Compton and Raman free electron laser stability properties for a warm electron beam propagating through a helical magnetic wiggler

Davies, John A.; Davidson, Ronald C.; Johnston, George L.

doi:10.1017/s0022377800012162

Cited by 8 publications

(2 citation statements)

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“…[7][8][9] The effect of beam quality on FEL mechanism that is related to energy spread was investigated for various types of energy spread analytically [10][11][12][13][14] or numerically by simulation. 15 The effect of an axial energy spread, based upon the assumption of a monoenergetic beam with a pitch angle spread, on the linear gain in FELs was considered for configurations, which employ both helical and planar wiggler fields.…”

Section: Introductionmentioning

confidence: 99%

“…16 Effects of independent parallel and perpendicular velocity spread on lasing wavelength were also evaluated and compared. 10 Dispersion relation was obtained to describe FEL stability properties 8,17 or study thermal properties of a plasma-loaded FEL 18 with axially warm electron beam. The nonlinear evolution of FEL in which the electron beam propagates with energy spread has also been investigated numerically.…”

Section: Introductionmentioning

confidence: 99%

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Efficiency enhancement of nonlinear odd harmonics in thermal free electron laser

Bazouband

Maraghechi

2013

Journal of Applied Physics

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The effect of axial energy spread on the radiation of third harmonic is studied in the free electron laser with planar wiggler and ion-channel guiding. Spread in the longitudinal momentum and so in the initial energy of electron beam, without any spread in the transverse velocity, is assumed in the form of Gaussian distribution function. The technique that is employed is a one-dimensional and steady-state simulation. A set of self consistent nonlinear differential equations that describes the system is solved numerically by Runge-Kutta method. Due to the sensitivity of harmonics to thermal effects, gain improvement of third harmonic radiation is achieved by using ion-channel guiding technique and efficiency enhancement is applied by tapering the magnetic field of wiggler to optimize radiation. The bunching parameter of the electron beam is also studied. It is found that the growth of the magnitude of the bunching parameter that is caused by the ponderomotive wave stops before the saturation point of the radiation. This means that ponderomotive wave saturates at a shorter distance compared to the radiation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficiency enhancement of nonlinear odd harmonics in thermal free electron laser

Bazouband

Maraghechi

2013

Journal of Applied Physics

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Pulse shapes for absolute and convective free-electron-laser instabilities

1988

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This paper contains an analysis of pulse shapes produced by a delta-function disturbance of the equilibrium state of a relativistic electron beam propagating through a constantamplitude helical magnetic wiggler field. Pulse shapes are determined by using the relativistic pinch-point techniques developed by Bers, Ram, and Francis. Two pulses are produced corresponding to a convective upshifted pulse (representing the production of the high-frequency radiation desired in a free electron laser) and a downshifted pulse. The downshifted instability may be convective or absolute, depending upon the beam density and momentum spread. Parameter regimes in which the downshifted instability is convective are investigated. It is found that momentum spreads sufficiently large to suppress the absolute instability reduce the growth rate of the upshifted pulse to negligible values. Pulse shapes computed by using the Raman and Compton approximations are compared with exact pulse shapes. It is found that the Raman approximation should be applied to the downshifted regime for most systems of practical interest.

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Generalized theory of a free-electron laser in a helical wiggler and guide magnetic fields using the kinetic approach

Misra

Мишра

2002

Physics of Plasmas

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A self-consistent theory of a free-electron laser is developed by the kinetic approach, using the method of characteristics in helical wiggler and guide magnetic fields. The detailed relativistic particle trajectories obtained in wiggler and guide magnetic fields are used in linearized Vlasov–Maxwell equations having variations in perpendicular and parallel momenta to obtain the perturbed distribution function in terms of perturbed electric and magnetic fields deviating from the vector potential approach. The perturbed distribution function thus obtained, having variations in perpendicular and parallel momenta for an arbitrary distribution function, is used to obtain current, conductivity and dielectric tensors. The full dispersion relation (FDR) and Compton dispersion relation (CDR) have been obtained. The dispersion diagram has been obtained and the interaction of the negative longitudinal space charge with the electromagnetic wave has been shown. The temporal growth rates obtained from the full dispersion relation and Compton dispersion relation for the tenuous cold relativistic beam in microwave region have been discussed.

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Compton and Raman free electron laser stability properties for a warm electron beam propagating through a helical magnetic wiggler

Cited by 8 publications

References 8 publications

Efficiency enhancement of nonlinear odd harmonics in thermal free electron laser

Efficiency enhancement of nonlinear odd harmonics in thermal free electron laser

Pulse shapes for absolute and convective free-electron-laser instabilities

Generalized theory of a free-electron laser in a helical wiggler and guide magnetic fields using the kinetic approach

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