Low SEY Surfaces for future particle accelerators

Abstract

Beam Induced Electron Multipacting (BIEM) and the Electron cloud (e-cloud) are a severe problem for many existing and future high intensity charged particle accelerators, such as the LHC, KEKB, ILC, CLIC, RHIC, and FCC. Secondary electrons play a key role in the e-cloud build-up and so significant attention has been put into researching materials and technologies for Secondary Electron Yield (SEY) reduction. The objective of this study was to find a surface treatment with a maximum SEY less than unity for e-cloud suppression in future particle accelerators like the Future Circular Collider (FCC). This study primarily focused upon a carbon coating and Laser Ablation Surface Engineered (LASE) treated surfaces. Both have previously been known to have a low SEY. A facility was designed and built at Daresbury Laboratory (DL) to measure the SEY at cryogenic temperatures between 4 and 120 K, to study the effects of cryosorbed gasses on the SEY and to measure the pumping speed and capacity of the surfaces tested. The facility was capable of measuring sticking probabilities and pumping capacities of samples at cryogenic temperatures with various gasses. The measured isotherms for hydrogen, nitrogen and argon were in good agreement with those published in literature. The key result of this study was the reduction of delta_max of copper from 1.89 to 0.81, stainless steel from 2.18 to 0.79 and aluminium from 2.54 to 1.24 respectively.

Date of Award	31 Dec 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Appleby (Supervisor) & Guoxing Xia (Supervisor)