Relationship between pulse-tube-induced noise and resistance-ratio performance

Clarify whether pulse-tube-induced high-frequency noise influences precision direct-current resistance-ratio measurements through rectification by superconducting quantum interference device nonlinearities.

Background

The appendix shows that pulse-tube operation increases the superconducting quantum interference device noise level at frequencies above approximately 80 Hz and produces periodic noise associated with the pulse-tube cycle. Although cryogenic current comparator resistance-ratio measurements are fundamentally direct-current measurements, high-frequency noise can potentially be rectified by superconducting quantum interference device nonlinearities and appear as an excess low-frequency contribution.

The authors found no direct evidence establishing whether pulse-tube-induced noise caused the observed difference between helium-gas and liquid-helium cooling. The unresolved relationship between this noise source and measurement performance is therefore a concrete subject for further investigation.

References

At present, however, no direct evidence is available to determine whether pulse-tube-induced noise was responsible for the difference observed between helium-gas cooling and liquid-helium cooling in Fig.~5(c). Clarifying the relationship between pulse-tube-induced noise and resistance-ratio measurement performance remains a subject for future investigation.

— Helium-Gas-Cooled Cryogenic Current Comparator Integrated with a Quantum Resistance Standard  (2609.01124 - Okazaki et al., 1 Sep 2026) in Appendix A, “Noise Properties under Pulse-tube Operation”