Conversion of the measured intensity into a scattering cross-section

4 Conversion of the measured intensity into a scattering cross-section 

The experimental set up of a scattering experiment includes collimation devices for angles and wave lengths. These collimations depend on a choice made by the experimentalist who must try to reconcile contradictory requirements of resolution and luminosity. 

Thus to each set up corresponds a constant KA whose approximate expression is 

to convert the measured quantity I q) into a cross-section, one performs the operation 

In general, it is impossible to calculate KA directly by starting from the elements of an experimental set-up. In practice, this constant is determined by calibration. A reference sample with a known cross-section is placed in the experimental apparatus. A measurement of the scattered intensity /, gives the value of the constant 

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