Laser energy calculation of BFEL facility

The laser energy is one of the key characteristics of Beijing Free Electron Laser(BFEL) facility. This paper calculated the gain and the laser energy of BFEL with a steady-state code and a time-dependent code. The calculation shows that by adopting suitable measures such as decreasing the emittance of the electron beam from 50 pmm·mrad to 30 pmm·mrad, the small signal gain of BFEL will grow from 16% to 28%, and the laser energy will increase approximately one order.