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EUV and VUV Spectra of NeIII-NeX Line Emissions Observed in the Impurity Gas-Puffing Experiments of the Large Helical Device
Get PDF0000-0002-1171-8603Extreme ultraviolet (EUV) and vacuum ultraviolet (VUV) wavelength spectra including line emissions released from neon (Ne) ions ranging from low to high charge states observed simultaneously in a single discharge are summarized for contribution to compile a fundamental spectral dataset for the Ne-seeded divertor heat load reduction experiments in Large Helical Device (LHD). NeIX and NeX lines were observed in the EUV wavelength range of 10∼50 Å and NeIII-NeVIII lines were observed in the VUV wavelength range of 400∼1000 Å. The temporal evolutions of the line intensities exhibited different behaviors between the edge emissions of NeIII-NeVIII with the ionization potential, Ei, of 63∼239 eV and the core emission of NeX with Ei of 1362 eV. NeIX with Ei of 1196 eV exhibited a marginal behavior between the edge emission and the core emission.journal articl
Feasibility Study of High-Efficiency Cooling of High-Temperature Superconducting Coils by Magnetic Refrigeration
Get PDF0000-0002-1565-8353As a high-efficiency cooling technology for high-temperature superconducting coils, we have begun research and development to examine the feasibility of a cooling assist technology that maintains a cryogenic state by combining the magnetic force generated by the superconducting coil with magnetic refrigeration technology. Magnetic refrigeration requires the magneto caloric material to change the magnetic field. In many cases, the magnetic field change is obtained by moving the magnetic source, but moving the superconducting coil is not a good idea. Although it is possible to generate a change in the magnetic field by turning on and off the power supply of the high-temperature superconducting coil, it is unlikely to be established as a system that assists cooling of the superconducting coil because the coil generates heat due to AC loss. Therefore, it was considered that the magnetic field change can be obtained if the magnetic force generated from the superconducting coil can be controlled by the magnetic shield. As a verification of the principle, it was clarified experimentally that a magnetic field change can be obtained by repeatedly inserting and removing the magnetic shield into and from the gap between the magnetic field generation source and the magneto caloric material, and the temperature change can be extracted by the magneto caloric effect. In the experiment, the temperature change obtained when a magnetic shield was inserted into the air gap was measured by a simple test device using an iron-based magneto caloric material having high magneto caloric effect performance at room temperature and a permanent magnet. The principle verification confirmation test was performed using several types of magnetic shielding materials such as Permalloy bulks and the electrical steel sheets. In addition, numerical analysis is performed on the magnetic shielding effect, and the shielding effect is improved by increasing the thickness of the shielding material and the possibility of using high temperature superconductors as magnetic shielding materials were also analyzed. In this study, we report the possibility of cooling the high-temperature superconducting coil with high efficiency by combining the magnetic field created by the superconducting coil and magnetic refrigeration.journal articl
Initial Measurement of Doppler-Shifted DD Neutron Energy Spectrum Using CLYC7 Scintillator in LHD
Get PDF0000-0002-6337-4080The compact neutron energy spectrometer (CNES), based on the Cs2LiYCl6 : Ce with a 7Li-enrichment (CLYC7) scintillator, has been developed for a neutron energy diagnostic in large helical device (LHD) plasma in the 2020 experimental campaign. The CNES, installed on a tangential sightline, is utilized to measure neutron energy spectra from tangentially-injected negative-ion-based neutral beam (N-NB) heated deuterium plasmas. In this paper, an initial result of the Doppler-shifted neutron spectrum is reported.journal articl
Commentary:Molecular dynamics simulation on tritium-induced damage of biopolymers and experimental system for validation
Get PDF0000-0002-0593-8810トリチウムの生体への影響は，トリチウム由来の線の飛程が水中や細胞中で数ミクロン程度と短いため，外部被ばくが問題となることはなく，内部被ばくに対する防護が重要となってくる．国内外の研究者によりマウスなどを用いての研究など同分野の研究は広く行われてきている．一方，我々は現実の生体そのものの階層ではなく，原子分子レベルの階層に絞り，トリチウムが生体分子（DNA）へ与える影響を分子動力学シミュレーションで解き明かすと共に，それにより生体分子の損傷機構解明をめざしてきた．さらに，シミュレーションと相補的に，蛍光顕微鏡を用いたDNA 一分子観察法によりトリチウム水中でのDNA の二本鎖切断メカニズムの測定も行ってきている．このような研究の試みは，複雑な生命体そのものに短絡的に結びつけるには，いまだ隔たりがあるが，生体分子そのもののトリチウム影響の必要な基礎情報の蓄積をめざすものである．このように核融合研究で培ってきたシミュレーション技法・測定技法を用いた「トリチウムの影響評価」の試みを紹介する．journal articl
ANNUAL REPORT OF NATIONAL INSTITUTE FOR FUSION SCIENCE April 2020 - March 2021
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Core size effects of laser fusion subcritical research reactor for fusion engineering research
