Cryogenic design of a superconducting magnet with a copper cable-in-conduit conductor filled with static superfluid helium

In the field of dark matter research, the MAgnetized Disk and Mirror Axion eXperiment (MADMAX) aims for the direct search of axions in a mass range around 100μeV. To have enough sensitivity on this range a dipole composed of 18 coils must reach a figure of merit of 100 T \mathbf {^{2}} m\mathbf {^{2}}. For this purpose, the use of a cable-in-conduit conductor (CICC) with a copper profile filled with static superfluid helium is under investigation. In order to prove the reliability of such a conductor in this magnet design as well as characterizing the quench propagation, a magnet solenoid mockup is tested within the JT60SA Cold Test Facility (CTF). To reproduce the thermal configuration of a MADMAX coil, the solenoid mockup is cooled down at 1.8 K directly through the void section of the CICC by pressurised superfluid helium and the mandrel, by conduction, without being immersed in a helium bath. The long distance to the heat exchanger coupled with the narrow helium section in the CICC limits the Gorter-Mellink heat transport, thus the cool down efficiency and heat losses must be tackled. This paper describes the thermal design of the experimental facility, the explanation of a thermal model for superfluid helium cool down and operation and the first experimental results.