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The use of film methods in small‐angle X‐ray scattering
Author(s) -
Vonk C. G.,
Pijpers A. P.
Publication year - 1981
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889881008583
Subject(s) - x ray , scattering , saturation (graph theory) , range (aeronautics) , optics , position (finance) , materials science , standard deviation , flux (metallurgy) , photon , computational physics , physics , mathematics , statistics , finance , combinatorics , economics , composite material , metallurgy
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.