Microsecond Measurement of the Phosphorescence of X-Ray Fluorescent Screens

Microsecond square-wave x-ray pulses, repeated a thousand times a second, were obtained by operating an x-ray tube directly from a radar pulser. The phosphorescent build-up and decay of light emitted by fluorescent materials when irradiated by the x-ray pulses was observed with a multiplier phototube connected to an oscilloscope. Oscillograms of CaWO4 (radiographic intensifying screen) and BaSO4 indicate simple exponential response, with decay to 1/eth intensity in 6 and 0.8 microseconds, respectively. MgWO4 and Patterson B (fluoroscopic) and D (photofluorographic) screens were found to complete their main response to microsecond excitation in 10 to 100 microseconds, but their decay is not exponential.