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Calculation of electronic excitation cross sections and rate coefficients for boron monohydride (BH)
Get PDF0000-0002-1021-0322Aiming at the quantitative diagnostics of boron monohydryde, BH, in fusion plasmas, we present elastic, electronic excitation, and ionization cross sections of BH for the first time. The calculations were performed by the R-matrix and Born Encounter Bethe methods utilized by Quantemol-EC software. To examine the uncertainty due to the calculation conditions, we compared the results by different basis sets and internuclear distances of the target model. We found that the uncertainties are typically within ∼10%. Rate coefficients were derived and fitted to an Arrhenius function. The derived decay rate per photon, , agreed with the value presented by Lieder et al (the ASDEX-Upgrade Team) (1994 Eur. Phys. Soc. Conf. Plasma Phys.2 722).journal articl
Measurement of thermal expansion anisotropy in Be12Ti and Be12V
Get PDFORCID 0000-0001-8067-8732Be12Ti and Be12V are promising candidates for neutron multipliers in solid breeding blankets, which is used in a bulk form to achieve the fuel tritium self-sufficiency. Previously, significant anisotropic thermal expansions were predicted for Be12Ti and Be12V along different crystallographic axes using density functional theory (DFT) calculations. Nevertheless, empirical confirmation through experimental data on thermal expansion anisotropy remains lacking. In this study, the thermal expansion behaviors of these materials were experimentally investigated by using high-temperature X-ray diffraction. Diffraction data were collected temperatures up to 873 K under vacuum condition, and structural refinement was carried out by Le Bail analysis using a partial structure. The results demonstrate that these materials exhibit moderate anisotropic expansion along the c-axis direction, contrary to previous prediction for Be12Ti. The average thermal expansion coefficients were compared with those of ceramic breeder pebble beds and structural steel material to discuss thermo-mechanical compatibility in a breeding blanket.journal articl
Feasibility study of a Heavy Ion Beam Probe for the Thailand Tokamak-1
No full textORCID 0000-0003-3956-8085The Heavy Ion Beam Probe (HIBP) diagnostic system offer non-disturbing, local measurement of plasma electric potential and various plasma parameters. This paper presents a conceptual design of implementing the HIBP system in the Thailand Tokamak-1 (TT-1). With successful plasma discharges achieved in early 2023, TT-1 is planed for upgrades and expansion of diagnostic capabilities to conduct experiments in high confinement modes. Port K is designated for the installation of the HIBP diagnostic system, where primary beam ions are injected through the top port and secondary beam ions emerge from the horizontal port. By employing a sweeper region with a 25 cm length and a 30-degree inclination, the vertical electric field ensures the secondary beam ions reach the energy analyzer entrance at the center with normal angles. Candidate ions, such as Cs+, Rb+, and K+, with varying injection energies, are evaluated for their suitability based on beam attenuation and plasma density conditions. Cesium ions exhibit optimal performance at lower densities (¯ne ≤ 1 × 1019 m−3), while Rb+ and K+ become preferable at higher plasma densities (¯ne ≥ 1 × 1019 m−3).
The analysis indicates that the ratio of the attenuation current is approximately in the range of 10−3 to 10−2. This feasibility study provides valuable insights for the integration of the HIBP diagnostic system into TT-1, enhancing its diagnostic capabilities and enabling in-depth investigations of H-mode plasma physics phenomenajournal articl
Correlation of the Orthogonal Basis of the Core Plasma Distribution to the Divertor Footprint Distribution in LHD
Get PDF0000-0002-8025-008XWe have applied the multivariable analysis technique called the proper orthogonal decomposition (POD) to both the divertor particle flux distribution and the electron pressure distribution in the core region of LHD. The cross-correlation analysis indicates that 3rd, 4th, and 5th POD modes of the electron pressure distribution are highly correlated with the divertor footprint index which is a measure of where the peak position of the particle flux distribution is located on the inner divertor plate. Both the 3rd and 4th modes seem to correspond to the shift of the electron pressure peak position from the magnetic-axis radius. In contrast, 5th mode has a strong influence on the peripheral gradient of the electron pressure distribution. Their relationships with the divertor footprint could be explained by the finite β and the Pfirsch-Schlüter current effects.journal articl
Tritium decontamination in vacuum vessel after deuterium plasma experiment due to air exposure
