CCD Camera for Intermediate Voltage Electron Microscopes

描述（由申请人提供）：电荷耦合器件（CCD）相机在电子显微镜中有广泛的应用。它们提供了比照相胶片更快的图像和衍射数据的可用性，并且这种周转时间的改善使得样品评估，显微镜操作和自动化以及数据记录的效率大大提高。对于某些类型的工作，用CCD收集的数据比记录在胶片上的数据质量更高。然而，CCD性能严重受损时，显微镜操作远高于100千伏，由于闪烁体的效率下降。较高的电压导致信号电平的降低和噪声的引入，以及闪烁体内的电子的横向散射的增加，这降低了分辨率。这些效应一起可以产生远低于胶片的探测量子效率（DQE），并且对于诸如蛋白质的低剂量成像之类的工作来说确实太低了。随着更高加速电压的许多优点得到更广泛的认可，在300 - 400 kV下工作的中压电子显微镜（IVEM）的使用正在增加，因此这些显微镜上的CCD性能变得越来越受到限制。我们正在建立一个新的CCD摄像机系统，旨在克服IVEMS上的CCD摄像机的性能差，通过减速电子之前，他们到达相机。我们安装CCD，使其可以浮动到200 kV左右，这样当显微镜在300 kV下工作时，我们可以获得IVEM的优势，但相机应该在100 kV显微镜上运行。将对闪烁体进行进一步改进，以产生比目前可用的更好的信号和分辨率特性。反过来，这一进步将使我们能够利用最新的、用更小像素制造的超大格式CCD。这些调整将在从蛋白质和病毒的高分辨率结构研究到细胞超微结构的三维研究等工作中产生实质性的好处。

DESCRIPTION (provided by applicant): Charge-coupled device (CCD) cameras have found wide application in electron microscopy. They provide much faster availability of image and diffraction data than photographic film, and this improvement in turnaround time has allowed a tremendous increase in the efficiency of specimen evaluation, microscope operation and automation, and data recording. For some types of work the data collected with a CCD is of higher quality than that recorded on film. However, the CCD performance is seriously compromised when the microscope is operated much above 100 kV, due to the decrease in efficiency of the scintillator. The higher voltages result in a decrease of the signal level and introduction of noise, as well as an increase in lateral scattering of the electrons within the scintillator, which decreases the resolution. Together these effects can produce a detective quantum efficiency (DQE) which is far below that of film, and indeed too low for work such as low-dose imaging of proteins. The use of Intermediate Voltage Electron Microscopes (IVEMs) operating at 300 - 400 kV is increasing as the many advantages of the higher accelerating voltage become more widely recognized, so the CCD performance on these microscopes is becoming more of a limitation. We are building a new CCD camera system designed to overcome the poor performance of CCD cameras on IVEMs by decelerating the electrons before they reach the camera. We mount the CCD so that it can be floated to around 200 kV, so that when the microscope is operated at 300 kV we obtain the advantages of the IVEM but the camera should perform as well as on a 100 kV microscope. Further improvements will be made to the scintillator to produce even better signal and resolution characteristics than currently available. This advance will, in turn, allow us to utilize the newest, very large format CCDs that are fabricated with smaller pixels. These adaptations will produce substantial benefits in work ranging from high-resolution structural studies of proteins and viruses to the three dimensional study of cell ultrastructure.