Development of a Picosecond X-Ray Spectroscopy System

该项目利用软x射线单色仪和飞行时间电子能谱仪，结合超快激光产生的等离子体x射线源，创建了一个亚皮秒时间分辨率的x射线研究新设备。这种装置将是同类中的第一个，并将用于使用时间分辨x射线技术研究材料的动态过程。它也将有可能以比以前更高的光谱和时间分辨率研究亚皮秒激光产生的等离子体的x射线发射的物理学。具体来说，使用高强度飞秒激光系统来创建超快x射线源。这是通过将激光脉冲聚焦到一个固体目标上，反复产生一个热的、密集的等离子体来实现的。等离子体发射出非相干的x射线爆发，持续时间小于1皮秒。一个收集光学装置将这些x射线的一部分聚焦到成像软x射线单色器中，该单色器将对x射线进行成像和能量选择，产生能量宽度约为十分之一电子伏的输出光束。x射线束用于超快过程的泵浦探测研究。可见波长的泵浦脉冲将激发固体表面，x射线脉冲用作探针。

This project makes use of a soft x-ray monochromator and a time-of- flight electron spectrometer in combination with an ultra fast laser-produced plasma x-ray source to create a novel facility for x-ray studies with sub-picosecond time resolution. This setup will be the first of its kind, and will be used to study dynamic processes in materials using time-resolved x-ray techniques. It will also be possible to study the physics of x-ray emissions from sub-picosecond laser-produced plasmas at higher spectral and temporal resolution than was previously possible. Specifically, a high-intensity femtosecond laser system is used to create an ultra fast x-ray source. This is done by focusing the laser pulses onto a solid target to repetitively create a hot, dense plasma. The plasma emits an incoherent burst of x-rays with time duration less than one picosecond. A collecting optic will focus a portion of these x-rays into an imaging soft x-ray monochromator, which will both image and energy select the x-rays, creating an output beam with an energy width of about one tenth of an electron volt. The x-ray beam is used for pump-probe studies of ultra fast processes. A visible wavelength pump pulse will excite a solid surface, with the x-ray pulse used as a probe.