Triggering of 1.5 MV SF6 Filled Blumlein Switches

PIM is a water filled Blumlein connected, in parallel, to one or two 1.5 MV, cavities which inductively add voltage on a high impedance vacuum transmission line to a load diode operating at 1-3 MV. The radiographic performance of this IVA pulsed power machine depends on the inductive rise-time of the Blumlein switches. Selection of either one or two simultaneously closing switches on PIM was used to investigate the effects of rise time, in addition to voltage on the diode. Two Blumlein switches, designed and built by Titan PSD were initially tested in a self-break mode at two charging rates, from the Marx, the time to peak voltage being 0.7 and 1.5 mus in the two cases. The breakdown curves are matched with the predicted curves from 0.5 to 1.7 MV. Under this self-break mode it was found that there was a tendency for the second switch to close 7 mus later. A model for this is proposed and its effect on the PFL output pulse is illustrated. Two types of lasers have been installed, the results from closing both switches within 2 ns of each other was investigated.