Improved Oscillator Phase Locking by Use of a Modulated Electron Beam in a Gyrotron

McCurdy, A.H.; Armstrong, C.M.; Bollen, W.M.; Parker, Robert K.; Granatstein, V.L.

doi:10.1103/physrevlett.57.2379

Cited by 44 publications

(5 citation statements)

References 17 publications

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“…We will instead compare our result of phase locking for the gyro-BWO with those for the gyromonotrons reported by two groups at NRL [16,17]. In one method [16,17], a circulator was used to isolate P m and P out . A fractional locking bandwidth of --0.03% was achieved with -20 dB injected power.…”

Section: P-/ / /^/ //////// /Yw / / / /Z?mentioning

confidence: 96%

“…A fractional locking bandwidth of --0.03% was achieved with -20 dB injected power. In an improved method [17] which employed a three-cavity gyroklystron configuration, the beam was premodulated in the first two cavities by a drive signal and went on to lock the third cavity, resulting in much greater locking bandwidth (Af/f^0.\l% at -20 dB drive power). The premodulation experiment was carried out in the C band with relatively low output powers (1-2 kW).…”

Section: P-/ / /^/ //////// /Yw / / / /Z?mentioning

confidence: 99%

“…By comparison, the present experiment achieved comparable locking bandwidth by the method of direct injection. As in the improved NRL scheme [17], input/output power isolation was achieved by the use of separate input/output ports.…”

Section: P-/ / /^/ //////// /Yw / / / /Z?mentioning

confidence: 99%

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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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Section: P-/ / /^/ //////// /Yw / / / /Z?mentioning

confidence: 96%

Section: P-/ / /^/ //////// /Yw / / / /Z?mentioning

confidence: 99%

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

et al. 1993

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“…For example [6,7], peak powers near 1 MW with microsecond pulse durations have been achieved at high frequencies ( -140 GHz) in highly overmoded cavities. Recent gyrotron amplifier experiments have included gyrotron traveling-wave tubes [8] and gyroklystrons [9,10]. Overmoded Our present efI'ort to increase gyroklystron power levels has focused on two issues.…”

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confidence: 99%

Efficient operation of a high-powerX-band gyroklystron

Lawson

Hogan

et al. 1991

Phys. Rev. Lett.

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Experimental studies of amplification in a two-cavity X-band gyroklystron are reported. The system utilizes a thermionic magnetron injection gun at voltages up to 440 kV and currents up Our present efI'ort to increase gyroklystron power levels has focused on two issues. The first involves increasing the beam voltage above conventional (long pulse) levels as described in previous design papers [11,12] [14]. In this paper, we briefly describe the experimental configuration, discuss the microwave diagnostics, and present optimal twocavity gyroklystron performance.Details of the experimental setup, tube stability, and flat-field amplifier experiments that achieved peak powers of 2.7 MW appear elsewhere [15].A schematic of the overall system is shown in Fig. 1(a). A 1.5-ps, 500-kV, 400-A line-type modulator provides the required voltages to the MIG. Eight water-

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“…Apart from increasing the structure size or utilizing the coaxial structure to enhance the power handling capacity of a single HPM source, [4][5][6][7][8][9] researchers have investigated power combination of multiple HPM sources. The power combination can be either the spatial coherent combination of an array of phase-locked sources [10][11][12][13][14][15] or the waveguide-based power summation of multiple sources. [16][17][18] Three typical parameters, i.e., output power, conversion efficiency, and pulse width interact with and constrain each other.…”

Section: Introductionmentioning

confidence: 99%

Power combination of two phase-locked high power microwave beams from a new coaxial microwave source based on dual beams

Li,

Zhang,

Zhang

et al. 2014

Physics of Plasmas

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The new coaxial high power microwave source based on dual beams has demonstrated two phaselocked output microwave beams generated by its two sub-sources. In order to achieve a single higher output power, we present a three-port waveguide-based power combiner to combine the two microwave beams. Particle-in-cell simulation results show that when the diode voltage is 675 kV and the guiding magnetic field is 0.8 T, a combined microwave with an average power of about 4.0 GW and a frequency of 9.74 GHz is generated; the corresponding power conversion efficiency is 29%. The combination effect of the combiner is further validated in the diode voltage range from 675 kV to 755 kV as well as in the pulse regime. The simulations indicate that the maximum surface axial electric field strength of the electrodynamic structure is 720 kV/cm, which is relatively low corresponding to an output power of 4.0 GW. The stable combined output suggests the probability of long-pulse operation for the combined source. V C 2014 AIP Publishing LLC.

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Improved Oscillator Phase Locking by Use of a Modulated Electron Beam in a Gyrotron

Cited by 44 publications

References 17 publications

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

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

Efficient operation of a high-powerX-band gyroklystron

Power combination of two phase-locked high power microwave beams from a new coaxial microwave source based on dual beams

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