ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
Various sources of random deviations occurring in the determination of X-ray intensities with the aid of film methods are discussed and corresponding mathematical expressions are derived. From a comparison with experimental values of the standard deviations obtained from measurements on homogeneously exposed films, it follows that the deviations are primarily caused by the variations of the X-ray photon flux due to the stochastic nature of the X-ray emission process. The accuracy attainable with most X-ray films is found not to be limited by saturation of the number of excited AgBr particles occurring at increasing exposures, but at low exposures film methods are at a disadvantage because of the presence of fog. If, however, small signals superimposed on a high sample background have to be measured, relatively high exposures are required; in this case film registration is found to be much faster than methods involving step-scanning counters, and in general little slower than registration with the aid of a position-sensitive counter. It is also shown that the dynamic range of the film method may be extended without sacrificing accuracy by resorting to slower films.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889881008583
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