Particle-in-cell/Monte Carlo simulation of plasma for inner coating of a pipe

A high-density plasma is generated inside a cylindrical target as a result of the hollow cathode discharge effect under a proper condition. The hollow cathode discharge plasma can be applied to the inner coating of the target. In order to analyze the plasma behavior near a cylindrical target, simulations have been carried out using the simulation software “PEGASUS” with a cylindrical coordinate system. The gas pressure was 0.1-600 Pa and a negative pulse or DC voltage (−30 eV∼−20 kV) was applied to the target. RF (13.56 MHz) and a superposed voltage of DC and RF were also applied. Effects of gas pressure, secondary electron emission coefficient, and length and inner diameter on the plasma generation were studied, and Paschen-like curves for a hollow cathode discharge were obtained for both centimeter-sized and millimeter-sized pipes. Plasma generation in the surroundings of a pipe with a grounded rod on the axis was also simulated. It was found that a hollow cathode discharge plasma works only for a short pipe of length vs. diameter less than 5. For a pipe of higher aspect ratio, a glow discharge plasma between the inside wall and a rod on the axis works well regardless of the length.