Investigation and application of soft X-ray emission from targets containing micron-sized liquid droplets irradiated with intense laser pulses

极紫外（XUV）和软x射线（SXR）光谱区与许多科学问题具有突出的相关性。一方面，这是由于极短的波长能够实现高空间分辨率。另一方面，这是由于物质在该光谱状态下的特征吸收行为，这使得元素组成甚至化学环境的识别成为可能。由于它们的高亮度和多功能性，同步加速器和后来的自由电子激光器注定要用于这一科学领域。尽管如此，研究人员仍在积极寻找其他XUV和SXR辐射源，以便提供更灵活的进入软x射线区域的途径。特别是激光驱动光源在过去已经取得了一些突破。例如，13.5纳米技术目前已在光刻技术中站稳脚跟，但仍面临着有关碎片的巨大挑战。到目前为止，还没有一个令人信服的解决方案，既聪明又具有成本效益的XUV和SXR辐射源，特别是在运营成本方面。基于波兰同事的一种很有前途的方法，该方法使用智能同轴双喷嘴布置来产生良好准直的密集目标光束，该喷嘴的新变体将被研究，以产生极宽带SXR辐射。虽然到目前为止使用的是原子和分子气体，但现在也将使用簇和气溶胶，从而实现更高的目标密度。这将导致更高的效率和更广泛的光谱。一种特别有前途的方法是将重元素溶解在待雾化的液体中。波兰和德国的研究小组有许多不同的激光器，它们的脉冲参数非常不同。与理论建模一起，这些使新目标的系统研究成为可能，包括表征。上述研究是由合作中的两个科学应用驱动的，这将在项目框架内得到推进。一方面，这是一种新的纳米级横断面成像方法，它依赖于相干断层成像，并依赖于宽带辐射的可用性。与目前使用的高谐波辐射不同，这个项目将提供进入SXR体制的途径。因此，更高的空间分辨率和特别有趣的光谱范围，例如磁性材料，将可用于实验室研究。为此，成像将由x射线吸收精细结构光谱（XAFS）补充。这使得非破坏性地获得样品的内部结构信息，包括它们的组成和化学环境。

The extreme ultraviolet (XUV) and soft X-ray (SXR) spectral region is of outstanding relevance for a manifold of scientific questions. On the one hand, this is due to the extremely short wavelength enabling high spatial resolution. On the other hand, it is due to the characteristic absorption behavior of matter in this spectral regime, which enables the identification of the elemental composition and even the chemical environment. By virtue of their high brilliance and versatility, synchrotrons and, latterly, free-electrons lasers are predestined for this field of science. Nevertheless, researchers are vigorously seeking for alternative XUV and SXR radiation sources, inter alia, in order to provide a more flexible access to the soft X-ray region. Particularly laser-driven sources have seen several breakthroughs in the past. For example, the 13.5-nm technology currently establishes itself in lithography, however still fighting massive challenges concerning debris. So far, there is no convincing solution for a brilliant and, at the same time, cost-effective XUV and SXR radiation source, particularly also with respect of operation costs.Building on a promising approach of the Polish colleagues, which uses a smart coaxial double-nozzle arrangement to generate a well-collimated dense target beam, novel variants of this nozzle will be investigated in order to generate extremely broadband SXR radiation. While atomic and molecular gases were used so far, now also cluster and aerosols will be employed, thus achieving much higher target densities. This will lead to higher efficiency and broader spectra. A particularly promising approach is to dissolve heavy elements in the liquids to be atomized. The Polish and German teams have available a number of different lasers with very different pulse parameters. Together with theoretical modeling, these enable systematic research on the new target, including characterization.Above research is driven by two scientific applications within the collaboration, which will be advanced in the framework of the project. On the one hand, this is a novel method for nanoscale cross-sectional imaging, which rests on coherence tomography and depends on the availability of broadband radiation. In contrast to high-harmonic radiation that has been used so far, this project will give access to the SXR regime. As a consequence, higher spatial resolution and a particularly interesting spectral range for, e.g., magnetic materials will become available for lab-based research. To this end, imaging will be complemented by X-ray absorption fine-structure spectroscopy (XAFS). This enables to non-destructively gain information of the internal structure of samples including their composition and chemical environment.