Spill ripple mitigation by bunched beam extraction with high frequency synchrotron motion

Abstract

Slow extraction of bunched beams is widely used for mitigating the formation of micro structures due to ripples of the accelerator magnets power supplies on the extracted beam which is also referred to as spill. That helps, in particular, experiments with slow detectors or with low extraction rates.Furthermore, this technique is widely used for avoiding long gaps in the spill measured in ionisation chambers which in turn would trigger interlocks.On the other hand, the bunches create spill structures on time scales defined by the rf frequency.In addition, macroscopic spill structures of duration up to some hundred milliseconds can be created by the synchrotron motion for a sufficiently large synchrotron tune.The aim of this report is to study the influence of the synchrotron tune determined by amplitude and harmonic number of the rf voltage which additionally depends on the transverse emittance and the longitudinal bunch area of the circulating beam as well as the distribution of the particles' transit times.