Issue 76

Beam Dynamics Newsletter

5.8 Design and Analysis of the Medium-\( \beta \) Elliptical Cavities for the European Spallation Source Accelerator

CANDIDATE: Gabriele Costanza, Lund University, Sweden
SUPERVISOR: Prof. Anders Karlsson
GRADUATION: January 2017



This thesis is dedicated to the design and analysis of superconducting elliptical cavities. Elliptical cavities play a central role in modern particle accelerators due to their high efficiency. After an introduction to the European Spallation Source project, the thesis goes through the design of the medium-\( \beta \) cavity. The RF design of the inner cell and end cell are presented in sequence in paper I. The design is completed by the chapter on the mechanical performances of the cavity (paper II). Papers III, IV and V are instead dedicated to the analysis of the cavity. The necessary mathematical tools for the analysis are presented in paper III which, after stating fundamental results on hollow cavities, presents a spectral decomposition used in the following papers. In paper IV, a time-domain model for the power dissipation induced by the excited higher-order-modes is presented. Such modes are excited by the particle beam that passes through the cavity and are detrimental to the performances of the accelerator. Paper V presents a time-domain model of the cavity coupled to an externa circuit to a coupler. The model is functional to the design of the cavity control system.