Optimization of phosphor screens for charge coupled device based detectors and 7{endash}34 keV x-rays
- Department of Chemical Engineering, Materials Science and Mining Engineering, Columbia University, New York, New York 10027 (United States)
Phosphor screens convert x-ray images to visible light images in two-dimensional charge coupled device (CCD) based detector systems used for x-ray diffraction. Some experimental and theoretical aspects of phosphor screen performance are described in this article. The efficiencies of x-ray-to-light conversion were measured using a CCD camera for transmission phosphor screens fabricated from two different phosphor powders, Y{sub 2}O{sub 2}S:Eu (P22R) and Gd{sub 2}O{sub 2}S:Tb (P43), for screen mass thicknesses of 3{endash}50 mg/cm{sup 2} and for x-ray energies of 7{endash}34 keV. A model was developed and evaluated for the dependence of the emitted light brightness on screen thickness and x-ray energy. Inputs to the model are x-ray absorption coefficients and light attenuation versus thickness data, which were determined experimentally for the phosphors and found to be dominated by scattering rather than absorption. The angular distribution of emitted light, was found to be nearly Lambertian. Broadening of image features in the x-ray-to-visible-light conversion by phosphors for 19.6 keV x-rays was found to increase approximately linearly with phosphor screen thicknesses in the range of 30{endash}160 {mu}m, but with a minimum width of 110 {mu}m for P22R phosphor and 70 {mu}m for P43 phosphor. In the range of 7{endash}15 keV, maximum brightness was obtained for P43 phosphor screens of about 10 mg/cm{sup 2} mass thickness (60 {mu}m). For P22R screens, the thickness for maximum brightness increased from about 8 mg/cm{sup 2} (50 {mu}m) for 7 keV to more than 46 mg/cm{sup 2} (210 {mu}m) for 15 keV. For 7 keV the maximum brightnesses for P22R and P43 phosphors were about the same. For 10 keV the maximum brightness for P43 phosphor was about 60{percent} greater than the maximum brightness for P22R phosphor samples tested. For 15 keV the maximum brightness for P43 phosphor was again about 60{percent} greater than that for the P22R samples tested. (Abstract Truncated)
- OSTI ID:
- 489253
- Journal Information:
- Journal of Applied Physics, Vol. 81, Issue 3; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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