Get PDFA multi-purpose high repetition laser facility, the so-called Japan establishment for power-laser community harvest (J-EPoCH) is proposed as a next generation laser facility. J-EPoCH will operate at the maximum rate of 100 Hz. The omnidirectional 12 laser beams with 8 kJ would yield ∼1013 neutrons with a large high aspect ratio target. As one of the applications of J-EPoCH, a laser fusion subcritical research reactor has been conceptually designed based on existing technologies. Moreover, a variety of fusion engineering studies: energy conversion, tritium breeding, neutron irradiation effects, etc, can be conducted. The feasibility of the subcritical research reactor is considered in terms of neutron-thermal (n-t) conversion and tritium breeding. Lead–lithium alloy (Li17Pb83) and boron carbide (B4C) have the potential to be studied for preliminary fusion power generation. The subcritical reactor will generate 21.4 W and 20.0 W of the thermal fusion power with the Li17Pb83 and the B4C layers of the thickness of 80 cm, respectively at 1 Hz operation. The Li17Pb83 layer of a 5 mm thickness will achieve the temperature rise of 0.203 mK per shot. The thermal fusion energy is detectable with conventional measurement techniques. The core with the Li17Pb83 layer thickness of 100 cm will yield more than one tritium from a deuterium–tritium fusion neutron. However, laser windows reduce the efficiency of n-t conversion and tritium yield.** After this version, the author still has made a few minor corrections.journal articl
Design for the distributed data locator service for multi-site data repositories
Get PDF0000-0001-6388-4489The Remote Experimentation Centre (REC) in Japan has been preparing to replicate the full dataset of ITER over 10 000 km distance. In such a multi-site data repository environment, the data location informing service will be essential to find and retrieve the data efficiently. Considering the long latency time and the self sustainability of remote sites, the data location database should be running at each repository site. Multi-master asynchronous replication between cooperating databases will be essential to realize the remote experimental collaborations in fusion research. This study has investigated the functional differences of some relational databases and found that Postgres BDR has the expected database replication capabilities. Bi-directional replication (BDR) tests by using the LHD database and SNET revealed that the throughputs are sufficient for remote collaborations in fusion experiments.journal articl
Identification of Normal Transition in a Bundle HTS Cable Used for an HTS Transformer
Get PDF0000-0001-8589-1735We have been developing an AC power source with a high-temperature superconducting (HTS) transformer that is small and can supply a large AC current. The HTS transformer needs a detection system of normal transition for high reliability. We have proposed the active power method as the detection system. The system enabled early detection of the normal transition in a secondary coil of the transformer, which was wound with a bundle of some HTS tapes. However, we could not identify the normally transited HTS tape in bundle conductors using the conventional method. Therefore, in this paper, we propose a method to identify the normally transited HTS tape in the bundle conductor by improving the active power method. The improved method is based on measuring the active power in each HTS tape in the bundle conductor. Experiment results show that the proposed method works successfully for early and accurate identification under outputting a secondary maximum current of 1 kApeak at 1 kHz.journal articl
Erratum: “Conceptual Design of HFIR Irradiation Experiment for Material Compatibility Study on Liquid Sn Divertor” [Plasma Fusion Res. 16, 2405040 (2021)]
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Results of All ITER TF Full-Size Joint Sample Tests in Japan
Get PDF0000-0002-1437-9467Nine toroidal field (TF) coils have been developed in Japan for the international thermonuclear experimental reactor (ITER). The joint resistance of TF coil should satisfy the requirement of smaller than 3 nano-ohm at 2 T of external magnetic field and 68 kA of transport current. Full-size joint sample (FSJS) tests were performed for joint development and for TF coil manufacture, as part of the process control. 11 FSJS tests are conducted in total. FSJS tests were conducted with assistance from a test faculty in the National Institute for Fusion Science as reported in a previous paper. All FSJS tests successfully satisfied the requirement of resistance less than 3 nΩ at 2 T. Additionally, the TF coil joints are subjected to cyclic electromagnetic force and warm-up/cool-down during the ITER operation. The authors investigated the joint performance for the abovementioned influence. The results showed no degradation in the joint resistance. Thus, the TF joint developed in Japan was qualified successfully.journal articl