Exploiting the European-XFEL for a New Generation of Static Compression Research

本项目拟在位于汉堡的欧洲x射线自由电子激光器（European-XFEL， x射线自由电子激光器）的钻石砧池（DAC）中研究x射线脉冲冲击下材料的转变动力学。该项目旨在研究材料对极端应变率、压力和温度的响应。目前，AWE可以静态地使用标准dac和环形dac（目前正在开发中），动态地使用激光冲击（在较小程度上，也可以使用气枪）来应对极端条件。在XFEL上部署DAC，本质上是结合了这两种技术，并且应该能够通过不同的热力学途径获得材料的新相空间。实验将在位于汉堡的欧洲XFEL设施中使用高能量密度（HED）光束线进行。只有XFEL才能提供这些实验所需的高重复率的硬x射线脉冲。最初的目标是将一列高能飞秒x射线脉冲送入样品（已经装入DAC），同时快速压缩和加热样品。极快的探测器将用于收集压缩过程中的衍射图样。温度将使用条纹光谱辐射测量技术进行光学测量。最终目标是通过控制x射线脉冲序列，开发一种调节高应变率的方法，从而调节样品中产生的压力和温度。理解动力学效应是理解极端条件下材料相变的关键。

This project proposes to study the transformation dynamics of materials shocked using X-ray pulses in a diamond anvil cell (DAC) at the European-XFEL (X-ray free electron laser) facility in Hamburg. This project aims to study the response of materials to extreme strain rates, pressures and temperatures. Currently, AWE can access extreme conditions statically using standard DACs and toroidal DACs (currently under development), and dynamically using laser shocking (and to a lesser extent, gas guns). Fielding a DAC at XFEL, in essence, combines both techniques and should enable, through different thermodynamic pathways, access to new phase space for materials.Experiments will be carried out at the European XFEL facility in Hamburg using the High Energy Density (HED) beamline. Only XFEL can provide the high repetition rate of hard X-ray pulses required for these experiments. The initial objective is to send a train of energetic femtosecond X-ray pulses into the sample (already loaded into a DAC) to simultaneously, and rapidly, compress and heat the sample. Extremely fast detectors will be used to collect diffraction patterns during compression. Temperatures will be measured optically using streak spectro-radiometry technology. The ultimate goal is to develop a means of tuning the high strain rates, and consequently the pressures and temperatures induced in samples, through control of the X-ray pulse train. Understanding kinetic effects is critical to understanding phase transformations in materials under extreme conditions.