In magnetized plasmas, when the charged particles' gyro-radii are smaller than the Debye length, the magnetic field will have an important impact on the collision dynamics. Many plasmas in laboratory and nature are situated in strong magnetic fields, for example, the strength of the external magnetic field in magnetic confinement fusion plasmas can reach 105 Tesla, the self-generated magnetic field in the inertial confinement fusion plasma exceeds Tesla, and the magnetic field in the white dwarf atmosphere is up to 104 Tesla, Therefore, investigation of collision and transport processes in a strong magnetic field is very important to fusion and astrophysics.
By adopting the coordinate transformation method, the general form of Fokker-Planck equation for a magnetized plasma is derived and the approach to calculating the Fokker-Planck coefficients is given. The Fokker-Planck coefficients and corresponding collision term are calculated by using different models. Then the resulting kinetic equation will be used to investigate the effects of the magnetic field on particle velocity slowing down, temperature relaxation, and cross-field particle and heat transport processes.
The goal of magnetic confined fusion is to solve the global energy problem in the long future. The fusion energy has the advantage of cleanness and abundance of fusion sources. Tokamak is believed to be one of the most promising candidate to achieve this goal. In Tokamak, the Alfvén modes will cause the fast particles lost and the fast particles will damage the first wall of the fusion device. Thus, it is necessary to investigate the Alfvén waves in Tokamak.
The fast-electron driven beta-induced Alfvén eigenmode (e-BAE) in toroidal plasmas is investigated for the first time using global gyrokinetic particle simulations, where the fast electron is described by the drift kinetic equation. The simulation shows that the e-BAE propagates in the fast-electron diamagnetic direction and its polarization is close to an ideal MHD mode. The phase space structure shows that only the fast electron processional resonance is responsible for the e-BAE excitations while fast-ion driven BAE can be excited through all the channels including transit, bounce, and processional resonance.
Then we investigate the nonlinear e-BAE. In weakly driven cases, we demonstrate a chirping phenomenon. Through the phase space of the fast electron perturbed distribution function shows a clear clump-hole structure in phase space，and more particles participate in the resonance. Test particles’ orbit in (ζ,P_ζ) phase space shows that the resonance island’s evolution is related to the chirping phenomenon. In strong driven cases, the BAAE (β-induced Alfvén-acoustic eigenmodes) frequency occurs. We investigate the mode structure and the phase space of distribution function and prove that the frequency exactly exists.
Developing A particle-in-cell kinetic code is developed based on gyro-kinetic electron and fully-kinetic ion model in general magnetic flux coordinate systems, which is particularly suitable for simulations of toroidally confined plasma. The application include simulating Lower Hybrid Wave, Ion Bernstein Wave and Ion Cyclotron Wave. The major language using is Fortran2003 with some C and Lua included.