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Proceedings Paper

Measurement Of The X-Ray-Induced Light Photons Emitted From Radiographic CaW04 Intensifying Screens
Author(s): H. Roehrig; B. Lum; S. Nudelman; M. P. Capp; C. E. Dick
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Paper Abstract

For calcium tungstate intensifying screens employed in film-screen imaging systems, Coltman found that approximately 1000 light photons of average energy 2.7 eV were produced for each 50 keV x-ray absorbed. Of this number, he found that only about 55% are emitted from the output side of a 109 mg/cm2 screen. We have developed a method based on counting single photons to determine this number for various thicknesses of calcium tungstate screens. Monoenergetic x rays in the energy range from 17-69 keV produce upon absorption, a shower of individual photon pulses which are detected by a low noise photomultiplier. After amplification and discrimination against the noise background of the phototube, the resultant pulses are counted in a 70 MHz scaler or a 150 MHz counter. The detection system has a pulse resolving time of less than 15 ns. The data are then corrected for the quantum efficiency of the detector and normalized to the number of absorbed x rays which is determined in a separate experiment. For calcium tungstate screens with thicknesses of 30, 50, 86, and 123 mg/cm2, the average numbers of light photons emitted per absorbed x ray are measured for 8 x-ray energies between 17- and 69-keV. The values for 50 keV are less than the values found by Coltman. Studies of the causes of this discrepancy are in progress.

Paper Details

Date Published: 6 July 1979
PDF: 8 pages
Proc. SPIE 0173, Application of Optical Instrumentation in Medicine VII, (6 July 1979); doi: 10.1117/12.957117
Show Author Affiliations
H. Roehrig, University of Arizona (United States)
B. Lum, University of Arizona (United States)
S. Nudelman, University of Arizona (United States)
M. P. Capp, University of Arizona (United States)
C. E. Dick, National Bureau of Standards (United States)

Published in SPIE Proceedings Vol. 0173:
Application of Optical Instrumentation in Medicine VII
Joel E. Gray, Editor(s)

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