Conditions for absolute instability in the cyclotron resonance maser

Davies, John A.

doi:10.1063/1.859127

Cited by 39 publications

(9 citation statements)

References 12 publications

(3 reference statements)

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“…The early theoretical studies of the absolute instability in gyrotron devices were focused on the calculations of marginally stability criteria for gyro-amplifiers, [28][29][30] but the analysis was based on the assumption of an infinite system. Meanwhile, the start oscillation condition of the gyro-BWO was also derived to exploit the backward wave oscillations as tunable millimeter wave sources.…”

Section: Linear Stability Properties: Absolute Instabilities In Amentioning

confidence: 99%

Linear and nonlinear behaviors of gyrotron backward wave oscillators

Chen

2012

Physics of Plasmas

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Linear and nonlinear behaviors of gyrotron backward wave oscillators (gyro-BWO) were investigated by both analytical theories and direct numerical calculations. Employing two-scale-length expansion, an analytical linear dispersion relation corresponding to absolute instabilities in a finite-length system has been derived. Detuning from the beam-wave resonance condition due to the finite amplitude radiation fields, meanwhile, was found to play the crucial roles in the nonlinear physics. Near the start oscillation of the gyro-BWO, the radiation field amplitude saturates when the resonance broadening is comparable to the linear growth rate. Far beyond the start oscillation threshold, the beam-wave resonance detuning effectively shortens the interaction length toward that corresponding to the critical oscillation length for the given beam current. The theoretically predicted scaling laws for the linear stability properties and nonlinear stationary states of the gyro-BWO are in good agreement with numerical results.

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Section: Linear Stability Properties: Absolute Instabilities In Amentioning

confidence: 99%

Linear and nonlinear behaviors of gyrotron backward wave oscillators

Chen

2012

Physics of Plasmas

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“…The consecutive switchovers of dominant saddle point for e ≈ 0.3 and Re z = 60 occur very near collisions of the distinct pinches into third-order saddle points (Davies 1989) or 'super branch points' (Healey 2004), satisfying simultaneously ∂ω/∂k = 0, ∂ 2 ω/∂k 2 = 0 and ω i = 0. Indeed, s 1 and s 2 collide while being neutral for e = 0.2839, Re z = 50.115, Re Ω = 403.21 while s 2 and s 3 coalesce with ω i = 0 for e = 0.3032 and Re z = 43.188, Re Ω = 353.60.…”

Section: Instability Mechanismmentioning

confidence: 99%

Absolute instabilities in eccentric Taylor–Couette–Poiseuille flow

2014

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The effect of eccentricity on absolute instabilities (AI) in the Taylor-Couette system with pressure-driven axial flow and fixed outer cylinder is investigated. Five modes of instability are considered, characterized by a pseudo-angular order m, with here |m| 2. These modes correspond to toroidal (m = 0) and helical structures (m = 0) deformed by the eccentricity. Throughout the parameter range, the mode with the largest absolute growth rate is always the Taylor-like vortex flow corresponding to m = 0. Axial advection, characterized by a Reynolds number Re z , carries perturbations downstream, and has a strong stabilizing effect on AI. On the other hand, the effect of the eccentricity e is complex: increasing e generally delays AI, except for a range of moderate eccentricites 0.3 e 0.6, where it favours AI for large enough Re z . This striking behaviour is in contrast with temporal instability, always inhibited by eccentricity, and where left-handed helical modes of increasing |m| dominate for larger Re z . The instability mechanism of AI is clearly centrifugal, even for the larger values of Re z considered, as indicated by an energy analysis. For large enough Re z , critical modes localize in the wide gap for low e, but their energy distribution is shifted towards the diverging section of the annulus for moderate e. For highly eccentric geometries, AI are controlled by the minimal annular clearance, and the critical modes are confined to the vicinity of the inner cylinder. Untangling the AI properties of each m requires consideration of multiple pinch points.

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“…3. The curves in this figure are parametrized by waveguide radius and by the degree of beamwave coupling e. For e -1 the beam current and ct are at values which correspond to absolute instability in a linear pinch-point analysis [31]. The beam ct which corresponds to the values of e and guide radius in Fig.…”

Section: This Acceleratoris Located At Our High Power Microwave Labormentioning

confidence: 99%

High frequency CARM driver for RF LINACS. Progess report, year 2

1991

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Superconducting Focusing / Magnet Magnets Wiggler CARM Interaction SLAC 5045 Elec*ron Gun Figure I:Schematic ofthelong-pulse CARM oscillator expcrimem. fusion plasmas. This experiment isbeing carried outunder the auspices ofthis program, utilizing equipment that was either already on handorwas procured forthe17GHz CARM amplifier program. This experiment was carried out with several objectives: 1) to better understand the CARM interaction and compareexperiment with theory, 2) to test Pierce-Wiggleroperationwith relativistic electron beams, and 3) to demonstrate efficient CARM oscillator operation with a Bragg Reflectorcavity. The basic schematic of the CARM oscillator experiment is shown in Fig. 1. The design parameters for this experiment are given in Table 2 and 3. The experiment employs a Bragg reflection cavity as the high-Q resonator. The resonator is designed to selectively reflect the TEll mode with 2kll __ks, where kB is the Bragg wavenumber of the reflector. A schematic of this resonatoris shown in Fig. 2.

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Conditions for absolute instability in the cyclotron resonance maser

Cited by 39 publications

References 12 publications

Linear and nonlinear behaviors of gyrotron backward wave oscillators

Linear and nonlinear behaviors of gyrotron backward wave oscillators

Absolute instabilities in eccentric Taylor–Couette–Poiseuille flow

High frequency CARM driver for RF LINACS. Progess report, year 2

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