Soft x-ray microscopy in the water window $({\sim}{285 {-} 535}\;{\rm eV}$) is an emerging and unique tool for 2D and 3D imaging of unstained intact cellular samples in their near-native state with few-10-nm detail. However, present microscopes rely on the high x-ray brightness of synchrotron-radiation sources. Having access to water-window microscopy in the home laboratory would increase the impact and extend the applicability of the method. In the present paper, we review three decades of efforts to build laboratory water-window microscopes and conclude that the method is now reaching the maturity to allow biological studies. The instruments as well as their key components are quantitatively and qualitatively compared. We find that the brightness and the reliability of the laboratory source are the most critical parameters, but that the optics as well as the sample preparation also must be optimized to enable high-resolution imaging with adequate exposure times. We then describe the two sister microscopes in Stockholm and Berlin, which allow reliable high-resolution biological imaging with short exposure times of a few tens of seconds in 2D and a few tens of minutes in 3D. They both rely on a liquid-jet laser-plasma source combined with high-reflectivity normal-incidence multilayer condenser optics, high-resolution zone-plate imaging optics, CCD detection, and cryogenic sample handling. Finally, we present several examples of biological imaging demonstrating the unique properties of these instruments.

中文翻译：

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实验室水窗X射线显微镜

水窗中的软X射线显微镜$（{\ sim} {285 {-} 535} \; {\ rm eV} $）是一种新兴且独特的工具，可用于未染色的完整细胞样品在接近自然状态的二维和3D成像，仅需10nm的细节。但是，目前的显微镜依赖同步辐射源的高X射线亮度。在家庭实验室中使用水窗显微镜将增加影响并扩展该方法的适用性。在本文中，我们回顾了建立实验室水窗显微镜的三十年努力，并得出结论，该方法现在已经成熟，可以进行生物学研究。对工具及其关键组成部分进行定量和定性比较。我们发现实验室光源的亮度和可靠性是最关键的参数，但光学和样品制备也必须进行优化，以实现具有足够曝光时间的高分辨率成像。然后，我们描述了斯德哥尔摩和柏林的两台姐妹显微镜，它们可以实现可靠的高分辨率生物成像，并且在2D模式下的曝光时间短于数十秒，而在3D模式下的曝光时间短于数十分钟。它们都依赖于液体喷射激光等离子体源，并结合了高反射率法向入射多层聚光器光学器件，高分辨率波带片成像光学器件，CCD检测和低温样品处理功能。最后，我们介绍了生物成像的几个例子，展示了这些仪器的独特性能。可以进行可靠的高分辨率生物成像，并且在2D模式下的曝光时间短至几十秒，而在3D模式下的曝光时间短至几十分钟。它们都依赖于液体喷射激光等离子体源，并结合了高反射率法向入射多层聚光器光学器件，高分辨率波带片成像光学器件，CCD检测和低温样品处理功能。最后，我们介绍了生物成像的几个例子，展示了这些仪器的独特性能。可以进行可靠的高分辨率生物成像，并且在2D模式下的曝光时间短至几十秒，而在3D模式下的曝光时间短至几十分钟。它们都依赖于液体喷射激光等离子体源，并结合了高反射率法向入射多层聚光器光学器件，高分辨率波带片成像光学器件，CCD检测和低温样品处理功能。最后，我们提供了生物成像的几个例子，展示了这些仪器的独特性能。