Superconducting detector magnets for the future

22 November 2022
Magnetic The large Nb-Ti superconducting magnet of the CMS detector being installed in 2007. Credit: CERN-EX-0702022-04

The Superconducting Detector Magnets Workshop, co-organised by CERN and KEK, was held at CERN from 12 to 14 September in a hybrid format. Joining were 90 participants from 36 different institutes and companies, with 57 on-site and 33 taking part remotely.

The workshop aimed to bring together the physics community, detector magnet designers and industry to exchange ideas and concepts, foster collaboration, and to discuss the needs and R&D development goals for future superconducting detector magnets. A key goal was to address the issue of the commercial availability of aluminium-stabilised Nb-Ti/Cu conductor technology.

Fifteen physics-experiment projects, which had either been approved or are in the design phase, presented their needs and plans for superconducting detector magnets. These experiments covered a wide range of physics programmes for existing and future colliders, non-colliders and a space-based experiment. The presented projects showed a strong demand for aluminium-stabilised Nb-Ti/Cu conductor technology. Other conductor technologies that were featured during the workshop included cable-in-conduit technology (CICC) and aluminium-stabilised high-temperature-superconducting (HTS) technology.

Presentations by leading industrial partners showed that the industrial capability to produce superconducting detector magnets does exist, as long as a suitable conductor is available. It was also shown that aluminium-stabilised Nb-Ti/Cu conductors are currently not commercially available, although an R&D effort is currently on-going with IHEP in China. In particular, the co-extrusion process needed to clad the Nb-Ti/Cu Rutherford cable with aluminium is a key missing ingredient in industry. At the same time, the presentations showed that other ingredients, such as Nb-Ti/Cu wire production, the cabling of strands into a Rutherford cable, the high-purity aluminium stabiliser itself and the technique for welding-on of aluminium-alloy reinforcements for high-strength conductors, are still available.

The main conclusion of the workshop was that, given the need for aluminium-stabilised Nb-Ti/Cu conductors for future superconducting detector magnet projects, it is important that the commercial availability of this conductor is re-established, which would require a leading effort from international institutes through collaboration and cooperation with industry. This world-leading effort will advance technologies to be transferred openly to industry and other laboratories. Of particular importance is the co-extrusion technology needed to bond the aluminium stabiliser to the Rutherford cable. Hybrid-structure technology through electron- beam welding or other approaches to maximise the performance of an Al-stabilised superconductor combined with high-strength Al-alloy is needed for high-stress detector magnets. Back-up solutions such as copper-coated and soldered aluminium stabilisers, copper-based stabilisers and CICC should also be considered. In the long term, aluminium-stabilised HTS technology will be important for specific detector-magnet applications.

The workshop was received with strong interest and enthusiasm, and it is expected that another will be organised in one to two years, depending on the progress being made.

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