We have developed a nuclear magnetic resonance spectrometer with a series tuned input circuit for measurements on samples at millikelvin temperatures based on an integrated two-stage super-conducting quantum interference device current sensor, with an energy sensitivity ε = 26±1 h when operated at 1.4 K. To maximize the sensitivity both the NMR pickup coil and tuning capacitor need to be cooled, and the tank circuit parameters should be chosen to equalize the contributions from circulating current noise and voltage noise in the SQUID. A noise temperature T_N = 7±2 mK was measured, at a frequency of 0.884 MHz, with the circuit parameters close to optimum.
|Number of pages||3|
|Journal||Applied Physics Letters|
|Publication status||Published - 24 Dec 2007|
- SQUID AMPLIFIER