Electrode erosion performance test of LTD stage gas spark switches

To extend the lifetime of gas switches used by linear transformer drivers (LTD), electrode erosion tests for different materials (molybdenum, brass, copper-tungsten alloy, high density graphite, stainless steel 304 and 321) were conducted. These electrodes were designed according to the geometry and switching ability of the 200 kV low jitter multi-gap switches made before. Measurements show that under the condition of 20 kA peak current and 15.4 mC transferring charge, volume erosion rates decrease following the order of high density graphite, brass, copper-tungsten alloy, molybdenum and stainless steel. This relation, together with the electrode surface morphology images, shows that stainless steel works better than the other materials as LTD switch electrodes. According to the obtained volume erosion rates, the theoretical lifetime of an LTD switch using stainless steel electrodes could exceed 1 million times, provided that the insulation strength of the switch shell doesn't fail. (authors)