The Tuning System for the HIE-ISOLDE High-Beta Quarter Wave Resonator

TL;DR

This paper details the design, simulation, and testing of a tuning system for superconducting quarter-wave resonators at CERN, addressing RF, mechanical, and thermal challenges for the HIE-ISOLDE project.

Contribution

It introduces a comprehensive tuning system design for QWRs, including specifications, simulations, prototype testing, and industrialization plans.

Findings

Successful prototype tuning system tests

Design meets RF, thermal, and structural requirements

Industrialization strategy outlined

Abstract

A new linac using superconducting quarter-wave resonators (QWR) is under construction at CERN in the framework of the HIE-ISOLDE project. The QWRs are made of niobium sputtered on a bulk copper substrate. The working frequency at 4.5 K is 101.28 MHz and they will provide 6 MV/m accelerating gradient on the beam axis with a total maximum power dissipation of 10 W on cavity walls. A tuning system is required in order to both minimize the forward power variation in beam operation and to compensate the unavoidable uncertainties in the frequency shift during the cool-down process. The tuning system has to fulfil a complex combination of RF, structural and thermal requirements. The paper presents the functional specifications and details the tuning system RF and mechanical design and simulations. The results of the tests performed on a prototype system are discussed and the industrialization strategy is presented in view of final production.