Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields

TL;DR

This paper evaluates and improves the magnetic field sensitivity of time-division SQUID multiplexers by introducing designs with enhanced gradiometry, significantly reducing external magnetic interference.

Contribution

The paper presents a new SQUID multiplexer design with improved gradiometry that lowers sensitivity to external magnetic fields compared to previous designs.

Findings

Reduced effective area in both first and second stage SQUIDs

Significant decrease in magnetic pickup sensitivity

Enhanced design robustness against external magnetic interference

Abstract

Time-division SQUID multiplexers are used in many applications that require exquisite control of systematic error. One potential source of systematic error is the pickup of external magnetic fields in the multiplexer. We present measurements of the field sensitivity figure of merit, effective area, for both the first stage and second stage SQUID amplifiers in three NIST SQUID multiplexer designs. These designs include a new variety with improved gradiometry that significantly reduces the effective area of both the first and second stage SQUID amplifiers.