Chopping high intensity proton beams

A novel E x B chopper system for high intensity proton beams is being developed to deliver 100 ns beam pulses in the low energy transport line of the accelerator driven neutron source FRANZ. It combines a static magnetic deflection field with a pulsed electric compensation field in a Wien filter-type E x B configuration. Behind the deflection unit a massless septum system is used for beam separation. The setup minimizes the risk of voltage breakdowns and provides secure beam dumping outside the transport line. The electric deflection field is driven by a HV pulse generator providing ±6 kV at a repetition rate of 250 kHz. Accurate layout of the deflection plates is required to tackle the issues of field quality, cooling and spark prevention. Careful matching of electric and magnetic deflection forces is required to prevent aberrations and emittance growth. Numerical studies for the field design and their effects on beam transport are presented and an overview of the hardware development is given.