Progress on the R&D for the New Cable-in-Conduit Conductor Type of the MADMAX Dipole

The concept of cable-in-conduit conductor (CICC) has been adopted for the large superconducting dipole of the magnetized disc and mirror axion experiment (MADMAX) project. It is based on a multistage cable inserted in a potentially prehardened copper profile and then compacted together down to the final rectangular shape. NbTi technology and internal cooling with stagnant superfluid helium is kept in order to operate at 1.8 K. On the other hand, the use of copper instead of stainless steel as for common CICCs for fusion magnets led to an extensive R&D phase. The need to improve the mechanical properties of the conduit to withstand the high level of mechanical stress in the magnet requires significant level of cold working, which can be obtained by compacting a profile with a large initial cross section. Manufacturing with high compaction over long lengths, within certain tolerances, represented a challenge to find the initial shape of the profile. To deal with it, different compaction scenarios were simulated by finite element methods on two copper profiles eventually manufactured. A mechanical tests campaign aimed to investigate the properties of the processed samples was also carried out. In the present work, the main characteristics of the new MADMAX CICC will be summarized, the R&D phase will be presented, and the results will be widely discussed.