Segmented ballasted electrodes for a large-volume, sub-atmospheric, transversely excited pulsed laser

Two prototype ballasted electrodes were fabricated and tested with a large-volume, reduced pressure, pulsed CO2 laser gas discharge, initiated by corona pre-ionization, and pumped by pulse widths up to 19 mu s. The design of segmented, ballasted cathodes is considered and equations are derived to quantify the degree of discharge arcing given partial collapse of the discharge. The number of segments passing the fault current was experimentally investigated as a function of the discharge power and found to increase until each segment passed the fault current. Compared with a planar-planar electrode geometry, under identical pulse excitation conditions, the ballast electrodes gave a factor of four improvement in the maximum discharge power depositions, prior to the development of instabilities. Higher frequencies were obtained with pulse trains below 50 ms, the maximum observed frequency being approximately 5 kHz. Arcing for the ballasted electrode configurations was observed in the middle of the electrodes, and its position corresponded to a measured non-uniform gas velocity