A 1 MHz chopper for injection into the TRIUMF KAON Factory

The proposed KAON Factory expansion to the TRIUMF facility requires a high repetition rate beam chopper for injecting a 450 MeV H ^- beam into the accumulator ring. The chopper must deflect the beam alternately for 49 or 92 ns. The rise and fall times of the field in the deflector must be less than 39 ns including the fill time of the deflector assembly. This represents a 22% duty cycle (including rise times) at a repetition rate of 1.0244 MHz to 1.0251 MHz. The chopper must provide an integral kick during the pulse of 200 kV/m×m (electric field×length). The deflector assembly will be between 1.8 m and 4.0 m long with the plate spacing between 5 cm and 10 cm. Traditional kickers were found to be inefficient, expensive or impractical when scaled to the high repetition rate and fast rise time required by the chopper. A novel technique for increasing the energy efficiency while maintaining pulse quality is being evaluated. The concept incorporates a low-loss transmission line on which pulses are stored; these pulses are used to deflect the beam and are then returned to the line for reshaping. Studies indicate that significantly less power is consumed compared to other techniques