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、具有成本效益的行波管（TWT）放大器，其峰值功率为263 GHz，连续波功率为5 W，瞬时带宽为5%，用于动态核极化（DNP）增强固态和溶液态NMR以及电子顺磁共振（EPR）光谱。使用DNP，NMR实验中固有的小信号强度可以增强高达两个数量级。这种显著增加的整体灵敏度对于NMR光谱的分析应用以及使用NMR方法的生物大分子的结构确定将是非常有益的。目前，DNP用低功率固态源（其输出功率在>300 GHz的频率下被限制为几mW）和在20-30 K范围内的低温下（以补偿低微波功率）或用可以产生50 W功率的大型回旋管系统来执行。回旋管是昂贵的，并且不具有足够的调谐带宽（<0.1%），这对于研究大范围的DNP实验是必要的，因此在NMR磁体中需要昂贵的扫描线圈。拟议的行波管将解决上述所有问题。该行波管还可用作商用263 GHz EPR谱仪的外部放大器，可将输出功率能力显著提高30 dB。该行波管的成本预计不到回旋管系统的四分之一，提供5%的瞬时带宽，将是一个紧凑的桌面系统。这些优势将使更多的研究人员能够在NMR实验中利用DNP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，以实现在如此高的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得以优化。该技术是可扩展的，可用于高达593 GHz（900 MHz NMR）的频率。该器件的更高峰值功率版本将推进高场EPR光谱的最新技术。作为该项目的最终成果，我们预计Bridge 12将为DNP-NMR和EPR光谱提供从263 GHz（400 MHz NMR）到593 GHz（900 MHz NMR）的商用行波管。这将极大地加快与NIH资助的人类疾病研究相关的生物大分子的结构测定。

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.