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Two-dimensional beam emission spectroscopy for hydrogen isotope negative neutral beam in Large Helical Device
Get PDF0000-0001-5669-1937A new beam emission spectroscopy system that has improved lines of sight is installed in the Large Helical Device (LHD), and routine measurement has been started in the 21st LHD experiment campaign in 2019–2020. The new system is optimized for hydrogen isotope experiments by equipping a rotatable large-diameter interference filter to be compatible with either the hydrogen or the deuterium beam emission component. An avalanche photo diode detector array having 8 × 8 pixels is used for obtaining a radial–vertical image of electron density fluctuation covering the mid-radius to the plasma periphery. Spatial resolution and wavenumber cutoff are derived from equilibrium reconstruction and plasma kinetic profiles. Obtained fluctuation data is presented for a low field high beta discharge. The spatiotemporal structure of the fluctuations is clearly shown by Fourier correlation analyses.journal articl
Identifications of extreme ultraviolet spectra of Br-like to Ni-like neodymium ions using an electron beam ion trap
Get PDF0000-0001-6536-9034Accurate extreme ultraviolet spectra of open N-shell neodymium (Nd) ions were recorded at the electron beam ion trap facility of the National Institute of Standards and Technology. The measurements were performed for nominal electron beam energies in the range of 0.90 keV to 2.31 keV. The measured spectra were then compared with the spectra simulated by a collisional-radiative model utilizing atomic data produced with a fully relativistic atomic structure code. Consequently, 59 lines from Br-like to Ni-like Nd ions were unambiguously identified, most of which were newly assigned in this study. The wavelengths of 9 known lines from Ni-, Cu- and Zn-like Nd ions were in excellent agreement with previous measurements.journal articl
Identification of visible lines from multiply charged W8+ and W9+ ions
Get PDF0000-0001-6263-6563We present an investigation of previously unidentified visible lines for W8+ and W9+ from the spectra observed using an electron-beam ion trap. The analysis is based on collisional-radiative (CR) modeling with fine-structure sublevel population kinetics. To ensure the identification of lines done by the CR model, we have also performed an accurate calculation of transition energies and transition probabilities within the multiconfigurational Dirac-Fock approach using grasp2018. In the spectrum, most of the observed lines are assigned as magnetic dipole transitions belonging to the first two lower-lying configurations of these ions.journal articl
Void Free Fuel Solidification in a Foam Shell FIERX Target
Get PDF0000-0002-9217-8812We study fuel layering for the Fast Ignition Realization EXperiment (FIREX) cryogenic target with a foam shell. A void free solid fuel layer within a porous foam material must be formed ideally. We have demonstrated the residual void fraction of ∼1% in a foam wedge with temperature controlled solidification. ANSYS simulations have shown that the residual void reduction technique will be applicable to the FIREX target. We examined each step in the simulated solidification process using a dummy foam shell target. In several attempts, solid fuel formation with a reduced void fraction in the foam shell succeeded.journal articl
Tuning of Density Functional Theory Simulation on Vector Processor System - Plasma Simulator Raijin -
Get PDF0000-0003-2345-0146We rapidly report the benchmark of density functional theory simulation on the Plasma Simulator composed of vector processor. The improved OpenMX code on the SX-Aurora TSUBASA of the vector processor achieved performance higher than the Intel Xeon Gold of the scalar processor.journal articl
Development of a Molecular Dynamics Method with Heat Transfer into Bulk for Ion Injection into Materials
Get PDFWhen an ion or atom is injected into a target material, the incident energy increases the temperature around the injection point. Owing to the energy transfer to the surrounding atoms, the temperature of the material recovers to the initial temperature in the real system because heat is transferred to the bulk of material which consists of an almost infinite number of atoms. However, if we simulate the system by the molecular dynamics (MD) method, it is difficult to prepare a sufficiently large system to calculate the process of heat transfer to the bulk. Therefore, in this study, we develop an MD simulation model which includes the effect of heat transfer to the bulk by solving heat conduction equation. The simulation result shows that the process of heat removal proceeds on a time scale of approximately 1000 times slower than the time scale of the incident energy transfer from the incident atom to the target material.journal articl
