PULSED NQR-FFT SPECTROMETER FOR N-14

A pulsed NQR spectrometer system with fast Fourier transform capabilities operating in the range 0.5 to 5 MHz is described. The transmitter and receiver use a heterodyne configuration to eliminate carrier feedthrough problems present in standard autodyne NQR spectrometers. A unique matching network containing the sample coil allows simultaneous tuning of both the transmitter and the receiver over a two-to-one frequency range. Gating of the system is controlled by a versatile pulse sequencer which can generate Carr-Purcell, Meiboom-Gill modified Carr-Purcell, and spin-locked spin-echo sequences, as well as a standard sequence of π 2 pulses suitable for T1 measurements or collection of FID signals. The sequencer also generates data collection control signals for a Digilab FTS data system with real-time co-adding and fast Fourier transform capabilities. Examples of experimental results obtained with the spectrometer and data system are presented. © 1979.