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.

Public Health Relevance

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. DNP has been demonstrated to increase the signal to noise ratio by more than 400 in NMR spectroscopy and has application in the study of membrane, soluble and amyloid proteins. TWTs are much smaller and less expensive than the gyrotrons currently used in DNP NMR so that the successful TWT development will allow the dissemination of DNP methods to hundreds of NMR laboratories worldwide.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Research Project (R01)
Project #
2R01EB004866-09
Application #
8959964
Study Section
Enabling Bioanalytical and Imaging Technologies Study Section (EBIT)
Program Officer
Sastre, Antonio
Project Start
2005-04-01
Project End
2019-06-30
Budget Start
2015-07-01
Budget End
2016-06-30
Support Year
9
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Type
Organized Research Units
DUNS #
001425594
City
Cambridge
State
MA
Country
United States
Zip Code
Nanni, Emilio A; Jawla, Sudheer; Lewis, Samantha M et al. (2017) Photonic-band-gap gyrotron amplifier with picosecond pulses. Appl Phys Lett 111:233504
Soane, Alexander V; Shapiro, Michael A; Jawla, Sudheer et al. (2017) Operation of a 140 GHz Gyro-amplifier using a Dielectric-loaded, Sever-less Confocal Waveguide. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 45:2835-2840
Ni, Qing Zhe; Yang, Fengyuan; Can, Thach V et al. (2017) In Situ Characterization of Pharmaceutical Formulations by Dynamic Nuclear Polarization Enhanced MAS NMR. J Phys Chem B 121:8132-8141
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Kowalski, Elizabeth J; Shapiro, Michael A; Temkin, Richard J (2014) Simple Correctors for Elimination of High-Order Modes in Corrugated Waveguide Transmission Lines. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 42:29-37
Michaelis, Vladimir K; Ong, Ta-Chung; Kiesewetter, Matthew K et al. (2014) Topical Developments in High-Field Dynamic Nuclear Polarization. Isr J Chem 54:207-221
Jawla, Sudheer K; Shapiro, Michael A; Idei, Hiroshi et al. (2014) Corrugated Waveguide Mode Content Analysis Using Irradiance Moments. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 42:3358-3364
Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander et al. (2013) Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy. J Infrared Millim Terahertz Waves 34:42-52

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