Investigations of UV radiation from superimposed microwave-silent discharge plasmas

Summary form only given. We are examining the feasibility of improving the efficiency with which short wavelength ultraviolet (UV) radiation is generated from microwave and related discharges. The ultimate goal is to develop high-efficiency UV light sources that can be used in a variety of high-technology applications, including water purification, semiconductor fabrication, polymer-curing and other industrial processes. We have designed, built and tested a hybrid discharge system combining aspects of two distinctly different discharges, each of which has been well-documented as reasonably efficient sources of UV radiation. Our experimental prototype is based on combining a diffuse microwave discharge with a dielectric barrier (silent) discharge. Microwave discharges have been shown to be reasonably efficient generators of UV light, but their efficiency is limited by the amount of microwave power that can be deposited in the plasma. Silent discharges, which contain many high-current microarcs in high pressure gases have also been shown to be efficient sources of UV radiation when excimer-forming gases are used. We believe that microwave fields superimposed on a silent discharge may increase the effective radiating volume of the microarcs, thereby enhancing the efficiency. A traveling wave tube (TWT) microwave amplifier capable of producing up to 2 kW peak pulsed power provides the microwave power to the discharge.