A modification of the silicon diode array camera tube has been carried out which permits X-ray images to be displayed on a television monitor. The silicon target, 50 to 150 μm thick, serves as the tube's vacuum window. Each X-ray photon generates a large number of holes in the silicon substrate. Most of these can be usefully collected, and effective quantum efficiencies over 1000 have been measured. Absolute measurements of the spectral sensitivity have been made and show good agreement with theoretical predictions made using values of hole lifetime and surface recombination velocity obtained from optical measurements on the same target. The silicon diode array offers a number of inherent advantages in X-ray imaging compared with the conventional amorphous selenium target. Among these are greater quantum efficiency, high sensitivity, and temperature stability. The diode array sensitivity greatly exceeds that of film in this X-ray energy range (5 to 20 keV). Moreover, because the video signal current is linear as a function of X-ray photon flux over a wide dynamic range, relative intensities may be compared directly rather than necessitating densitometer measurements as does film. The performance of the many types of X-ray imaging systems in different applications is compared in some detail.
