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: 9296139
• 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/9296139
• 关键词: Amplifiers; Amyloid Proteins; Area; Biomedical Research; Code; Communities; Cost Savings; Coupling; Dependence; Development; Devices; Electromagnetics; Electron Beam; Electrons; Engineering; Equipment; Frequencies; Heating; Intercept; Laboratories; Magic; Measurement; Mediating; Membrane; Methods; Modeling; Modernization; 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; enhancing factor; experimental study; innovation; magnetic field; metallicity; microwave electromagnetic radiation; millimeter; novel; operation; programs; public health relevance; 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)在 DNP 实验中，使用高频微波源照射电子-核跃迁，并将电子自旋库中存在的高自旋极化转移到核。 spi 系统通过超精细和偶极相互作用产生的 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为在毫米到太赫兹范围内 - 263 GHz、395 GHz 和 527 GHz（g=2 电子，400 MHz、600 MHz）迄今为止，DNP 实验依赖于为 DNP 魔角旋转 (MAS) 实验开发的连续功率输出为 20 至 50 瓦的回旋管振荡器，并且已经安装了大约 30 个此类系统。然而，回旋管成本高昂且体积较大，而行波管源会造成成本大幅降低。如果 TWT 源开发成功，将能够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。更高频率和功率的 TWT 是现代真空电子器件研究中的一个深入探索的领域，我们小组正在进行一项研究计划，研究 W 频段 95 GHz 的 TWT 放大器，并且最近成功展示了一种创新的技术。超调制结构中的 95 GHz TWT 所提议的研究将建立在 20 瓦、250 GHz TWT 振荡器的设计、制造和演示的成功基础上。所提议的设备将使用一种新颖的相互作用结构，该结构允许相对较大的电子束隧道。 ，从而最大限度地减少连续运行中的光束拦截和结构加热。 TWT 将与现有的 380 MHz NMR 波谱仪一起用于 DNP 研究，从而通过实验证明 TWT 在我们的结构概念可扩展到更高的频率，例如 395 或 527 GHz 放大器对于 DNP NMR 实验也非常有吸引力，其中时域光谱技术可以产生很大的增强，而 CW 交叉效应机制则不会表现出来。我们将构建一个 TWT 放大器，以在 250 GHz 下使用脉冲电子束实现更高的输出功率。该放大器可以在几微秒的时间尺度上实现。通过使用现有硬件进行测试，可以节省大量成本，我们还将演示从 TWT 到 NMR 探头中的样品的高效传输。总的来说，这些研究将代表 TWT 应用的完整解决方案。 DNP 核磁共振。