Ultrafast electron microscope with high energy electron pulses produced by an intense femtosecond laser

我们用340keV的电子脉冲对单晶金箔的电子衍射图进行了单次测量，电子脉冲被强度为2.1×10~(-1)W/cm~2的强飞秒激光脉冲加速。通过对电子轨迹的数值模拟，真实地再现了测得的电子束轮廓，证明了电子脉冲由于加速过程中产生的速度扩散而自发地随时间扩展，但不是以不可逆的非线性方式扭曲的。研究表明，激光加速对单发飞秒电子衍射脉冲压缩方法的发展具有很好的应用前景。

We have demonstrated single-shot measurement of electron diffraction patterns for a single-crystal gold foil using 340keV electron pulses accelerated by intense femtosecond laser pulses with an intensity of 2 10^<18>W/cm^2. The measured electron beam profile is faithfully reproduced by the numerical simulation of the electron trajectory, providing evidence that the electron pulse spontaneously expands in time owing to the velocity spread produced in the acceleration process, but is not distorted in an irreversible nonlinear manner. This study shows that the laser acceleration is promising for the development of pulse compression methods for single-shot femtosecond electron diffraction.