基于光电子脉冲展宽的高时间分辨成像技术

为获取超快光脉冲信号,提出了一种基于光电子脉冲准线性展宽的高时间分辨二维成像技术。利用高频时变电场的线性工作区加速光电子脉冲信号,通过优化阴极激励源的电参数,选择光电子进入加速区的时刻实现光电子脉冲的准线性展宽。利用曝光时间100ps的门控选通微通道板在脉冲展宽模块的记录面进行选通曝光成像,实现高时间分辨的二维成像。为改善系统的空间分辨和成像畸变,添加轴向聚焦磁场解决电子漂移区中由电子空间电荷效应引起的时间和空间弥散,对于能量4 keV、出射角0.1°的电子束,聚焦磁场的最佳强度为0.057 T,此时阴极中心位置的空间分辨可达5 1p/mm,阴极边缘位置空间分辨稍差。基于光电子脉冲准线性展宽技术,可将漂移距离50 cm,初始脉宽10 ps的电子脉冲展宽10倍,从而可将门控MCP探测器的时间分辨提高1个量级(即10 ps以内)。

Ultrafast time resolution 2D imaging technology based on photoelectron pulse quasi-linearly dilation

In order to record the ultrafast light pulse signal, a technology based on photoelectron pulse quasi-linearly dilation was presented. The photoelectron pulse went in the acceleration region on the calculated time to be accelerated by a high frequency varying electrical field, and then came into the uniform speed drift region to be quasi-linearly dilated. Using the gated Micro-channel Plate (MCP) detector whose time resolution was 100 ps on the recording surface to accept the electron pulse，the time resolved 2D imaging could be achieved. The system spatial resolution and image distortion were improved by an axial focusing magnetic field. For an electron beam whose energy was 4 keV and emit angle was 0.1, the optimal intensity of the focusing magnetic field was 0.057 T which could lead a 5 lp/mm resolution at the center of the photocathode while lower at the edge. Based on this technology, when the drift distance was 50 cm, the dilation magnification came to be 10, thus the temporal resolution of the 2D imaging system could be reduced to 10 ps.