Computation Of Cathode Layer Thickness For Normal Glow Discharge

Abstract

Hollow cathode discharges (HCDs), especially microhollow cathode discharges (MHCDs), have more and more applications. For the optimal operation of HCD, the cavity in the cathode should be small just enough to house two opposing glow discharges, i.e., $D \approx 2 d_{n}$ where D is the diameter of the cavity; $d_{n}$ is the cathode layer thickness of normal glow discharge. Therefore, knowing the value of $d_{n}$ is important. In this paper, a computational method for the estimation of the thickness of the cathode layer in normal glow discharge was developed. The results showed that the reduced cathode layer thickness $p \cdot d_{n}$ monotonically decreases and finally saturates with the increase of the cathode fall. It was found that $p \cdot d_{n}$ is a constant for the given cathode fall and secondary electron emission coefficient, which physically implies that the cathode layer will automatically adjust its thickness so as to keep $p \cdot d_{n}\mathrm {a}$ constant when the gas pressure changes. The values of $p \cdot d_{n}$ obtained with this method were compared with that from one dimensional fluid simulation of glow discharge, which shows a good agreement.