EXPERIMENTS WITH A FAST CHOPPER SYSTEM FOR INTENSE ION BEAMS

Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations [1]. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ [2], an E× B chopper system [1] is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50ns at a repetition rate of 250kHz for 120keV, 200mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed [3] using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6kV and the resulting response was measured using a beam current transformer. A comparison between experimentsand theoreticalcalculations as well as numerical simulations are presented.