In this study, we investigate a new simple scheme using a planar undulator (PU) together with a properly dispersed electron beam (e beam) with a large energy spread (~1%) to enhance the free-electron laser (FEL) gain. For a dispersed e beam in a PU, the resonant condition is satisfied for the center electrons, while the frequency detuning increases for the off-center electrons, inhibiting the growth of the radiation. The PU can act as a filter for selecting the electrons near the beam center to achieve the radiation. Although only the center electrons contribute, the radiation can be enhanced significantly owing to the high peak current of the beam. Theoretical analysis and simulation results indicate that this method can be used for the improvement of the radiation performance, which has great significance for short-wavelength FEL applications.
Feng Ke, Yu Changhai, Liu jiansheng, Wang Wentao, Zhang Zhijun, Qi Rong, Fang Ming, Liu Jiaqi, Qin Zhiyong, Wu Ying, Chen Yu, Ke Lintong, Wang Cheng, Li Ruxin. Dispersion effects on performance of free-electron laser based on laser wakefield accelerator[J]. High Power Laser Science and Engineering, , (): .
