National Institutes for Quantum and Radiological Science and Technology
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Radiation tolerance analysis of space solar cells under increased irradiance conditions
No full textIn this study, we obtained the electrical performance of concentrator photovoltaics (CPV) using InGaP/GaAs/Ge triple-junction solar cells before
and after high-energy particle irradiation to examine the effects of solar concentration on radiation tolerance. The conversion efficiency before
radiation exposure increased in proportion to the received solar irradiance mainly because of the solar concentration effect of the open-circuit voltage (Voc). Additionally, our experimental results revealed that the solar concentration effect of Voc was enhanced after radiation exposure, which mitigated Voc degradation. To investigate the solar concentration effect on Voc in detail, the recombination current dependencies of the external luminescence efficiency (hext) of InGaP and GaAs single-junction (1J) cells were measured before and after radiation exposure. It was found that the hext of InGaP 1J cells after radiation exposure increased with increasing recombination current, which is considered to suppress the degradation of the Voc of the CPV. These findings demonstrate the significant advantages of CPV for space applications.journal articl
Concurrent Alzheimer's disease pathologies in Lewy body diseases affect cognition and glucose metabolism in the posterior cingulate gyrus: A multimodal PET study
No full textBackgroundLewy body disease (LBD) is a neurodegenerative disease characterized by Lewy bodies, and it clinically presents dementia with Lewy bodies (DLB) and Parkinson's disease (PD). Alzheimer's disease (AD) pathologies frequently coexist with LBD, complicating the clinical manifestation.ObjectiveWe evaluated the impact of AD pathologies, including amyloid-β and tau depositions, on cognitive dysfunction and glucose metabolism in LBD using multiple positron emission tomography scans.MethodsOur study cohort consisted of 14 patients diagnosed with LBD, including five from the PD spectrum and nine from the DLB spectrum. In addition, 12 amyloid-negative cognitively healthy controls (HCs) and 13 amyloid-positive AD-spectrum patients were included. We subsequently explored the influence of amyloid and tau deposition on cognitive dysfunction and glucose metabolism among the LBD patients.ResultsIn the LBD group, 44.4% of the DLB patients were amyloid-positive, and all PD patients were amyloid-negative. While tau accumulation was lower than in AD and similar to HCs at the group level, tau accumulation in the AD signature region was correlated with cognitive dysfunction. Among the changes in glucose metabolism, the cingulate island sign (CIS) index was elevated compared to AD. However, as cognitive impairment progressed, the CIS index decreased, reflecting reduced metabolism in the posterior cingulate gyrus, which was closely associated with tau accumulation in the same region.Conclusions: Our findings indicate that AD pathologies, and particularly tau accumulation, significantly impact both cognitive dysfunction and glucose metabolism in LBD. This underscores the importance of addressing AD-related changes in the clinical management of LBD patients.journal articl
Rotating waveplate Stokes polarimeter using anisotropic transmittance in waveplate
No full textOne of well-known polarization measurement techniques is a rotating waveplate Stokes polarimeter. This technique modulates the polarization state by rotating a quarter waveplate, and the polarization state can be identified from the second and the fourth harmonics of the modulated detector signal. This study presents a new signal model and a new calibration method for the rotating waveplate Stokes polarimeter using an anisotropic-transmittance quarter waveplate. It was found that anisotropic transmittance enables identification of the light intensity and the degree of polarization without measuring the DC (direct current) component of the intensity of the modulated polarized light. In addition, anisotropic ransmittance enables the calibration of the rotating waveplate Stokes polarimeter by using only linearly polarized light. The experiment was carried out to demonstrate the measurement capability of the polarimeter using the anisotropic-transmittance waveplate and the 95% confidence interval of the error was 0%?1.9%.journal articl
Analysis of Background Plasma Behavior Under External Fields in the Low Energy Beam Transport Section of LIPAc
No full textBackground plasma behaviour in the low energy transport section of the LIPAc is analysed with 3-dimensional particle-in-cell simulation. The simulation showed some characteristic effect under external field elements in the LEBT: a positive biased chopper absorbed the electron plasma in the surrounding drift region, that is limited by the solenoid lenses, though indicating some electron leakage through the solenoid still be there. Analytically estimated flux of the electron leakages through solenoid is compared to the simulation results. Results of experiments still has a mysterious transient motion of beam pulse shape that is not shown in the simulations, while saturated state is roughly reproduced in it.IAEA FEC 2025 IFMIF/EVEDA ワークショップconference poste
