UK delivers first state-of-the-art cryomodule to CERN for the High-Luminosity LHC upgrade

The first pre-series cryomodule equipped with superconducting Radio Frequency Dipole (RFD) crab cavities was completed in October 2023 at Science and Technology Facilities Council (STFC)’s Daresbury Laboratory as a collaboration between HL-LHC-UK and CERN


Technicians Luke Bladen and Tom Hanley from the STFC Technology Department who supported the build of the cryomodule. (Image credit: STFC Daresbury Laboratory)

The High-Luminosity Large Hadron Collider (HL-LHC) project will rely on a number of key innovations that push accelerator technology well beyond its present limits. One of the key components is compact superconducting “crab” cavities which will rotate the proton bunches to provide head-on collisions in the two largest detectors: ATLAS and CMS. The United Kingdom has been a key partner in the development of compact crab cavities for HL-LHC since 2011.

“Crab cavities allow bunches to be fully aligned at collision and this substantially increases the luminosity reach, but HL-LHC will be the first to operate them with a proton beam. Implementing these novel structures requires significant R&D to ensure their robust performance when installed, so providing CERN with prototypes is essential.” said Prof Graeme Burt, HL-LHC-UK project manager and Professor at Lancaster University.

Operating at 2 Kelvin, these cavities are housed in complex, state-of-the-art cryomodules which provide precise alignment, mechanical support, cryogenic cooling, thermal and magnetic shielding, tuning capability, vacuum isolation, radio frequency power, monitoring of key parameters, and all other connections to the outside world.

A team comprising staff from the Cockcroft Institute and STFC’s Accelerator Science and Technology Centre and Technology Department, has delivered the first prototype of these cryomodules that uses the Radio Frequency Dipole (RFD) cavity design. It was designed by a team at Old Dominion University, in the United States and developed by a team at CERN. The cryomodule has taken almost two years of assembly work at Daresbury and contains around 10,000 components, of which over 5,000 are unique. The team has built upon existing expertise in mechanical and RF engineering, cryogenics, instrumentation and controls, vacuum science, survey and alignment, welding, and project management. This exceptionally challenging project has also supported significant upskilling of staff with support from CERN, and the building of substantial new infrastructure for cryomodule assembly at Daresbury which will be used in future projects.

The teams from STFC, Lancaster University, and CERN who worked on the technology. (Image credit: STFC Daresbury Laboratory)

"The RFD pre-series is the first module of its kind ever built. It was only possible because HL-LHC-UK and CERN worked together at an unprecedented level to solve many complex challenges to bring the design to reality. The know-how and the experience will be essential to face the challenges ahead to complete Phase 2" said Dr Rama Calaga, HL-LHC WP4 Leader at CERN.

“Building this state-of-the-art technology is a huge coup for the UK. After making several design contributions to the cryomodule including the thermal screen, cold and warm magnetic shields, the engineering team developed and delivered a suite assembly infrastructure and tooling for the build. The team also delivered over 900 pages of detailed procedures which form the build quality assurance. Every step from cleanroom assembly to welding, cryostating and testing had to be developed and approved before execution. The team overcame many complex challenges which developed and demonstrated their multi-disciplinary skillsets and commitment. Truly great work!” said Niklas Templeton, Technical Manager for the cryomodule build and Project & Mechanical Engineer in STFC’s Technology Department.

The team at Daresbury said farewell to the cryomodule on 18 October 2023, where it then undertook a three-day journey to CERN. To ensure safe transportation to CERN, STFC developed a custom anti-shock transport frame. Before the cryomodule embarked on its journey, the frame was successfully drop-tested with a dummy cryomodule, with results showing up to 80% damping.

Arrival and transport of the RFD cryomodule in the SM18 hall at CERN. (Image credit: M. Brice/CERN)

“I’m incredibly proud of what the team has accomplished over the last two years” said Dr Andrew Blackett-May, Senior Cryogenics Engineer in ASTeC and Task Manager for the cryomodule build. “We have faced a myriad of technical and logistical challenges getting to the point of successfully delivering the RFD cryomodule to CERN and huge credit is due to everyone involved for working so effectively as a team and delivering their work to such a consistently high standard. This really is a fantastic achievement for us at Daresbury Laboratory, as well as for UKRI-STFC and for UK science and engineering more widely on this world-class project. We’ll be continuing to work very closely with our colleagues at CERN as they undertake the SM18 and SPS tests, and we look forward to sharing further news from these in due over the coming months.”

Following the success of this first phase of the project, the team at Daresbury are moving on to Phase 2 which will see the delivery of a further four cryomodules to be installed in the LHC, this time using a Double Quarter Wave (DQW) cavity designed by colleagues from Brookhaven National Laboratory in the US and developed at CERN. The testing of the RFD prototype cryomodule in SPS will allow the team to better understand its behaviour when operating on proton beams.