Generation of high current and pico-second scale spin polarized beam by using transmission photocathode

为了研究透射型偏振光电阴极的时间响应特性，我们研制了一套脉冲长度测量系统。该系统由一个射频偏转腔和一个光束轮廓监测器组成。射频偏转腔的谐振频率为2612.9 MHz，与泵浦激光同步，利用脉冲长度测量系统和20千伏高亮度电子枪，对自旋极化电子束的脉冲长度进行了观测。在泵浦激光脉宽为40ps的情况下，获得了46ps的电子脉冲宽度。这些值与基于光电阴极厚度的估计值是一致的。此外，我们还证实了使用透射型光电阴极可以获得ps级的偏振光束。

In order to study the temporal response of transmission-type polarized photocathodes, we developed a pulse length measurement system. The system consists of an rf deflecting cavity and a beam profile monitor. The rf deflecting cavity has the resonance frequency of 2612.9 MHz and is synchronized to the reputation of pump laser light.By using the pulse length measurement system and 20-kV high brightness electron gun, we observed the pulse length of spin polarized electron beam. As a result, the electron pulse duration of 46 ps was observed with the pump laser duration of 40 ps. These value is consistent with the evaluated value based on the photocathode thicknes. Futhermore, we confirmed that a ps-scale polarized beam could be obtained by using the transmission-type photocathodes.