Analysis of a Digital SQUID Magnetometer Utilizing a Direct Coupled DC SQUID for Improved Magnetic Field Resolution

Magnetometers utilizing digital SQUIDs are good candidates for high sensitive measurements of rapidly varying magnetic fields in a wide range. The association of its very large dynamic range together with the very high field resolution of an analog SQUID leads to new generation of SQUID sensors. This paper describes a hybrid magnetometer system, which is designed for applications in unshielded environment. It uses the flux quanta counting digital SQUID to operate in large environmental fields. We present a detailed study for the dynamic properties of the sensor system with focus on the digital SQUID part. We use a numerical simulation technique to investigate the interference between analog and digital sub-systems and characterize the hybrid magnetometer system performance.