Steady state high power test system at 3.7 GHz

Abstract

A Lower Hybrid Current Drive (LHCD) system would be the prime method to drive current in SST-1. The LHCD system is based upon two TH2103D klystrons of M/s Thomson CSF at 3.7 GHz capable of delivering 500 kW CW microwave power. The klystrons have been commissioned and deliver the microwave power through two standard WR-284 waveguides. It is electrically isolated from the main system using DC breaks. Two high power circulators protect the tube from high reflection. Directional couplers measure forward and reflected power in the system. The output power is deposited on two matched dummy loads during testing. In the event of arcing or any other fault, the high voltage from the klystron is removed in less than 5 μs, with the help of a crowbar system, based on a pressurized rail gap switch, for the protection of the klystron. High power (up to 200 kW), 1000-s tests of two klystrons have been conducted and detailed test results are described in this paper. It also describes the high power microwave system at 3.7 GHz that is being used to test the high power microwave components, being designed and fabricated for use in the LHCD system on SST-1.