A5022561132- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Physics of Superconductivity and Magnetism
- Dust and Plasma Wave Phenomena
- Fusion materials and technologies
- Gyrotron and Vacuum Electronics Research
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Nonlinear Waves and Solitons
- Nonlinear Photonic Systems
- Atomic and Molecular Physics
- Advanced Data Storage Technologies
- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- Gas Dynamics and Kinetic Theory
- Nuclear reactor physics and engineering
- Advanced Fiber Laser Technologies
- Ocean Waves and Remote Sensing
- Radar Systems and Signal Processing
- Particle Accelerators and Free-Electron Lasers
- High voltage insulation and dielectric phenomena
National Cheng Kung University
2024
Sunrise Medical (United States)
1999-2006
General Atomics (United States)
1991-2002
Stem Cell Network
1997
Okayama University
1990
Max Planck Society
1990
Rockefeller University
1973-1978
Lehigh University
1974
University of Michigan–Ann Arbor
1969-1970
The scaling of cross-field heat transport with relative gyroradius ρ* was measured in low (L) and high (H) mode tokamak plasmas using the technique dimensionally similar discharges. scalings electron ion thermal diffusivities were determined separately a two-fluid analysis. For L-mode plasmas, diffusivity scaled as χe∝χBρ1.1±0.3* (gyro-Bohm-like) while χi∝χBρ−0.5±0.3* (worse than Bohm-like). results independent method auxiliary heating (radio frequency or neutral beam). Since fluids had...
Runaway electrons are calculated to be produced during the rapid plasma cooling resulting from “killer pellet” injection experiments, in general agreement with observations DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] tokamak. The time-dependent dynamics of kinetic runaway distributions obtained CQL3D [R. W. Harvey M. G. McCoy, “The Code,” Proceedings IAEA Technical Committee Meeting...
The paper presents calculations of the efficiency fast wave current drive at reactor-like densities and temperatures, including toroidal effects. Accessibility competitive absorption mechanisms are estimated. Two bands frequencies found to be interest for reactor applications – one in ion cyclotron range other higher harmonics but below lower hybrid frequency.
The problem of electromagnetic fluctuations in a cavity is treated some generality using the fluctuation-dissipation theorem. general line shape energy spectrum derived. This reduces to Lorentzian when ${\ensuremath{\epsilon}}^{\ensuremath{'}\ensuremath{'}}(\ensuremath{\omega})$, imaginary part dielectric constant, small and varies slowly with frequency. Deviations from Stefan-Boltzmann law are calculated detail for cubical cavity.
The avalanche of runaway electrons in an ohmic tokamak plasma triggered by knock-on collisions traces energetic with the bulk is simulated bounce averaged Fokker-Planck code, CQL3D. It shown that even when electric field small for production Dreicer runaways, can produce significant a fraction second at typical reactor parameters. energy spectrum these runaways has characteristic temperature. growth rate and temperature distribution are determined compared theory. In simulations pellet...
The scaling of heat diffusion with relative gyroradius ${\ensuremath{\rho}}_{*}$ is measured on the DIII-D tokamak using dimensionally similar discharges. For first time, a two-fluid transport analysis allows electron and ion fluids to be determined separately. diffusivity found scale like ${\ensuremath{\chi}}_{e}\ensuremath{\propto}{\ensuremath{\chi}}_{B}{\ensuremath{\rho}}_{*}^{1.1\ifmmode\pm\else\textpm\fi{}0.3}$ (gyro-Bohm-like) while...
By means of generalized Wronskian relations an operator formulation is developed allowing one to generate a class discrete evolution equations which are soluble by inverse scattering. This includes nonlinear difference–difference as well differential–difference equations. The development the method exhibits significance dispersion relation associated linearized equation. technique also permits obtain Bäcklund transformations.
For s -wave and one-dimensional scattering, the discrete Marchenko equations with respect to nontrivial comparison systems have been derived. A relation Gel'fand-Levitan equation is obtained. The continuum versions are obtained by a limiting process.
Measurements of low power (≃ 1 mW) antenna loading are used to study the coupling a compact loop structure plasmas in divertor configuration DIII-D heated by neutral beam injection (NBI) or electron cyclotron heating (ECH). When transition H-mode regime occurs during NBI, resistance drops approximately factor two. This decrease is due steepening edge density profile near separatrix, accompanied reduction scrape-off layer. During localized modes, opposite effects occur, and increases...
ICRF heating in the Large Helical Device is studied applying two global simulation codes; a drift kinetic equation solver, GNET, and wave field TASK/WM. Characteristics of energetic ion distributions phase space are investigated changing resonance position; i.e. on-axis off-axis cases. A clear peak distribution can be seen case because stable orbit resonant ions. The results also compared with experimental evaluating count number neutral particle analyzer relatively good agreement obtained.
Analytical and numerical results of physical processes taking place around the second-harmonic resonance surface in ICRF heating are presented. It is shown that (1) symmetry transmission coefficients follow from Onsager's reciprocity relation dielectric tensor, (2) direct dissipation cyclotron harmonic layer mostly due to Bernstein branch depends on k||, becoming low for k||. The latter has consequence mode conversion reflection sensitively reduced by damping, but not.
