Correcting Emittance Growth Due to Stray Sextupole Fields

TL;DR

This paper analyzes how sextupole fields cause emittance growth in solenoidal focusing systems and demonstrates that a corrector sextupole can effectively cancel this growth, improving beam quality.

Contribution

It derives the sextupole emittance in combined fields and shows that a corrector sextupole can mitigate this growth, enhancing control over beam emittance.

Findings

Sextupole emittance is mainly due to radial non-linearity.

A corrector sextupole effectively cancels emittance growth caused by sextupole fields.

Growth from the solenoid's spherical aberration remains uncorrected.

Abstract

This paper discusses the emittance growth produced by sextupole fields in conjunction with a solenoidal focusing. The sextupole emittance is derived and compared with numerical simulations using a measured sextupole field for a vacuum chamber in a solenoidal field. It is found that the sextupole emittance is dominated by the field's radial non-linearity and the growth due to the skew angle is much smaller. It is shown that a corrector sextupole placed after the sextupole-solenoid system is effective at cancelling this emittance growth. Leaving only the growth due to the solenoid's spherical aberration.