Characterisation and mitigation of RF knockout during beam stacking

TL;DR

This paper characterizes RF knockout during beam stacking in FFAs and demonstrates suppression techniques to reduce beam loss, enhancing the potential of FFAs for high-intensity applications like spallation neutron sources.

Contribution

The study provides a detailed characterization of RF knockout resonance and introduces experimental methods to suppress RF knockout losses in FFAs.

Findings

RF knockout resonance can be characterized precisely.

Suppression techniques effectively reduce RF knockout-induced beam loss.

Experimental validation at ISIS demonstrates practical mitigation strategies.

Abstract

Beam stacking allows a Fixed Field alternating gradient Accelerator (FFA) to increase the extracted beam current whilst also allowing for a flexible time structure making FFAs a promising candidate for future spallation neutron sources and high beam intensity applications. For successful beam stacking, beam loss caused by RF knockout must be avoided. RF knockout can occur during beam stacking because of the finite dispersion function at the RF cavity location, which is unavoidable in a scaling FFA. In this work, the RF knockout resonance is characterised and through a series of experiments at the ISIS Neutron and Muon Source, we show that it is possible to suppress the loss from RF knockout.