Second harmonic operation at 460 GHz and broadband continuous frequency tuning of a gyrotron oscillator

We report the short-pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a microsecond pulse length regime with 13-kV beam voltage and 110-mA beam current, the instrument genera...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2005-05, Vol.52 (5), p.798-807
Main Authors: Hornstein, M.K., Bajaj, V.S., Griffin, R.G., Kreischer, K.E., Mastovsky, I., Shapiro, M.A., Sirigiri, J.R., Temkin, R.J.
Format: Article
Language:English
Subjects:
Applied sciences
Broadband
Circuit properties
Cyclotron resonance
Devices
Dynamic nuclear polarization
Electric, optical and optoelectronic circuits
Electronic circuits
Electronic tubes, masers
Electronics
Exact sciences and technology
Field strength
Frequency conversion
frequency tuning
gyrotron
Gyrotrons
harmonic
Harmonics
Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits
NMR
Nuclear magnetic resonance
nuclear magnetic resonance (NMR)
Nuclear power generation
Oscillators
Oscillators, resonators, synthetizers
submillimeter
Tuning
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Summary:We report the short-pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a microsecond pulse length regime with 13-kV beam voltage and 110-mA beam current, the instrument generates several watts of power in two second harmonic modes, the TE/sub 2,6,1/ at 456.15 GHz and the TE/sub 0,6,1/ at 458.56 GHz. Operation in the fundamental modes, including the TE/sub 0,3,1/ mode at 237.91 GHz and the TE/sub 2,3,1/ at 233.15 GHz, is observed at output powers up to 70 W. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone. We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. The 460 GHz gyrotron is currently being processed for continuous duty operation, where it will serve as a microwave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) studies at 16 T (700 MHz /sup 1/H), a field strength which is two-fold higher than has been accessible with previous technology.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2005.845818