用于VHF范围的低温恒温、快速扫描、宽带NQR光谱仪
A cryostatic, fast scanning, wideband NQR spectrometer for the VHF range
摘要：
在寻找一种新的MRI造影剂，它依赖于T1缩短由于Bi核和质子之间的四极相互作用，快速扫描宽带系统的零场核四极共振（NQR）光谱是必需的。具有电机驱动的调谐匹配级的已建立的NQR探头通常体积庞大且速度缓慢，如果涉及具有低SNR（过度平均）和长四极T1时间的Bi化合物，则这可能是禁止的。此外，许多实验在低温如77 K（液氮，LN）下产生更好的结果，因此需要易于使用的低温探针头。在本文中，我们提出了电子调谐宽带探头的频带在20 - 120 MHz的频率范围内，可以沉浸在LN，使非常快速的探索性扫描在整个范围内。为此，我们应用一个交织子频谱采样策略（ISS），它依赖于电子调谐能力。新概念的优越性证明了实验扫描三苯基铋从24-116 MHz在室温下，在LN。特别是对于表现出极长的T1时间（64 ms）和低信号的第一次跃迁，新方法允许超过100的加速因子相比，经典的方法。
英文摘要：
In the search for a novel MRI contrast agent which relies on T1 shortening due to quadrupolar interaction between Bi nuclei and protons, a fast scanning wideband system for zero-field nuclear quadrupole resonance (NQR) spectroscopy is required. Established NQR probeheads with motor-driven tune-match stages are usually bulky and slow, which can be prohibitive if it comes to Bi compounds with low SNR (excessive averaging) and long quadrupolar T1 times. Moreover many experiments yield better results at low temperatures such as 77K (liquid nitrogen, LN) thus requiring easy to use cryo-probeheads. In this paper we present electronically tuned wideband probeheads for bands in the frequency range 20 - 120 MHz which can be immersed in LN and which enable very fast explorative scans over the whole range. To this end we apply an interleaved subspectrum sampling strategy (ISS) which relies on the electronic tuning capability. The superiority of the new concept is demonstrated with an experimental scan of triphenylbismuth from 24-116 MHz both at room temperature and in LN. Especially for the first transition which exhibits extremely long T1 times (64ms) and low signal the new approach allows an acceleration factor by more than 100 when compared to classical methods.
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