| An innovative ceramic insulation has been developed by CEA Saclay for Nb3Sn cables. As the ceramic cures during the heat treatment of the Nb3Sn, there is no need for an impregnation afterwards. This process eliminates the epoxy-impregnation steps which present the risk to damage the conductor. The porosity of this insulation is expected to enable the high heat evacuation needed by the next magnets generation. However, in high field magnets, the transverse compressive stress on the cables, due to Lorentz forces, can be higher than 150 MPa. It is well known that Nb3Sn is very sensitive to the strain. The degradation of the Nb3Sn critical current under pressure has been investigated at CEA Saclay in collaboration with CERN using two experiments. This paper reports the first quench data measured on ceramic-insulated cables. The measurements are carried out under stress with an external field up to 11 T. The samples are compared to a witness sample in order to compute the degradation. It finally appears that the ceramic insulation gives a weaker mechanic support than epoxy-impregnation, leading to a worse critical current decrease at high fields. However, the heat evacuation is better, allowing to reach higher currents at low fields. |