The non-inductive current drive from directional fast Alfven and electron cyclotron waves was measured in the DIII-D tokamak order to demonstrate these forms of radiofrequency (RF) compare efficiencies with theoretical expectations. wave frequency 8 times deuterium at plasma centre, while twice frequency. Complete achieved using a combination (FWCD) (ECCD) discharges for which total inductively ramped down 400 170 kA. For steady discharges, an analysis loop voltage revealed up 195 kA (out...
Plasma rotational shear is potentially important for controlling the formation and positioning of internal transport barriers that could stabilize tokamak microturbulence improve plasma confinement. A new physical mechanism capable inducing rotation via ion cyclotron resonance frequency (ICRF) heating minority species in a has been proposed [Perkins, White, Bonoli, Chan, Phys. Plasmas 8, 2181 (2001)]. The present work evaluates validity this under realistic condition when fast ions are...
A systematic study of ICRF fusion reactivity enhancement has been conducted, using a new bounce-averaged two-dimensional Fokker-Planck code. Second-harmonic heating deuterium in 50–50 DT plasma is assumed, and the results are obtained as function background density temperature. An factor ten achieved at low Q (= power/RF power), which important for ion-tail diagnostics, but = 0.5 ⪅ 2. Significant poloidal variations ion (up to 14%) (by up 2.5) found.
The toroidal current induced by a travelling electron cyclotron wave in tokamak is estimated, taking into account toroidal-geometry effects. It found that the anisotropic-resistivity effect opposed neoclassical trapped-particle effects away from centre of plasma. This leads to reduction generation efficiency toward outside.
Fast wave current drive has been used to substantially modify the central density profile in a tokamak plasma. Counter-fast (FWCD) applied discharges with negative magnetic shear enhances reversal and leads distinct transition mode of improved core confinement. In this state, electron thermal diffusivity decreases by $(50\ifmmode\pm\else\textpm\fi{}20)%$ ion $(80\ifmmode\pm\else\textpm\fi{}20)%$, compared just before transition. The FWCD heating elucidates role on confinement stability.
Efficient direct heating of electrons by fast waves has been observed on the DIII-D tokamak. The measured fast-wave efficiency was independent magnetic field, in contrast to strong inverse field scaling predicted theory single-pass damping, indicating multiple-pass absorption. central had a dependence target eelctron temperature. H-mode plasmas were obtained with alone for first time electron regime.
The equations for the triad resonance interactions of gravity-capillary waves are derived by Krylov–Bogoliubov–Mitropolski method. Some special two-dimensional solutions found.
The problem of steady-state nonlinear wave-plasma coupling at the lower hybrid frequency is considered. A equation for electric field in low-density region plasma surface derived self-consistently. Analytical and numerical solutions different models show a decrease efficiency with increasing power level. This result interpreted using simple physical picture. Its relevance to experiments discussed.
The self-induced transparency effect of the three-wave resonance is studied by inverse scattering method. By transforming to characteristic coordinates background wave, inverse-scattering theory becomes greatly simplified. With presence a constant process dispersive, and solitons continuum behave in different way from those spatially bounded wavepackets. decays away, depositing energy background. have velocities which are amplitude dependent.
Current drive experiments have been performed on the DIII-D tokamak using fast waves, electron cyclotron and neutral injection. Fast wave were a 4-strap antenna with 1 MW of power at 60 MHz. These showed effective heating electrons, global efficiency equivalent to that injection even when single pass damping was calculated be as small 5%. The probably due effect multiple passes through plasma. current toroidally directional phasing straps. Currents driven by (FWCD) in direction main plasma...
A generalized fluctuation–dissipation theorem is obtained for current and density correlation spectrum of a nonequilibrium plasma. Although normally significant fluctuations occur in only electrostatic modes, the fast mode lower-hybrid range frequencies gives an exceptional example which nontrivially electromagnetic, yet are comparable to slow mode, well approximated by approximation. This fact has quite important implications on scattering electromagnetic waves plasmas such as fusion with...
Antenna loading measurements carried out during high power ion Bernstein wave (IBW) heating experiments on the DIII-D tokamak indicate that efficient, direct coupling to IBW at ω ≲ 2ωci as predicted by linear theory did not occur. Whereas strong peaking in resistance near cyclotron harmonics is for edge densities (ω < ωLH|edge), observed nearly independent of toroidal magnetic field. The anomaly can be explained invoking ponderomotive force which decreases density immediately front antenna,...
Current generation by asymmetric heating of a minority ion species in the cyclotron range frequencies is calculated weak RF limit toroidal geometry. Both trapped ions and electrons produce significant modifications to current generated. Depending on ratio charge majority species, generated can be either sharply peaked at centre or flattened towards outside.
To investigate the experimentally observed interaction between beam ion species and fast Alfvén wave (FW), a Monte Carlo code, ORBIT-RF [V. S. Chan, C. Chiu, Y. A. Omelchenko, Phys. Plasmas 9, 501 (2002)], which solves time-dependent Hamiltonian guiding center drift equations, has been upgraded to incorporate steady-state neutral slowing-down distribution, quasilinear high harmonic radio frequency diffusion operator fields from two-dimensional cyclotron resonance full code (TORIC4) [M....