Numerical investigation of a radio frequency sheath with supra-thermal electrons in the presence of the magnetic field

Abstract

The structure of the magnetized radio-frequency (RF) sheath of plasma containing supra-thermal electrons is studied numerically with a one-dimensional hybrid model consisting of a collisionless sheath model and an equivalent circuit model of the sheath. It is found that effect of the external magnetic field on the sheath structure depends on the direction of the disturbance current source. As the plasma magnetization or angle between the magnetic field and the wall is increased, both the sheath thickness and sheath potential drop increase during the positive disturbance current source at the wall, while they change slightly during the negative disturbance current source at the wall. For the different supra-thermal electron populations parameterized by Kappa velocity distribution, both the sheath thickness and sheath potential drop are always larger in the magnetized sheath than in the unmagnetized sheath. Compared with in the unmagnetized sheath, the width of the ion energy distribution (IED) in the magnetized sheath expands towards the high energy regime, and the low-energy peak of the IED decreases while the high-energy peak of the IED changes a little.