Development of low inductance high power plastic case capacitors for the SNS polyphase resonant converter-modulator

Los Alamos´s development of the polyphase resonant converter-modulator is the critical high-voltage klystron power conditioning system for the Oak Ridge National Laboratory´s Spallation Neutron Source Linear Accelerator. Sixteen systems each can operate up to 11 MW peak, 1.1 MW average, with pulse voltages to 140 kV. This converter-modulator system requires seven unique, low inductance plastic case capacitors with applications ranging from 2 to 120 kV, with voltage and current reversals up to 100%. The high-power switching waveforms require capacitors capable of running at high frequencies with high RMS currents coupled with high reliability. Following a competitive technical performance and cost evaluation of these critical components, Los Alamos determined capacitors from General Atomics Energy Products, Division of Sorrento Electronics met or exceeded all design requirements. This paper covers the different applications, the resulting capacitor designs, their characteristics, and operating history to date.