APPLICATION OF A POST-COLUMN ENERGY FILTER

H700H低温电子显微镜上的一种先进的能量过滤器正在研制中。 生物结构的数字成像和分析评估. 高灵敏度。 该过滤器配备有YAG耦合的、冷却的、 慢扫描CCD相机，完全由计算机控制。 的 CCD的探测量子效率大于0.7， 入射通量从每像素10电子到每像素10000电子 象素 低强度性能相对于 一个冷却的光电二极管阵列，因为它的读出噪声低得多。 由于CCD图像可以 准确地进行增益归一化。 使正常化成为可能 因为CCD的小像素（24平方微米）更小 而不是输入信号的典型空间变化。 它有 已经证明可以在正常模式下获得光谱， 每个通道包含多达1亿个快电子， 相当于0.01%水平的统计数据。 这预计将 降低生物样品元素分析的检测限 甚至比光电二极管所能达到的更低 阵列探测器 成像滤波器的使用也在探索中 用于获取低剂量的光束敏感的显微照片， 标本

An advanced energy-filter on a H700H cryo-electron microscope is being assessed for digital imaging and analysis of biological structures at high sensitivity. The filter is equipped with a YAG-coupled, cooled, slow-scan CCD camera, and is entirely computer-controlled. The detective quantum efficiency of the CCD is greater than 0.7 for incident fluxes from 10 electrons per pixel to 10000 electrons per pixel. The low-intensity performance is improved relative to that of a cooled photodiode array because of its much lower read-out noise. The high-intensity performance is improved because the CCD images can be accurately gain-normalized. The normalization is made possible because the small pixels of the CCD (24 microns square) are smaller than the typical spatial variation of the incoming signal. It has been demonstrated that spectra can be acquired in the normal mode that contain as many as 100 million fast electrons per channel, corresponding to statistics at the 0.01% level. This is expected to reduce detection limits for elemental analysis of biological specimens to a point that is even lower than can be achieved with a photodiode array detector. The use of the imaging filter is also being explored for the acquisition of low-dose micrographs of beam-sensitive specimens.