Continuous-Wave Operation of a 460-GHz Second Harmonic Gyrotron Oscillator |
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| Authors: | Hornstein Melissa K Bajaj Vikram S Griffin Robert G Temkin Richard J |
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| Affiliation: | M. K. Hornstein was with the Department of Electrical Engineering and Computer Science and the Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA. She is now with the Naval Research Laboratory, Washington, DC 20375 USA (e-mail: hornstein@alum.mit.edu ). V. S. Bajaj and R. G. Griffin are with the Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 USA. R. J. Temkin is with the Department of Physics and the Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA. |
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| Abstract: | We report the regulated continuous-wave (CW) operation of a second harmonic gyrotron oscillator at output power levels of over 8 W (12.4 kV and 135 mA beam voltage and current) in the TE(0,6,1) mode near 460 GHz. The gyrotron also operates in the second harmonic TE(2,6,1) mode at 456 GHz and in the TE(2,3,1) fundamental mode at 233 GHz. CW operation was demonstrated for a one-hour period in the TE(0,6,1) mode with better than 1% power stability, where the power was regulated using feedback control. Nonlinear simulations of the gyrotron operation agree with the experimentally measured output power and radio-frequency (RF) efficiency when cavity ohmic losses are included in the analysis. The output radiation pattern was measured using a pyroelectric camera and is highly Gaussian, with an ellipticity of 4%. The 460-GHz gyrotron will serve as a millimeter-wave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) experiments at a magnetic field of 16.4 T. |
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