A Compact, High-power Terahertz Amplifier for DNP-NMR and EPR Spectroscopy

描述（由申请人提供）：我们建议开发一种紧凑，经济高效的行波管（TWT）放大器，其峰值功率为50 W，连续波功率为5 W，瞬时带宽为5%，用于动态核极化（DNP）增强的固态和溶液态核磁共振和电子顺磁共振（EPR）光谱。使用DNP，核磁共振实验中固有的小信号强度可以提高两个数量级。总体灵敏度的显著提高将对核磁共振光谱的分析应用以及利用核磁共振方法测定生物大分子的结构非常有益。目前，DNP是在低功率固态源（其输出功率限制为几兆瓦，频率为bbb300 GHz）和20-30 K范围内的低温（以补偿低微波功率）或大型回旋管系统中进行的，可以产生50瓦的功率。回旋管价格昂贵，并且没有足够的调谐带宽（<0.1%）来研究大范围的DNP实验，因此需要在核磁共振磁体中使用昂贵的扫描线圈。拟议的行波隧道将解决上述所有问题。该波管也可以用作商用263ghz EPR光谱仪的外部放大器，显著提高输出功率30dB。TWT的成本预计不到回旋管系统成本的四分之一，提供5%的瞬时带宽，将是一个紧凑的桌面系统。这些优点将允许更多的研究人员利用DNP在核磁共振实验中提供的灵敏度提升。在第一阶段，我们将设计、建造和测试行波管的关键子系统，包括电子枪、紧凑型永磁系统和相互作用结构。后者将建立在最先进的纳米计算机数控（CNC）铣床上，以实现在如此高频率下操作所需的高精度和表面质量。关键子系统的成功测试将使第二阶段完整原型的设计优化成为可能。该技术是可扩展的，可以在高达593 GHz （900 MHz NMR）的频率下使用。该设备的更高峰值功率版本将推动高场EPR光谱技术的发展。作为该项目的最终结果，我们预计Bridge12将提供263 GHz（400 MHz NMR）至593 GHz（900 MHz NMR）的商用行波管，用于DNP-NMR和EPR光谱。这将大大加快由NIH资助的与人类疾病研究相关的生物大分子的结构确定。

DESCRIPTION (provided by applicant): We propose to develop a compact, cost-effective Traveling Wave Tube (TWT) amplifier at 263 GHz with 50 W of peak power, 5 W of continuous wave power and 5% instantaneous bandwidth for application in Dynamic Nuclear Polarization (DNP) enhanced solid-state and solution-state NMR and Electron Paramagnetic Resonance (EPR) spectroscopy. With DNP, the inherently small signal intensities in a NMR experiment can be enhanced by up to two orders of magnitude. This significantly increased overall sensitivity will be highly beneficial for analytical applications of NMR spectroscopy as well as in the structure determination of bio- macromolecules using NMR methods. Currently, DNP is performed with either low power solid-state sources (whose output power is limited to a few mW at frequencies >300 GHz) and at low temperatures in the range of 20-30 K (to compensate for low microwave power) or with large, gyrotron systems which can generate 50 W of power. Gyrotrons are expensive and do not possess sufficient tuning bandwidth (<0.1%) necessary for investigating a wide range of DNP experiments and thus require expensive sweep coils in the NMR magnets. The proposed TWT will address all the above concerns. The TWT can also be used as an external amplifier on a commercial 263 GHz EPR spectrometer to significantly improve the output power capability by 30dB. The TWT is expected to cost less than one-fourth of the cost of a gyrotron system, provide 5% instantaneous bandwidth and will be a compact table-top system. These advantages will allow a larger number of researchers to take advantage of the sensitivity boost offered by DNP in NMR experiments. In Phase I, we will design, build and test key subsystems of the of the TWT including the electron gun, the compact permanent magnet system and the interaction structure. The latter will be built on a state-of-the-art nano-computer numerical controlled (CNC) milling machine to achieve the high precision and surface quality necessary for operation at such high frequencies. The successful testing of the key subsystems will enable optimization of the design for a full prototype in Phase II. The technology is scalable and can be used at frequencies as high as 593 GHz (900 MHz NMR). A higher peak power version of the device will advance the state-of-the-art in high field EPR spectroscopy. As an ultimate result of this project, we expect Bridge12 to offer commercial TWTs from 263 GHz(400 MHz NMR) to 593 GHz (900 MHz NMR) for DNP-NMR and EPR spectroscopy. This will greatly accelerate structure determination of bio-macromolecules of relevance to human disease research funded by NIH.