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- SQUID-based setup for the absolute measurement of the Earth’s magnetic field
SQUID-based setup for the absolute measurement of the Earth’s magnetic field
in: Superconductor Science & Technology (2013)
We present a configuration of LTS dc SQUID magnetometers that is capable to measure the absolute values of the vector components of the Earth’s magnetic field with a white noise level of about 6 fT/Hz1/2. The periodic voltage-flux characteristic of a single SQUID only enables the measurement of magnetic field variations. This problem has been overcome by using a set of coplanar SQUIDs integrated on one chip with different effective areas. A special signal processing routine is introduced that iteratively calculates the absolute values of the magnetic field components. The SQUIDs are realized with 0.8 µm cross-type Josephson junctions that withstand high background fields of up to 3.9 mT during cool-down and operation. A first one-dimensional experimental implementation successfully measured the modulation of the magnetic field component perpendicular to the sensor surface with amplitudes exceeding 50 µT. The overall dynamic range of the SQUID magnetometer system achieves 190 dB.