The high current bus-bars of the LHC from conception to manufacture

Abstract

The main magnets of the LHC are series-connected electrically in different excitation circuits by means of superconducting bus-bars, carrying a maximum current of 13 kA. These superconducting bus-bars consist of a superconducting cable thermally and electrically coupled to a copper section all along length. The function of the copper section is essentially to provide an alternative path for the magnet current in case the superconducting cable loses its superconductivity and returns to normal state because of a transient system disturbance or normal zone propagation coming from the neighboring magnets. When a superconducting bus-bar quenches to normal state its temperature must always stay below a safe values of about 100 ° C while the copper is conducting. With regard to that, a quench signal is initiated, which in turn triggers the ramping down of the current from 13000 A to 0. The ramping down rate must not exceed a maximum value to avoid the transition of still superconducting state magnets series-connected with the quenched ones. This paper concerns the design and the manufacture of the high current superconducting bus-bars needed to interconnect the magnetic elements of the main dipoles of the LHC