A Pulse Selection and Shortening System for Cyclotrons

The design and performance of a system for selecting and shortening beam pulses near the cyclotron center is reported. The pulse selector gates from one in two to one in 79 pulses in the cyclotron beam. The pulses selected for acceleration are shortened by a unique axial RF deflection system which allows the central portion of the pulse to pass unattenuated. The external cyclotron beam has been measured to be 0.3 × 10-12 coulomb per pulse with 0.8 ns width at 10% above the baseline. The rejection of unwanted pulses is typically over 400 to 1 for long term measurements.