A5102969618- Fusion materials and technologies
- Ion-surface interactions and analysis
- Magnetic confinement fusion research
- Diamond and Carbon-based Materials Research
- Plasma Diagnostics and Applications
- Metal and Thin Film Mechanics
- Nuclear Materials and Properties
- Ionosphere and magnetosphere dynamics
- High-pressure geophysics and materials
- Graphene research and applications
- Microwave Engineering and Waveguides
- Dust and Plasma Wave Phenomena
- Laser-induced spectroscopy and plasma
- Particle accelerators and beam dynamics
- Boron and Carbon Nanomaterials Research
- Laser-Plasma Interactions and Diagnostics
- Electromagnetic Simulation and Numerical Methods
- Hydrogen Storage and Materials
- Force Microscopy Techniques and Applications
- Vacuum and Plasma Arcs
- Catalytic Processes in Materials Science
- Superconducting Materials and Applications
- Fluid Dynamics and Turbulent Flows
- Advanced materials and composites
- Advanced Chemical Physics Studies
National Institute for Fusion Science
2011-2023
National Institutes of Natural Sciences
2001-2023
The Graduate University for Advanced Studies, SOKENDAI
2023
Nagoya University
2014
Kyushu University
2013
Kyoto University
1995-1998
For the purposes of long-term use tungsten divertor walls, formation process fuzzy nanostructure induced by exposure to helium plasma was studied. In present paper, nanostructure's has been successfully reproduced new hybrid simulation method in which deformation material due pressure bubbles simulated molecular dynamics and diffusion atoms random walk based on Monte Carlo method. By results, surface height increased only when retention under steady state. It proven that growth brought about...
A Monte Carlo (MC) impurity code IMPMC has been coupled self-consistently with a divertor SOLDOR/NEUT2D by overcoming the intrinsic problems of MC modelling for transport. is required transport in order to take into account kinetic effect and complex dissociation processes hydrocarbons. The integrated SONIC enables us investigate details including erosion/redeposition on plates further coupling an 3D plasma–surface interaction EDDY. dynamic evolution X-point MARFE observed JT-60U...
The bursting and expansion of helium bubbles near the surface a tungsten material were investigated by using molecular dynamics (MD) simulation. These bubble processes are considered to be important in formation mechanism fuzzy nano-structures. phase diagram occurrence was obtained our MD results simulation indicate that with radius 1.0 nm needs high pressure several tens GPa burst expand structures under scale ten nanometers. Moreover, from viewpoint dynamics, imply concavities convexities...
It was observed that the vacuum magnetic island produced by an external error field in large helical device shrank presence of plasma. This evidenced disappearance flat regions electron temperature profile obtained Thomson scattering. behavior depended on configuration which plasmas were produced.
Tungsten was exposed to pure Ar or Ne plasmas over 1550 K at several incident ion energies. Even under the irradiation condition that tungsten nanostructure is formed by He plasma irradiation, holes/bubbles and fiberform nanostructures were not on surface exposure plasmas. In addition, results from energy dispersive X-ray spectroscopy supported facts did remain in sample. We will discuss reason for differences damage noble gas
We report the chemical interaction between a single hydrogen atom and graphene via classical molecular dynamics simulation using modified Brenner empirical bond order potential. Three interactions, that is, adsorption, reflection, penetration, are observed in our simulation. The rates of interactions depend on incident energy temperature. This dependence can be explained by following mechanisms: (1) experiences repulsive force due to π electrons. (2) adsorbs transforms its structure an...
We examine the binding energy of helium trapped in a tungsten monovacancy using first-principles calculation based on density functional theory (DFT) and investigate trapping multiple atoms within monovacancy. Calculation shows that can contain at least nine atoms. find six monovacancy-trapped form kind cluster structure with an octahedral configuration, is tightly bound around located center W cube.
To represent the formation of fuzzy nanostructures produced on a tungsten surface by exposure to helium plasma, we have developed hybrid simulation method that combines binary collision approximation, molecular dynamics, and kinetic Monte Carlo calculations (BCA-MD-KMC). Since MD code has been parallelized using domain decomposition (DDM) for execution in multi-CPU environment, BCA from scratch mesh it efficiently with DDM. The BCA-MD-KMC achieved irradiation time 0.1 seconds or longer,...
