Study of plasma characteristics of hollow cathode in glow discharge

In order to further investigate the conditions and the coupling mechanisms for generating the hollow cathode effect (HCE) for the process optimization in the field of surface modification, the plasma distribution and density in single glow and double glow hollow cathode discharge (HCD) were explored by experiments and simulations based on the two-dimensional fluid model. Additionally, we investigated the effects of the key parameters on the plasma density, the electron temperature and the potential field during the HCD. The experimental and simulation results showed that the high plasma density is owing to the HCE in the hollow cathode. It is found that there is a critical pore diameter for generating HCE, which is approximately the sum of the thickness of the plasma sheath and four times the electron-neutral mean free path in the single glow discharge while twice thickness of the plasma sheath and four times the electron-neutral mean free path in the double glow discharge. The HCE in the double glow discharge can be observed when the ignition voltage that the source cathode voltage be 250 V greater than the workpiece cathode voltage can be met while the PD value is about 1.5 ∼ 3.8 Torr ⋅ mm. Consequently, we believe that our investigation on the plasma characteristics of hollow cathode in glow discharge will contribute to the development of the more optimal processing parameters for the application of the glow plasma discharge phenomena.