Dispersion relation and growth rate in electromagnetically pumped free-electron lasers with ion-channel guiding

2008 ◽  
Vol 15 (7) ◽  
pp. 073103 ◽  
Author(s):  
H. Mehdian ◽  
A. Hasanbeigi ◽  
S. Jafari
Keyword(s):  
Growth Rate ◽  
Dispersion Relation ◽  
Ion Channel ◽  
Free Electron ◽  
Free Electron Lasers

scholarly journals Theory of terahertz Smith-Purcell radiation from a cylindrical grating

2019 ◽  
Vol 11 ◽  
pp. 110007
Author(s):  
Z. Rezaei ◽  
B. Farokhi
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Electron Beam ◽  
Dispersion Relation ◽  
External Magnetic Field ◽  
Free Electron ◽  
Free Electron Lasers ◽  
Annular Electron Beam ◽  
High Efficient ◽  
Beam Thickness

An analysis of an annular electron beam propagating along a cylindrical grating with external magnetic field Bo is presented. The grating comprises a dielectric in its slots. The dispersion relation of the modes is derived. The results demonstrate that the dielectric shifts the frequencies of the system modes to smaller values. The growth rates of the modes which are in phase with the beam are also considered. It is found that the decline in the growth rate is brought about by the dielectric. In addition, increasing the thickness of the dielectric and decreasing the height of the slots cause it to rise. The effect of beam thickness on growth rate is considered too. This is shown to increase and then fall as beam thickness increases. These results show that utilizing cylindrical grating loaded with dielectric has a promising effect on developing new kinds of compact high-efficient THz free-electron lasers based on Smith–Purcell radiation. Edited by: A. B. Márquez

Growth rate and start current in Smith–Purcell free-electron lasers

2012 ◽  
Vol 100 (19) ◽  
pp. 191101 ◽  
Author(s):  
M. Hangyo ◽  
Y. Tsunawaki ◽  
Z. Yang ◽  
Y. Wei ◽  
S. Miyamoto ◽  
...  
Keyword(s):  
Growth Rate ◽  
Free Electron ◽  
Free Electron Lasers

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

1987 ◽  
Vol 37 (2) ◽  
pp. 255-298 ◽  
Author(s):  
John A. Davies ◽  
Ronald C. Davidson ◽  
George L. Johnston
Keyword(s):  
Growth Rate ◽  
Electron Beam ◽  
Dispersion Relation ◽  
Free Electron ◽  
Free Electron Laser ◽  
Equilibrium Distribution ◽  
Equilibrium Distribution Function ◽  
Numerical Characterization ◽  
Detailed Mathematical Analysis ◽  
The Individual

This paper gives an extensive analytical and numerical characterization of the growth-rate curves (imaginary frequency versus wavenumber) derived from the free electron laser dispersion relation for a warm relativistic electron beam propagating through a constant-amplitude helical magnetic wiggler field. The electron beam is treated as infinite in transverse extent. A detailed mathematical analysis is given of the exact dispersion relation and its Compton approximation for the case of a water-bag equilibrium distribution function (uniform distribution in axial momentum pz). Applicability of the water-bag results to the case of a Gaussian equilibrium distribution in pz is tested numerically. One result of the water-bag analysis is a set of validity conditions for the Compton approximation. Numerical and analytical results indicate that these conditions are applicable to the Gaussian case far outside the parameter range where the individual water-bag and corresponding Gaussian growth rate curves agree.

Wave interaction and low-frequency magnetic field generation in planar free-electron lasers

1990 ◽  
Vol 44 (3) ◽  
pp. 483-488 ◽  
Author(s):  
F. B. Rizzato
Keyword(s):  
Dispersion Relation ◽  
Free Electron ◽  
Low Frequency ◽  
Wave Interaction ◽  
Transversality Condition ◽  
Free Electron Lasers ◽  
Magnetic Field Generation ◽  
Transverse Modes ◽  
Frequency Magnetic Field ◽  
Simplified Analysis

In recent work by the present author the full dispersion relation for multi-dimensional perturbations propagating in saturated free-electron lasers was derived. A number of approximations were used in order to derive a simplified description of the unstable modes. Although this simplified analysis was shown to be appropriate for quasi-transverse modes, it was not possible to describe the generic case of non-transverse ones. In the present paper, via a numerical analysis of this dispersion relation, we argue that a considerable number of modes do indeed not satisfy the quasi-transversality condition. The generation of low-frequency maenetic fields is also analysed.

Gain enhancement in two-stream electromagnetically pumped free electron laser with ion-channel guiding

2010 ◽  
Vol 88 (1) ◽  
pp. 15-28 ◽  
Author(s):  
S. Saviz ◽  
H. Mehdian
Keyword(s):  
Electromagnetic Wave ◽  
Ion Channel ◽  
Free Electron ◽  
Small Signal ◽  
Free Electron Lasers ◽  
Electron Trajectories ◽  
Maximum Gain ◽  
Single Beam ◽  
Gain Enhancement ◽  
Normalized Gain

A theory of two-stream electromagnetic wave-wiggler free-electron lasers (TSEMWFEL) with an ion-channel guiding is proposed and investigated. An analysis of the two-stream steady-state electrons trajectories is obtained by solving the equation of motion in the electromagnetic wave wiggler and ion-channel guiding. The electron trajectories and the small signal gain are derived. Numerical calculations show that there are seven group trajectories rather than the two groups reported for conventional free-electron lasers. The characteristics of the linear-gain and the normalized maximum gain are studied numerically. It was also shown that the normalized gain of groups I and II is decreased and for groups (IV–VII) are increasing by growing [Formula: see text]. Furthermore, it was found that the two-stream with ion-channel field enhances the maximum gain in comparison with that for single beam.

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