Experimental and theoretical determination of the transient radiation characteristics of a high power water vortex stabilized argon arc lamp

Abstract

Summary form only given, as follows. An investigation of the transient characteristics for a high power high-pressure argon arc stabilized by vortexing gas and a water wall in LTE is presented. The 30 cm long arc is operated in a current range from 50 to 400 A and is short circuited for brief durations (typically 100 /spl mu/s to 2 ms) such that the arc does not extinguish. Transient arc voltage, arc current, and radiant intensity at 900 nm resulting from this arc lamp notching are recorded. The arc is shorted using a crowbar circuit consisting of several high power IGBTs in parallel, chosen for their ruggedness and fast response times in the order of 500 ns. The arc is operated in such way that a quartz envelope is cooled on the inside by a spiraling film of deionized water. This effective cooling allows for electrical, input power into the arc lamp of up to 300 kW. The experimental setup is described, with reference to electrical, water, and gas system design and results are interpreted with reference to expected arc behaviour. Experimental results are compared to a numerical model describing transient characteristics of a cylindrical argon high-pressure arc column. Resonance lines are assumed fully trapped in this model. All other arc radiation losses are assumed optically thin in this model. The numerical modeling approach is discussed and verified by comparison with experimental results. A close agreement between theoretical results and experimentally observed transient radiation characteristics and arc voltage is found. This indicates the radiation loss term in the model is represented with sufficient accuracy. This study is aimed at determining a maximum arc-interruption-interval that does not require re-ignition of the plasma. Such brief interruption of the radiative output allows for various in-situ diagnostics on samples during processing with the high-power Vortek arc lamp.