Efficiency of Spurious Signal Cancellation under the NQR Detection of Some Explosives by the SLIME-Type Pulse Sequences

摘要

Two versions of the spin-lock inversion mid-echo pulse sequence used for the prompt nuclear quadrupole resonance detection of explosives have been studied experimentally. These sequences are modifications of the conventional multiple pulse spin-locking sequence and differ from it by additional groups of pulses which invert echo signals. It was found that spurious signals produced by some magnetic objects are suppressed by one of these sequences much stronger than by the other. The attenuation of echo signals due to their inversion by the group of the inverting pulses is measured. The number of pulses is optimized in both the sequences to obtain maximum signal-to-noise ratio, taking into account some loss in the magnitude of inverted echoes.