A5012802811- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Gyrotron and Vacuum Electronics Research
- Electrostatic Discharge in Electronics
- Dust and Plasma Wave Phenomena
- Particle Accelerators and Free-Electron Lasers
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Quantum and electron transport phenomena
- Mass Spectrometry Techniques and Applications
- Gas Dynamics and Kinetic Theory
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Ion-surface interactions and analysis
- Nanopore and Nanochannel Transport Studies
- Metal and Thin Film Mechanics
- Atomic and Subatomic Physics Research
- GaN-based semiconductor devices and materials
- Vacuum and Plasma Arcs
Keio University
2015-2024
Naruto University of Education
2011-2019
University of Jyväskylä
2017-2018
European Organization for Nuclear Research
2018
Sumitomo Heavy Industries (Japan)
2017
High Energy Accelerator Research Organization
2017
National Institutes for Quantum Science and Technology
2017
College of Industrial Technology
2009-2016
Japan Atomic Energy Agency
1982-2013
National Institute for Fusion Science
2012
Abstract Several applications of PIC simulations for understanding basic physics phenomena in low‐temperature plasmas are presented: capacitive radiofrequency discharges Oxygen, dusty and negative ion sources heating fusion plasmas. The analysis these systems based on their microscopic properties as accessible with gives improved insight into complex behavior. These studies results joint efforts over about one decade research groups from Greifswald University, Germany; Bari Italy; Keio Japan...
This paper describes the recent progress in divertor simulation research using GAMMA 10/PDX tandem mirror towards development of divertors fusion reactors. During a plasma flow generation experiment end cell 10/PDX, ICRF heating anchor successfully extended particle flux up to 3.3 × 1023 m2 s−1. Superimposing short pulse ECH also attained maximum heat ~30 MW m−2. We have succeeded achieving and characterizing detachment high-temperature plasma, which is equivalent SOL tokamaks, by...
Abstract CSD (Core, SOL and Divertor) models sampling a fusion device with three points aim at understanding plasmas in wide range of parameter space. Conventional estimate interactions among plasmas, neutrals impurities, which are incorporated as loss factors basic equations models, the use physical quantities sampled points. Physical assumed to be uniform each regions. Neglecting plasma spatial distributions divertor prevents from accurately evaluating low temperatures. This is because...
We review the evolution of volume production negative hydrogen ion sources since discovery in 1977 new phenomenon, designated as and attributed to dissociative electron attachment low energy electrons rovibrationally excited molecules. The experimental verification 2005 reality this mechanism is reported. magnetically filtered tandem sources, using hot filaments or inductively coupled radio frequency discharges, proposed order make use mechanism, are used continuous wave for cyclotrons short...
We report on the characteristics of electronegative plasma in a large-scale hydrogen negative ion (H−) source. The measurement has been made with time-resolved Langmuir probe installed beam extraction region. H− density is monitored cavity ring-down system to identify electrons charges. electron-saturation current decreases rapidly after starting seed Cs, and ion-ion observed steps down during electron jumps up correspondingly. time integral decreasing charge agrees well collected probe....
We present a fully-implicit electromagnetic Particle-In-Cell Monte Carlo collision code, called NINJA, written for the simulation of inductively coupled plasmas. NINJA employs kinetic enslaved Jacobian-Free Newton Krylov method to solve self-consistently interaction between field generated by radio-frequency coil and plasma response. The simulated includes description charged neutral species as well processes them. algorithm allows simulations with cell sizes much larger than Debye length...
CERN's Linac4 45 kV H− ion sources prototypes are installed at a dedicated source test stand and in the tunnel. The operation of pulsed hydrogen injection, RF sustained plasma, high voltages described. first experimental results two relying on 2 MHz RF-plasma heating presented. plasma is ignited via capacitive coupling, by inductive coupling. light emitted from collected viewports pointing to chamber wall middle solenoid axis. Preliminary measurements optical emission spectroscopy photometry...
CERN’s 160 MeV H− linear accelerator (Linac4) is a key constituent of the injector chain upgrade Large Hadron Collider that being installed and commissioned. A cesiated surface ion source prototype tested has delivered beam intensity 45 mA within an emittance 0.3 π ⋅ mm mrad. The optimum ratio co-extracted electron- to ion-current below 1 best production efficiency, defined as current 2 MHz RF-power transmitted plasma, reached 1.1 mA/kW. first tests new optics, electron-dump, front end...
Recently, in large-scale hydrogen negative ion sources, the experimental results have shown that ion-ion plasma is formed vicinity of extraction hole under surface production case. The purpose this paper to clarify mechanism formation by our three dimensional particle-in-cell simulation. In present model, electron loss along magnetic filter field taken into account “τ///τ⊥ model.” simulation show due field. Moreover, potential profile for case has been looked carefully order discuss...
The compact reversed shear tokamak CREST is a cost competitive reactor concept based on high β plasma and water cooled ferritic steel components. moderate aspect ratio A = 3.4 the elongation κ 2.0 of are very similar to case ITER advanced mode plasma. Presentation such project should be worth while for formulating fusion development strategy. achievement electricity (COE) first priority electric power industries. High thermal efficiency most effective parameters achieving COE. In order...
