对中国科学院上海光学精密机械研究所(SIOM)即将开展的基于激光尾场加速(LWFA)电子束的自由电子激光（FEL）实验(SIOM-FEL)进行了数值模拟研究，提出利用直接外种子激光驱动的方案来获得FEL辐射。理论和仿真结果表明，采用直接外种子激光驱动模式，在束流能散为1%，发射度为0.3 mm·mrad的情况下，提高峰值电流强度到10 kA可以得到接近200倍增益的FEL辐射，而利用具有横向梯度的波荡器也可以在较低的束流强度条件下获得较高的辐射增益。

Simulations of free electron laser (FEL) experiments based on the laser-wakefield accelerator, which will be conducted at Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Acadomy of Sciences, are performed. Direct-seeding with high harmonic generation (HHG) is proposed as the scheme for free-electron laser experiments at SIOM (SIOM-FEL). The theoretical and simulation results show that the FEL signal will be amplified about 200 times compared with the initial high harmonic generation when the electron beam energy spread is 1%, the emittance is 0.3 mm·mrad and the peak current is about 10 kA. What′s more, the application of the transverse gradient undulator (TGU) can furtuer improve the FEL performance even with a relatively low peak current.