Presheath-sheath coupling for kinetic trajectory simulation of a magnetized plasma sheath

Abstract

The coupling of presheath-sheath parameters is extended for the study of magnetized plasma sheath using the kinetic trajectory simulation (KTS) method, in which the final self-consistent states are obtained iteratively by solving the kinetic equations. In our case, it is assumed that the ion and electron velocity distribution functions are cut-off Maxwellians at the sheath entrance. The results show that the cut-off and Maxwellian maximum velocities have equal magnitudes at the sheath entrance and at wall. The presheath electron temperature has a considerable effect on the self-consistent potential profile which affects the Child sheath thickness. The latter increases from 3.8320 μm to 5.4190 μm when the presheath electron temperature increases from 10 eV to 20 eV. It is found that the number of ions reaching wall is higher than that of the electrons and hence the space charge density has its maximum value there. Furthermore, the temperature of ions in the sheath region increases with the increase in presheath ion temperature. Moreover, the cut-off distribution causes our simulation result to deviate from the theoretical result found for the Boltzmann distribution by about 3%. The coupling scheme presented here provides a basis for smooth transition of plasma parameters at the presheath-sheath interface. The proper understanding of the magnetized plasma-wall transition plays a vital role for further exploring the plasma sheath characteristics which has useful applications in fusion and industrial plasma devices.