Recent progress in numerical modeling of H(-) ion sources has been reviewed. The following two topics are mainly the focus: (1) origin nonuniformity production and beam large (2) extraction physics, especially role "weak" transverse magnetic field on extraction. present understanding is reviewed discussed with results by a series Monte Carlo transport electrons, neutrals, ions. Also, physical mechanism enhancement due to weak particle cell modeling. In addition, some new effect surface...
This numerical study focuses on the physical mechanisms involved in extraction of volume-produced H− ions from a steady state laboratory negative hydrogen ion source with one opening plasma electrode (PE) which dc-bias voltage is applied. A weak magnetic field applied transversely to extracted beam. The goal highlight combined effects and PE bias (upon process electrons). To do so, we focus behavior electrons within two-dimensional model using particle-in-cell method. No collision processes...
Two volume sources equipped with DESY and CERN plasma generators a low voltage electron dump were operated at 45 kV in the Linac4 tunnel on dedicated test stand. These delivered approximately 20 mA ensured commissioning of Radio Frequency Quadrupole accelerator first section Drift Tube Linac. CERN's prototype cesiated surface source this was continuously from November 2013 to April 2014 ion stand is being commissioned tunnel. Before cesiation, conditioned mode provided up 30 H− beam. Short...
A meniscus of plasma-beam boundary in H− ion sources largely affects the extracted beam optics. Although it is hypothesized that shape one main reasons for halo observed experiments, a physical mechanism formation not yet fully understood. In this letter, first shown by 2D particle cell simulation ions from periphery cause since surface produced penetrate into bulk plasma, and, thus, resultant has relatively large curvature.
To understand the physical mechanism of beam halo formation in negative ion beams, a two-dimensional particle-in-cell code for simulating trajectories ions created via surface production has been developed. The simulation reproduces observed an actual beam. extracted from periphery plasma meniscus (an electro-static lens source plasma) are over-focused extractor due to large curvature meniscus.
In order to obtain a better understanding of tungsten (W) transport processes, we are developing the Monte-Carlo W code IMPGYRO. The has following characteristics which important for calculating transport: (1) exact Larmor motion ions is computed so that effects drifts automatically taken into account; (2) Coulomb collisions between impurities and background plasma modelled using Binary Collision Model provides more precise kinetic calculations friction thermal forces. By IMPGYRO code,...
The linear divertor analysis with fluid model (LINDA) code has been developed in order to simulate plasma behavior the end-cell of fusion device GAMMA 10/PDX. This paper presents basic structure and simulated results LINDA code. atomic processes hydrogen impurities have included present investigate energy loss mechanism detachment. A comparison among Ar, Kr Xe shows that is most effective gas on reduction electron ion temperature. injection leads strong temperature ion. terms for both are...
We have investigated the synergistic effect of a combination various impurity gases and hydrogen gas on plasma detachment high temperature plasma, equivalent to scrape-off layer tokamaks in GAMMA 10/PDX end region, utilizing an open magnetic field configuration. A small puff (N2, Ne, Ar, Kr, Xe) with H2 is examined evaluate their formation detached plasma; following results are obtained. (i) N2 puffs showed clear decrease electron density ion flux; (ii) form strong gradient along axial...
The origin of longitudinal beam non-uniformity, which is one the key issues in large caesium (Cs)-seeded negative ion sources for fusion application, was experimentally investigated JAERI 10 A source. sufficient seeded source to enhance production. intensity with Cs typically four times higher than that without Cs, and relatively high upper region where electron temperature plasma density were high. This distribution significantly different from Cs. From correlation between parameters, it...
The present status of kinetic modeling particle dynamics in hydrogen negative ion (H−) source plasmas and their comparisons with experiments are reviewed discussed some new results. main focus is placed on the following topics, which important for research development H− sources intense high-quality beams: (i) effects non-equilibrium features electron energy distribution function volume surface production, (ii) origin spatial non-uniformity giant multi-cusp arc-discharge sources, (iii)...
The influence of magnetic filter configuration on the beam uniformity was examined to improve in a large Cs-seeded negative-ion source. By reducing strength transverse field used typical source, largely improved with improvement plasma while intensity kept be nearly constant. However, coextracted electron current greatly increased. To suppress current, tent-shaped applied together modifications cusp magnets form multicusp positive-ion source arrangement. longitudinal profile deviation local...
The production and transport processes of H0 atoms are numerically simulated using a three-dimensional Monte Carlo code. code is applied to the large JAEA 10ampere negative ion source under Cs-seeded condition obtain spatial distribution surface-produced H− ions. In this analysis, amount produced through dissociation H2 molecules calculated from electron temperature density obtained by Langmuir probe measurements. high-energy tail electrons, which greatly affects atom production, taken into...
For optimization and accurate prediction of the amount H-ion production in negative ion sources, analysis electron energy distribution function (EEDF) is necessary. We are developing a numerical code which analyzes EEDF tandem-type arc-discharge source. It three-dimensional Monte Carlo simulation with realistic geometry magnetic configuration. Coulomb collision between electrons treated “binary collision” model collisions hydrogen species “null-collision” method. applied this to JAEA 10 A...