A 3D simulations of FEL oscillator

A code for simulation of 3D FEL oscillator has been established on 386 PC. Using this code, several calculations were done as follows: 1. In single mode cases, (a) the influences of non-ideal injection, emittance and energy spread on FEL saturated power in certain region are not distinctive, moreover, they become weakened when output coupling is small. Specially in the calculation with output coupling 2%, the saturated power for slight degree of non-ideal injection exceed that of ideal injection. (b) the influences of non-ideal injection on optical beam quality are not severe, they also become weakened when output coupling is small. 2. In multimodes (16) cases, the calculations show that side bands can not grow up when output coupling is large, and non-ideal injection, emittance can slow down the growth side bands