Pressure dependence of XeCl excimer plasmas excited by microwaves

Summary form only given, as follows. High-pressure excimer lamp discharges are of interest in the manufacturing industry as a source of intense ultraviolet light for such applications as the curing of inks, coatings, and adhesives. Microwave pumped excimer discharges play an important role in the development of such lamps by eliminating the use of electrodes and thus increasing lifetimes, providing intense ultraviolet emission in desired wavelength bands, and offering high overall coupling efficiency. In this work, an Asmussen microwave resonant cavity is used to excite a XeCl excimer discharge within a range of 50W-150W of absorbed power at pressures up to several hundred Torr. A continuous wave power supply at a fixed frequency of 2.45 GHz is used to produce a XeCl excimer discharge in a resonant cavity operating in the TM/sub 012/ cavity mode. Coupling efficiencies from the microwave supply to the discharge are typically greater than 80% and as high as 94%. The discharge is contained within a quartz tube that runs along the center of the resonant cavity with Xe:Cl/sub 2/ ratios ranging from as low as 1:2 to as high as 10: 1. Forced airflow is used to cool the surface of the discharge,tube and improve molecular formation at higher pressures. As pressure is increased, the diffuse volume of the plasma shrinks to form very intense filaments within the discharge. Higher power levels are needed to sustain a stable discharge at higher pressures.