Direct-coupled electronics for high-temperature superconductor DC SQUID-based magnetometer

摘要

A low-volume, high-performance, direct-coupled electronic system for high-T/sub c/ dc SQUID magnetometers has been developed and tested. This system is based on a liquid nitrogen-cooled amplifier and a modified integrator. The amplifier has a white noise voltage level close to 0.25 nVHz/sup - 1/2 /, a current noise of the order of 3 pAHz/sup - 1/2 /, a gain equal to 3000, a 3 dB bandwidth of about 370 kHz, and a package volume less than 3 cm/sup 3/. The modified integrator has an input resistance of the order to 10 k/spl Omega/ and a considerably high output drive current of about 30 mA. This unique combination results in the typical electronic 3 dB bandwidth of about 1 MHz, a dynamic range of /spl plusmn/5/spl times/10/sup 6/ Hz/sup - 1/2 / for frequencies up to 1.6 kHz, and a slew rate of 1/spl times/10/sub 6/ flux quanta/s in a wide signal frequency range for a middle-quality high-T/sub c/ dc SQUID sensor.