Ultrasound diagnostics of the superconducting cable connections between the main ring magnets of LHC

As part of the LHC assembly program, the superconducting magnets are interconnected after installation. Electrical continuity between the magnets is ensured via a specifically designed cable junction box which allows the cables to be electrically joined by an automated low temperature soldering technique. The electrical resistance and mechanical strength of the cable junctions depend on the quality of the soldered joint. An ultrasound diagnostic of the soldered junction has been developed to accompany the visual inspection and reinforce the quality control process. Non-standard ultrasound diagnostic techniques, without using matching liquids or gel in the harsh and congested working environment, applied to the sandwich structure of the cable junction box, which presents high ultra-sonic losses due to multiple scattering, have been developed. The equipment and methods implemented are described in detail, together with results of quality control tests made in the production environment.