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, in the LHC tunnel, on either side of Point 1 and Point 5.
Eight systems plus two spares of two different types, X for the Inner Triplets and M for the Matching Section, are being constructed for installation in the HL-LHC underground as from mid-2028.
The systems rely on Superconducting Links (SC Links), electrical transfer lines based on novel MgB2 technology that transport a DC current of up to about 117 kA in a temperature range from 4.5 K to about 20 K, and on High Temperature Superconducting (HTS) REBCO technology operated at up to 60 K.
Figure 1. Layout of the Triplets (X) and Matching Section (M) Cold Powering Systems at Point 5 right. The DFHs are cryogenic distribution boxes installed in the new HL-LHC underground and the DF is a cryogenic distribution box to connect the SC Links to the magnet chain in the LHC tunnel. CERN
After the successful validation of the first Cold Powering System, which was completed in spring 2024, a second Cold Powering System of the type needed for the Triplets (X) was constructed. In the meantime, the first Cold Powering System was installed in the IT String, where it successfully underwent leak tightness and high voltage tests, performed for the first time after important handling, transport and unspooling activities which are representative of the installation steps to be carried out during LS3 in the tunnel.
Installation of the Cold Powering System in the IT String required re-spooling the 75 m-long SC Link, attached to its DFHX cryostat, onto a reel with a diameter of 4 m, and lifting and installing it on the 3 m-high IT String platform. By the end of 2024, after stringent quality controls, the DFX cryostat was assembled in-situ, allowing the connection to the cryogenic services in the first quarter of 2025 and finally to the magnet busbars. This important milestone demonstrated the robustness of the system and confirmed its compatibility with delicate transport operations, bringing high confidence for future installation in the underground galleries.
Figure 2 (left). Superconducting Link and DFHX being transported to the IT Sting facility. Chetna Krishna / CERN. Figure 3 (right). DFX cryostat produced by the University of Southampton installed in the String facility (right). CERN
Significant progress has been made on the construction of the series components. Collaborations with universities have born the fruit of an effective and cooperative effort: all DFHX and DFHM cryostat components have been delivered by Uppsala University, all DFX and the first DFM cryostats have been produced by the University of Southampton. Swedish and UK industry was involved in these productions. In addition, all resistive parts of the HTS current leads have been completed in CERN’s Main Workshop, and the assembly of about 150 HTS current leads, rated at currents ranging from 2 kA to 18 kA, proceeded at CERN according to schedule.
The procurement from industry of the HTS REBCO tape has been launched and completed, and about 50 % of the high-current REBCO round cables, interconnected to the MgB2 SC-links, have been produced at CERN with the purposefully developed and constructed cabling machine.
For the installation aspects in the LHC underground, in addition to the lessons learnt from the installation in the IT String, a collaborative effort between WP6a and WP15 enabled completion of the installation sequence studies in the UR galleries as well as the integration studies of all auxiliary equipment.