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

TL;DR

This paper investigates how high-frequency synchrotron motion influences spill ripple mitigation in bunched beam extraction, aiming to optimize slow extraction techniques for improved beam stability and reduced spill structures.

Contribution

It provides a detailed analysis of the effects of synchrotron tune, RF voltage parameters, and beam properties on spill ripple characteristics in bunched beam extraction.

Findings

Synchrotron motion can create macroscopic spill structures up to hundreds of milliseconds.

Adjusting RF voltage and harmonic number influences spill ripple mitigation.

Beam properties like transverse emittance affect the synchrotron tune and spill quality.

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.