• P.K. Mishra
  University of Ottawa, Ottawa, Ontario

The full dispersion relation obtained for free-electron laser using helical wiggler circularly polarized magnetic field and an axial guide magnetic field using particle trajectories, their interaction with electric field by method of characteristics making the treatments quite general is reduced to Raman regime approximations in case of tenuous electron beam. The temporal and convective growth rates have been compared between full dispersion relation and Raman dispersion relation in microwave region. Results show the maximum of temporal growth in full dispersion relation and Raman dispersion relation is at the same locations. Whereas the maximum of convective growth rate in full dispersion relation is slightly deviated with respect to the Raman dispersion relation. The growth rates in Raman regime in both the cases are enhanced with respect to full dispersion relation for the same plasma frequency and cavity parameters.