INSPIRE: Compact X-Ray Laser in "Water Window" and Microscopy of Cell Membranes

这一多学科INSPIRE奖的最终目标是实现一种新型的、非常高分辨率的显微镜，它能够通过使用比普通可见光更有能量，但不像传统医疗X射线中使用的光那样能量的光来观察生物细胞内部。具体地说，该项目寻求产生和使用在光(波长3.4和4.0 nm)每次振荡期间传播3到40亿分之一米的“软x射线”光。这些波长落在所谓的“水窗口”(2.3-4.4 nm)，在这个窗口中，水是透明的，但细胞的许多其他部分不是。使用这些波长的光可以透过细胞内的水，以高分辨率清晰地显示细胞的功能部分。关键的使能工具被称为X射线激光(XRL)，该项目寻求生产一种足够小和负担得起的工具，使其能够广泛用于对自然环境中的活生物细胞进行成像。这项工作是基于高电荷态离子的使用，这种原子的大部分电子都被移除了。该项目的目标是通过成像天然细胞膜来展示新的XRL的实用性。这项工作由NSF综合活动办公室、原子、分子和光学实验物理计划、NSF/DOE在基础等离子体科学和工程方面的合作伙伴关系、生物研究仪器开发计划和生物主管的新兴前沿办公室共同资助。最近，在4.0 nm的复合X射线激光器中首次展示了高增益。这一结果激发了一个新的想法，即利用4.0 nm的XRL与红外(IR)场相结合，直接在复合XRL的倒置介质中产生阿秒脉冲。这一想法是在德克萨斯农工大学(TAMU)基于量子光学的理论基础上发展起来的，并被提议在普林斯顿大学进行实验测试，作为INSPIRE项目的一部分。预期用于生物成像的XRL的实际应用需要激光脉冲具有每个脉冲2-4微焦耳的能量。因此，该项目的关键问题将是寻找大的XRL束流强度放大。这项研究的自然延伸将是在另一个水窗口波长产生高XRL光束强度，在这种情况下是3.4 nm。通过使用Schwarzschild多层镀膜物镜和高灵敏度的二维电荷耦合器件探测器，细胞的辐射暴露将保持在较低的水平，以便对活细胞进行成像。

The ultimate goal of this multidisciplinary INSPIRE award is to enable a new, very high resolution microscope which is able to see inside biological cells by using light which is more energetic than ordinary visible light, but not as energetic as the light used in conventional medical x-rays. In specific, this project seeks to produce and use "soft x-ray" light that will travel between 3 and 4 billionths of a meter during each oscillation of the light (wavelengths 3.4 and 4.0 nm). These wavelengths fall in the so-called "water window" (2.3-4.4 nm) in which water is transparent, but many other parts of cells are not. Using light with these wavelengths allows one to see through the water inside cells to clearly visualize the functional parts of the cells in high resolution. The key enabling tool is called an X-ray laser (XRL), and this project seeks to produce one that is sufficiently small and affordable that it can be put into widespread use to image live biological cells in their natural environment. The work is based on the use of highly charged ions, atoms which have most of their electrons removed. Included in this project is the goal of demonstrating the utility of the new XRL by imaging natural cell membranes. This work is co-funded by the NSF Office of Integrative Activities, the Atomic, Molecular, and Optical Experimental Physics Program, the NSF/DOE Partnership in Basic Plasma Science and Engineering, the Instrument Development for Biological Research Program, and the Emerging Frontiers Office of the Biology Directorate.Recently, high gain was demonstrated for the first time in a recombination X-ray laser at 4.0nm This result stimulated a new idea to efficiently generate attosecond pulses by utilizing an XRL at 4.0 nm in combination with an infrared (IR) field directly in the inverted media of a recombination XRL. This idea was developed theoretically at Texas A&M University (TAMU) based on quantum optics and is proposed here to test this idea experimentally at Princeton as part of this INSPIRE project. It is expected that the practical application of an XRL for biological imaging requires the laser pulses to have an energy of 2 - 4 micro-Joules of energy per pulse. Therefore the crucial issue for this project will be the search for large XRL beam intensity amplification. The natural extension of this search will be the generation of high XRL beam intensity at another water window wavelength, in this case 3.4nm. By using a Schwarzschild multilayer coated objective and a high sensitivity two dimensional charge-coupled device detector, the cell radiation exposure will be kept low to allow the imaging of live cells.