Tables for
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 7.1, p. 630

Section Light-sensitive semiconductor PSD's

U. W. Arndtb Light-sensitive semiconductor PSD's

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Standard light-sensitive semiconductor imaging devices can be used for X-ray detection if the X-rays are first converted to light by means of a phosphor. One 8 keV X-ray photon produces several hundred light photons in a good phosphor (see Table[link]). Because of the low noise levels possible with cooled CCD's (∼10 electrons r.m.s.), only 1 to 3% of these photons need to reach the device to produce a perfect X-ray detector. Unfortunately, even this is possible only with optics that do not demagnify to any considerable extent (see Subsection[link]) and one is thus restricted to a small detector. However, CCDs are now available that can be butted along two or three edges and these make possible the construction of `tiled' detectors that contain four or six of such CCD chips (Burke, Mountain, Harrison, Bautz, Doty, Ricker & Daniels, 1991[link]; Fordham, Bellis, Bone & Norton, 1991[link]; Allinson, 1994[link]). Individual channels can be read simultaneously (Hopf & Rodricks, 1994[link]), thus making possible a relatively rapid read out of a large number of pixels.

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X-ray phosphors (from Arndt, 1982[link])

PhosphorTypeBulk densityNo. of photons per 8 keV quantumMax. emission wavelength (nm)Decay to 1% (s)
ZnS (Ag) Polycrystal 4.1 750 300 450 3 × 10−7 + slow components
Gd2O2S Polycrystal 7.1 500 200 550 10−3
CsI (Tl) Monocrystal 4.5 240 62 580 10−6
These figures are for collection on a photocathode on the opposite side of a fibre-optics face plate, in the absence of a reflective coating.


Allinson, N. M. (1994). Development of non-intensified charge-coupled device area X-ray detectors. J. Synchrotron Rad. 1, 54–62.
Arndt, U. W. (1982). X-ray television area detectors. Nucl. Instrum. Methods, 201, 13–20.
Burke, B. E., Mountain, R. W., Harrison, D. C., Bautz, M. W., Doty, J. P., Ricker, G. R. & Daniels, P. J. (1991). An abuttable CCD imager for visible and X-ray focal plane arrays. IEEE Trans. Electron Devices, 38, 1069–1076.
Fordham, J. L. A., Bellis, J. G., Bone, D. A. & Norton, T. J. (1991). The MIC photon-counting detector. Proc. SPIE, 1449, 87–98.
Hopf, R. & Rodricks, B. (1994). A VXI-based high-speed X-ray CCD detector. Nucl. Instrum. Methods, A348, 645–648.

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