National Institutes for Quantum and Radiological Science and Technology
National Institute of Radiological Science: NIRS-Repository / 放射線医学総合研究所 学術機関リポジトリNot a member yet
37195 research outputs found
Sort by
Theoretical Study of Spin-Lattice Relaxation for Superconducting State in UTe2
No full textRecently, UTe2 has attracted much interest as a strong candidate for the spin-triplet superconductor due to its large upper critical field exceeding the Pauli limiting field. A lot of experimental and theoretical approaches have been attempted, however, the superconducting symmetry in UTe2 remains unclear and an important problem. To investigate the superconducting symmetry in UTe2, we constructed an “f-d-p model” that is an effective model of UTe2. This model reproduces the quasi-two-dimensional Fermi surfaces and the antiferromagnetic fluctuations peak at (0, , 0). Solving the linearized Eliashberg equation within third-order perturbation theory (TOPT) using the f-d-p model, we have obtained the point-node-like s-wave superconducting state as the most likely pairing state. This obtained gap structure is consistent with the specific heat measurements. Nuclear magnetic resonance measurements show the absence of the Hebel-Slichter peak in the spin-lattice relaxation (1/T1). To confirm that the point-node-like s-wave pairing state is consistent with the NMR measurements, we calculated 1/T1 in the f-d-p model. In numerical calculations, we use the gap function of the point-node-like and isotropic s-wave pairing state and compare the scale of the Hebel-Slichter peak in both cases. As a result, we show that although the Hebel-Slichter peak becomes smaller due to the anisotropy of the gap structure, the Hebel-Slichter peak is too large to ignore. Moreover, we show the result of 1/T1 using the random phase approximation (RPA). In the calculation based on RPA, we consider not only the point-node-like s-wave pairing state but also various spin-triplet states, for instance, Au, B1u, B2u, or B3u states.Conference on Strongly Correlated Electron Systems 2025conference poste
電荷・LETパラメータ線質係数の宇宙放射線LET測定への適応手法
No full text宇宙環境はHからFeまでの荷電粒子が主要な放射線混在場である。地上の線量評価ではこれらの粒子に単一の放射線荷重係数WRが割り当てられている。ただし、これは主にアルファ線放出核種の内部取り込みを想定した値であり、重粒子線の外部被ばくに対する重み付けとして妥当でない。特に宇宙放射線に対する線量評価ではWR以前の線質係数QICRPが今日でも用いられているが、近年になってこれに代わるQNASAが提案されている。QICRPが粒子のLETのみに依存する値であるのに対し、QNASAはLETと電荷で決定される値である。一方で、従来の宇宙での重荷電粒子に対する線量評価は主にLET計測に基づいて行われており、QNASAをそのまま従来測定に適応することは困難である。本研究では、宇宙環境の吸収線量の電荷・LET分布を評価することで、これらによって決定される線質係数を従来のLET測定に適応する手法を提案する。提案手法を計算と実測に基づいて検証し、その適応性の評価を行った。日本保健物理学会第58回研究発表会conference presentatio
Tau-derived remote cortical network for frontal cognitive symptoms in PSP
No full text[Objectives] To elucidate the network mechanisms of frontal cognitive symptoms of Progressive Supranuclear Palsy (PSP), a neurodegenerative disease primarily characterized by heterogeneous subcortical tau deposits.[Methods] We conducted tau-network mapping, in which tau-PET using high-contrast probe florzolotau (18F) was combined with normative connectome from 100 healthy subjects to identify a network commonly connected from tau deposition sites across 37 patients with PSP-Richardson syndrome.[Results] Remote cortical network commonly connected from tau deposition sites, but not from atrophy sites, could be significantly identified. The tau-derived cortical network was primarily overlapped with canonical action-mode and frontoparietal networks. The degree of local tau deposition or atrophy explained motor, but not frontal cognitive, symptoms. In contrast, the connectivity strength between tau deposition sites and the tau-derived network explained frontal cognitive symptoms.[Conclusion] Beyond heterogeneous local pathology, tau-network mapping reveals common remote network substrates of PSP, providing mechanisms of frontal cognitive symptoms derived from subcortical tau deposits.認知症学会学術大会conference poste
クロレラ(Parachlorella kessleri)の内部倍数性と重イオンビーム照射による染色体断片化
No full textParachlorella kessleriは、デンプンおよび中性脂質を生産する能力を有する単細胞緑藻であり、バイオマス資源として注目されている。緑藻類における多分裂型の細胞周期は種によって異なるが、P. kessleri における細胞周期および分裂の理解は未だ不十分であった。本研究では、顕微鏡観察およびパルスフィールドゲル電気泳動により、7本のA染色体と3本のB染色体（n = 7 + 3B）を同定した。定常期の平均核DNA量を1Cとした場合、対数増殖期における核DNA量は1.1Cから9.7Cの範囲にあり、染色体数は一定であったことから、核内倍加が生じていることが示唆された。重イオンビーム（LET: 640、290、30 keV/μm）による照射実験では、LETおよび線量の増加に伴い染色体断片化が観察され、断片の一部は継代培養後も安定に継承された。変異解析のためにリファレンスゲノムを改良し、N50が2.5 Mbpの52スキャフォールドを得た。安定な染色体断片を持つ変異体の全ゲノム解析により、テロメア反復配列に影響を与える転座、大規模な重複および欠失が検出された。これらの結果は、重イオンビームが微細藻類に対して有効な変異原となり得ることを示し、大規模な遺伝子変異を誘導することで新規表現型変異体の創出に貢献する可能性を示している。日本メンデル協会第２回大会conference poste
In situ calibration of charge exchange spectroscopy and measurements of absolute density profiles in the plasma with high boron concentration
