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

研究激光驱动的冲击现象是物质在极端条件下研究的一个热门领域。在这个项目中，我们将研究激光驱动的冲击波与密集障碍物的相互作用、使用反射冲击的低熵压缩、激光冲击实验中的辐射预热研究和快速辐射加热作为产生高密度物质状态的手段等现象。对于致密等离子体，可见光光子只能进入物质分布的表面，而x射线提供了对物质分布的三维形态成像的机会。在密度变化较小的情况下，如实验室实验中典型的情况，x射线相衬可以比标准x射线衰减实现更高的图像对比度。在这个项目中，我们将研究基于光栅的x射线相对比方法，用于在GSI的高功率激光philix上成像上述激光驱动的冲击现象。具有挑战性的方面是成像系统的稳定性和对准，优化塔尔博特参数的成像和图像分析。将进行模拟以产生真实的密度分布，通过这些目标传播x射线并模拟图像签名。模拟数据和实测数据的比较将用于量化结果。

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.