National Institutes for Quantum and Radiological Science and Technology
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Development of Low Inductive Electric Field Plasma Start-up in JT-60SA
No full textJT-60SAの統合試験運転期におけるプラズマ立ち上げの実験結果について報告する。特に、ITERの約半分という低いトロイダル誘導電場を用いたプラズマ立ち上げにおいて、電子サイクロトロン波により加速される電子の閉じ込めを利用した捕捉磁場配位方式の着火手法が、一般に用いられているヌル磁場配位方式と比較して有利になることを、実験結果及びシミュレーション計算により示す。QSTフュージョンエネルギーワークショップconference presentatio
Multiscale Synchrotron X-ray Scattering Study on the Interaction between Phase Evolution and Elasticity of CSH/PCE Composites Subjected to High Temperatures
No full textさまざまな Ca/Si 比におけるケイ酸カルシウム水和物 (CSH)/ポリカルボン酸塩 (PCE) 複合材料の残留機械的特性に対する格子構造と原子間距離の熱変形の影響は明らかではない。本研究では、Ca/Si 比が0.6～1.0の範囲のCSH/PCE複合材料のマルチスケール構造変態と機械的特性の間の相関関係を、小角 X 線散乱とその場負荷印加のX線全散乱によって調べた。journal articl
Saturable absorption in highly excited laser-irradiated silicon and its suppression at the surface
No full textNonlinear electronic excitation in laser-irradiated silicon at finite electron temperatures is numerically investigated by first-principles calculations based on the time-dependent density functional theory.
In bulk silicon at finite temperatures under near-infrared laser irradiation, we found that the absorbed energy is saturated when using a certain laser intensity even with a few-cycle pulse.
Although one-photon processes of conduction-to-conduction and valence-to-valence transitions
are dominant at such a laser intensity, the Pauli blocking inhibits further one-photon transition.
With higher intensities, multi-photon excitation across the bandgap overwhelms the one-photon excitation and the saturable absorption disappears.
At the surface of finite-temperature silicon, the Pauli blocking is suppressed by the symmetry breaking and the absorbed energy is relatively enhanced from the energy of the saturable absorption in the bulk region.journal articl
Methodology for Optical Path Transmittance Identification Using a Cat’s Eye Retro-Reflector
No full textIn the optical system utilized in nuclear fusion reactors, it is possible that the reflectance of the mirrors positioned within the vacuum vessel may undergo alteration as a consequence of the deposition of impurities or corrosion. To address this issue, a methodology was proposed whereby light is introduced from outside the vessel, and the transmittance of the optical system is determined by measuring the light reflected by a retro-reflector that is temporarily placed at the tip of the optical system. However, as the reflectance of the retro-reflector itself is not always constant, a reliable method for absolute sensitivity calibration has yet to be established. In this study, we developed a method for measuring the reflectance of the cat’s-eye retro-reflector and, consequently, the transmittance of the optical system. This entailed an analysis of the differences in reflection positions and times within the cat’s-eye retro-reflector.journal articl
Electronic structures of blue copper centers of amicyanin and azurin in solution state
No full textX-ray absorption near edge structure (XANES) spectra of blue copper proteins, amicyanin and azurin, in solution state were measured in the copper L3-edge energy region. The absorption peak energies were quite similar for both proteins while the main edge region for azurin was broader than that for amicyanin owing to more pronounced shoulder spectral features in the former. Ab initio calculations at the whole protein level qualitatively reproduced the experimental spectra well. The relative X-ray absorption intensities suggest that the degree of covalency of the copper-ligand bond at the active site was weaker for amicyanin than that for azurin.journal articl
イオンビーム照射における元素種および吸収線量がストック （Matthiola incana (L.) R.Br.）の生存率および変異誘発効率に及ぼす影響
No full textGarden stock (Matthiola incana (L.) R.Br.) is a major floricultural plant in the winter season. In this study, dry seeds of
Matthiola incana were irradiated with carbon (C) and iron (Fe) ion beams to investigate the effective element species and
absorbed doses. The survival rate of the M1 generation tended to decrease with increasing absorbed dose, and the absorbed
dose-survival rate curve showed a shoulder at absorbed doses of 100 Gy in C-irradiation and 10 Gy in Fe-irradiation. Some shoot
and flower morphogenetic mutants were obtained in the M2 progenies. The shoot mutants contained dwarf, multibranch, and
enlarged floral axis individuals, while the flower mutants had darker petal colors, narrowed petals, and an increased number of
