Feedback optimization of pulse width in the SORC sequence

A method for increasing the signal-to-noise ratio (SNR) of nuclear quadrupo le resonance (NQR) measurements by automatically adjusting a pulse paramete r in real-time is presented. This approach is useful in situations where th e optimal pulse parameters cannot be chosen beforehand due to lack of knowl edge regarding the system. For example, NQR provides a means for detecting explosives by revealing the presence of N-14. In this particular applicatio n, the distance between the search coil and the explosive, as well as the t emperature of the explosive, is unknown. As a result, a fixed set of pulse parameters will not yield the largest SNR for all possible search applicati ons. This paper describes a feedback algorithm that uses measurements of th e NQR signal to automatically adjust the pulse width in the strong off-reso nant comb sequence to maximize the SNR of the NQR measurement. Experimental results obtained using a sample of sodium nitrite are presented. (C) 1999 Academic Press.