A nuclear magnetic resonance spectrometer for operation around 1 MHz with a sub 10 mK noise temperature based on a two stage dc SQUID

Abstract

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 superconducting quantum interference device current sensor, with an energy sensitivty e = 26 +/-1 h when operated at 1.4K. To maximise the sensitivity both the NMR pickup coil and tuning capacitor need to be cooled, and the tank circuit parameters should be chosen to equalise the contributions from circulating current noise and voltage noise in the SQUID. A noise temperature TN = 7 +/-2 mK was measured, at a frequency of 0.884 MHz, with the circuit parameters close to optimum.

arXiv comment3 pages, 3 figures. The following article has been submitted to Applied Physics Letters. After it is published it will be found at http://apl.aip.org/ Typos corrected, an additional reference included

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