PROXIMITY EFFECT OF Cu CLAD Nb AND Cu CLAD NbTi WIRES

Abstract

The Meissner screening length in Cu of Cu clad Nb and Cu clad NbTi wire has been measured over temperature range from Tc down to 25 mK. The temperature dependence of the screening length is expressed by (T+T0)-1/2 from about 1.5 K to the minimum temperature. The length becomes 12 µm for Cu clad Nb and 7 for Cu clad NbTi wire at 25 mK. The measurement has been also done for Cu clad fine multiple NbTi wire. In this case, the screening length shows a drastic increase above 1 K, and the slope becomes remarkably small below 1 K. Some comments for application are also presented.