Cross-section Data File

This file is required by the EGS4 subroutines, and contains most of the physics of the simulation. The cross-section data is created by program PEGS4, the EGS4 preprocessor. PEGS4 has to be run once for each material type in an EGS4 simulation. The material can be an element, compound or mixture. The resulting data file is an ascii text file that an EGS4 subroutine will parse and store as cross-section data. One normally pre-calculates a number of materials and combine the individual cross-section files into a larger file. A file with several material types that have been used at APS is provided in the distribution.

Program shower looks for this file in the environment variable EGS4_CROSSSECTION. If EGS4_CROSSSECTION is undefined, the program looks for the file fort.12 in the current directory. (The name fort.12 comes from the conventional implementation of EGS4.)