A Proposal to Pulse the Bevatron/Bevalac Main Guide Field Magnet with SCR Power Supplies

The Bevatron/Bevalac main guide field power supply was originally designed to provide a 15250-V DC at 8400-A peak magnet pulse. Protons were accelerated to 6.2 GeV. The 128-MW pulse required two large motor-generator (MG) sets with 67-ton flywheels to store 680 MJ of energy. Ignitron rectifiers are used to rectify the generator outputs. Acceleration of heavy ions results in an operating schedule with a broad range of peak fields. The maximum field of 12.5 kG requires a peak pulse of 80 MW. Acceleration of ions to 1.0 kG requires an 8-MW peak pulse. One MG set can provide pulses below 45 MW. Peak pulses of less than 15 MW are now a large block of the operating schedule. A proposal has been made to replace the existing MG system with eight silicon controlled rectifier (SCR) power supplies for low field operation. The SCR supplies will be powered directly from the Lawrence Berkeley Laboratory's 12.3-kV power distribution system. It is concluded that the implementation of this proposal will benefit Bevaton/Bevalac operations by reducing operating costs and improving beam quality. It is noted that the ability to achieve a requested field without extensive Ignitron warmup would, by itself, be justification for the concept. >