High current ignitron development

An experimental 9 in demountable ignitron has been built and tested. It has passed 178 pulses with peak currents up to 925 kA, with 39 at 740 kA or greater. Drop in ignitor resistance which is the usual failure mode, has not been significant. The discharge is nearly critically damped with 160 μs to peak and a charge transfer of 280 coulombs with reverse current of 5% to 7%. This unique tube design has an annular stainless steel anode much closer to the memory cathode than the wall, which inhibits arc transfer to the wall. With an anode-cathode spacings of 6 mm and at 850 kA the voltage drop is about 100 V; with a spacing of 12 mm and at 925 kA it increases to 140 V. The voltage waveform is quite reproducible and free from the usual noise transients, especially with the shorter spacing