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 temporal microstructures on the extracted beam due to ripples of the accelerator magnets power supplies. That helps in experiments with slow detectors or measurements with low event rates. Additionally, in ion cancer therapy machines, this technique is widely used for avoiding long gaps in the spill measured in ionization chambers which in turn would trigger interlocks. It is also well known that extraction of a bunched beam creates spill structures on time scales defined by the rf frequency which limits its usability for faster detectors. In this report, we show that further macroscopic spill structures of duration up to some hundred milliseconds can be created during bunched beam extraction for a sufficiently large synchrotron tune. The aim of this work is to study the influence of the synchrotron tune and its interplay with slow extraction settings on the slow extraction quality. Further dependencies on transverse emittance and longitudinal bunch area of the circulating beam are discussed.