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Wakefield Damping in a Distributed Coupling Linear Accelerator for the Compact Linear Collider

Date

2023-06-27

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

0000-0002-2561-184X

Type

Thesis

Degree Level

Masters

Abstract

Particle accelerators are made of series of metal coupled pillbox cavities. The dimensions of the cavities are tuned to resonate at a particular frequency when excited by radio frequency (RF) waves. This thesis studies a new accelerator design for the Compact Linear Collider (CLIC). The number of cells in a $\pi$-mode standing wave (SW) accelerating structure for the CLIC project is limited by mode overlap with nearby modes. The distributed coupling scheme avoids mode overlap by treating each cell as independent. Designs of cells suitable for distributed coupling with strong wakefield damping have not previously been studied. In this thesis we develop a SW cell to be used in a distributed coupling structure that can satisfy the CLIC transverse wake potential limit. From the middle cell of the CLIC-G* travelling wave (TW) structure, we design a SW cell. We match the cell with a power coupler so the cell to be suitable for distributed coupling. To increase the wakefield damping of the cell in an ideal case where all extracted wakefields are damped outside the cell, we adjust the higher order mode (HOM) waveguide dimensions. We evaluate the effect of total wakefield reflections at the distribution network. We find a coupling power from a distribution network to the cell through the side of one of the HOM waveguides reduces the reflected wakefields to levels similar to the open boundary case. To increase the efficiency of a distributed coupling structure for CLIC, we add nose cones to the cell design and evaluate its high-gradient performance and wakefield damping properties. We evaluate the wakefield damping performance of combinations of coupler cells and normal cells which take advantage of cell-to-cell coupling. We find the wakefield damping performance of distributed coupling structures can be improved by forming triplet modules consisting of a coupler cell flanked by two normal cells. To account for the longer filling time of a SW structure, we calculate the RF pulsed heating of a structure made of our designed cell. We compare the performance of distributed coupling structures operating at room and cryogenic temperatures when fed by different power sources.

Description

Keywords

particle accelerator, linear accelerator, finite element, simulation, wakefield, impedance, damping

Citation

Degree

Master of Science (M.Sc.)

Department

Physics and Engineering Physics

Program

Physics

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DOI

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