Novel Traveling Wave Tubes for CW and Pulsed DNP NMR

用于 CW 和脉冲 DNP NMR 的新型行波管

• 批准号: 9069845
• 负责人: RICHARD J TEMKIN
• 金额: $ 47.55万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-02-07 至 2019-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9069845
• 关键词: Amplifiers; Amyloid Proteins; Area; Biomedical Research; Code; Communities; Cost Savings; Coupling; Dependence; Development; Devices; Electromagnetics; Electron Beam; Electrons; Engineering; Equipment; Exhibits; Frequencies; Heating; Laboratories; Magic; Measurement; Mediating; Membrane; Methods; Modeling; Motivation; NMR Spectroscopy; Noise; Nuclear; Output; Physiologic pulse; Research; Resolution; Sampling; Sapphire; Signal Transduction; Site; Source; Structure; System; Techniques; Testing; Time; Torsion; Travel; Tube; Vacuum; cost; design; innovation; magnetic field; microwave electromagnetic radiation; millimeter; novel; operation; programs; public health relevance; research study; success; transmission process

 DESCRIPTION (provided by applicant): This application proposes the development of a 250 GHz traveling wave tube (TWT) oscillator (years one and two) and a 250 GHz TWT amplifier (years three and four) for utilization in dynamic nuclear polarization (DNP) NMR experiments. In DNP, a high frequency microwave source is used to irradiate electron-nuclear transitions and the high spin polarization present in the electron spin reservoir is transferred to the nuclear spi system through the hyperfine and dipolar interactions. The resulting enhancements in NMR signals have been demonstrated to exceed a factor of 400, and thus DNP NMR is now considered a major advance in NMR spectroscopy. The required microwave frequency for the electron spin system excitation is in the millimeter to terahertz regime - 263 GHz, 395 GHz and 527 GHz for g=2 electrons at 400 MHz, 600 MHz and 800 MHz 1H frequencies respectively. To date, DNP experiments have relied on gyrotron oscillators with continuous power output of 20 to 50 Watts developed for DNP magic angle spinning (MAS) experiments. Gyrotrons are now commercially available and about 30 such systems have been installed worldwide in the past five to ten years. However, gyrotrons are both costly and relatively large, the latter creating issues with siting. A TWT source will dramatically lower the cost and size of the microwave source for DNP spectrometers. If the TWT source is successfully developed, it will allow dissemination of DNP NMR techniques to hundreds of laboratories worldwide, thus making the breakthrough DNP method widely available to the biomedical research community. Extending the operation of TWTs to higher frequency and power is an area of intensive exploration in modern vacuum electron device research. Our group has an ongoing research program to investigate TWT amplifiers at 95 GHz in W-Band and have recently successfully demonstrated an innovative 95 GHz TWT in an overmoded structure. The proposed research will build upon that success in the design, fabrication and demonstration of a 20 Watt, 250 GHz TWT oscillator. The proposed device will use a novel interaction structure that allows a relatively large electron beam tunnel, thus minimizing beam interception and structure heating in continuous operation. The TWT will be used with an existing 380 MHz NMR spectrometer for DNP research, thus demonstrating experimentally the application of a TWT to DNP. Our structure concept is scalable to higher frequencies, such as 395 or 527 GHz. An amplifier is also very attractive for DNP NMR experiments, where time-domain spectroscopic techniques can produce large enhancements and in contrast to CW Cross Effect mechanisms do not exhibit a magnetic field dependence. We will build a TWT amplifier to achieve higher output power, 200 W at 250 GHz, using pulsed electron beams on the time scale of several microseconds. The amplifier can be tested with existing hardware, a large cost savings. We will also demonstrate highly efficient transmission of the output power from the TWT to the sample located in the NMR probe. Collectively, these studies will represent a complete solution of the application of the TWT to DNP NMR.

 描述（由申请人提供）：本申请提出开发250 GHz行波管（TWT）振荡器（第一年和第二年）和250 GHz TWT放大器（第三年和第四年），用于动态核极化（DNP）NMR实验。在DNP中，高频微波源用于照射电子-核跃迁，并且存在于电子自旋库中的高自旋极化通过超精细和偶极相互作用转移到核自旋系统。由此产生的NMR信号增强已被证明超过400倍，因此DNP NMR现在被认为是NMR光谱学的重大进步。电子自旋系统激发所需的微波频率在毫米到太赫兹范围内-对于g=2的电子，分别在400 MHz、600 MHz和800 MHz 1H频率下为263 GHz、395 GHz和527 GHz。迄今为止，DNP实验依赖于为DNP魔角旋转（MAS）实验开发的具有20至50瓦的连续功率输出的回旋管振荡器。回旋管现在已经可以在市场上买到，在过去的五到十年里，全世界已经安装了大约30个这样的系统。然而，回旋管既昂贵又相对较大，后者产生了选址问题。行波管源将大大降低DNP光谱仪微波源的成本和尺寸。如果TWT源成功开发，它将允许向全球数百个实验室传播DNP NMR技术，从而使突破性的DNP方法广泛应用于生物医学研究界。将行波管的工作频率和功率扩展到更高的范围是现代真空电子器件研究中的一个深入探索的领域。我们的团队正在进行一项研究计划，以研究W波段95 GHz的行波管放大器，最近成功地展示了一种创新的95 GHz过模结构行波管。拟议的研究将建立在20瓦，250 GHz行波管振荡器的设计，制造和演示的成功。所提出的设备将使用一种新的相互作用结构，允许一个相对较大的电子束隧道，从而最大限度地减少连续操作中的束拦截和结构加热。该行波管将与现有的380 MHz NMR光谱仪一起用于DNP研究，从而通过实验证明了行波管在DNP中的应用。我们的结构概念可扩展到更高的频率，如395或527 GHz。放大器对于DNP NMR实验也是非常有吸引力的，其中时域光谱技术可以产生大的增强，并且与CW交叉效应机制相反，不会表现出磁场依赖性。我们将建立一个行波管放大器，以实现更高的输出功率，在250 GHz的200 W，使用脉冲电子束的时间尺度上的几微秒。该放大器可以用现有的硬件进行测试，节省了大量的成本。我们还将展示从行波管到位于NMR探针中的样品的输出功率的高效传输。总的来说，这些研究将代表TWT应用于DNP NMR的完整解决方案。