ballistic phonon reflection off the absorber border, with a strong thermal coupling to the bolometer’s central sensor. With these findings, we also investigate the effects of cosmic rays on the Athena X-Ray Integral Field Unit (X-IFU), producing simulated timelines and testing the average RMS temperature increase on the detector wafer, showing that the expected cosmic ray thermal flux is within the same order of magnitudeas the maximum allowed ΔTRMS, posing a threat to the instrument’s energy resolution budget.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

Cosmology space missions have been known to be particularly sensitive to systematic effects arising from the interaction between cosmic rays and highly sensitive detectors below 200 mK. To remove this signal, one must first understand the deposition and dissipation of energy into these detectors. Using a well-known NTD germanium composite bolometer, we simulate the effect of cosmic rays using a radioactive source in the laboratory. Through analysis of experimental data, we find that the glitch signal shape is a function of incoming particle position, as well as the incoming particle energy. We report also on nonlinear effects in the fit, in order to lay the groundwork towards a new physical model for this energy propagation in the bolometer.

DOI： 10.1088/1748-0221/14/01/P01012

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

The next generation of cosmology space missions will be sensitive to parasitic signals arising from cosmic rays. Using a composite bolometer, we have investigated pulses produced by alpha particles in order to understand the movement of energy produced by ionising radiation. Using a series of measurements at 100 mK, we have compared the typical fitting algorithm (a mathematical model) with a second method of pulse interpretation by convolving the detector's thermal response function with a starting profile of thermalised athermal phonons, taking into account the effects of heat propagation. Using this new fitting method, we have eliminated the need for a non-physical quadratic nonlinearity factor produced using more common methods, and we find a pulse form in good agreement with known aspects of thermal physics. This work is carried forward in the effort to produce a physical model for energy deposition in this detector. The modelling is motivated by the reproduction of statistical features in the experimental dataset, and the new interpretation of alpha pulse shapes represents an improvement in the current understanding of the energy propagation mechanisms in this detector.

DOI： 10.1117/12.2313968

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

Cosmic rays affect the performance of any detector in space through the creation of spurious signal and/or slow build-up of radiation damage. To mitigate the effects of these high-energy particles on the observations of next-generation space missions, the interaction between state-of-the-art detectors will have to be understood through simulation and experimental verification. We present the first measurement results of a new cryogenic system designed to become a common-user test facility to evaluate the effects of high-energy particles on arrays of these high-sensitivity detectors. The system is based on pulse-tube precooled dilution refrigerator with a large experimental volume (phi = 29 cm, H = 30 cm). At 100 mK the system provides 650 mu W of cooling power and an out-of-the box thermal stability of 76 mu K rms. A first experiment with a semiconducting bolometer from the DIABOLO experiment shows a responsivity and noise level consistent with previous measurement in different cryogenic systems. However, the pulse-tube induced vibrations show as clear features in the noise. To irradiate the detectors a particle beam, such as the 25 MeV proton beam of the nearby ALTO facility, can be coupled to one of four ports. Simulations show that the aluminum-coated Mylar windows do not significantly affect the 25 MeV proton beam of TANDEM. First experiments at the ALTO facility for system verification are expected early 2019. Until that time, the thermal stability, vibration damping and EMI shielding will be improved and a flexible wiring will be developed, to accommodate multiple detector types.

DOI： 10.1117/12.2311686

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掲載種別：研究論文（学術雑誌）  

PILOT is a balloon-borne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy at wavelengths 240 and 550 µm with an angular resolution of about two arc-min. PILOT optics is composed of an off-axis Gregorian telescope and a refractive re-imager system. All these optical elements, except the primary mirror, are in a cryostat cooled to 3K. We used optical and 3D measurements combined with thermo-elastic modeling to perform the optical alignment. This paper describes the system analysis, the alignment procedure, and finally the performances obtained during the first flight in September 2015.

