National Institutes for Quantum and Radiological Science and Technology
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JT-60SA Central Solenoid Conductor Hotspot Risk Analysis for High Voltage Protection
No full textThe upgrade to JT-60SA tokamak (R=3m, a=1.2m) was conducted within a Europe-Japan collaboration agreement featuring the implementation of superconducting magnets. In 2021, an arcing issue on EF1 coil led to an overall magnets insulation reinforcement against high voltage. The Central Solenoid (CS), less accessible for repair, deserves specific attention versus its voltage exposure. Risk mitigation was initiated by decreasing the power supply voltage during plasma scenario current transients. But to further minimize risk, it was decided to address the case of fast discharge events, less frequent but likely to be the risk-driver case as inducing the highest voltage. Its value during discharge being proportional to the external dump resistance, it is envisaged to decrease this resistance of 30%. The consequence is a slower current decrease after a quench event, inducing a higher Joule energy absorbed by conductor, therefore a higher temperature rise in the conductor, increasing the risk of thermo-mechanical degradation due to hotspot occurrence.It is therefore needed to conduct a risk analysis associated to this mitigation action and the present paper exposes the different steps passed in this aim. The first step includes the development and cross-check of two thermo-hydraulic models of CS winding pack that independently evaluate the maximum temperature of CS conductor components using THEA and GANDALF tools. Then, several standard reference cases of quench events and associated CS discharges are investigated for different quench detection conditions. The overall results are presented and discussed regarding the influence of detection settings. Further to the reference cases in question, several parametric studies are conducted considering variants on parameters bearing uncertainties in their definition. This encompasses e.g. the quench location, the quench zone length, the current variation pattern or the copper RRR value. This step aims to establish a more accurate estimation of the impact derived from those intrinsic uncertainties on quench event features. In addition some potential investigations on the use of possible margins are shown. For this risk evaluation, a particular emphasis is given to the methodology followed to define hotspot risk criteria, and to the rationale and references supporting the establishment of those methodologic elements. After application of those rules to the above mentioned modelling results, the risk evaluation outcomes are discussed with the aim of issuing a consolidated assessment on the absolute risk faced by the CS magnet in case of quench event. Finally, recommendations are made regarding the possibility to validate and implement the decision to decrease the CS magnet dump resistance by the JT-60SA project team in order to better protect the CS from applying high voltage.journal articl
HP1γ self-assembles and cooperates with KAP1 in repression of long noncoding RNA AI662270 in ESCs
No full textHP1s are involved in the assembly of heterochromatin and transcriptional regulation. Here, we report the molecular mechanisms underlying binding of chromoshadow domain of HP1γ (HP1γCSD) to transcriptional co-repressor KAP1 and the HP1γ self-assembly. Using crystallography, NMR and mass photometry we show that HP1γCSD recognizes the HP1 box of KAP1 (KAP1Hbox) and forms a relatively stable dimer of dimers, assembled in an antiparallel manner, in contrast to the corresponding HP1αCSD complex that shows concentration-dependent oligomerization and the arrangement of HP1αCSD protomers in a parallel manner. The β-sheet interface between HP1γCSD dimers is stabilized through electrostatic interactions, unlike the hydrophobic β-sheet interface of HP1αCSD. In vivo rescue experiments using KAP1 and HP1s knock out mouse embryonic stem cells (ESCs) reveal a unique cooperative action of KAP1 and the HP1γ isoform, but not other HP1s, in the repression of the long noncoding RNA (lncRNA) AI662270, underscoring the notion that cellular functions of HP1 proteins are not redundant.journal articl
Results on superconductivity in (nearly) uniform electron systems
No full textWe present two results:(i) Efficient implementation of the Eliashberg equations with GW0-level dynamical screened Coulomb interaction(ii) Solution to the minimal modeling problem of peculiar electronic states in 200K superhydride superconductor H3S.Fourth Workshop on Density Functional Theory: Fundamentals, Developments, and Applications (DFT2026)conference poste
Registration accuracy of amyloid/tau-PET to brain MRI using modified SPM method
