Effect of Nitrogen Gas Pressure and Hollow Cathode Geometry on the Luminous Intensity Emitted from Glow Discharge Plasma

The paper investigates the luminous intensity emitted from dc hollow cathode glow discharge plasma (HCGD) .The experiments were conducted at different nitrogen gas pressures ranged from (0.015 to 0.75Torr) and constant discharge current (Id=1.88 mA).The influence of both pressure and hollow cathode geometry such as diameter and depth of hollow cathode have been studied .The results show that the Photo-Luminous Efficiency emitted from the hollow cathode glow discharge decrease nearly exponentially with the increasing gas pressure. This is due to the characteristics of hollow cathode at the low pressures to produce more energetic excitation. On the other hand, the luminous efficiency increase linearly with the increasing inter-cathode distance of hollow, this is because increasing the inter - cathode distance of hollow cathode is equivalent to the decreasing of gas pressure. However the luminous intensity increase linearly with the depth of hollow cathode ranged from (1up to2.5) cm and then decrease. This behavior of the intensity with both the gas pressure and hollow cathode geometry is satisfactory agreement with previous works.