Obtaining slow beam spills at the SSC collider

In addition to rf noise excitation, other methods should be able to provide slow controlled beam spills onto SSC targets. The most convenient and easily controlled of such methods is to move operating tunes so as to keep the large amplitude beam halo on an edge of the open-quotes operating diamondclose quotes. This positions the dynamic aperture to cause short lifetimes before loss for large amplitude particles. The target is naturally located for nominal SSC operation outside the edge of the dynamic aperture, where effective diffusion velocities are large. This ensures that spill intensities remain uniform and are minimally modulated by orbit movements from cultural and seismic disturbances. The authors believe that both rf noise emittance growth and movement of the edge of the dynamic aperture are likely to satisfactorily provide controlled beam loss and that a final choice of method may be determined by operational experience at current accelerators or with the SSC