Ultra-Low Heat Leak YBCO Superconducting Leads for Cryoelectronic Applications

摘要

Recent developments in fuel-cell research have led to the availability of commercially manufactured flexible polycrystalline sheets of yttria stabilized zirconia (YSZ) in thicknesses of 50 to 100 m, which are ideal substrates for laying down low-current DC leads of YBa2Cu3O7- (YBCO) that conduct very little heat at cryogenic temperatures. Production of thick films of YBCO (several tens of microns thick), albeit at lower current densities than thin films (approx. 1 m), was well established by the mid-nineties using relatively simple low-tech methods. As was shown in the phase I proposal, the combination of these two materials can, in theory, create a superconducting DC lead which achieves our target for specific heat load (heat-load per unit amp for 35mA current passing between a 60K and a 4K heat station), i.e. 1mW per amp of current delivered. See appendix A. Calculations also showed that the same materials could also produce higher performance coplanar waveguides than normal metals at a range of RF frequencies.