We calculated the binding and migration energies of mono-vacancies di-vacancies in tungsten material using density functional theory. Mono-vacancies diffuse [111] direction easier than [001] direction. The are almost same; moreover, is nearly similar. di-vacancy zero or negative. interactions between two vacancies repulsive from second to fifth nearest neighbors. difficult aggregate because less stable mono-vacancies.
The dependence of bulk modulus and Young's on mass density for hydrogen-free amorphous carbon structures were investigated by using the first principle calculation functional theory. with various densities generated numerical operations structure relaxation from random volume relaxation. increased in proportion to density. We uses number sp2 sp3 atoms place these fractions or ratios as a classification parameter material because can fit both diamond one straight line modulus. By this...
Our group has been developing a hybrid simulation of the molecular dynamics (MD) and binary collision approximation (BCA) simulation.One main problems this hybridization model is that multi-body potential suddenly appears at moment when method switches from BCA to MD.This instantaneously emerged causes acceleration or deceleration atoms system.To solve problem, kinetic energy should be corrected conserve total in system.This paper gives solution.The for hydrogen atom injection into graphite...
Using the binary-collision approximation simulation with atomic collision in any structured target code AC∀T, we calculated sputtering yield, range, and retention rate for tungsten a rough surface under argon atom irradiation. The revealed yield decreases increases as becomes rougher. Because these quantities strongly depend on surface, suggest that it is necessary to consider structure of when estimating effects walls.
Abstract We reveal the hydrogen isotope effect of three interactions, i.e, reflection, adsorption and penetration ratios, by classical molecular dynamics simulation with a modified Brenner's reactive empirical bond order (REBO) potential potential. find that reflection π ‐electron does not depend on mass incident isotope, but peak nuclear moves to higher side energy. In addition we also ratio in positive z graphene becomes larger, as larger. On other hand, negative smaller. Last, it is found...
By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated effect source H/C ratio, which is ratio number hydrogen atoms to in a gas, on process. present following two gas conditions were tested: one that injected as isolated atoms, other hydrocarbon molecules. Under former condition, found increases, rate decreases exponentially. This exponential decrease with increasing agrees...
Nonlinear evolution of interchange mode produces both vortex flow and shear in a scrape-off layer (SOL) plasma with unfavorable magnetic curvature. When the Rayleigh number becomes order 105, exceeds zonal counterstreaming appears perpendicular direction to ambient field. Simultaneously, fluctuation level decreases associated cross-field transport almost classical. However, since reduction saturation weakens generation, an intermittent oscillatory behavior continues. Transport due measured...
We have investigated plasma–surface interactions by performing molecular dynamics (MD) simulations. However, such simulations a high computation cost and are limited to of materials nanometer order. In order overcome this limitation, complementary model based on the binary collision approximation (BCA) can be established. employed BCA-based simulation code ACAT extended it handle any crystalline or amorphous structure. The code, named “AC∀T”, stores positions all projectile target atoms...
Nonlinear evolution of two dimensional pressure-driven interchange mode produces relaxation oscillations in the presence poloidal shear flow for Reyleigh number R a ∼10 4 . Here velocity has symmetric profile with respect to center slab plasma where disappears. There is tendency that becomes weak after saturatioin. When almost disappears, fluctuations grow rapidly. Then again generated suppress growth fluctuations. This kind oscillation may be related ELM [Edge Localized Mode] H-mode tokamak.
Abstract Dynamics of dust particles in a divertor plasma is simulated using numerical solutions momentum and charging equations an electrostatic sheath ionizing presheath, where force drag due to absorption ions are taken into account. Spatial distributions parameters obtained with particle simulations including ionization by electron‐impact. We found that the critical radius exists. Dust larger than this one incapable come off plate because ion stronger compared force. Control potential can...
The diffusion process of hydrogen and helium in plasma-facing material depends on the grain boundary structures. Whether a accelerates or limits speed these impurity atoms is not well understood. In present work, we proposed automatic modeling kinetic Monte-Carlo (KMC) simulation to treat an asymmetric structure that corresponds target samples used fusion experiments for retention permeation. this method, local minimum energy sites migration paths are automatically found using localized...