Development of test procedures and results of helium leak testing of Nb-Ti superconductor billets

India has successfully fabricated several kilometers of multifilament Nb-Ti superconductor wire. Helium leak testing of very high order of sensitivity at intermediate stage of fabrication is a prerequisite for successful fabrication of such wires. Nb-Ti rods are stacked in copper jacket and seal welded by EB welding procedure. Before these billets undergo extrusion, these are helium leak tested by back-pressure techniques to ensure the leak integrity of better than 1 x 10-8 std. cc/sec. of the billets. The paper describes the development of test procedures and presents the important test results data obtained during helium leak testing of several of such billets. (author)