Experimental study of a Ka-band gyrotron backward-wave oscillator

Park, S.Y.; Kyser, R.H.; Armstrong, C.M.; Parker, Robert K.; Granatstein, V.L.

doi:10.1109/27.55901

Cited by 76 publications

(18 citation statements)

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“…On the other hand, a gyro-device operating with a traveling-wave and a nonresonant-microwave structure can provide a broadband smooth frequency tuning by variation of the magnetic field or the electron beam energy. The gyro-BWO operation has been theoretically analyzed in detail (see, e.g., [1]- [4]) and successfully realized in a number of experiments [5]- [7]. In the experimental studies at the Naval Research Laboratory [5] and the National Tsing Hua University [6], pulsed Ka-band gyro-BWO operation at the fundamental cyclotron harmonic and fundamental mode of a smooth cylindrical waveguide was demonstrated with voltage-and magnetic-frequency tuning of up to 5% and 13%, respectively, a very high efficiency (for BWO) of nearly 20% and a pulsed power up to 100 kW.…”

Section: Introductionmentioning

confidence: 99%

“…The gyro-BWO operation has been theoretically analyzed in detail (see, e.g., [1]- [4]) and successfully realized in a number of experiments [5]- [7]. In the experimental studies at the Naval Research Laboratory [5] and the National Tsing Hua University [6], pulsed Ka-band gyro-BWO operation at the fundamental cyclotron harmonic and fundamental mode of a smooth cylindrical waveguide was demonstrated with voltage-and magnetic-frequency tuning of up to 5% and 13%, respectively, a very high efficiency (for BWO) of nearly 20% and a pulsed power up to 100 kW. The use of a novel microwave system in the form of a helically corrugated waveguide [8], [9] opens up new potentials of the gyro-BWO and allows realization of a high-power continuous wave (CW) device attractive for applications.…”

Section: Introductionmentioning

confidence: 99%

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Frequency-Tunable CW Gyro-BWO With a Helically Rippled Operating Waveguide

Самсонов

Денисов

Bratman

et al. 2004

IEEE Trans. Plasma Sci.

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Operation of a continuous wave gyrotron backward-wave oscillator (gyro-BWO) with a helically rippled operating waveguide has been experimentally studied. The gyro-BWO exploits a dc oil-cooled magnet with magnetic field up to 0.5 T and utilizes a weakly relativistic (20 keV) electron beam produced by a magnetron injection gun. Stable generation at the second cyclotron harmonic with a maximum power of 7 kW and an efficiency of 15% at a frequency of 24.7 GHz was achieved. Smooth oscillation frequency tuning by varying the magnetic field was measured to be as wide as 5% at the half-power level. The first gyro-BWO operation with a single-stage energy recovery system was realized. The use of a depressed collector provided an efficiency increase up to 23% and an opportunity for reduction of the main power supply voltage down to 10 kV.Index Terms-Continuous wave (CW) high-power microwave device, cyclotron-resonance maser, gyrotron backward-wave oscillator (gyro-BWO), smooth-frequency tuning.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Frequency-Tunable CW Gyro-BWO With a Helically Rippled Operating Waveguide

Самсонов

Денисов

Bratman

et al. 2004

IEEE Trans. Plasma Sci.

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“…Potential applications of such sources include electron cyclotron heating of fusion plasmas, deep space communications, high resolution radars, spectroscopic studies, and drivers of ultra-high-power free-electron-laser amplifiers. A promising candidate, the gyrotron backward-wave oscillator (gyro-BWO), has been theoretically analyzed [1][2][3][4][5][6][7][8] and experimentally demonstrated [9][10][11]. The gyro-BWO is based on the electron cyclotron maser instability on a backward waveguide mode resonantly driven by a forward propagating electron beam (Fig.…”