Get PDF0000-0001-9941-1958The deuterium plasma experiment using Large Helical Device (LHD) has been conducted since 2017. A small amount of tritium was produced in the vacuum vessel and a part of tritium remained in the plasma-facing materials. After the deuterium plasma experimental campaign, the vacuum vessel was opened for the LHD maintenance activity. Then, the plasma-facing material was exposed to room air and remained tritium was released at ambient temperature. The tritium release rate increased rapidly immediately after the vacuum vessel was opened to the atmosphere, but it turned to decrease soon after. After several weeks of opening the vacuum vessel, the tritium release rate became low and almost constant. The total tritium decontamination rate, defined as the ratio of tritium released by air exposure to tritium produced during the plasma experimental campaign, was achieved at several percent. The air exposure operation is expected to have a decontamination effect due to isotope exchange reactions on the surface of the plasma-facing material.journal articl
An Inductively Coupled Plasma System for Investigating Spectropolarimetric Responses of Solar Plasmas to Anisotropic Fields
Get PDFHigh precision measurements and accurate modeling of atomic polarization under three-dimensional radiation transfer are crucial to understand the structures of magnetized solar plasmas. To develop and validate spectropolarimetric measurements and analyses, we set up an inductively coupled plasma (ICP) generator designed especially for ∼ 1-eV plasmas interacting with radiation and weak magnetic fields. The device was put in front of the focal plane of the Horizontal Spectrograph of the Domeless Solar Telescope at Hida Observatory of Kyoto University. In helium discharges, the typical electron temperature, electron density, and helium column density of the ICP are comparable values to those of solar prominences, and the direct comparison of spectra shows almost the same opacity at He I 1083 nm. Magnetic and radiation fields were introduced to the ICP, and the system successfully reproduced reasonable spectropolarimetric signals as compared with those from the solar prominences.journal articl
統計数理核融合学 ～統計数理による核融合研究課題の取り組み～
Get PDF0000-0001-8856-14832022年7 月の第14回核融合エネルギー連合講演会にて特別講演「データ駆動核融合科学」を行った。核融合研究におけるデータ駆動アプローチによる研究遂行の大きな可能性を述べたものであり、その内容を文章としてまとめておくのが本記事の主旨である。特に、リアルタイム制御や、そのための予測や判断が必要とされる課題への挑戦には重要な視点であると考えている。また、核融合の研究課題を、学問分野を超えて共有・協働する上で効果的な視点であり、核融合コミュニティの拡大、学問としての拡がりにも大いに寄与する．特に、統計数理分野との協働を意図して、“統計数理核融合学”（統計数理による核融合研究課題への取り組み）という言葉とともに問いたい。journal articl
Identification of Magnetic Islands in Optimized Configuration
Get PDFTo aim at the realization of a helical fusion reactor, we study multi-objective optimization of coil shapes, which satisfy various requirements. In the magnetic field configuration created by these coils, several unfavorable examples are found: some of them have magnetic islands or doublet configurations. In order to automatically and quickly exclude such cases that hinder the optimization, we have developed a new method to detect unfavorable magnetic surfaces by using image recognition. Binarization and erosion are performed as preprocessing, and then blanks of magnetic islands and doublets are extracted as recognition targets. Consequently, we have developed a classifier with high performance. Using this trained classifier, we have shown that almost all cases with unfavorable magnetic surfaces in various magnetic configurations can be excluded in a short time and with high precision.journal articl
Hot electron and ion spectra on blow-off plasma free target in GXII-LFEX direct fast ignition experiment
Get PDFPolystyrene deuteride shell targets with two holes were imploded by the Gekko XII laser and additionally heated by the LFEX laser in a direct fast ignition experiment. In general, when an ultra-intense laser is injected into a blow-off plasma created by the imploding laser, electrons are generated far from the target core and the energies of electrons increase because the electron acceleration distance has been extended. The blow-off plasma moves not only to the vertical direction but to the lateral direction against the target surface. In a shell target with holes, a lower effective electron temperature can be realized by reducing the inflow of the implosion plasma onto the LFEX path, and high coupling efficiency can be expected. The energies of hot electrons and ions absorbed into the target core were calculated from the energy spectra using three electron energy spectrometers and a neutron time-of-flight measurement system, Mandala. The ions have a large contribution of 74% (electron heating of 4.9 J and ion heating of 14.1 J) to target heating in direct fast ignition.journal articl
Numerical Analysis of Hysteresis Loss in Stacked REBCO Tapes for Large Current-Carrying Conductors
Get PDF0000-0002-1989-867XTo evaluate the hysteresis loss in stacked HTS tapes for large current-carrying conductors, a single REBCO tape and 50 stacked REBCO tapes were modeled with the finite element method, including T-A formulation. Using the model, hysteresis losses in the single and stacked tapes were calculated under a condition that the direction of an external varying magnetic field was perpendicular to the tape plane. The calculation results were in good agreement with the measurement results. Consequently, the developed models are valid for a hysteresis loss calculation. In addition, we investigated magnetic field penetration into the stacked tapes using the model. The investigation shows that the external varying magnetic field used in the measurements cannot penetrate the center of the stacked tapes.journal articl