No full textA boron charge exchange spectroscopy system has been applied to measure the radial profiles of absolute boron density. The in situ calibration of charge exchange spectroscopy was performed using the boron pellet in a Large Helical Device. The calibration factor was derived by comparing the increment of boron density measured with a charge exchange spectroscopy system by the increment of electron density measured with a YAG Thomson scattering system. The radial profiles of absolute boron density are derived for the plasma using boron pellets, tracer-encapsulated solid pellets (TESPEL), and boron impurity power drops (IPD). By using boron pellets, TESPEL, and IPD, the boron concentration (nB/ne) was controlled in the wide range from 4% to 17%. The radial profiles of boron are peaked in the core for the boron pellet and TESPEL discharge, while they are slightly hollow for the boron IPD plasma.journal articl
Modeling for ELMs and H-mode pedestal transport: MHD, gyrokinetic, neoclassical and integrated simulations
No full textThis paper provides a comprehensive review of recent advances in modeling and simulation studies investigating edge localized modes (ELMs) and transport physics in edge pedestal of tokamak plasmas. Following an overview of H-mode characteristics, including ELMy and ELM-free regimes, ELM control techniques, and pedestal transport physics, this review focuses on three key areas: advancements in linear and nonlinear MHD simulations to improve understanding ELM physics and access the effectiveness of ELM control techniques; progress in understanding of transport physics of both bulk and impurity plasmas in the edge pedestal, analyzed using gyrokinetic and neoclassical simulations; and the development of predictive models for H-mode pedestal profiles. Notably, the maturity of these approaches now enables meaningful validation through experimental comparisons, including the pplication of synthetic diagnostics. Building on these developments, this paper addresses critical simulation and modeling challenges that must be resolved to successfully predict robust operation scenarios for ITER and future fusion reactors, aiming to achieve high plasma performance while avoiding destructive transients such as ELMs.journal articl
Development of a portable battery-powered total reflection X-ray fluorescence spectrometer
No full textThe detection of nuclear materials is crucial in cases of potential leaks or accidents; however, transporting samples out of such locations may be challenging, necessitating on-site analysis. While total reflection X-ray fluorescence (TXRF) analysis is a highly useful method for determining nuclides with long half-lives, such as uranium isotopes, no commercially available portable TXRF spectrometers can currently operate without an external power source, which may not always be accessible on-site. In this study, we modified the design of a commercially available portable TXRF spectrometer to develop a battery-powered device, enabling TXRF analysis outdoors and in locations without an external power supply. To test the applicability of the device, we analyzed the uranium content in a sample solution, using yttrium as an internal standard. The relative sensitivity coefficient was the same as that of the commercial spectrometer but the limit of detection was deteriorated. Addressing the equipment issues identified in this study is expected to enable efficient and rapid on-site TXRF analysis.journal articl
Local Position Control of NV Centers in Diamond by Combining of Picosecond Laser Irradiation and Nitrogen Ion Implantation
No full textNitrogen-vacancy (NV) centers in diamond are attracting attention as quantum bits that can operate at room temperature and are expected to be applied in the fields of quantum sensing, quantum computing and quantum communication. Precise control of the position of NV centers especially within 10-1000 nm is essential for the realization of highly efficient single-photon sources using optical resonators and quantum memories. Until now, local NV center formation at arbitrary positions using electron beam lithography or femtosecond laser irradiation has been reported, but this is still an under-developed technology and there are still problems such as process complexity, cost and three-dimensional position control. In this study, we propose a precise three-dimensional NV formation position control method that combines picosecond lasers and ion implantation as a simpler and more economical method.The 18th International Conference on New Diamond and Nano Carbons 2025conference presentatio
低温・高圧力下におけるNV−中心のゼロフォノンライン観測
No full textダイヤモン ド中の点欠陥である負に帯電した窒素一空孔(NV-)中心は、スピン量子数S= 1を持つ量子系であり、基底状態が温度 •圧力 •磁場に応答 して変化する こと から、これ ら物理量の高感度センサと して機能する。近年、高圧力下でも量子センサと して動作する 利点を生かし、 水素化物超伝導体のマイスナー効果観測への応用が報告されている [1]O 常温・常圧ではNV一中心のゼロフォノンライン (ZPL) が約 637nm に現れる。ZPL の位置は温度や圧力に伴ってシフ トするが、高圧力印加時には図 1 に示すよ う に短波 長側へ移動することが知られている [2,3]。これまでに温度変化あるいは圧力変化の一方 の効果を詳細に調べた研究は多いものの、両者を同時に制御した測定は限られている。特 にダイヤモンドアンビルセル (DAC) では、温度変化に伴い試料室圧力が変動するため、 温度 . 圧力を独立に校正しつつ ZPL を計測する こ と は容易ではない。本研究では、SPring-8 BL10XU において放射光 X 線回折 と 分 光測定を同時に実施し、状態方程式に基づく 圧力校正の下で低温 ・ 高圧力環境における ZPL の計測を試みた。図2に10Kに おける各圧力のフォ トルミネッセンス (PL)スペク トルを示す。 圧力は Mg。 の状態方程式 [4]よ り 推定 した。低温において も加 圧に伴いZPL が短波長側にシフ トする。実験の詳細および他の 結果については、講演当日 に報告する。日本物理学会第80回年次大会conference poste
JT-60SA Activities
No full textJT-60SA実験チームの実験リーダーとして、JT-60SAの運転計画、装置増強の状況、実験に向けた統合試験の準備状況、研究活動について報告する。ITPA Coordinating Committeeconference presentatio