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Turbulence Spreading into an Edge Stochastic Magnetic Layer Induced by Magnetic Fluctuation and Its Impact on Divertor Heat Load
Get PDF0000-0002-0990-7093Turbulence spreading into the edge stochastic magnetic layer induced by magnetic fluctuation is observed at the sharp boundary region in the large helical device. The density fluctuation excited at the sharp boundary region with a large pressure gradient does not propagate into the boundary region due to the blocking of turbulence spreading by the large second derivative of the pressure gradient. Once the magnetic fluctuation appears at the boundary, the density fluctuation begins to penetrate the edge stochastic layer and the second derivative of the pressure gradient also decreases. The increase of density fluctuation in this layer results in the broadening and reduction of the peak divertor heat load. It is demonstrated that magnetic fluctuation plays a key role in controlling the turbulence spreading at the boundary of plasma which contributes to the reduction of divertor heat load.journal articl
Refractive index measurements of solid deuterium–tritium
No full text0000-0001-8343-491XPhysical properties of tritium (T) and deuterium (D) have been of great interest as a fuel for nuclear fusion. However, several kinds of the physical properties in a cryogenic environment have not been reported. Optical properties in liquid and solid phases are indispensable for the quality control of the DT fuel. We study the dependence of the refractive index of solid DT on temperature. A dedicated cryogenic system has been developed and forms a transparent solid DT in a prism cell. Refractive index measurements based on Snell’s law were conducted. The refractive indexes of solid DT are from 1.1618 ± 0.0002 to 1.1628 ± 0.0002 in the temperature range of 19.40 K to 17.89 K.journal articl
Trial of Deep Learning for Image Reconstruction of Lens-Less Microwave Holography
Get PDFWe perform the principal verification of reconstructing object surface images by using deep learning. Using the deep learning neural network based on convolutional neural networks, simple object surface images with 128 × 128 pixels are reasonably reconstructed with up-converting from rough microwave signal images with 16 × 16 pixels. The model captures large structural features of the object surface images even with small number of training data. As the number of training data increases, it captures small structures of objects. It is also found that noises of input signal images affect reconstructions of small structures of objects.journal articl
Numerical Investigation on Applicability of jC-Measurement Method to Multiple High-Temperature Superconducting Tape
Get PDF0000-0003-4355-8293A numerical code has been developed in order to investigate the applicability of the permanent magnet method to vertically-stacked multiple high-temperature superconducting (HTS) tapes. The permanent magnet method was proposed to simply and contactlessly measure the critical current density in the HTS tape. By this method, the critical current density is estimated from the proportional relation between the critical current density and the Lorentz force working on the permanent magnet. The Maxwell equation, coupled with the superconductivity characteristics, is solved by the edge-based finite element method to investigate the effect of the number of HTS tapes on the Lorentz force. As a result, it is clear that the permanent magnet method can be applied to measurement of the critical current density in the multiple HTS tapes although there is an upper limit of the number of HTS tapes in which the critical current density can be measured. In addition, by using stronger magnet, the permanent magnet method can measure the critical current density when more number of HTS tapes are stacked.journal articl
Fast-ion orbit analysis in Thailand Tokamak-1
Get PDF0000-0002-0801-5106Thailand Tokamak-1 (TT-1) will be a small research tokamak being operated by the Thailand Institute of Nuclear Technology (TINT) in Nakhonnayok province, Thailand. The device partly uses the infrastructure of the former HT-6M alongside new hardware. Auxiliary heating sources, such as ion cyclotron range of frequency (ICRH) and/or neutral beam injection (NBI), maybe also included in subsequent operations. This study aims to investigate the characteristics and behavior of fast ions produced by NBI heating in various operation scenarios. This work employs the collisionless Lorentz-orbit (LORBIT) code for simulating the motion of ions in the TT-1. When a hydrogen ion (H+) with an energy of 20 keV travels in the plasma with the plasma current of 100 kA, the toroidal magnetic field of 1.0 T, the average Larmor radius is found to approximately be 0.48 cm for a passing transit particle and 2.17 cm for a trapped particle. The Larmor radius reduces as the plasma current is increased or a stronger magnetic field is used. Furthermore, when the ion has pitch angles in the range of 85°-100°, the ion orbit clearly demonstrates a banana shape with a width and height of 7.0 and 18.8 cm, respectively. The size of the banana orbit shows an inverse correlation with the plasma current. In the last part of this work, we investigate the motion of ions that had initial positions along the paths of a co-current and counter-current NBI. It is shown that the number of lost ions can be reduced if the initial radial positions of the ions are in the range of 0.64–0.68 m.journal articl
Monthly Precipitation Collected at Hirosaki, Japan: Its Tritium Concentration and Chemical and Stable Isotope Compositions
