Temperature and density measurements in high intensity microwave-excited excimer lamps

Abstract

Summary form only given. Electrodeless microwave-excited rare-gas halide lamps are presently among the most powerful ultraviolet light sources, capable of emitting cw radiation power of several kilowatts in the spectral range between 200 and 350 nm. Development and optimization of high-pressure microwave-excited excimer lamps depends on the knowledge of the excimer plasma parameters, particularly electron temperature and density. Non-coherent excimer light sources are relatively new devices and the information on their plasma parameters is still incomplete. Standard diagnostic techniques of high density discharges are inapplicable in this case, because of the molecular excited state structure and absence of self-absorption. We will present description of two techniques for determination of plasma temperature and electron density. Temperature measurement is based on the equilibrium population of certain vibrational levels of excimer excited states. Electron density was determined from the measurements of Stark profiles of H/sub /spl beta// radiation from a small amount of hydrogen mixed with rare-gas halides. Lamps were specially designed and constructed to meet the basic diagnostic requirements, to permit axial radiation detection preserving microwave coupling characteristics of the commercial microwave cavity. Description of lamps, diagnostic apparatus and the method will be presented. Variation of plasma parameters depending on the initial partial pressures of gas components will be shown.