Institute Jozef Stefan, Solid State Physics, Jamova 39, 1000 Ljubljana, Slovenia.
J Magn Reson. 2009 Dec;201(2):131-6. doi: 10.1016/j.jmr.2009.08.013. Epub 2009 Sep 6.
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.
利用高 Q 探头来提高 NMR 和 NQR 的灵敏度是一种众所周知的技术，然而，非常高的 Q 值与几个限制有关。本文探讨了作为拾波线圈 Q 因子函数的三硝基甲苯（TNT）的 (14)N NQR 多脉冲检测的信噪比，特别强调了“超 Q”范围，其中探头带宽变得比 NQR 线宽更窄。我们使用了混合实验-理论方法来找到 TNT 的 Q 相关的信噪比值，避免了在每个 Q 值下构建探头的不便。该过程已针对一系列激励/检测频率重复进行，并且获得了二维灵敏度图。我们的分析表明，当 400<Q<4000 时，灵敏度最大且实际上与 Q 无关。然而，由于 SLSE 激励和“超 Q”检测的相互矛盾的要求，与传统的 Q 约为 100 的线圈相比，仅获得了大约 6 dB 的增益。
