Ion-Channel and Axial Magnetic Field Effects on Growth Rate of waves in Free Electron Laser with Helical Wiggler

Dispersion relation of waves in a free electron laser with helical wiggler and ion-channel and axial magnetic field is derived. This dispersion relation is solved numerically to study the instable interaction among all waves modes. It is found that the growth rate for group I orbits has been affected by the presence of the ion-channel and axial magnetic field.