Thermometric measurements of the self-field losses in silver sheathed PbBi2223 multifilamentary tapes.

Self-field ac losses in Ag sheathed PbBi-2223 tapes were measured using a thermometric method, which determines the losses by measuring the temperature profile of a vacuum insulated sample with both ends at a fixed temperature. In practice, the samples were placed in a vacuum capsule immersed in LIN bath. By minimizing the bath superheat, thermal emf and heating at the current contacts, a loss induced temperature increase as low as 2mK was measured using a Si diode thermometer. With a typical sample length of 600mm, self-field losses between 7x10(-6) W/m and 4x10(-3) W/m were measured at different frequencies. The results are in good agreement with both the electric measurement and theoretical calculation. This provides the first independent confirmation that electric measurement with carefully placed voltage loops can give the true losses of the sample.