Gyro-kinetic study of residual zonal flow for slowing down distribution function

Abstract

In the burning plasma, fusion reaction produces fast alpha particles for which the production energy is about 3.5 MeV. They saturate to equilibrium by slowing down collisional process, and the equivalent temperature of alpha particle is much greater than that of ion. It suggests that the alpha particle gyro-radius is large compared to ions, and its contribution to zonal flow gets larger in the long wavelength regime. In the previous research, residual zonal flow level (and also zonal flow itself) is calculated in the Maxwellian equilibrium. However, for alpha particle, the equilibrium distribution function is different from the Maxwellian distribution. Hence, the research of residual zonal flow level for slowing down distribution is needed. In this study, we calculated the residual zonal flow level of alpha particle using slowing down distribution function. In this procedure, we use modern gyro-kinetic pull-back transformation method for residual zonal flow calculation. The results are compared with those obtained in the equivalent Maxwellian distribution function and those of plasma ion. Finally, the combined version of residual zonal flow level is introduced and be compared with the different initial particle energy