Get PDFMonthly precipitation samples were collected at Hirosaki, Aomori Prefecture from January 2018 to December 2020 to measure the ion species and stable hydrogen and oxygen isotope ratios in order to understand the regional properties. The tritium concentration ranged from 0.28 to 1.20 Bq/L, with mean values (±S.D.) of 0.52 ± 0.18, 0.67 ± 0.25 and 0.63 ± 0.21 Bq/L in 2018, 2019 and 2020, respectively. This concentration level was almost the same as for Rokkasho, Aomori Prefecture. The tritium concentration had clear seasonal variation: high in the spring and low in the summer. This trend was thought to arise from seasonal fluctuations in the atmospheric circulation. On the other hand, the pH tended to be low, and the electrical conductivity (EC) tended to be high from the winter to the spring. The ion components, which major ion species contained in sea salt, also tended to be high in the winter, and these components had a strong influence on EC. The d-excess values were high in the winter and low in the summer, and when this trend was considered from the viewpoint of the wind direction data in Hirosaki, these dust components were attributed to the northwest monsoon in the winter to the spring coming from the Asian continent.journal articl
マイクロ波CTマンモグラフィの開発
Get PDF24個の固定ダイポールアンテナを用いて三次元マイクロ波CT実験を行い，スーパーコンピュータを用いてForward-Backward Time Stepping（FBTS）法によるCT計算を行った．その結果得られた知見は，FBTS法が雑音に強いこと，及び計算の初期設定やキャリブレーション設定が精度向上に重要なことである．また計算モデル化が容易な広帯域平面アンテナの開発も行った．これらの知見を生かし，FBTS法マイクロ波CTマンモグラフィ装置の概念設計を行った．journal articl
Effects of titanium concentration on microstructure and mechanical properties of high-purity vanadium alloys
Get PDF0000-0001-5706-0221Effects of Ti concentration on microstructure and mechanical properties of high-purity V-4Cr-xTi alloys have been studied by means of scanning electron microscopy, transmission electron microscopy, Vickers hardness and tensile tests. Results show that precipitation occurs with 1 wt% Ti addition and above, whose diameter gradually increases as Ti concentration rises. Vickers hardness and tensile strength increase with increasing Ti concentration. Moreover, strengthening mechanisms consisting of solid solution strengthening (σSS), grain boundary strengthening (σGB), and precipitation strengthening (σP) are theoretically estimated. The strength contribution sequence is σSS > σGB > σP. Solid solution strengthening from Ti increases with increasing Ti concentration, and precipitation strengthening is not significantly dependent on Ti concentration. Additionally, 1 wt% Ti is probably sufficient to scavenge the interstitial impurities and provide comparable precipitation strengthening with V-4Cr-4Ti alloy.journal articl
Isotope effects under the influence of global radial electric fields in a helical configuration
Get PDF0000-0003-2513-0453Isotope effects under the influence of a radial electric field are examined in a helical magnetic field configuration. We perform global gyrokinetic simulations with additional poloidal rotations to estimate quasi-linear heat flux due to ion temperature gradient mode under the mixing length model. In single-ion-species plasmas, the mass number dependency of heat flux agrees with gyro-Bohm scaling in the absence of a radial electric field. Favorable mass number dependencies violating gyro-Bohm scaling are observed in the presence of a global radial electric field or a heavy hydrogen component in multi-ion-species plasmas. The radial electric field and the heavy hydrogen component affect the heat flux through an increase of wavelength as well as mode stabilization. Poloidal Mach number characterizes the transition from unfavorable to favorable mass number dependency under radial electric fields. While the heat flux is independent of mass number for a given poloidal Mach number, the heat flux decreases for higher mass numbers in a given radial electric field. The heat flux is also independent of average mass number in multi-ion-species plasmas because the heavy hydrogen component effectively enhances the light hydrogen heat flux. The present results are potentially relevant to the violation of gyro-Bohm scaling observed in the recent deuterium experiments in the Large Helical Device.journal articl
A gamma ray spectrometer with Compton suppression on the HL-2A tokamak
Get PDF0000-0002-9269-3996A new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression function has been developed recently in the HL-2A tokamak to obtain the gamma ray information in the energy range of 0.1–10 MeV. This is the first time to develop an anti-Compton GRS for a magnetic confinement fusion device. The anticoincidence detector consists of a large-volume high purity germanium (HPGe) crystal (Φ63 × 63 mm2) as the primary detector and eight trapezoidal bismuth germinate (BGO) scintillators (trapezoid crystal with 30 mm thickness) as the secondary detector. The anti-coincidence data processing is implemented by a digital-based data acquisition system with fast digitization and software signal processing technology. Using radioisotope gamma ray sources and Monte Carlo N-Particle code, the energy and efficiency of the spectrometer have been calibrated and quantitatively tested. The Compton continuum suppression factor reaches 4.2, and the energy resolution (Full Width at Half Maximum) of the 1.332 MeV full energy peak for 60Co is 2.1 keV. Measurements of gamma ray spectra with Compton suppression using the spectrometer have been successfully performed during HL-2A discharges with different conditions. The performance of the spectrometer and the first experimental results are presented in this paper.journal articl