High Power Millimeter Wave/Terahertz Sources for Magnetic Resonance

描述(由申请人提供)：建议的研究重点是开发用于磁共振研究的1000W、250 GHz回旋管放大器。时间域DNP/核磁共振和EPR实验已经成为阐明生物系统的结构、功能和动力学性质的重要技术。由于缺乏微波功率，这些技术在高频下的充分实施一直受到限制。这项提案要求提供资金，以开发一种高功率回旋管放大器，在9T下产生纳秒到微秒的脉冲，用于DNP/核磁共振和EPR应用。这项更新方案建立在我们之前的研究计划成功的基础上，该计划设计、制造和演示了一种适用于5T的新型100 W、140 GHz陀螺放大器。140 GHz陀螺放大器在140 GHz的两微秒脉冲工作时，功率水平为400W，带宽为1 GHz。放大器是稳定的，除非施加输入驱动信号，否则检测不到输出功率。该放大器已经达到了它的所有主要目标，现在将应用于磁共振研究。拟议的250 GHz回旋管放大器研究计划还得益于麻省理工学院一项非常成功的计划，该计划针对DNP/核磁共振和EPR应用的高频回旋管振荡器进行了研究。提出的新的250 GHz陀螺放大器将工作在30kV，0.75A，9T的磁场中，饱和增益超过60d B。为了优化高频微波(太赫兹辐射)磁共振系统的性能，我们还建议开发传输线、纳秒开关和谐振器等优化组件。太赫兹技术的进步对生物样品的常规光谱、癌症成像以及可能的癌症治疗也是有价值的。对于核磁共振，由于观察到的原子核的旋磁比很小，信号强度本质上很低。因此，开发提高核磁共振实验灵敏度的方法是至关重要的。DNP光谱已被开发用于常规记录膜和可溶性蛋白质的一维和二维DNP增强魔角旋转(MAS)光谱，该光谱以双自由基为偏振剂。强微波脉冲的可获得性将使基于相干过程的新的极化转移方案的发展成为可能，例如在强磁场下更有利的电子-核Hartmann-Hahn交叉极化方案。对于EPR，所提出的陀螺放大器的强微波脉冲的激发带宽的增加将为我们提供进行高场傅里叶变换光谱和DQ EPR实验的可能性，以确定生物感兴趣系统中两个电子自旋之间的距离和方向。对这一延续建议的资助对于保持生物分子光谱研究这一重要领域的进展至关重要。 与公众健康相关：拟议的研究旨在建立一种高频微波源，它将极大地提高核磁共振(NMR)和电子顺磁共振(EPR)光谱仪的灵敏度，从而有助于阐明生物分子的性质。改进的技术将增加对淀粉样蛋白和膜蛋白结构的了解，这是了解它们在生物系统中作用的关键。高频微波还可以用于组织成像、检测癌症，甚至可能用于癌症治疗。

DESCRIPTION (provided by applicant): The proposed research is focused on the development of a 1000 W, 250 GHz gyrotron amplifier for Magnetic Resonance research. Time domain DNP/NMR and EPR experiments have emerged as important techniques for elucidating the structure, function, and dynamic properties of biological systems. The full implementation of these techniques at high frequency has been limited by the lack of microwave power. This proposal requests funding to develop a high power gyrotron amplifier producing nanosecond to microsecond pulses for DNP/NMR and EPR applications at 9T. This renewal proposal builds on the success of our previous research program to design, fabricate and demonstrate a novel 100 W, 140 GHz gyroamplifier for application at 5T. The 140 GHz gyroamplifier has demonstrated a power level of 400 W and bandwidth of 1 GHz in two microsecond pulsed operation at 140 GHz. The amplifier is stable, with no output power detected unless an input drive signal is applied. The amplifier has met all of its major goals and will now be applied to Magnetic Resonance re- search. The proposed 250 GHz gyrotron amplifier research program also benefits from a highly successful program of research at MIT on high frequency gyrotron oscillators for DNP/NMR and EPR applications. The proposed new 250 GHz gyroamplifier will operate at 30 kV, 0.75 A in a magnetic field of 9T with over 60 dB of saturated gain. In order to optimize the performance of the Magnetic Resonance systems operating with high frequency microwaves (THz radiation), we also propose to develop optimized components such as transmission lines, nanosecond switches, and resonators. Progress in THz technology is also valuable for conventional spectroscopy of biological samples, cancer imaging and, possibly, cancer therapy. For NMR, signal intensities are intrinsically low due to the small gyromagnetic ratios of the observed nuclei. It is therefore crucial to develop methods to enhance the sensitivity of NMR experiments. DNP spectroscopy has been developed to routinely record 1D and 2D DNP enhanced magic angle spinning (MAS) spectra of membrane and soluble proteins using biradicals as polarizing agents. The availability of intense microwave pulses will allow the development of new polarization transfer schemes based on coherent processes, such as electron-nuclear Hartmann-Hahn cross polarization schemes, which are more favorable at high magnetic fields. For EPR, the increased excitation bandwidth of the intense microwave pulses of the proposed gyroamplifier will provide us with the possibility to perform high-field Fourier transform spectroscopy and DQ EPR experiments to determine the distance and the orientation between two electron spins in systems of biological interest. Funding of this continuation proposal is crucial to maintaining progress in this important field of spectroscopic research on 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) and Electron Paramagnetic Resonance (EPR) spectrometers and will therefore help to elucidate the properties of biomolecules. 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. High frequency microwaves can also be used in imaging tissue, in detecting cancer and, possibly, in cancer therapy.