A 28 kV + 0.020% 200 kW DC Power Supply

Design, construction and testing of a prototype HV power supply for the klystrons of the 300 MeV racetrack microtron (MUSL) of the University of Illinois are described. Regulation of 0.02% is achieved with three voltage feedback loops. Two loops to thyristor phase control circuits on the ac primary of a 12-phase rectifier transformer regulate its output to within ± 0.2% (line regulator). A third loop controls a series-connected tetrode to bring the output to within ± 0.02% of the preset value. The voltage drop across the tetrode can be set between 800 V and 1600 V; this setting is maintained by one of the loops to the line regulator. Other unique features are protective circuits that limit the fault current to 150% of the rated current when the klystron and/or the tetrode spark over. Voltage spikes generated by the thyristors are attenuated with LP-filters.