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arXiv physics/0502059physics.opticscond-mat.mtrl-sci
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X射线衍射显微术中辐射损伤对分辨率限制的评估

An assessment of the resolution limitation due to radiation-damage in x-ray diffraction microscopy

M. R. Howells, T. Beetz, H. N. Chapman, C. Cui, J. M. Holton, C. J. Jacobsen, J. Kirz E. Lima, S. Marchesini, H. Miao, D. Sayre, D. A. Shapiro, J. C. H. Spence

摘要:

X射线衍射显微镜(XDM)是一种新形式的X射线成像,目前正在实践中的几个第三代同步辐射X射线设施。虽然这项技术首次引入至今只有五年时间,但它在展示高分辨率三维成像方面取得了快速进展,并承诺在比透射电子显微镜更大的样品上实现几纳米的分辨率。XDM的生命科学和材料科学应用都是预期的,并且预计分辨率的主要限制将是生命科学的辐射损伤和材料科学可用的X射线源的相干功率。在本文中,我们解决的问题,辐射损伤的作用。我们使用基于Hegerl和Hoppe的所谓“剂量分级定理”的统计分析来计算通过XDM以给定分辨率对生命科学样本进行成像所需的剂量。我们的结论是,所需的剂量尺度与分辨率的倒数四次方,并提出实验证据来支持这一发现。为了确定最大耐受剂量,我们收集了从文献中获取的大量数据以及我们自己的一些测量值,这些测量值涵盖了文献中报告未充分涵盖的分辨率范围。本研究的初步结论是,XDM应该能够在约10 nm的分辨率与“玫瑰标准”的图像质量的冷冻水合蛋白质样品的图像。

英文摘要:

X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Although only five years have elapsed since the technique was first introduced, it has made rapid progress in demonstrating high-resolution threedimensional imaging and promises few-nm resolution with much larger samples than can be imaged in the transmission electron microscope. Both life- and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available x-ray sources for material science. In this paper we address the question of the role of radiation damage. We use a statistical analysis based on the so-called "dose fractionation theorem" of Hegerl and Hoppe to calculate the dose needed to make an image of a lifescience sample by XDM with a given resolution. We conclude that the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered by reports in the literature. The tentative conclusion of this study is that XDM should be able to image frozen-hydrated protein samples at a resolution of about 10 nm with "Rose-criterion" image quality.

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