Test and operation of high-power RF system for KSTAR helicon current drive system

Abstract The helicon current drive system for the efficient off-axis current drive of KSTAR is currently being upgraded with 476 MHz, 1.2 MW klystrons and a new high-voltage power supply (HVPS). Four klystrons, which were used in PEP-II, were transferred to NFRI from the Stanford Linear Accelerator Center. Each klystron can generate 1.2 MW of CW RF power at 476 MHz with an 84 kV 24 A beam. Two klystrons will be powered in parallel using a single pulse step modulator HVPS with a rating of 92 kV and 64 A. Herein, a detailed description of the klystron test setup and results obtained during its test is presented. A high-power test of the klystrons is performed, wherein an RF power of 620 kW is generated by a 70 kV and 18.8 A beam.