Theory of the quasioptical electron cyclotron maser

Sprangle, P.; Vomvoridis, J. L.; Manheimer, Wallace M.

doi:10.1103/physreva.23.3127

Cited by 72 publications

(14 citation statements)

References 23 publications

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“…Another case of transverse continuous states to which we can still apply the longitudinally constrained recoil expressions derived in this section is the case of the magnetic bremsstrahlung FEL, for conditions when the electron propagates along the wiggler axis [zero canonical momentum (Sprangle and Smith, 1980)] and the radiative emission is on axis (0=0 This equation is in full agreement with the conventional classical limit condition, which was derived earlier for FEL's in the highly relativistic beam limit (/3 gz ->1) (Philips, 1960;Kurizki and Mclver, 1982). Equation (2.48) indicates that it may be easier to observe quantum effects with nonrelativistic beams.…”

Section: The Classical Limitmentioning

confidence: 99%

Spontaneous and stimulated emission from quasifree electrons

et al. 1988

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This article presents a unified formulation and review of an extensive class of radiation effects and devices based on free or quasifree electrons. The effects and devices reviewed include slow-wave radiators [such as Cerenkov, Smith-Purcell, and TWT (traveling-wave tube) effects and devices], periodic bremsstrahlung radiators [such as undulator radiation, magnetic bremsstrahlung FEL's (free-electron lasers), and coherent bremsstrahlung in the crystal lattice], and transverse-binding radiators [such as the CRM (cyclotron resonance maser) and channeling radiation]. Starting from a general quantum-electrodynamic model, both quantum and classical effects and operating regimes of these radiation devices are described. The article provides a unified physical description of the interaction kinematics, and presents equations for the characterization of spontaneous and stimulated radiative emission in these various effects and devices. Universal relations between the spontaneous and stimulated emission parameters are revealed and shown to be related (in the quantum limit) to Einstein relations for atomic radiators and (in the classical limit) to the relations derived by Madey for magnetic bremsstrahlung FEL for on-axis radiative emission. Examples for the application of the formulation are given, estimating the feasibility of channeling radiation x-ray laser and optical regime Smith-Purcell FEL, and deriving the gain equations of magnetic bremsstrahlung FEL and CRM for arbitrary electron propagation direction, structure (wiggler) axis, and radiative emission angle.

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Section: The Classical Limitmentioning

confidence: 99%

Spontaneous and stimulated emission from quasifree electrons

et al. 1988

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“…With this definition, the peak heat load is twice the value &hm. In terms of the normalized field amplitude F , &hm can then be written as: ( 3 ) where U is the electrical conductivity of the mirror, f is the RF frequency expressed in gigahertz and g is the curvature parameter of the mirror defined as with d and R being, respectively, the mirror separation and the mirror radius of curvature. It has been assumed that the resonator is symmetrical (identical mirrors).…”

Section: B Ohmic Heating Of the Mirrorsmentioning

confidence: 99%

Prospects for high-power quasi-optical gyrotrons operating in the millimeter-wave range

Tran

Alberti

et al. 1989

IEEE Trans. Electron Devices

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The prospects for high-power (several megawatts) quasioptical gyrotrons operating in the high-frequency region ( > 150 GHz) are considered. The analysis is mainly concerned with the physics of interaction between the annular electron beam and the electromagnetic field within the quasi-optical resonator, together with the constraints required by long-pulse or CW operations. It is shown that powers of several megawatts at Frequencies exceeding 150 GHz are possible if one can maintain single-mode operation in the overmoded quasi-optical resonators. A thorough performance study of the magnetron injection gun (MIG) For such high-power gyrotrons is also carried out using the adiabatic theory as well as numerical simulations.

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“…2 However, this gyrotron configuration is limited at high frequencies by high Ohmic heating and problems with transversemode competition, due to the highly overmoded configuration, and with beam collection, since the beam must be collected along a section of the output waveguide. The quasioptical gyrotron (QOG), first proposed by Sprangle, Vomvoridis, and Manheimer, 3 features an open resonator formed by a pair of spherical mirrors instead of a waveguide cavity and has the potential for overcoming each of these limitations. The resonator mirrors can be well removed from the beam-wave interaction region, allowing a large volume for the interaction and low Ohmic heating densities at the mirrors.…”

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confidence: 99%

Operation of a quasioptical gyrotron with variable mirror separation

et al. 1989

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Results from a quasioptical gyrotron experiment with a 20-28-cm mirror separation are presented showing operation from 95 to 130 GHz at powers up to 148 kW and output efficiencies up to 12%. The output coupling could be varied from 0.4% to 3% by changing the mirror separation and operating frequency. Efficiency optimization by variation of output coupling and by tapering the magnetic field has been demonstrated and regions of single-mode operation at powers up to 125 kW have been characterized.PACS numbers: 42.52,+x There is currently a need for megawatt average power sources of 100-300 GHz radiation for electron cyclotron heating of fusion plasmas. The leading candidate for such a source, the waveguide-cavity gyrotron, 1 has produced output powers of 765 kW and efficiencies of 30% at 148 GHz in a cw-relevant configuration. 2 However, this gyrotron configuration is limited at high frequencies by high Ohmic heating and problems with transversemode competition, due to the highly overmoded configuration, and with beam collection, since the beam must be collected along a section of the output waveguide. The quasioptical gyrotron (QOG), first proposed by Sprangle, Vomvoridis, and Manheimer, 3 features an open resonator formed by a pair of spherical mirrors instead of a waveguide cavity and has the potential for overcoming each of these limitations. The resonator mirrors can be well removed from the beam-wave interaction region, allowing a large volume for the interaction and low Ohmic heating densities at the mirrors. The beam direction is transverse to the cavity so that beam collection is separate from the output waveguide. The QOG operates in the lowest-order transverse (TEMoo/) Gaussian mode of the resonator, higher-order transverse modes being effectively suppressed by higher diffraction losses. Output coupling is via diffraction around the mirrors and can be controlled independently of other interaction parameters. The axial mode separation is small compared to the interaction bandwidth in cwrelevant configurations so that multimode effects are important. The theory of multimode operation was developed by Bondeson, Manheimer, and Ott. 4 The first QOG experiment was carried out by Hargreaves et al. 5 and used a resonator with a 4-cm mirror separation. Consistent with the relatively low axial mode density of this resonator, single-mode operation was observed at powers up to 80 kW at a frequency of 110 GHz and an efficiency of 11%.This Letter presents results from a thorough and extensive experimental study of the first QOG to operate at powers over 100 kW using a cw-relevant resonator. The ability to vary the separation of the resonator mirrors from 20 to 28 cm allowed the resonator output coupling to be optimized with respect to the electron beam power.The QOG was tunable from 95 to 130 GHz and operated at powers up to 148 kW and output efficiencies up to 12%. The peak electronic efficiency is estimated to be 18% and is believed to be limited by the relatively low velocity pitch ratio, a =v ±/v\\, of the electron...

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Theory of the quasioptical electron cyclotron maser

Cited by 72 publications

References 23 publications

Spontaneous and stimulated emission from quasifree electrons

Spontaneous and stimulated emission from quasifree electrons

Prospects for high-power quasi-optical gyrotrons operating in the millimeter-wave range

Operation of a quasioptical gyrotron with variable mirror separation

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