The LHC sectors are cooled by eight similar helium refrigerators. P4 needs more cooling capacity due to the superconducting RF. This has not limited LHC so far but would be a bottleneck for the HL-LHC era.

Following conceptual studies ranging from completely new cryogenic infrastructure to partial modifications, it was decided to upgrade the existing refrigerator of Sector 3-4 without touching the work and not limiting cryogenic distribution, while Sector 4-5 will recover cooling capacity with its extremity L5 cooled by the new HL infrastructure. More efficient expansion turbines will replace the original ones, thus allowing the provision of the required higher cooling capacity (+12%) with the same original compressors and identical power consumption.

The modifications were done last winter, and all new rotating machinery are delivered on site. For the upper cold box at the surface, it was necessary to enter inside the box for cutting pipes and welding larger housing. For the lower cold box, specific adapters were engineered as access inside the box was not possible.

Performance assessment will be performed this summer 2020, before re-cooling LHC.

For other cryogenic activities, the last round of evaluation of heat loads for P1/P5 has been launched to prepare for a formal heat load review to be held this autumn. In combination with refined process studies going on, this will define the cooling capacity to be installed. In parallel, the procurement phase for these refrigerators and for the entire cryo-distribution line have started with formal Market Surveys to be sent out this summer. The qualified companies will be invited for technical studies this autumn as the last preparatory step before formal tendering foreseen in 2021.