Roughness Tolerance Studies for the Undulator Beam Pipe Chamber of LCLS-II

TL;DR

This study assesses how wall roughness impacts energy variation caused by wakefields in the LCLS-II undulator beam pipe, finding a modest increase in energy variation with increased roughness.

Contribution

It provides quantitative analysis of wall roughness effects on wakefield-induced energy variation in the LCLS-II beam pipe.

Findings

Wall roughness with 30 mrad rms slope increases energy variation by 20%.

Roughness effects are modest but significant for beam stability.

Results inform manufacturing tolerances for beam pipe surfaces.

Abstract

We investigate the effect of wall roughness on the wakefield-induced energy variation in the undulator beam pipe of LCLS-II. We find that a wall roughness equivalent to an rms surface slope of 30 mr increases the total induced energy variation within the bunch (due to the resistive wall wake) by a modest 20%.