Single-shot X-ray phase-contrast imaging of dense plasmas

激光驱动激波现象的研究是极端条件下物质研究的一个热点领域。在这个项目中，我们将研究激光驱动的冲击波与致密障碍物相互作用的现象，使用反射激波进行低熵压缩，并研究激光冲击实验中的辐射预热和作为产生高密度物质态的一种手段的快速辐射加热。对于高密度等离子体，可见光子只能进入物质分布的表面，而X射线提供了成像物质分布的3D形态的机会。在密度变化很小的情况下，如实验室实验中的典型情况，X射线相位对比度使图像对比度比标准X射线衰减更高。在这个项目中，我们将研究基于光栅的X射线位相衬度方法，用于在GSI的高功率激光螺线上对上述激光驱动冲击现象进行成像。具有挑战性的方面包括成像系统的稳定性和对准、用于莫尔成像的Talbot参数的优化以及图像分析。将进行模拟，以产生真实的密度分布，传播X射线通过这些目标，并模拟图像签名。模拟数据和测量数据的对比将被用来量化结果。

The investigation of laser-driven shock phenomena is a topical field of research of matter at extreme conditions. Within this project, we will investigate phenomena like laser-driven blast waves interacting with dense obstacles, low-entropy compression using reflecting shocks and studies of radiative preheat in laser-shock experiments and rapid radiation heating as a means to generate high density matter states. For dense plasma, visible photons give access to the surface of the matter distribution only, while X-rays offer the opportunity to image the 3D morphology of the matter distribution. In the case of small density variation as typically the case in laboratory experiments, X-ray phase-contrast enables higher image contrast than standard X-ray attenuation. In this project we will investigate grating-based X-ray phase-contrast methods for the imaging of the above mentioned laser-driven shock phenomena at the high power laser PHELIX at GSI. Challenging aspects are the stability and alignment of the imaging system, the optimization of the Talbot parameters for moiré imaging and the image analysis. Simulations will be performed to generate realistic density distributions, to propagate X-rays through such targets and to simulate image signatures. The comparison of simulated and measured data will be employed to quantify the results.