Ironless Cryogenic Current Comparators for AC and DC Applications

The ac and dc errors of cryogenic current comparators with toroidal-shield configurations are reported. Based on these experiments and on theoretical considerations, geometric parameters of the superconducting shields could be determined, which govern the errors. These results may be used for the construction of cryogenic current comparators with predictably low errors. It seems to be possible to decrease the dc error far below our present resolution limit of 3 X 10-11.