Adaptation of the Cryogenic System Capacity for the LHC Dynamic Heat Load - Operational Experience

During second LHC physics operation period (Run2), between 2015 and 2018, the accelerator operation modes and beam parameters have been adapted thus allowing significantly improved integrated luminosity production. Increased energy, intensity and adapted beam operation schemes with 25 ns of inter-bunches spacing have an essential influence on the dynamic heat load generation with direct impact on the cryogenic cooling system. In order to cope with significantly higher than expected beam induced thermal load, the cryogenic system was tuned and optimized to adapt the required refrigeration capacity to the beam operational requirements. The most challenging part of tuning was focused on the dynamic heat load compensation on the beam screens circuits. The paper will provide the overview on the main differences between the theoretical heat load values considered for initial design and the on-line measurements performed on cryogenic LHC sectors. Finally, the paper will summarize the methodology and tools implemented in the cryogenic process control system allowing the highly efficient on-line adaptation of the refrigeration power with respect to the beam induced heat load distribution.