Paper  Title  Page 

MOPPH011  Comparison Between Kinetic and Fluid Description of PlasmaLoladed FreeElectron Laser  42 


In the kinetic treatment of the plasmaloaded FEL in Ref.* single particle equation of motion, for both beam and plasma electrons in the radiation fields, are used. Therefore, interaction terms between the wiggler and the spacecharge wave, in the transverse velocity of electrons, which are important elements in the fluid model, are neglected. A dispersion relation of a plasmaloaded FEL with kinetic theory is found in Ref.* that takes into account the velocity spread of both beam and plasma electrons. In the present analysis, a dispersion relation is obtained, by the fluid theory, with the interaction terms between the wiggler and the spacecharge wave in the transverse velocity of electrons taken into account. Since these interaction terms are inherently missing in the kinetic theory the two dispersion relation are compared to find out about the importance of these terms. It was found that although the absence of these terms has considerable effects on the growth rate, the general kinetic dispersion relation may be used to study the temperature effects of a warm beam/plasma on the instability of a freeelectron laser with a plasma background.
* S. Babaei and B. Maraghechi, "Kinetic description of plasmaloaded freeelectron laser", Phys. Plasmas, to be published. 