Improved Cryogenic Current Comparator Setup With Digital Current Sources

Abstract

We have realized an improved resistance calibration setup based on a cryogenic current comparator (CCC). The new comparator with 18 windings and a total of 4647 turns suits well for all the necessary comparisons of a 100-Omega standard resistor with the quantum Hall effect (QHE) and within the range of standard resistance values from 1 Omega to 1 MOmega. The new state-of-the-art setup is equipped with a dc superconducting quantum interference device (SQUID) and a digital double current source, allowing a reduction in the ramping time by at least one order of magnitude and significantly improving the dynamic stability of the system. The latter also benefits from the internal wideband feedback that we present in this paper.