The effect of the electron-beam energy jitter on gain in FEL oscillator

The FEL oscillators with high-power, high-efficiency require stable electron beam as a pump. That means energy, current and period of e-beam should stabilize pass by pass during a macro-pulse. Actually, it is impossible to keep an absolute stabilization of electron beam during a micro-pulse. The jitter of e-beam will affect gain of laser seriously. The effects of energy jitter of e-beam on the gain are studied using the FEL 1D code (W1D) developed by the authors based on the parameters of the CAEP FIR-FEL. The results show that the energy jitter should be less than 0.5% for CAEP FIR-FEL