Radiometric and electrical characterization of medium-power inductively coupled uv-radiation source

Inductively coupled low-pressure discharge lamps have been known since 19^th century and are commercially available at power levels up to 300 W for general lighting applications. These lamps are operated at frequencies in the range from hundreds of kHz to several MHz and are characterized and modeled. Higher power levels are only available as ICETRON/ENDURA lamp types and not in a re-entrant coupler geometry. Since the re-entrant coupler system is more compact and exhibits a better surface to volume ratio, a higher radiometric efficacy is expected. A major drawback is caused by the increased operating frequency, which leads to lower efficiency of the electronic control gear and consequently to lower radiant efficacy. Actually, this drawback can be overcome by utilization of new wide band-gap power semiconductor devices like silicon carbide (SiC) or gallium nitride (GaN) transistors, which can significantly reduce switching and conduction losses. However, a reliable and accurate lamp model is needed for optimum system design. In this work, an electrodeless lamp based on the re-entrant coupler topology operated at power levels up to 500 W is radiometric and electrically characterized by means of radiant flux and electrical input power. Since the re-entrant coupler of the experimental setup is exposed to higher operating temperatures due to limited convective heat-flow inside the lamp-vessel, it was cooled by a water-cooling system. Optimization of the system is intended to gain higher efficiency and thus to remove the water cooling system. First results have been obtained using a linear power amplifier at operating frequencies between 2.0 and 2.65 MHz and verified by means of the lamp models.