Spectral properties of low-temperature plasma of microwave discharge in sulfur vapors

Summary form only given, as follows. The technology of sulfur lamps that has physical and electrical characteristics comparable to current HID source has been reported. The fundamental principles of the operation of microwave discharges that are used to convert microwave energy to broad spectrum visual light are known. We have been studying threshold conditions of microwave discharges in mixtures of sulfur vapors with noble gases. It is shown that the excitation of this gaseous mixture is carried out in two phases: (1) ionization of noble gas atoms by a microwave field and (2) the consequent maintenance of slightly ionized nonequilibrium plasma by the field. These two processes have essentially various thresholds for the microwave pump. The purpose of this work is to investigate spectral properties of the high-frequency discharges in a mixture sulfur vapors with noble gases. It is found that an envelope maximum of emission spectrum is shifted in a short-wave range as the excitation power is increased. The shift and change of the envelope depend on a power pump and the composition of the gaseous mixture. The theoretical analysis of the spectral measurements allowed us to separate mechanisms that are responsible for the intensity changes and redistribution in the various spectrum ranges. These results are important for the development low-power efficient electrodeless sulfur lamps.