Significant enhancement of the critical current of MgB2 wires through a reduction of the diameter using HIP method

Abstract We have succeeded in the fabrication of high– J c MgB 2 wires applying hot isostatic pressure process through a reduction of the wire diameter. The results show that annealing at 570 °C in pressure of 1.1 GPa allows for high critical current density in undoped MgB 2 wires e.g. at 4.2 K-1000 A/mm 2 in 8.1 T, 100 A/mm 2 in 13 T and at 20 K–100 A/mm 2 in 5.2 T. The reduction of the MgB 2 wire diameter induces the number of connections between the grains retaining the circular shape of the wires and increasing the density of pinning centers active at 20 K.