Space-Charge Effects During Half-Integer Resonance Crossing in the CERN PSB

TL;DR

This paper investigates how space charge effects influence beam dynamics during half-integer resonance crossing in the CERN PSB, combining experimental measurements and simulations to understand beam loss mechanisms.

Contribution

It provides the first detailed experimental and simulation study of space charge effects during half-integer resonance crossing in the CERN PSB.

Findings

Space charge significantly affects beam behavior during resonance crossing.

Experimental data aligns with simulation predictions.

Insights into optimizing resonance crossing to minimize beam loss.

Abstract

The survival of charged particles in synchrotrons requires avoiding setting the beam on machine resonances, the most dangerous of which are the integer and half-integer. Nevertheless, operationally, the transverse tunes may change dynamically, crossing these resonances, and resulting in unwanted beam quality degradation and beam loss. For high intensity beams the process of resonance crossing is even more critical as space charge, in addition to the incoherent effects, may generate also coherent effects on the beam envelope dynamics. The interplay of the speed of resonance crossing, the space charge incoherent tune spread, and half-integer resonance width are fundamental for the beam behavior. In this paper we study the crossing of the half-integer resonance $2Q_y=9$ in the CERN Proton Synchrotron Booster~(PSB) for a range of parameters using a coasting beam. We take advantage of the newly commissioned PSB to investigate the beam response experimentally. The experimental findings are also discussed with the support of simulations.