Computation Of Cathode Layer Thickness For Normal Glow Discharge

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 ≈ 2d_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·d_n monotonically decreases and finally saturates with the increase of the cathode fall. It was found that p·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·dn a constant when the gas pressure changes. The values of p·d_n obtained with this method were compared with that from one dimensional fluid simulation of glow discharge, which shows a good agreement.