DC SQUID Modulation Electronics for Operation With HTS DC SQUID Magnetometers in the Unshielded Environment

The new variant of DC SQUID modulation electronics for functioning with HTS DC SQUID magnetometers in the unshielded environment, was designed, manufactured and tested. The electronics was optimized for operation with new ultrasensitive HTS DC SQUID magnetometer providing magnetic field resolution of about 15 fT/radicHz at frequencies above 10 Hz and 30 fT/radicHz at 1 Hz. The central commutation core of electronics was based on a complex programmable logic device (CPLD). It has allowed to include into the SQUID-electronics the flexible system of a bias reversal which provides a stable magnetometer operation for various configurations of wiring in the cryostat and various HTS DC SQUID topologies. The electronics was manufactured in one compact box with size 110 mm times60 mm times 15 mm. The channel has standard bandwidth of about 100 kHz with greatly increased dynamic range due to high coupling (8 mV/Phi0) of feedback signal with main SQUID's loop.