Dynamic transport critical current measurements of MgB2 superconductor

Measurements of transport critical current of superconducting conductors with respect to temperature and magnetic field are of particular importance for medical and energy applications. The main interest of using the superconducting materials such as MgB2, Bi-based and YBa2Cu3O7 is in the range of 4–40 K and testing facilities covering such a range of temperatures and magnetic fields can be costly, especially when considering the cooling power required in the cryogenic system and also a dramatically growing cost of liquid helium and its shortage. Transport critical currents in excess of 1000 A at temperatures above LHe are common for commercial wires, making the testing of such samples difficult in setups cooled via a cryocooler even by force gas cooling. There is also a fundamental interest in the study of superconducting conductors in magnetic fields higher than B = 20 T; such magnetic flux density can be obtained by using pulse techniques, however data interpretation can be difficult and there are some potential discrepancies. In the current paper we present how improved stepwise pulse current and signal averaging procedure combined with stepwise pulse transport current and flat-top pulse magnetic field measurements can deliver results identical to the combined DC transport current and DC magnetic field in milliseconds and also with a minimum boil-off of helium