Absolute calibration of a three-axis SQUID-cascade vector magnetometer

Abstract

We report on the absolute calibration of a three-axis SQUID-cascade vector magnetometer suited for mobile operation in the Earth’s magnetic field. It is based on low temperature superconductor (LTS) dc SQUIDs with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT Hz−1/2. Due to the cascaded operation principle, the huge dynamic range required to resolve a measurement range of more than 50 µT with sub-pT resolution is split onto several electronic channels of less demanding precision. As a result, the measurement accuracy is less vulnerable to parameter drifts. Furthermore, the intrinsic redundancy of the setup can be used to check for systematic errors of measurement. The offset as well as scaling and directional errors of the magnetometer have been obtained by the method of scalar calibration in our laboratory, resulting in a residuum with a standard deviation of less than 0.64 nT.

Flux trapping in multi-loop SQUIDs and its impact on SQUID-based absolute magnetometry

“…During several years our group has been working on the development of a low-T c SQUID-based absolute vector magnetometer suited for mobile operation in Earth's magnetic field. This kind of sensor, denoted as SQUID cascade in previous publications [1][2][3], might be of great interest for airborne and ground-based geomagnetic surveys, since it outperforms conventional absolute magnetometers like optically pumped magnetometers (OPM) [4][5][6][7][8] in terms of noise, bandwidth, and due to its ability to measure the magnetic vector components.…”

An Adaptive △M-ICCP Geomagnetic Matching Algorithm

“…Even in the magnetic anomaly field with more obvious local variations, the measurement problem cannot be ignored. Although geomagnetic compensation (Papoyan et al, 2016; Teixeira, 2012) and magnetometer calibration (Schönau et al, 2017; Nemec et al, 2017) technologies can effectively reduce the interference of the environment magnetic field, the residuals after compensation and the magnetic sensor's measurement noise may still cause confusion and match failure. Besides, if the sampling interval is too small, the magnetic changes of all matching points are small.…”