HIGH-SENSITIVITY LENS-COUPLED SLOW-SCAN CCD CAMERA FOR TRANSMISSION ELECTRON-MICROSCOPY

A lens-coupled slow-scan CCD camera has been built for transmission electron microscopy (TEM) applications. In this design, a leaded glass window, which is coated with a 20 mum layer of red P20 phosphor, is mounted on the bottom of the microscope. A lens assembly and mirror prism, located outside the microscope vacuum below the leaded glass, relays the image onto a back-thinned 1k x 1k charge-coupled device (CCD) detector. This CCD is electronically cooled to below -30-degrees-C during operation. It is found that X-ray irradiation, generally found to be annoying in fiber-optically coupled CCD cameras, is completely eliminated by this configuration. The collection efficiency of this system, although not as high as some of the fiber-optically coupled CCD cameras, is high enough to achieve single-electron sensitivity under a high-gain mode.