Superconductivity & Particle AcceleratorS 2026

The development of superconducting (SC) undulators at the Karlsruhe Institute of Technology (KIT) has been closely connected to the development of dedicated magnet and cryogenic measurement infrastructure. For more than 15 years, KIT has collaborated with Bilfinger Nuclear & Energy Transition GmbH on the development and production of SC undulators based on low-temperature superconductors. This collaboration has resulted in several full-scale SC undulators and driven the development of specialized facilities for their testing and characterization.

A central part of this infrastructure is provided by CASPER I and CASPER II (Characterization Setup for Field Error Reduction). These stationary facilities enable magnetic characterization of SC coils and undulators under cryogenic conditions, including current-carrying capability, training, and local as well as integral magnetic field measurements. To complement the stationary facilities, mobile measurement systems were developed for the characterization of SC devices directly in their final cryostats. This enables magnetic field measurements and acceptance testing at the customer site and extends the capabilities of the KIT infrastructure beyond the laboratory.

The next step is COMPASS, a new high-current cryogenic test facility currently being commissioned. With a current capability of up to 10 kA, COMPASS will extend the range of SC magnet systems that can be tested at KIT. A key focus is the investigation of mixed-refrigerant cooling (MRC) for superconducting magnet systems, enabling operation at temperatures above liquid helium conditions. An important application is the development and characterization of mixed-refrigerant-cooled current leads, with the potential to reduce cryogenic heat loads and overall cooling power requirements.

This contribution presents the evolution of the KIT Magnet and Cryogenics Facilities from SC undulator testing towards a broader platform for superconducting magnet and cryogenic technology, supporting current and future developments including high-temperature SC applications.