Hi-Lumi Crab Cavity Cryomodules
23 Oct 2023



The High Luminosity upgrade (Hi-Lumi) aims to maximise the discovery potential of the Large Hadron Collider (LHC) by increasing its luminosity (rate of collisions) by a factor of five.




​Increasing the luminosity will allow us to better observe extremely rare processes and could unlock the secrets of dark matter and dark energy. Hi-Lumi will push accelerator technology beyond its current limits with innovations like the flagship crab cavities. 

Bunches colliding without crab crossing (left) and with crab crossing (right)

The superconducting crab cavities are ultra-precise and compact to fit within the LHC beamlines. They are designed to rotate the proton bunches to mimic a head-on collision.

The UK team from the Daresbury Laboratory (including the Technology Department, the Cockcroft Institute and ASTeC) made several important contributions to the DQW (Double Quarter Wave​) Prototype Cryomodule including design, analysis, testing and delivery.

DQW Prototype Cryomodule Design

​After the prototype cryomodules were installed at CERN for beam testing (resulting in the world’s first “crabbing” of a proton beam demonstrated on 31 May 2018), the UK team continued to lead the development of several systems for the RFD (Radio Frequency-dipole) Pre-Series Cryomodule design.

The successful Crab Cavity contributions and Daresbury Laboratory's experience on superconducting radio-frequency (SRF) projects such as the ​​Daresbury International Cryomodule Collaboration
and European Spallation Source led to STFC being awarded a contract to assemble five Crab Cavity Cryomodules. 
This included one RFD Pre-Series Cryomodule (beginning in 2021) and four DQW Series Cryomodules (from 2023 to 2025).

The multi-million-pound cryomodules will be assembled, and vacuum and cryogenically tested in Daresbury's Engineering Technology Centre (ETC). The build combines knowledge and expertise from Technology's Projects and Mechanical Engineering and Mechanical, Metrology and Technical Engineering groups as well as ASTeC's Vacuum Solutions, RF, and cryogenics groups.

A full suite of bespoke assembly tooling is also required for both cryomodule types. Technology Department staff are leading the design, development, delivery, and verification of the precise tooling for each stage of the 12-step build.

First RFD Crab Cavity delivered to DL

An infrastructure upgrade was completed in 2021 which included a bespoke 4-tonne Lifting Frame, ISO 4 cleanroom modifications, and ETC layout optimisation. 

A Cryomodule in the lifting frame

STFC must ensure safe transport from Daresbury to Geneva and have developed a custom anti-shock transport frame. The frame was successfully drop-tested with a dummy cryomodule at Daresbury Laboratory with results showing up to 80% damping.   

The anti-shock transport transport frame undergoing drop testing

The first RFD crab cavity was delivered to Daresbury in September 2021 with the pre-cleanroom assembly complete in April 2022. The ISO4 beamline connections and FPC installations were completed in June and July 2022 respectively.

Written by Phil Atkinson, group leader of the Mechanical, Metrology and Technical Engineering team.