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This paper presents the experimental demonstration of a high power backward-wave oscillator (BWO) that uses a negative index mode in a waveguide filled with a metamaterial (MTM). The MTMBWO uses a 500 keV, 80 A electron beam. Initial tests of a 352 mm long metamaterial structure generated 40 W of power at 2.83 GHz. The measured frequency vs. electron beam voltage is in very good agreement with theory...
Megawatt power level gyrotrons operate in high order cavity modes that face severe mode competition. During the voltage rise and start-up of the gyrotron, modes are excited in a sequence that determines the final operating state. We have completed a wide-ranging study of the modes excited during the start-up of a 1.5 MW, 110 GHz pulsed gyrotron operating at 96 kV and 42 A. We found that at the operating...
We report on the design studies of a >20W, continuous wave 527 GHz gyrotron for the Dynamic Nuclear Polarization (DNP) enhanced solid state Nuclear Magnetic Resonance (NMR) spectroscopy on a 800 MHz spectrometer. A 9.8 T helium-free superconducting magnet with a warm bore diameter of 76mm is planned for the gyrotron operation. The gyrotron resonator cavity is designed to operate in the TE11, 3...
Signal-to-noise is a key ingredient in successful NMR experiments, a fact that has stimulated the development of dynamic nuclear polarization (DNP). In solid state magic angle spinning (MAS) NMR experiments, we have observed signal enhancements of 50–400 at 140 and 250 GHz operating frequencies, depending on a variety of experimental conditions. These experiments are possible because of the development...
We present experimental results on the operation of a 1.5 MW, 110 GHz, 3 μs pulsed gyrotron with an advanced internal mode converter (IMC). We have designed and installed an IMC that uses smooth curved mirrors rather than mirrors with phase correcting surfaces which are more sensitive to alignment. Hot and cold test experiments of the new IMC show over 95% Gaussian mode content in the output beam...
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