Development and Testing of an Aberration-Correction System for Photoelectron Microscopes and Other High Resolution Imaging Systems.

这个项目的目标是在电子光学中实现两百多年前在光光学中所做的事情：即开发相当于acromat的电子光学。一旦完成，这将是第一个同时校正电子光学中球面和色差的实用装置。两个关键部件是电子镜和光束分离系统。这种镜面的像差与传统电子透镜的像差符号相反，因此提供了一种消除像差的方法。这项补助金的续期寻求资金来执行这个项目的第三阶段。第一阶段包括电子反射镜、光束分离器和电子透镜的设计和构造，以及反射镜特性的理论和实验研究（G. F. Rempfer J appll）。物理学报，37(2),1990,21 - 21。第二阶段（刚刚完成）首次成功演示了利用电子镜对色差进行校正（G. F. Rempfer和M. S. Mauck, Optik(1992) 86, 3-8），并完成了先进的电子光学台架，用于对像差校正器进行高精度测试。提出的第三阶段的目标是利用这一独特的资源（新的电子光学平台，目前唯一一个为分支系统设计的平台）来演示球像差的校正，以及色差和球像差的同时校正。当校正条件确定后，将进行分辨率测试。测试将首先在探测模式下进行。然后调整校正参数以消除光电子显微镜（PEM）中的像差，并在PEM模式下进行分辨率测试。台架研究将导致光学系统组件的最佳定位以及馈线，操纵器和端口的位置，因此可以设计一个体积较小的真空外壳，这将有助于提供一个可行的原型仪器。新的外壳将释放光学工作台，以便与其他分支系统继续进行实验。本研究的一个很有前景的副产品是光束分离器，它可以在低能电子显微镜/镜像电子显微镜（LEEM/MEM）中分离入射和返回光束。事实上，生物标本（培养的哺乳动物细胞）的第一张LEEM和MEM图像是最近用该项目开发的光束分离系统获得的（O H. Griffith et al., J Micros. 168,249 -258(1991)）。由于分支系统适用于LEEM/MEM和校正后的PEM，因此校正后的PEM的新型真空外壳也可以用于LEEM和MEM的研究。这项为期五年的NSF拨款更新计划的研究将产生一个像差校正透镜系统（即电子光学acromat）和一个模块化仪器，主要用于校正PEM，但也能用于LEEM和MEM。更高分辨率的质子交换膜应该产生清晰的DNA和DNA-蛋白质复合物的图像，具有目前成像方法无法提供的信息（光电子对比）。其他应用包括正常和恶性细胞表面的受体分布，以及成像膜和细胞骨架元件。这项由物理学和工程团队（位于波特兰的波特兰州立大学）和分子生物学团队（位于俄勒冈大学尤金分校）合作的研究的一个标志是由美国国家科学基金会资助的仪器进步在生物科学领域的快速应用。

The goal of this project is to achieve in electron optics what was done in light optics over two hundred years ago: that is, to develop the electron optical equivalent of the acromat. When completed, this will be the first practical device to simultaneously correct both spherical and chromatic aberrations in electron optics. The two key elements are an electron mirror and a beam separating system. The mirror has aberrations of opposite sign from those of conventional electron lenses and thus provides a means of canceling out aberrations. This grant renewal seeks funds to carry out the third phase of this project. The first phase covered the design and construction of an electron mirror, beam separator, and the electron lenses, and theoretical and experimental investigations of the mirror properties (G. F. Rempfer J Appl. Phys. 67, 6027-6040 (1990)). The second phase (just completed) produced the first successful demonstration of the correction of chromatic aberration by means of an electron mirror (G. F. Rempfer and M. S. Mauck, Optik (1992) 86, 3-8), and the completion of an advanced electron optical bench to carry out high precision testing of an aberration corrector. The goal of the proposed third phase is to utilize this unique resource, (the new electron optical bench, the only one in existence designed for branched systems), to demonstrate correction of spherical aberration, and simultaneous correction of chromatic and spherical aberration. When the conditions for correction have been established, resolution tests will be performed. Tests will be done first in the probe mode. The correction parameters will then be adjusted for cancellation of aberrations in the photoelectron microscope (PEM), and resolution tests will be performed in the PEM mode. The bench studies will lead to optimum positioning of the components of the optical system and locations of the feedthroughs, manipulators, and ports, so that a less bulky vacuum housing can be designed which wi ll serve the purpose of providing a workable prototype instrument. The new housing will free up the optical bench for continuing experiments with other branched systems. A promising byproduct of this research is the beam separator, which can serve to separate the incident and returning beams in a low energy electron microscope/mirror electron microscope (LEEM/MEM). In fact, the first LEEM and MEM images of biological specimens (cultured mammalian cells) were recently obtained with the beam separating system developed as part of this project (O H. Griffith et al., J Micros. 168, 249-258 (1991)). Because the branched system is common to both LEEM/MEM and corrected PEM, the new vacuum housing for the corrected-PEM can be designed to enable LEEM and MEM studies as well. The research planned for this proposed five-year NSF grant renewal will result in an aberration-corrected lens system (i.e. an electron optical acromat) and a modular instrument intended primarily for corrected PEM, but capable also of LEEM and MEM. The higher resolution PEM should produce sharp imagines of DNA and DNA-protein complexes having information (photoelectron contrast) not available in the present imaging methods. Other applications include receptor distributions on the surfaces of normal and malignant cells, and imaging membranes and cytoskeletal elements. A hallmark of this research collaboration between a physics and engineering team (at Portland State University in Portland) and a molecular biology group (at the University of Oregon, Eugene) is the rapid application in the biological sciences of the instrumental advances funded by this NSF grant.