Critical current measurements at electric fields in the pV m(-1 ) regime

We describe a technique for characterising sample lengths of commercial superconducting wire in closed loop configuration. This enables the measurement of critical current, as a function of applied magnetic field, at electric field criteria in the range 10(6) to 1 pV m(-1) by detecting the decay of current in the closed loop. How these measurements relate to the more traditional 4 terminal measurements made on short sample coils is discussed and representative data from both NbTi and Nb(3)Sn samples are presented and analysed