ABSTRACT
The through transmission and image production characteristics of radiography make the technique particularly amenable to being applied in some very specialized ways. In one case, the penetrating capability of radiography combined with a large computer memory and ordinary optical principles provide the basis for computer tomography (CT). In another case, the use of very small sources makes possible microfocus radiography that is useful for detecting smaller defects. Real-time radiography (radioscopy) can produce images quickly on a CRT monitor for instant analysis and data transmission. Radiography can also be used in a stop-action mode with high power, short duration pulses in flash radiography. Other specialized applications of radiography include scanning electron microscopes where the secondary effects resulting from the radiation excited on a target material being studied are used as the investigative tool. The significant differences in the absorption characteristics of neutrons and protons, as compared to photons, creates a field of inspection capabilities far beyond that of x-radiography alone. Materials analysis and stress measurement are important applications of radiographic technology. In most cases, either beam attenuation or diffraction is used in order to investigate the parameter of interest. Attenuation has already been covered and will not be repeated here but a brief overview of diffraction techniques seems fitting.
