Multi-gap Pseudospark Switches for High Voltage Applications

The long-term goal of the described experiments is to construct multi-gap pseudospark switches, which can handle reliably the specifications of the pulse forming network (PFN) for the injection/extraction kicker magnet system of the future heavy ion synchrotron accelerator complex SIS100/300 at the Gesellschaft fuer Schwerionenforschung (GSI). The PFN requires an high-voltage switch, that can handle an hold-off voltage up to 70 kV, peak currents up to 6 kA and pulse durations up to 7 mus. In this paper most of the reported experimental data have been obtained by using a two-gap prototype pseudospark switch with total hold-off voltage up to 30 kV. There are two major problems correlated with the development of such multi-gap systems. The first one concerns efficient and reliable triggering of switch for the overall switch lifetime. Two trigger systems have been studied, the so-called high-dielectric trigger (HDT), which already has proven its long term capability, and second, a novel system, based upon the electron emission from carbon nanotubes (CNT). The CNT- trigger still suffers from an insufficient small lifetime of 104 discharges. The second critical part concerns the instant breakdown initiation in the individual gaps, separated by a drift space. In the experiments with this prototype an active pre-ionization of the drift space was nor foreseen. For both trigger systems the measured delay and jitter in the first gap vary from 50 to 60 ns and 15 to 30 ns, respectively; corresponding the second gap has a delay and a jitter of up to 200 and 45 ns, respectively.