Experimental conditions for self-organized luminous pattern formation in helium glow discharge from low to atmospheric pressure

In atmospheric pressure direct-current glow discharge, self-organized luminous patterns form on the anode surface, but the detailed mechanism remains unclear. We investigated experimental conditions under which self-organized luminous patterns form on the anode surface by generating direct current glow discharge in helium between needle-plate electrodes by changing the pressure from 0.1 atm to 1 atm. The patterns were more likely to form under high pressure and long electrode distances. Similar trends were observed when nitrogen or neon was mixed with helium. It was found that the product of pressure and electrode distance (pd) is the key parameter for the formation of luminescent patterns.