No full textObjective Mutual information-based algorithms, such as those in statistical parametric mapping (SPM), are widely used in multimodal image registration, but they may lose accuracy when tracer uptake patterns diverge from magnetic resonance imaging (MRI) contrast, as in amyloid and tau- positron emission tomography (PET). This study assessed the registration accuracy of MRI and amyloid/tau-PET images using SPM’s default settings and a modified approach (Modified SPM) incorporating a repeated optimization process. Registration accuracy was also examined in PET images without scatter/attenuation correction (uncorrected PET), mimicking PET-only systems lacking structural imaging for attenuation correction. Methods Four PET tracers were analyzed: two amyloid tracers ([11C]PiB, [18F]florbetapir) and two tau tracers ([11C]PBB3, {18F]THK5351). The MR images were manually registered on the PET scans, then misaligned with known perturbations, and re-registered using the default SPM and the Modified SPM. The registration error was defined as the difference between the applied perturbations and re-registration parameters. A voxel size of 2.0×2.0×3.27 mm3 was used; errors less than one voxel were considered acceptable. Results The average errors were less than one voxel overall; however, when stratified by PET-negative and PET-positive cases, rotational displacements were observed in tau-PET images with the default SPM only.The Modified SPM reduced these errors and improved the accuracy of uncorrected PET images. Conclusions Registration accuracy between amyloid/tau-PET and MR images using default SPM was generally acceptable, although larger errors were observed in tau and uncorrected PET images. Incorporating a repeated optimization process (Modified SPM) improved registration robustness, particularly in these challenging casesjournal articl
Estimation of Mutual Inductance Caused by Misalignment of JT-60SA TF Coil
No full textThe JT-60 Super Advanced (JT-60SA) was built as part of a project aimed at the early realization of fusion energy. The JT-60SA is used to support and complement work for ITER and to develop young fusion scientists and engineers. The superconducting coil system of the JT-60SA includes the toroidal field (TF) coils, equilibrium field (EF) coils, and central solenoid (CS) modules. Each TF coil is monitored by the quench detection voltage (QDV) system, which compares voltages at adjacent TF coils using a bridge circuit. The EF coils do not produce a voltage in the TF coils because, ideally, the TF coils are orthogonal to the EF coils. However, when the EF coils are energized, the QDV in the TF coils sometimes exceeds the threshold, falsely detecting quenches, which leads to the discharge of a TF current. It is believed that a magnetic flux from the EF coils passing through the TF coils may occur due to coil misalignment during installation and inadequate clearance design. As a result, an induced voltage could be generated in the TF coils. To understand how other coils influence the TF QDV system and to ensure the stable operation of the JT-60SA, it is crucial to investigate the cause of the induced voltage in the TF coils. In this study, a coil misalignment model was developed using finite element analysis software. This model was used to calculate the mutual inductance between the TF and EF coils. Furthermore, a circuit simulation model of the TF QDV system was created to quantitatively analyze the induced voltage caused by the misalignment of superconducting coils.journal articl
Optical Design and Efficiency Measurement of an Extreme Ultraviolet High-Resolution Spectrometer for Unresolved Transition Array Research
No full textUnderstanding the structures of the unresolved transition array (UTA) observed in extreme ultraviolet (EUV) spectra from many-electron atoms is crucial for various applications, including fusion science and nanolithography. To measure the fine structure of the UTA from tungsten and tin at around 5 and 13.5 nm at the Tokyo electron beam ion trap, we developed a high-resolution EUV spectrometer. The designed spectrometer achieves a resolving power of λ/dλ > 5000 at 5 and 13.5 nm. The fabricated large-area grating was experimentally examined at beamline BL5B of the UVSOR synchrotron facility to evaluate the diffraction efficiencies and their variation across the ruled area. The measured diffraction efficiencies are 0.65% ± 0.07% at 5 nm (second order) and 7.9% ± 0.2% at 13.5 nm (first order). The variation in the diffraction efficiency across the ruled area is 2.2%, 13.6%, and 10.0% in zeroth, first, and second order diffractions, respectively. The discrepancies in diffraction efficiencies between the experiments and the calculations were 5.2%, 29%, and 35% for the zeroth, first, and second diffraction orders, respectively.journal articl
生体内環境を模倣したECMゲルと多臓器連結型MPSチップの開発
No full text近年、創薬や疾患メカニズム解析において、生体模倣システム（Microphysiological Systems: MPS）の重要性が高まっている。従来の二次元培養や単一臓器モデルでは、細胞外マトリックス（ECM）の構造的・機能的特性や臓器間相互作用を十分に再現できず、薬物応答や病態の予測精度に限界がある。また、複数臓器を連結することで臓器間相互作用を評価可能な、より高精度な生体模倣モデルの構築が求められている。本シンポジウムでは、放射線加工技術を駆使して開発した「生態環境を模倣したECMゲル」「多臓器連結型MPSチップ」、これらを組み合わせた、次世代MPSの開発研究について紹介する。MPS実用化推進協議会 第３回学術シンポジウムconference poste
核融合エネルギー講座
No full text核融合エネルギーは軽い原子核同士が融合して別の原子核に変わる際に放出されるエネルギーであり、カーボンニュートラル方針への適合や豊富にある燃料、固有の安全性などからエネルギー問題と地球環境問題を同時に解決する次世代のエネルギーとして期待されています。ここでは、核融合に関する最新の研究成果とともに、核融合エネルギーを新たな産業と捉え、実用化に向け加速化が図られている状況をご紹介します。朝日カルチャーセンターconference presentatio
口腔を含む頭頸部悪性腫瘍に対するマルチイオン治療の線量平均LET増加第I相臨床試験
No full text頭頸部癌症例に対してマルチイオン治療を行い、生物線量分布をこれまでの炭素イオン線治療単独と同等に保ちながら正常組織の線量制約を満たすことによって安全性を維持しつつ、腫瘍標的内の線量平均LETを最適化し、目標線量平均LET中央値を70 keV/μmから段階的に増加させ、最終的には至適な線量平均LET中央値と予想される90 keV/μmを臨床的に用いる事の安全性と有効性を評価する第44回日本口腔腫瘍学会総会・学術大会conference presentatio
平衡フローの駆動するバルーニングモード乱流のバーストダイナミクス
No full textELMはトカマク周辺におけるバースト現象である。ELMの非線形ダイナミクスを理解することは重要な課題である。本研究では、簡約化二流体シミュレーションコードR2Fを用いた、熱源と新古典フローを含む抵抗性バルーニングモード乱流の非線形シミュレーションを行った。平衡フローが存在しない場合には、定常的な乱流が維持されるのに対して、平衡フローが存在する場合には、繰り返すバーストが発生することが分かった。バーストの駆動の有無は、シアフローによる径方向に伸びた乱流渦の生存時間で理解できることが分かった。発表においては、詳細なパラメータスキャンを行った場合にバースト特性がどのように変化するかについても紹介した。NIFS共同研究研究会「閉じ込め・輸送研究会」conference presentatio