Low‐frequency sheath admittance of a sphere in a collisionless plasma

Abstract

A systematic theoretical study of the low-frequency sheath admittance of a spherical electrode immersed in a collisionless, nonflowing, Maxwellian plasma with no magnetic field is done for the following ranges of plasma parameters: nondimensional electrode dc bias potential -25 _< eckp/kT e _< 25, ion to electron temperature ratio 0 _< Tilt e • 1, electrode radius to Debye length ratio 0 _< rp//•a g 200. A surprising feature of the results is the existence of double and triple peaks in the sheath capacitance as a function of dc bias potential at certain values of rv//•a. The same capacitance results also show discontinuous behavior at space potential. Various plasma-diagnostics applications are suggested.