DC SQUID-BASED NMR DETECTION FROM ROOM-TEMPERATURE SAMPLES

The authors have shown that a DC SQUID with a tuned input circuit can be used as a low noise NMR preamplifier for small, room temperature samples at low field. They were interested to observe that the SQUID maintains its bias point over periods of several hours, despite the absence of a Q-spoiler in the input circuit. The 30 ms dead time following NMR excitation pulses would be unacceptable for imaging, but earlier experiments lead the authors to expect that by including a Q-spoiler junction array in the input circuit they would be able to reduce this to well below 1 ms to allow detection after much shorter echo times.