Development and Performance of RFD Crab Cavity Prototypes for HL-LHC AUP

TL;DR

This paper reports on the design, manufacturing, and testing of RFD crab cavity prototypes for the HL-LHC upgrade, highlighting challenges, modifications, and initial performance results.

Contribution

It presents the development and validation of RFD crab cavity prototypes tailored for HL-LHC, including design revisions, manufacturing processes, and cold test outcomes.

Findings

Prototype cavities met design specifications in cold tests.

HOM dampers effectively reduced higher-order modes.

Manufacturing processes are ready for industry transfer.

Abstract

The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and cold tested. Challenges specific to the RFD cavity were the stringent interface tolerances, the pole symmetry, and the higher-order-mode impedance spectrum. Chemical processing and heat treatments were performed initially at FNAL/ANL and are now being transferred to industry for the production phase. HOM dampers are manufactured and validated by JLAB. A summary of cold test results with and without HOM dampers is presented.