Life Time Testing Of High Power Ignitrons

Abstract

Introduction Life time tests are being performed on high power, Size E ignitrons for possible use in the Nova upgrade facility with is currently designed by Sandia and Livermore National Laboratories. The testing is done up to the 300 kA level with a charge transfer of 200 C. The bank used in the experiments is a large electrolytic bank containing over 4000 electrolytic capacitors. The maximum charging voltage of the bank is limited to 4000V; giving 1000 volts margin to the absolute maximum bank voltage of 5000V. Two ignitrons are connected in series to enable High-Pot testing of the tubes after recovery with a low power, H V supply without the need to disconnect any high current connections. Tests were performed on a NL-9000A and a NL-1057 tube, both made by Richardson Electronics. The current as well as the differential voltage drops across both tubes were recorded along with the charging voltage and the differential voltage drops at peak current (dI/dt=O). The forward voltage drop of the NL-1057 was about twice as high than the voltage drop across the NL-9OOOA. Detailed waveforms and data evaluations are shown. The ignitor resistance, which is a barometer for the life expectancy of a tube, was also recorded frequently. In addition, new PSpice circuit models for the ignitrons and the test stand were developed using many of the advanced features of PSpice 6.0 for Windows. Many pulsed power applications that use capacitor banks for energy storage need a reliable closing switch to release the energy into the load. Up to the present day, those switches are a focus of many developments and concerns. In the latter part of the 80's and the beginning of the ~ O ' S , ignitrons have been redesigned for high peak current, high charge transfer capability1 >2, The new high power Ignitrons like the NL_9000A, made by Richardson Electronics, and the BK-1002, made by EEV, have inverted, cup-style anodes with drastically reduced Anode-Cathode spacing as well as center ignitors. The test program reported here was conducted in order to evaluate the performance and lifetime of these ignitrons for pulsed power applications.