The development of compact Z-polarization multi-bunch photocathode gun

自2006年以来，我们研制了一种新型的激光诱导肖特基效应门控光电阴极电子枪。这种新型火炮利用激光的相干性，利用光电阴极上的Z偏振，将紧凑的飞秒激光振荡器作为红外光源。这种Z偏振方案由于肖特基效应降低了阴极功函数，从而降低了激光脉冲能量。中空激光入射采用中空凸透镜，光束通过径向偏振器后被聚焦。根据我们的计算(凸透镜：NA=0.15)，对于1 GV/m的Z场，基波(792 Nm)的峰值功率需要1.26 mW，倍频(396 Nm)的峰值功率需要0.316 mW。在第一次演示中，用铜阴极在THG(264 Nm)处进行了Z场发射增强。因此，通过比较径向和方位向极化，我们观察到在1.6 GV/m的平均激光Z场作用下，铜阴极表面的光电发射增强了1.4倍。

We have developed a novel photocathode gun gated by laser-induced Schottky-effect since 2006. This new type of gun utilizes a laser's coherency to aim at a compact femtosecond laser oscillator as an IR laser source using Z-polarization on the photocathode. This Z-polarization scheme reduces the laser pulse energy by reducing the cathode work function due to Schottky effect. A hollow laser incidence is applied with a hollow convex lens that is focused after passing the beam through a radial polarizer. According to our calculations (convex lens : NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm) and 0.316 MW for the SHG (396 nm). In the first demonstration of Z-field emission enhancement was done with copper cathode at THG (264 nm). Consequently, we observed 1.4 times enhancement of photoemission at 1.6 GV/m of an averaged laser Z-field on the copper cathode surface by comparing radial and azimuthal polarizations.