Monotonic sheath conditions of partially magnetized plasma sheaths*

Plasma sheaths in the presence of an applied, oblique magnetic field is studied using a one-dimensional, particle-in-cell (PIC) simulation. In particular, the Bohm condition and sheath potential play an important role in understanding the plasma-wall interaction, such as the heat flux and particle flux. The simulation results show truncation of the electron velocity distribution function (VDF), similar to a loss cone in magnetic mirrors, within the magnetized sheath region depending on the magnetic field angle. Taking the first moment of the truncated electron VDF gives the electron bulk velocity at the sheath edge, from which a magnetized Bohm condition (ion injection velocity at the sheath edge) and the sheath potential can be defined as a function of magnetic field angle. Both the potential drop and sheath edge velocity decrease at larger field angle.   

 

 

This work is supported by the Office of Naval Research under Grant No. N00014-21-1-2698 and by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award No. DE-SC0020623.