This program provides an accurate and reliable analysis of small-angle scattering data. Using an iterative approach it calculates the size distribution of scatterers of a specified form, with the maximum entropy, whose scattering pattern is consistent with the data. The consistency test is the ChiSquared statistic. A full description of the program’s methodology and of its rigorous validation can be found in [Culverwell, 1986] and [Potton, 1988a].
The MaxSas code is an interactive program, and users must be prepared to answer the questions that the program will ask. The questions are grouped into two major sections: input data selection and scattering model selection. The input data selection is by file name and Q-vector range. The scattering model selection is by form factor, diameter range, and number of histogram bins. It may be necessary to run this program several times, with slight changes in user-adjustable parameters, in order to obtain a satisfactory analysis.
The running of the program will be demonstrated by example, using synthetic scattering data calculated from a hypothetical bimodal particle size distribution (ref 3). This distribution consists of a narrow Gaussian peak centered at 80 Angstroms with a standard deviation of 20 A, together with a broader secondary Gaussian peak, half the size of the primary one, centered at 200 A with a width of 60 A. In order that they can become familiar with the questions that the program will ask them, prospective users are advised to run the program using this data set, reproducing verbatim the example responses quoted in this guide.