Performance of high-TC dc SQUID magnetometers for use in a magnetically disturbed environment

Abstract

PACS 85.25.Dq YBCO dc SQUID magnetometers based on bicrystal Josephson junctions on 10 mm × 10 mm STO substrates have been fabricated. We have designed three different types of pickup coils for the SQUID magnetometers, i.e., solid-type, 12 and 16 parallel loops with 50 µm line width to test performances of the SQUIDs for use in a magnetically disturbed environment. Magnetometer with 16-parallel-loop pickup coil exhibit most stable FLL operation under external dc magnetic field. Finally, we could obtain optimised direct coupled YBCO SQUID magnetometer design having flux transfer coefficient B Φ of 4.5 nT/Φ 0 and magnetic field noise B N of 30 fT/Hz 1/2 measured at 100 Hz.