Images of single x-ray photons from x-ray phosphor screens

Photographs show efficiency and resolution characteristics of single x-ray photons converted to optical photons in a variety of commercial x-ray phosphor screens. The recording system uses a cooled, two-stage image intensifier system with fiber optics coupling to the phosphor screen. High efficiencies in the energy range 20–100 keV with position resolution of the order ∼200 μ are readily achievable, although the sensitive area is presently limited. Potential applications include x-ray astronomy, high-speed x-ray diffractometry, and extremely low dose radiography.