HTS superconducting current comparator: dynamic range and noise limits

The dynamic range, ratio balance error, and current resolution have been evaluated for an upgraded prototype high-temperature superconductor (HTS) dc current comparator, which has been previously developed and demonstrated for the noninvasive sensing of charged particle beams. The addition of a custom-designed 2-SQUID gradiometer coupled to an S-shaped current concentrator is expected to provide an improvement in the flux sensitivity, as well as a reduction in the stray coupling of external fields. In the longer term, when the limiting factors have been fully identified, the technique may be considered for potential applications in fundamental metrology, for example, in a physical determination of the faraday by an ion-collection method.