RESULTS FOR THE 150 kW PROTOTYPE 1 MHz CHOPPER AT 100 % DUTY CYCLE

Abstract

The KAON Factory at TRIUMF requires a 1 MHz chopper to create appropriate holes in the extracted 1 GeV/c H- cyclotron beam to allow sufficient time to operate kicker magnets. Deflection of beam bursts to be eliminated by the 1 MHz chopper will be predominantly provided by an electric field between a set of deflector plates. A novel design concept for the 1 MHz chopper has been developed involving an energy storage system where the electric pulses are stored in low loss coaxial cable. The beam chopper “kick” must have a rise and fall time of less than 39 ns and a flat top of at least 49 ns for “narrow” pulses and 92 ns for “wide” pulses. Results of the latest measurements on the single tetrode (“reference”) design, at 100 % duty factor on a 2.2 MHz prototype using a 150 kW tetrode, are presented and compared with theoretical predictions. The measured rise and fall times for narrow pulse pattern meet the design goal, but rise and fall time for the wide pattern are not quite so satisfactory. However the rise and fall times are all expected to be within specification for a fully engineered version.