TRANSITION CROSSING IN PROTON SYNCHROTRONS USING A FLATTENED RF WAVE

The problems of beam loss and emittance growth during transition cross ing in a proton synchrotron have been major issues for many years. Rec ently we have developed a scheme that resolves some of these problems by eliminating rf focusing during transition crossing. The technique u ses a flattened (nonsinusoidal) rf wave form which delivers the correc t acceleration to all particles in the beam. This scheme has been test ed in the Fermilab Main Ring accelerator by the addition of 13% of a t hird harmonic rf voltage to the fundamental accelerating rf voltage du ring the nonadiabatic period near the transition energy. Beam loss was completely eliminated, and longitudinal emittance dilution after tran sition remained below 15%. Simulations of longitudinal beam dynamics r eproduce the data well.