petals. The mutation rate increased with elevating absorbed dose and showed a negative correlation with the survival rate. Based
on these results, it was suggested that absorbed doses of 100 Gy in C and 10 Gy in Fe, which are the shoulders of the absorbed
dose-survival rate curve, are effective indicators for generating Matthiola incana mutants. The mutated flower phenotype was
stably inherited, but the shoot mutant inheritance varied. These results demonstrate that ion beam irradiation of Matthiola incana
dry seeds can produce mutants.journal articl
Bioassay for multiple actinides in large-size feces using ICP-MS/MS after borate fusion and chromatographic separation by AG MP-1 M and DGA resins
No full textFecal radiobioassay is an essential and sensitive tool to conduct dose assessment as internal exposure of actinides just after a radiological or nuclear accident. Since the distribution of radionuclides in fecal samples is uneven, total digestion of the whole fecal samples is required. Thus, there is a high demand for rapid and efficient chemical and chromatographic separation methods prior to analysis of large-size fecal samples. After shortening the time for drying and ashing to 8 h, we conducted a complete decomposition based on borate fusion for the ash of a 150 g fecal sample, and followed it by sequential column chromatographic separation using AG MP-1M resin and DGA resin. The overall chemical fractionations between 237Np and 242Pu for the whole analytical procedure were 0.993?1.002, allowing us to measure 237Np and Pu isotopes using 242Pu as a yield tracer with yields of approximately 80%. Using ICP-MS/MS with helium collision gas provided the method detection limits for 237Np, 239Pu, 240Pu, 241Pu, 241Am, and 244Cm of 1.33, 4.05, 2.43, 2.21, 2.21, and 0.660 ag/g, respectively, for the 150 g fecal sample. For method validation, we analyzed the standard reference materials provided by PROCORAD (Association for the PROmotion of Quality COntrol in RADiotoxicological Analysis), France, and we obtained satisfactory results with |Z-score| < 2. The high throughput (18 h for 12 samples) and high sensitivities (approximately 7 Mcps/ppb) of the fecal bioassay will allow greater numbers of related laboratories to be involved in screening activities for unexpected actinide exposure.journal articl
Global gyrokinetic simulations of isotope effects under ambipolar electric fields and code development towards whole-volume modeling
No full textヘリカル型磁場閉じ込め装置LHDプラズマを対象として、大域的full-fジャイロ運動論コードXGC-Sによる解析を行った。論文では、新古典輸送や線形ITG乱流について検証を行い、さらにITG乱流については水素同位体効果が乱流に与える影響について調べた。また、ヘリカルダイバータ領域を含むシミュレーションを可能とする、新たなメッシュ生成法の結果について議論した。journal articl
Monte Carlo simulation to optimize measurement geometry of continuous air monitor with Si semiconductor detector
No full textOne of the challenges in real-time monitoring of airborne alpha-emitting radionuclides using Continuous Air Monitors (CAMs) is to discriminate alpha particles emitted by artificial radionuclides from those emitted by natural radionuclides, as the alpha energy spectrum is easily degraded due to its high stopping power. Although the measurement geometry significantly affects the alpha energy spectrum, there are no reports that have investigated the optimized geometry. This study conducted a Monte Carlo simulation to optimize the measurement geometry of the CAMs. The CAM was modelled using a radiation transport simulation code, and the counting efficiencies for 218Po and 239Pu and the overlapping ratio were simulated. The Minimum Detectable Concentration (MDC) of 239Pu was then estimated as an indicator to optimize the geometry. Although a constant counting efficiency is generally used for the same geometry regardless of the alpha energy, the counting efficiency differed up to ∼0.04 by the alpha energy depending on the measurement geometry. The overlapping ratio for a 50-mm diameter detector ranged from 0.22 to 0.35, while those for a 25-mm diameter detector was below 0.25. This discrepancy is because of the incident angle distribution biased towards large angles. The lowest MDC was estimated to be ∼3 Bq m−3 at 20 L min−1 under 25 Bq m−3 of 218Po. The MDC was low for small filter diameters and Filter-to-Detector Distances (FDDs) under most of the simulated conditions. The results indicate that a shorter filter diameter and FDD would be preferable for alpha spectrometry under normal air pressure.journal articl
頭頸部がん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70回公益社団法人日本口腔外科学会総会・学術大会conference presentatio