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confidence: 99%

Experimental study of an injection-locked gyrotron backward-wave oscillator

et al. 1993

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A Ka-band gyrotron backward-wave oscillator (gyro-BWO) experiment has been performed to investigate the phase control, fast tunability, and power capability. Efficient injection locking was accomplished by novel circuit arrangements. Maximum power of 113 kW at -19% efficiency was achieved, showing favorable scaling to still higher powers. Stable voltage tuning bandwidth of 5% at 67 kW peak power was also observed. The measured performance has demonstrated a strong potential of the gyro-BWO for new applications requiring high-power tunable millimeter-wave sources.PACS numbers: 42.52,+x, 85.10.JzResearch on tunable high-power coherent radiation sources in the millimeter through submillimeter spectral range has been a subject of growing interest. Potential applications of such sources include electron cyclotron heating of fusion plasmas, deep space communications, high resolution radars, spectroscopic studies, and drivers of ultra-high-power free-electron-laser amplifiers. A promising candidate, the gyrotron backward-wave oscillator (gyro-BWO), has been theoretically analyzed [1][2][3][4][5][6][7][8] and experimentally demonstrated [9][10][11]. The gyro-BWO is based on the electron cyclotron maser instability on a backward waveguide mode resonantly driven by a forward propagating electron beam (Fig. 1). Counter streaming between the beam and the wave establishes an internal feedback loop, thus allowing the oscillation to take place in a nonresonant structure and its frequency tunable through either the magnetic field or the beam voltage. Also, the cyclotron frequency shift makes resonant interaction possible in a fast-wave circuit which gives the gyro-BWO much greater power handling capability than the conventional BWO.An experimental study of a Ka-band TEfo mode gyro-BWO at the Naval Research Laboratory (NRL) [9,11] achieved a maximum power of 7 kW at nearly 20% efficiency. The 3 dB voltage and magnetic tuning ranges were, respectively, 3% and 13% (with the beam parameters optimized during the tuning). A 140 GHz TE°2FIG. 1. co-k 2 diagram showing the operating conditions of the gyro-BWO. fl e is the rest mass cyclotron frequency of the electron. v z is the average axial velocity. mode gyro-BWO experiment is being conducted at MIT [10] and a 55 GHz TE°i mode gyro-BWO experiment is planned by the UCLA group [7]. All these experiments employ a reflection-type output circuit, that is, the oscillation power is extracted at the collector end after being reflected from the beam entrance end.The NRL experiment [11] has demonstrated broadband magnetic tunability and unexpectedly high efficiency at a relatively low beam voltage (33 kV). These encouraging properties have generated a great deal of current interest in gyro-BWO research. On the other hand, there are issues of physical interest as well as practical importance which remain to be addressed, such as the spectral purity, the phase and frequency controllability, and the stability of fast voltage tuning. In addition, the peaking of output power (at a few kW) at a relat...

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“…This mutual agreement between simulation and experiment validates the predictability of our code. Meanwhile, this backward wave which one tries very hard to suppress in gyro-TWT's has recently been exploited as a tunable millimeter wave source for driving free electron laser amplifiers (Caplan 1987, Gangnly and Ahn 1989, Park et al 1990). The starting oscillation condition of a gyro backward wave oscillator was derived (Wachtel andWachtel 1980, Park et al 1984) earlier.…”

Section: Introductionmentioning

confidence: 99%

Absolute instability in finite length electron cyclotron maser systems

Lin

Kaw

1992

International Journal of Electronics

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The temporal growth rate of the absolute instability in finite length electron cyclotron maser systems has been theoretically calculated and confirmed by particle simulations. The non-linear saturation mechanism is due to that in the unstable system, the non-linear electron phase shift induced by the wave field gives rise to a virtual end plane which tends to shorten the effective interaction length and brings the system into the marginal stable state. In the system far above threshold, the virtual plane first oscillates and eventuallyapproaches a steady state location. This early oscillating behaviour strongly correlates to the initial pronounced spiky temporal structure in the output power.

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Experimental study of a Ka-band gyrotron backward-wave oscillator

Cited by 76 publications

References 4 publications

Frequency-Tunable CW Gyro-BWO With a Helically Rippled Operating Waveguide

Frequency-Tunable CW Gyro-BWO With a Helically Rippled Operating Waveguide

Experimental study of an injection-locked gyrotron backward-wave oscillator

Absolute instability in finite length electron cyclotron maser systems

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