Aplicability of TNT "super-Q detection" to multipulse sequences.

The use of high-Q probes to increase the sensitivity in NMR and NQR is a well-known technique, however very high Q values are associated with several limitations. This paper explores the (14)N NQR multipulse detection of trinitrotoluene (TNT) signal-to-noise ratio as a function of the pickup coil Q factor, with a particular emphasis on the "super-Q" regime, where probe bandwidth becomes narrower than the NQR linewidths. We have used a mixed experimental-theoretical approach to find the TNT Q-dependent signal-to-noise value which avoided the inconvenient construction of a probe at every Q. The process has been repeated for a range of excitation/detection frequencies and a 2D sensitivity map was obtained. Our analysis suggests, that sensitivity is maximum and practically Q-independent when 400<Q<4000. However, because the conflicting requirements of the SLSE excitation and the "super-Q" detection, only a gain of approximately 6 dB is obtained compared to a conventional Q approximately 100 coil.