The HL-LHC cold powering systems transfer the current from the power converters, located in the new underground galleries, to the superconducting magnets of the HL-LHC inner triplets and matching sections at Point 1 and Point 5. Eight systems plus two spares of each of the two different types – 'X' for the inner triplets; 'M' for the matching sections – are being constructed for installation in the HL-LHC underground galleries from mid-2027. The systems rely on superconducting links (SC-links), superconducting transfer lines based on novel MgB2 technology, spanning a length of about 100 metres. These transport a direct current of up to 120 kA in a temperature range of 4.5 K to about 20 K.
The SC-links terminate at each end into complex cryostats. The DF cryostats will be installed in the LHC tunnel at the cold end. They host the splices between MgB2 and Nb-Ti, which operate in a saturated helium bath at 4.5 K. The DFH cryostats will be installed in the new underground galleries, close to the power converters, providing connectivity to the warm powering system of the circuits. They host the splices between MgB2 and REBCO cables in helium gas at about 20 K. They also host the high temperature superconducting current leads, which bring the current to the room temperature environment, where the resistive cables are connected.
An important milestone for the HL-LHC WP6a has been the successful qualification at CERN, in Q1 2024, of the first cold powering system of the type needed for the HL-LHC triplets. This system included a DFX, produced by the University of Southampton, and a DFHX, produced by CERN, with some mechanical components manufactured by RFR Solutions AB in Sweden.
In the meantime, series production of the DF and DFH cryostats is successfully progressing at the industrial partners of the University of Southampton and University of Uppsala respectively. The frequent collaborative meetings and the strong commitment of the collaborators and their industrial partners (Puma Engineering for the DF in the UK and RFR Solutions AB for the DFH in Sweden) have enabled important milestones to be achieved in 2024. The University of Southampton has successfully produced and delivered the second, fully assembled, DF cryostat. The University of Uppsala has successfully produced and delivered all mechanical components that will enable the assembly of two DFH cryostats at CERN. In both cases, a strict quality assurance plan has been implemented. Experience and results from the production of these components, together with their successful qualification via the test of the first cold powering system at CERN, help give confidence in the design and its capability to meet the challenging requirements of the series.
