Transition crossing in proton synchrotrons using a flattened rf wave

The problems of beam loss and emittance growth during transition crossing in a proton synchrotron have been major issues for many years. Recently we have developed a scheme that resolves some of these problems by eliminating rf focusing during transition crossing. The technique uses a flattened (nonsinusoidal) rf wave form which delivers the correct acceleration to all particles in the beam. This scheme has been tested in the Fermilab Main Ring accelerator by the addition of 13{percent} of a third harmonic rf voltage to the fundamental accelerating rf voltage during the nonadiabatic period near the transition energy. Beam loss was completely eliminated, and longitudinal emittance dilution after transition remained below 15{percent}. Simulations of longitudinal beam dynamics reproduce the data well. {copyright} {ital 1997} {ital The American Physical Society}