Experimental V-I characteristics for the post ignition/pre arc phase in a vortex water wall high pressure argon arc lamp

Summary form only given. Vortex water wall high pressure argon arc lamps are used to generate intense light and are capable of operating at radiative efficiencies greater than 50%. These lamps are being considered for use in a pulsed DC mode of operation in the next generation of rapid thermal processing applications. The design of an ignition circuit which can reliably trigger and generate a sustainable arc current is a major task. To this end an experimental circuit has been devised to investigate the post breakdown and pre arc phase. Transient V-I characteristics taken for a number of operating conditions indicate that the breakdown process consists of a prethermionic electrode phase and a non LTE positive column phase. The experimental findings have been used to derive a set of design guidelines for the ignition and sustaining current power supply. The ignition power supply used to trigger the discharge consists of a high frequency resonant converter cascaded with a Cockcroft-Walton rectifier. The experiments have confirmed the need to define the following parameters so as to design the power supply: (a) gas heating time, (b) sustaining glow voltage, (c) minimum sustaining arc current, and (d) minimum sustaining arc voltage.