Development of Vacuum ultraviolet emission source using a Cone-shaped O₂/He hollow cathode discharge

A compact vacuum ultraviolet (VUV) lamp using helium and oxygen plasma has been developed to emit atomic oxygen triplet³S₁–³P₂₁₀ lines, which can be applied to measure absolute oxygen density by a method of absorption spectroscopy. The VUV lamp consists of a negatively biased micro-hollow cathode with a hole of 700 m diameter and grounded hole-electrode carrying the gasses. The discharge was confined in the hollow cathode hole when the operating pressure was near 30 Torr in both the pure helium and helium based oxygen diluted plasma. In this condition, the spectral lines of the atomic oxygen triplet emission (130.2, 130.5, 130.6 nm) were observed and the atomic excitation temperature showed higher value than that of a normal glow phase. Typical I–V characteristic of hollow cathode mode such as negative resistivity was also discussed in both the helium and helium-oxygen discharge at the pressure of 30 Torr.