Dispersion relation and growth rate in two-stream thermal plasma-loaded free-electron laser with helical wiggler

S Meydanloo,S Saviz

doi:10.1007/s40094-014-0158-0

Abstract

Linear theory of the two-stream free-electron laser consisting of a relativistic electron beam transported along the axis of thermal plasma-loaded helical wiggler 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 in that in the special values of the plasma temperature the growth rate is considerably enhanced. It is also shown that the growth rate after critical plasma density gradually decreases. Moreover, in the presence of the two-electron beam the growth rate of electrostatic mode is two times greater than that for electromagnetic mode.

Highlights

In the recent years, the free-electron laser (FEL) in the presence of the plasma has been widely discussed
We have investigated the instability of twostream FELs that contain thermal plasma
The dispersion relation is obtained by employing the linear fluid theory and calculated numerically

Summary

Introduction

The free-electron laser (FEL) in the presence of the plasma has been widely discussed. Pei et al [1] have proposed and examined cold plasma-loaded FEL. They have shown that the efficiency of the FEL considerably enhanced in the presence of the dense plasma. Pant et al [2] illustrated that in the whistler mode FEL the growth rate considerably enhanced in the presence of the plasma. We investigated the effect of plasma density and temperature on the electrostatic and electromagnetic mode of the two-stream FEL. We show that because of the presence of the two-stream instability, the growth rate of the electrostatic mode is two times greater than that of the electromagnetic mode. The numerical results and discussion are given in ‘‘The characteristic of dispersion equation’’ and conclusions are given in ‘‘Conclusion’’

Physical model

The general dispersion equation

The characteristic of dispersion equation

Conclusion