Transient Electron Thermal Transport Analysis Accounting Oblique Electron Cyclotron Resonance Heating Injection to Magnetic Field Line
Get PDF0000-0001-5669-1937In response to recent upgrade of the raytracing code for the electron cyclotron resonance heating (ECH) in LHD, transient electron thermal transport is reanalyzed. The upgraded code LHDGauss-U takes into account the oblique injection of the ECH ray to magnetic field line. The obtained results show reduced transport hysteresis widths by up to ∼ 20% where the heating absorption is less significant, but qualitative features of the transport hysteresis reported in previous studies are found to be preserved.journal articl
Measurements of D/H Ratio Using Compact Neutral Particle Analyzer in LHD Deuterium Experiments
Get PDFThe deuterium/hydrogen ratio in the plasma strongly affects against the plasma heating and other behaviors. The ratio in high energy region is measured by the charge exchange neutral particle analyzer instead of the spectroscopic technique. The ratio has obtained by reducing the electrostatic plate voltage in the compact neutral particle analyzer, which is tuned for hydrogen measurement. When the voltage is adjusted for deuterium, hydrogen simultaneously enters as contamination because the hydrogen orbit is closed to the mid-plane. Here, the mass rejection factor has been evaluated and the time variation of the ratio in the low and high energy regions during hydrogen and deuterium neutral beam injection is described. The behavior of the ratio in high and low energy regions can be explained by the classical slowing down process of the energetic particle.journal articl
Preliminary Investigation of Pretreatment Methods for Liquid Scintillation Measurements of Environmental Water Samples Using Ion Exchange Resins
Get PDF0000-0002-0580-0328This paper presents an evaluation of a rapid pretreatment method for tritium analysis, that uses ion exchange resins (the batch method). The standard water samples were prepared with river water collected in Okinawa, Japan. Powdex resin was used in this study, which is an ion exchange resins in the form of powder beads. First, 100 mL of the standard sample was stirred with the cation exchange (PCH) and anion exchange (PAO) resins, as well as with activated carbon. To determine the optimal stirring time, we tested stirring times of 5, 10, 20 and 30 min. Additionally, to determine a suitable amount of ion exchange resin for environmental water samples, variations in the amount of resin and activated carbon were tested. Under the conditions of Experiment-3 (0.3 g, 0.3 g and 0.6 g of PCH, PAO and activated carbon, respectively) and with a stirring time of 5 min, electrical conductivity values of less than 1 mSm−1 were achieved. These results demonstrate the effectiveness of the removal of impurities in the sample water by ion exchange resins and confirm that such an effect can be achieved during a short period of time (i.e., in 5 min).journal articl
Observation of a nuclear-elastic-scattering effect caused by energetic protons on deuteron slowing-down behaviour on the Large Helical Device
Get PDF0000-0002-7498-4191A first attempt to observe a nuclear-elastic-scattering (NES) effect caused by energetic protons on deuteron slowing-down behaviour was made on the Large Helical Device located at the National Institute for Fusion Science. The NES effect on the slowing-down of fast ions can influence the confinement of fast ions, ion heating, fusion reaction rate coefficient, etc. An intense hydrogen beam was injected into a deuterium plasma to create a knock-on tail, i.e. a non-Maxwellian energetic component in the deuteron velocity distribution function. We conducted two types of experiment: (1) observation of the slowing-down of the knock-on tail and (2) observation of the NES effect on the slowing-down time of fast ions. The phenomena are discussed in terms of the difference in the decay process of the D(d,n)3He neutron generation rate after neutral beam heating is terminated between the cases when the knock-on effect is influential and not influential, and also from the difference in the neutron decay times. The results of a series of experiments indicate that the NES effect caused by energetic protons can have an impact on the slowing-down of fast deuterons.journal articl