Figure 1. RFD02 at TRIUMF, Canada. Naeem Huque / TRIUMF

By Florence Thompson (CERN)

The first dressed series RF dipole crab cavity, RFD02, has been successfully delivered to TRIUMF, Canada, from JLAB, USA.

This begins the cavity’s journey towards cryostating, when it will be integrated – along with the second dressed series cavity expected to arrive still in the first half of 2026 – into the first series cryomodule.

‘This is the first critical path item delivered to TRIUMF for the RF dipole series production,’ says Rama Calaga, who leads the crab cavity project for HiLumi LHC.

Dressing a crab cavity refers to its assembly with the peripheral subsystems needed for operation, which was a step performed – along with the subsequent validation at 1.9K – at JLAB as part of the US-AUP contribution to the HiLumi LHC Project.

‘The delivery of a first-of-its-kind is always a major milestone, especially for these very demanding technical objects,’ says Giorgio Apollinari, leader of the of US-AUP effort. ‘We plan to follow-up with several other deliverables, like is presently happening for the Q1/Q3 cryomodules.’

‘It is a big day for TRIUMF’ says Bob Laxdal, Project Technical Coordinator for the TRIUMF/HiLumi collaboration. ‘We have been training on prototypes to date and now we are excited to move to the real thing.’

At this stage, RFD02 has undergone visual inspection, and warm RF checks are being performed before the cavity will be re-validated at nominal temperature of 2K. As soon as the second cavity arrives and is validated at the TRIUMF facility, the string assembly will start, marking the first step of the cryomodule assembly.

Figure 2. RFD02 being loaded onto truck at Jlab, USA (top left) before arriving safely at TRIUMF the following week (bottom and top right). Naeem Huque / TRIUMF.

Integration of the crab cavities into the final cryomodule provides the operational housing, with the necessary vacuum insulation and cryogenic infrastructure for the installation and operation of the crab cavities in the accelerator. A global overview of the cryostating steps are outlined in figure 3.

Figure 3. RF dipole cryostating sequence split into 12 principle steps. Courtesy of Teddy Capelli / CERN.

Video explanation of crab cavities