A novel low energy fast chopper for H-injectors

The Fermilab H-injector will be upgraded from a Cockcroft-Walton system to a 750 keV RFQ (radio frequency quadrupole) system. Part of the upgrade is the addition of a fast chopper in the LEBT (low energy beam transport) just before the RFQ. The novelty of this chopper is that it reflects rather than deflects beam. It also has low capacitance <10pF so that the rise and fall times of the beam pulse are dominated by cabling and the MOSFET switches. In fact, the measured rise and fall time of the chopped beam have been measured and they are better than 150 ns at 15 Hz.