Simulations of higher order modes in the ACC39 module of FLASH

TL;DR

This paper develops and simulates higher order mode-based beam position monitoring systems for the ACC39 module at FLASH, using finite element and scattering matrix methods to analyze cavity modes for improved diagnostics.

Contribution

It introduces a comprehensive simulation approach combining finite element and scattering matrix methods to analyze higher order modes for beam diagnostics in accelerator cavities.

Findings

Coupled inter-cavity modes are effectively simulated.

Trapped modes are characterized within a limited frequency band.

Guidance is provided for using HOMs as beam diagnostics.

Abstract

This study is focused on the development of a HOM-based BPM system for the ACC39 module currently installed and in operation at FLASH. A similar system is anticipated to be installed at XFEL. Coupled inter-cavity modes are simulated together with a limited band of trapped modes. A suite of finite element computer codes (including HFSS and ACE3P) and globalised scattering matrix calculations (GSM) are used to investigate the modes in these cavities with a view to providing guidance on their use as a cavity beam diagnostic.