The History of EGS
The "seed" for the EGS computer program was brought to SLAC around 1965 by Hans-Hellmut Nagel of Bonn University. Nagel's program was useful in designing elements of accelerator machinery (such as beam stoppers, collimators, and targets) during construction of the two-mile accelerator and beam lines at SLAC. However, Nagel's code proved to be too specific to solve many problems still facing the high-energy physics community.
Two physicists took on the task of redesigning the code from the bottom up to achieve the necessary generalization. Working independently at first, W. