CW RF system of the Project-X accelerator front end

TL;DR

This paper describes the design, development, and testing of superconducting single spoke resonators for the Project-X CW linac, demonstrating high gradients and successful initial tests to support future low and high-beta cavity development.

Contribution

It presents the electromagnetic and mechanical design of SSR cavities and reports initial test results, advancing superconducting RF technology for continuous wave accelerators.

Findings

Achieved 2.5 times the design accelerating gradient in tested cavities

Successful CW regime tests of beta=0.21 SSR cavities

Confidence in using SSR for low and high-beta sections of the linac

Abstract

Front end of a CW linac of the Project X contains an H source, an RFQ, a medium energy transport line with the beam chopper, and a SC low-beta linac that accelerates H- from 2.5 MeV to 160 MeV. SC Single Spoke Resonators (SSR) will be used in the linac, because Fermilab already successfully developed and tested a SSR for beta=0.21. Two manufactured cavities achieve 2.5 times more than design accelerating gradients. One of these cavities completely dressed, e.g. welded to helium vessel with integrated slow and fast tuners, and tested in CW regime. Successful tests of beta=0.21 SSR give us a confidence to use this type of cavity for low beta (0.117) and for high-beta (0.4) as well. Both types of these cavities are under development. In present report the basic constrains, parameters, electromagnetic and mechanical design for all the three SSR cavities, and first test results of beta=0.21 SSR are presented.