High Frequency Gyrotron for DNP/NMR Research.

描述（由申请人提供）：拟议的研究计划的重点是研究和开发一个广泛可调谐的，高频（527 GHz）回旋振荡器的应用动态核极化固态核磁共振光谱（DNP/SSNMR）。在NMR中，由于所观察到的核的小旋磁比，信号强度本质上是低的。DNP/NMR实验可以提供20至400的信号增强，使DNP/NMR成为阐明生物系统结构，功能和动态特性的重要技术。这些技术在高磁场下的完全实施受到两个问题的限制：1.）在140 - 600 GHz范围内产生微波的高功率微波源的缺乏，以及2.）事实上，基本上所有的NMR磁体都以持久模式在固定场下操作，使得难以将微波频率与EPR谱中的正确频率匹配以优化DNP。该提案要求提供资金，以开发一种高稳定性的回旋振荡器，为这两个问题提供解决方案。10至50瓦，527 GHz回旋管，可调谐带宽为2 GHz，将与800 MHz NMR光谱仪结合使用，使其成为世界上磁场最高的DNP/NMR光谱仪。这种光谱仪应提供显着的信号增强在非常高的磁场，当代NMR研究目前正在进行。527 GHz回旋管的发展带来了独特的科学和工程挑战，包括：在低电压和二次谐波回旋频率下工作时，回旋管增益大大降低;高频下的高欧姆损耗;以及超导磁体的有限孔径尺寸。具有高Q腔的传统回旋管振荡器中的束参数的变化给出了小于0.1%的频率调谐范围，对于该应用是不够的。我们建议建立一个新的调谐方法的527 GHz的回旋管：即，通过改变磁场，并通过利用回旋腔耦合一系列高阶轴向模式。建议的527 GHz回旋管振荡器将大大受益于我们的研究的高度成功的结果上的可调谐330 GHz回旋管振荡器。我们最近已经证明了超过21瓦的输出功率从330 GHz的回旋管在1.2 GHz的调谐范围。调谐是通过改变磁场、电压和腔体温度来实现的。因此，无需提供谐振器的机械调谐即可完成调谐，从而确保更稳定、简单和方便的操作条件。该建议提出了一个完整的设计527 GHz的回旋管显示，预测的功率电平和调谐范围是可行的。在拟议的研究的第一年，我们将完成大范围的测试，优化和调试的可调谐330 GHz的回旋管，同时设计和订购的527 GHz的回旋管长交货期项目。资助这一延续提案对于维持生物分子核磁共振光谱学这一重要领域的进展至关重要。 公共卫生相关性：拟议的研究旨在建立一个高频微波源，这将大大提高核磁共振（NMR）光谱仪的灵敏度，因此将大大加快生物固体NMR实验中的光谱采集。这种新型回旋管微波源将成为世界上用于增强型NMR研究的最高频率源，当应用于800 MHz NMR光谱仪时，将揭示独特的分子结构信息。改进的技术将导致对淀粉样蛋白和膜蛋白结构的更多理解，这是理解它们在生物系统中作用的关键。

DESCRIPTION (provided by applicant): The proposed research program is focused on the research and development of a widely tunable, high frequency (527 GHz) gyrotron oscillator for application to dynamic nuclear polarization solid-state nuclear magnetic resonance spectroscopy (DNP/SSNMR). In NMR, signal intensities are intrinsically low due to the small gyromagnetic ratios of the observed nuclei. DNP/NMR experiments can provide signal enhancements of 20 to 400, making DNP/NMR an important technique for elucidating the structure, function, and dynamic properties of biological systems. The full implementation of these techniques at high magnetic fields has been limited by two problems: 1.) the paucity of high power microwave sources that generate microwaves in the region 140 - 600 GHz and 2.) the fact that essentially all NMR magnets operate at fixed field in persistent mode, making it difficult to match the microwave frequency to the correct frequency in the EPR spectrum to optimize DNP. This proposal requests funding to develop a high-stability gyrotron oscillator that provides a solution to these two problems. The 10 to 50 Watt, 527 GHz gyrotron with a tunable bandwidth of 2 GHz will be used in conjunction with an 800 MHz NMR spectrometer, making it the highest magnetic field DNP/NMR spectrometer in the world. This spectrometer should provide dramatic signal enhancement at the very high magnetic fields where contemporary NMR research is currently being performed. The development of the 527 GHz gyrotron presents unique scientific and engineering challenges, including: greatly reduced gyrotron gain when operating at a low voltage and at the second harmonic gyro-frequency; high ohmic loss at high frequency; and the limited bore size of the superconducting magnet. Variation of beam parameters in a conventional gyrotron oscillator with a high Q cavity gives a frequency tuning range of less than 0.1 %, inadequate for this application. We propose to build the 527 GHz gyrotron with a novel tuning approach: namely, by varying the magnetic field and by utilizing a gyrotron cavity that couples a series of high order axial modes. The proposed 527 GHz gyrotron oscillator will benefit greatly from the highly successful results of our research on a tunable 330 GHz gyrotron oscillator. We have recently demonstrated more than 21 Watts of output power from a 330 GHz gyrotron over a tuning range of 1.2 GHz. Tuning was accomplished by varying the magnetic field, the voltage and the cavity temperature. The tuning was thus accomplished without having to provide mechanical tuning of the resonator, assuring more stable, simple, and convenient operating conditions. The proposal presents a complete design of a 527 GHz gyrotron showing that the predicted power level and tuning range are feasible. During year one of the proposed research, we will complete wide-range testing, optimization and commissioning of the tunable 330 GHz gyrotron while designing and ordering long lead time items for the 527 GHz gyrotron. Funding of this continuation proposal is crucial to maintaining progress in this important field of NMR spectroscopy of biomolecules. PUBLIC HEALTH RELEVANCE: The proposed research is directed at building a high frequency microwave source that will greatly enhance the sensitivity of Nuclear Magnetic Resonance (NMR) spectrometers and will therefore dramatically speed up spectral acquisition in NMR experiments on biological solids. The novel gyrotron microwave source will be the highest frequency source in the world for use in enhanced NMR research and, when applied to an 800 MHz NMR spectrometer, should reveal unique molecular structure information. The improved techniques will lead to increased understanding of the structure of amyloid and membrane proteins which are key to understanding their role in biological systems.