Beam-dynamic effects of a droop in an induction accelerating voltage

Abstract

Proof-of-principle experiments on the induction synchrotron concept are scheduled using the KEK 12-GeV proton synchrotron, in which rf bunches and a superbunch will be accelerated with a long step voltage generated in the induction accelerating gaps. An unavoidable droop in the induction voltage gives an additional focusing or defocusing force in the longitudinal direction. It largely deforms the barrier bucket confining the superbunch, leading to a nonuniform particle distribution. The effects are serious in an induction synchrotron with a transition energy. Longitudinal emittance blowup beyond the transition energy is not acceptable. The necessity of compensating for the droop is discussed.