ITER Magnets Superconducting Joints Prototype Tests in the CEA SELFIE Facility for Operators Qualification

The Central Solenoid (CS) is the core element of the ITER magnet system, contributed as in-kind procurement by the US Domestic Agency. Each CS module uses a Nb₃Sn conductor internally cooled by circulation of supercritical helium at 4.5 K and individually supplied up to a 45 kA current by two superconducting leads each connected through a Compacted Coaxial Joint (CCJ) and a Main Busbar (MB) joint to the Feeders system. This paper presents the results of the CCJ and MB prototypes cryogenic qualification in the dedicated SELFIE facility (ITER SELf-FIEld joint test facility). We will first introduce the specific SELFIE samples design, assembly and dedicated instrumentation used during the nominal current test and outline the main SELFIE interfaces. This will include in particular the indium-compacted electrical connection to the facility and the lower joint, which are necessary for a total facility secondary loop resistance. Then, we will detail the training environment and procedures, stressing out the knowledge transfer and risk mitigation strategy to avoid underperforming joints, which are only detectable after full assembly and cool-down of the tokamak. Finally, we will outline the first results and statistical analysis of the CCJ and MB joints testing, explaining the data-reduction scheme, comparing with SULTAN results and showing the effectiveness of the CCJ re-designing for a low-resistance simpler and more robust joint concept. Using these results, along with previous SULTAN results, we will try to estimate the in-coil performance of the joints.