Improvements of Magnet Power Supply System and Achievements in Coil Energization Tests for First Plasma of JT-60SA
No full text本発表では、2021年のJT-60SA統合試験運転で発生したEF1コイルの絶縁不良事象を受けて、コイル保護と運転リスク低減の観点から実施した(i)中点接地位置変更、(ii)ブースタ電源電圧リップル低減フィルタの設置及び(iii)地絡時の過電圧保護用バリスタの設置について述べるとともに、改良後の2023年8月から再開された統合試験運転での超伝導コイル通電試験の手順及び成果について述べる。QSTフュージョンエネルギーワークショップconference presentatio
Frequency Hysteresis of MHD Instabilities in Helical and Tokamak Plasmas
No full text本研究では、環状磁場閉じ込めプラズマにおけるMHD不安定性による磁場揺動の振幅と周波数の関係を調査した。その結果、ヘリカルおよびトカマクプラズマにおいて、周波数の増加・低下の両過程で振幅と周波数の関係にヒステリシスが存在することを初めて明らかにした。このヒステリシスは、電磁減速力と粘性加速力のトルクバランスモデルによって説明可能である。装置間の比較から、ヒステリシスは装置の種類ではなく、主に減速力の起源や周波数範囲の違いによって決定されることが示唆された。本研究の成果は、振幅と周波数の包括的なモデルの構築に貢献する。QSTフュージョンエネルギーワークショップconference presentatio
Development of the Direct Deuteration Method for Amino Acids and Characterization of Deuterated Tryptophan
No full textProteins and peptides are essential biomolecules involved in the maintenance of biological functions and disease development. Their structural and functional analyses are crucial for drug discovery and pathology. Amino acids, the fundamental building blocks of these biomolecules, are increasingly utilized in deuterated forms in diverse fields, such as metabolic tracing and neutron scattering studies. In this study, we have developed an efficient deuteration method that targets all 20 proteinogenic amino acids, including their side chains, and established techniques for the separation of optical isomers. Using a Pt/C-catalyzed hydrogen–deuterium exchange reaction, the reaction parameters were optimized to achieve the selective and stable incorporation of deuterium. In addition, the resulting deuterated compounds, focusing on tryptophan, were characterized in order to assess their physicochemical properties. Because the deuteration reaction caused significant racemization of amino acids, deuterated D/L-tryptophan was isolated using a chiral separation method. Deuterated tryptophan characterization studies confirmed that the photostability was markedly enhanced by deuteration, whereas the acid stability showed no clear isotopic effect. Structural analyses revealed minimal changes upon the hydrogen-to-deuterium substitution. These results provide a robust platform for the supply of deuterated amino acids, facilitating their application in drug development, structural analysis, and creation of advanced functional biomaterials.journal articl
The properties of the nitrogen-vacancy center in milled chemical vapor deposition nanodiamonds
No full textFluorescent nanodiamonds (FNDs) containing negatively charged nitrogen-vacancy (NV-) centers are vital formany emerging quantum sensing applications from magnetometry to intracellular sensing in biology. However,developing a scalable fabrication method for FNDs hosting color centers with consistent bulk-likephotoluminescence (PL) and spin coherence properties remains a highly desired but unrealized goal. Here, weinvestigate optimized ball milling of single-crystal diamonds produced via chemical vapor deposition (CVD) andcontaining 2 ppm of substitutional nitrogen and 0.3 ppm of NV- to achieve this goal. The NV charge state, PLlifetime, and spin properties of bulk CVD diamond samples are directly compared to milled CVD FNDs andcommercial high-pressure high-temperature (HPHT) FNDs. We find that on average, the relative contribution ofthe NV- charge state to the total NV PL is lower and the NV PL lifetime is longer in CVD FNDs compared toHPHT FNDs, both likely due to the lower Nsaverage show similar average T1 spin relaxation times of 3.2 ± 0.7 ms and 4.7 ±1.6 ms, respectively, compared tothe large-scale fabrication of NV ensembles in FNDs with bulk-like T1 spin relaxation properties.journal articl
QST量医研加速器施設における宇宙放射線試験への取組
No full textQST量医研は、主に陽子ビームを供給するNIRS-930サイクロトロンと、主に重イオンビームを供給するHIMACの2つの加速器施設を運用している。両施設は週1日程度、外部利用が可能で、宇宙放射線試験などに活用されている。本稿では、宇宙放射線試験に用いられるNIRS-930とHIMACの概要、最近の利用状況、そして今後の展望について紹介する。第69回宇宙科学技術連合講演会conference presentatio
Efficient photoelectric single-spin detection in silicon carbide
No full textA silicon vacancy in 4H-silicon carbide (SiC) is a promising candidate for quantum applications due to its excellent spin-coherent properties even at room temperature. In addition, electron spins of silicon vacancies can be electrically detected by the photo current-detected magnetic resonance (PDMR) technique. Therefore, it is expected to realize a scalable integrated quantum device with peripheral circuits using silicon vacancies. However, although PDMR detection has been expected to have a superior spin-readout efficiency compared to optical methods, this has not been realized. In this study, we report the enhancement of the spin-readout efficiency of PDMR detection for a single silicon vacancy in SiC.The International Symposium on Quantum Science, Technology and Innovation 2025 (Quantum Innovation 2025)conference poste