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Title: Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field

Abstract

Free electron lasers (FEL) play major roles in the Raman Regime, due to the charge and current densities of the beam self-field. The method of perturbation has been applied to study the influence of self-electric and self-magnetic fields. A dispersion relation for two-stream free electron lasers with a helical wiggler and an axial magnetic field has been found. This dispersion relation is solved numerically to investigate the influence of self-fields on the FEL coupling and the two-stream instability. It was found that self-fields can produce very large effects on the FEL coupling, but they have almost negligible effects on two-stream instability.

Authors:
;  [1]
  1. Department of Physics, Faculty of Basic Sciences, University of Mazandaran, Babolsar (Iran, Islamic Republic of)
Publication Date:
OSTI Identifier:
22304510
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CURRENT DENSITY; DISPERSION RELATIONS; FREE ELECTRON LASERS; MAGNETIC FIELDS; PERTURBATION THEORY; TWO-STREAM INSTABILITY

Citation Formats

Mohsenpour, Taghi, E-mail: mohsenpour@umz.ac.ir, and Rezaee Rami, Omme Kolsoum. Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field. United States: N. p., 2014. Web. doi:10.1063/1.4889870.
Mohsenpour, Taghi, E-mail: mohsenpour@umz.ac.ir, & Rezaee Rami, Omme Kolsoum. Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field. United States. doi:10.1063/1.4889870.
Mohsenpour, Taghi, E-mail: mohsenpour@umz.ac.ir, and Rezaee Rami, Omme Kolsoum. Tue . "Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field". United States. doi:10.1063/1.4889870.
@article{osti_22304510,
title = {Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field},
author = {Mohsenpour, Taghi, E-mail: mohsenpour@umz.ac.ir and Rezaee Rami, Omme Kolsoum},
abstractNote = {Free electron lasers (FEL) play major roles in the Raman Regime, due to the charge and current densities of the beam self-field. The method of perturbation has been applied to study the influence of self-electric and self-magnetic fields. A dispersion relation for two-stream free electron lasers with a helical wiggler and an axial magnetic field has been found. This dispersion relation is solved numerically to investigate the influence of self-fields on the FEL coupling and the two-stream instability. It was found that self-fields can produce very large effects on the FEL coupling, but they have almost negligible effects on two-stream instability.},
doi = {10.1063/1.4889870},
journal = {Physics of Plasmas},
number = 7,
volume = 21,
place = {United States},
year = {Tue Jul 15 00:00:00 EDT 2014},
month = {Tue Jul 15 00:00:00 EDT 2014}
}
  • The dispersion relation of a two-stream free-electron laser (TSFEL) with a one-dimensional helical wiggler and an axial magnetic field is studied. Also, all relativistic effects on the space-charge wave and radiation are considered. This dispersion relation is solved numerically to find the unstable interaction among the all wave modes. Numerical calculations show that the growth rate is considerably enhanced in comparison with single-stream FEL. The effect of the velocity difference of the two electron beams on the two-stream instability and the FEL resonance is investigated. The maximum growth rate of FEL resonance is investigated numerically as a function of themore » axial magnetic field.« less
  • A dispersion relation for the plasma loaded free-electron laser (FEL), with a helical wiggler and an axial magnetic field is derived. The cold fluid formulation is used with self-fields of the electron beam taken into account. By solving the dispersion relation numerically the influence of self-fields on the FEL resonance and the two-stream instability is investigated. It was found that although self-fields have strong effect on the FEL resonance, their effects on the two-stream instability is much weaker.
  • The linearized theory of two-stream free electron lasers (FELs) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The dispersion relation is derived employing linear fluid theory. The characteristics of the dispersion relation are analyzed by numerical solutions. The results show that the growth rate is considerably enhanced on suitable ranges of normalized axial guiding magnetic field and normalized wave number. The effect of the difference between the velocities of the two beams, {delta}v=v{sub 1}-v{sub 2}, in this configuration of FELs ismore » also considered and found that the growth rate is remarkably affected by velocity differences. It is also shown that the effect on the electrostatic mode is stronger than electromagnetic.« less
  • A theory for gain in a free-electron laser with helical wiggler and axial magnetic field in the presence of self-fields is presented. It is found that for group I orbits, gain decrement is obtained relative to the absence of the self-fields, while for group II orbit gain enhancement is obtained. The gain decrement and enhancement are due to the diamagnetic and paramagnetic effects of the self-magnetic field, respectively.
  • The effects of two-stream on electromagnetic wiggler free electron lasers (TSEMWFEL) with an axial guiding magnetic field are studied. An analysis of the two-stream steady-state electron trajectories is given by solving the equation of motion in the axial guiding magnetic field and the electromagnetic wiggler. Numerical calculations are made to illustrate the effects of the dual electron beam on the trajectories. The dispersion relation is derived employing linear fluid theory. The characteristics of the dispersion relation are analyzed numerically. The result shows that the growth rate is considerably enhanced in comparison with single-stream. The maximum growth rate is studied numericallymore » as a function of axial guiding magnetic field for multiple electron trajectories. It is shown that the maximum growth rate of TSEMWFEL increases and decreases with respect to the axial guiding field for different trajectories.« less