DOI： 10.1007/s12567-017-0159-3

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LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to
observe the cosmic microwave background (CMB) $B$-mode polarization over the
full sky at large angular scales. The challenges of LiteBIRD are the wide
field-of-view (FoV) and broadband capabilities of millimeter-wave polarization
measurements, which are derived from the system requirements. The possible
paths of stray light increase with a wider FoV and the far sidelobe knowledge
of $-56$ dB is a challenging optical requirement. A crossed-Dragone
configuration was chosen for the low frequency telescope (LFT : 34--161 GHz),
one of LiteBIRD's onboard telescopes. It has a wide field-of-view ($18^\circ
\times 9^\circ$) with an aperture of 400 mm in diameter, corresponding to an
angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0
and the crossing angle of the optical axes of 90$^\circ$ are chosen after an
extensive study of the stray light. The primary and secondary reflectors have
rectangular shapes with serrations to reduce the diffraction pattern from the
edges of the mirrors. The reflectors and structure are made of aluminum to
proportionally contract from warm down to the operating temperature at $5\,$K.
A 1/4 scaled model of the LFT has been developed to validate the wide
field-of-view design and to demonstrate the reduced far sidelobes. A
polarization modulation unit (PMU), realized with a half-wave plate (HWP) is
placed in front of the aperture stop, the entrance pupil of this system. A
large focal plane with approximately 1000 AlMn TES detectors and frequency
multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous
antennas have broadband capability. Performance specifications of the LFT and
an outline of the proposed verification plan are presented.

DOI： 10.1117/12.2561841

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arXiv

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その他リンク： http://arxiv.org/pdf/2101.06342v1

LiteBIRD is a JAXA-led strategic Large-Class satellite mission designed to
measure the polarization of the cosmic microwave background and cosmic
foregrounds from 34 to 448 GHz across the entire sky from L2 in the late
2020's. The primary focus of the mission is to measure primordially generated
B-mode polarization at large angular scales. Beyond its primary scientific
objective LiteBIRD will generate a data-set capable of probing a number of
scientific inquiries including the sum of neutrino masses. The primary
responsibility of United States will be to fabricate the three flight model
focal plane units for the mission. The design and fabrication of these focal
plane units is driven by heritage from ground based experiments and will
include both lenslet-coupled sinuous antenna pixels and horn-coupled orthomode
transducer pixels. The experiment will have three optical telescopes called the
low frequency telescope, mid frequency telescope, and high frequency telescope
each of which covers a portion of the mission's frequency range. JAXA is
responsible for the construction of the low frequency telescope and the
European Consortium is responsible for the mid- and high- frequency telescopes.
The broad frequency coverage and low optical loading conditions, made possible
by the space environment, require development and adaptation of detector
technology recently deployed by other cosmic microwave background experiments.
This design, fabrication, and characterization will take place at UC Berkeley,
NIST, Stanford, and Colorado University, Boulder. We present the current status
of the US deliverables to the LiteBIRD mission.

DOI： 10.1117/12.2562978

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arXiv

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その他リンク： http://arxiv.org/pdf/2101.05306v1

記述言語：英語   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

We present three Monte Carlo models for the propagation of athermal phonons
in the diamond absorber of a composite semiconducting bolometer `Bolo 184'.
Previous measurements of the response of this bolometer to impacts by $\alpha$
particles show a strong dependence on the location of particle incidence, and
the shape of the response function is determined by the propagation and
thermalisation of athermal phonons. The specific mechanisms of athermal phonon
propagation at this time were undetermined, and hence we have developed three
models for probing this behaviour by attempting to reproduce the statistical
features seen in the experimental data. The first two models assume a phonon
thermalisation length determined by a mean free path $\lambda$, where the first
model assumes that phonons thermalise at the borders of the disc (with a small
$\lambda$) and the second assumes that they reflect (with a $\lambda$ larger
than the size of the disc). The third model allows athermal photons to
propagate along their geometrical line of sight (similar to ray optics),
gradually losing energy. We find that both the reflective model and the
geometrical model reproduce the features seen in experimental data, whilst the
model assuming phonon thermalisation at the disc border produces unrealistic
results. There is no significant dependence on directionality of energy
absorption in the geometrical model, and in the schema of this thin crystalline
diamond, a reflective absorber law and a geometrical law both produce
consistent results.

