Nuclear magnetic resonance spectrometer with a frequency range extended below the megahertz region

A conventional nuclear magnetic resonance (NMR) spectrometer with an original low-frequency limit of 2 MHz and equipped with an electromagnet is rebuilt to allow performing NMR experiments at resonance frequencies down to 100 kHz. The instrument is intended for accurate field-dependent spin relaxation studies. The preamplifier and the duplexer are completely replaced by new designs that provide low noise figure, large gain and fast recovery. The receiver, the transmitter, and the magnet power supply are modified to operate at low frequency (receiver and transmitter) and at low current (power supply). The performance of the instrument is demonstrated by H-2 NMR experiments in the 500 kHz-2 MHz region and is compared to that of instruments based on direct current-superconducting quantum interference device and operated on room-temperature samples. (C) 2000 American Institute of Physics. [S0034-6748(00)02902-6].