GAIN ANALYSIS OF A WAVE-GUIDE FREE-ELECTRON LASER

Both the gain in the low-gain regime and the growth rate in the high-g ain regime of a waveguide free electron laser are derived within the 1 D approximation. The effects of waveguide on the gain are analyzed. Nu merical simulations are made using a 1D time-dependent code. It is sho wn that the slippage between the electron beam and the radiation resul ts in a greater reduction of gain in the high-gain regime than in the low-gain regime, but the slippage can be eliminated more fully by a wa veguide in the high-gain than in the low-gain regime.