Phased Array Ultrasonic Nondestructive Tests of Soldered Current-Carrying Bus-Bar Splices of Superconducting Magnets

The main magnets of the Large Hadron Collider are powered by 13-kA superconducting bus-bars. The bus-bars from these magnets are electrically connected by the so-called splices, which are assembled by inductive soldering of the Rutherford-type cables and the copper profiles of the stabilizer. The quality of the soldering is of uttermost importance. Therefore, the electrical continuity of the splice in its normal conducting state has to be accurately controlled. The Phased Array Ultrasonic testing technique has been applied for the quality control of the soldered joints between the Large Hadron Collider 13-kA superconducting bus-bars. This technique consists in analyzing the internal structure of the pieces by studying the behavior of the ultrasonic propagation through the material. The results of this inspection, performed on different samples (joints), showed various types of soldering defects; which proves the potential of this type of nondestructive quality control technique. Other quality control methods, based on pulsed currents, eddy-currents and X-rays have been assessed to verify the results. The information obtained within the test has been evaluated and used for benchmarking.