DOI： 10.1117/12.2561969

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arXiv

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その他リンク： http://arxiv.org/pdf/2101.03318v1

We present the first far infrared (FIR) dust emission polarization map
covering the full extent Milky Way's Central molecular zone (CMZ). The data,
obtained with the PILOT balloon-borne experiment, covers the Galactic Center
region $-2\,^\circ<l<2\,^\circ$, $-4\,^\circ<b<3\,^\circ$ at a wavelength of
240 $\mu$m and an angular resolution $2.2\,'$. From our measured dust
polarization angles, we infer a magnetic field orientation projected onto the
plane of the sky that is remarkably ordered over the full extent of the CMZ,
with an average tilt angle of $\simeq 22\,^\circ$ clockwise with respect to the
Galactic plane. Our results confirm previous claims that the field traced by
dust polarized emission is oriented nearly orthogonal to the field traced by
GHz radio synchrotron emission in the Galactic Center region. The observed
field structure is globally compatible with the latest Planck polarization data
at 353 GHz and 217 GHz. Upon subtraction of the extended emission in our data,
the mean field orientation that we obtain shows good agreement with the mean
field orientation measured at higher angular resolution by the JCMT within the
20 km/s and 50 km/s molecular clouds. We find no evidence that the magnetic
field orientation is related to the 100 pc twisted ring structure within the
CMZ. We propose that the low polarization fraction in the Galactic Center
region and the highly ordered projected field orientation can be reconciled if
the field is strong, with a 3D geometry that is is mostly oriented $\simeq
15\,^\circ$ with respect to the line-of-sight towards the Galactic center.
Assuming equipartition between the magnetic pressure and ram pressure, we
obtain magnetic field strengths estimates as high as a few mG for several CMZ
molecular clouds.

DOI： 10.1051/0004-6361/201935072

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arXiv

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その他リンク： http://arxiv.org/pdf/1901.06196v1

出版者・発行元：arXiv e-prints  

The Polarized Instrument for Long-wavelength Observation of the Tenuous
interstellar medium (PILOT) is a balloon-borne experiment aiming at measuring
the polarized emission of thermal dust at a wavelength of 240 mm (1.2 THz). A
first PILOT flight (flight#1) of the experiment took place from Timmins,
Ontario, Canada, in September 2015 and a second flight (flight#2) took place
from Alice Springs, Australia in april 2017. In this paper, we present the
inflight performance of the instrument during these two flights. We concentrate
on performances during flight#2, but allude to flight#1 performances if
significantly different. We first present a short description of the instrument
and the flights. We determine the time constants of our detectors combining
inflight information from the signal decay following high energy particle
impacts (glitches) and of our internal calibration source. We use these time
constants to deconvolve the data timelines and analyse the optical quality of
the instrument as measured on planets. We then analyse the structure and
polarization of the instrumental background. We measure the detector response
flat field and its time variations using the signal from the residual
atmosphere and of our internal calibration source. Finally, we analyze the
detector noise spectral and temporal properties. The in-flight performances are
found to be satisfactory and globally in line with expectations from ground
calibrations. We conclude by assessing the expected in-flight sensitivity of
the instrument in light of the above in-flight performances.

arXiv

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その他リンク： http://arxiv.org/pdf/1804.05645v2

記述言語：英語   会議種別：口頭発表（招待・特別）  

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記述言語：英語   会議種別：口頭発表（招待・特別）  

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記述言語：英語   会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

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会議種別：ポスター発表  

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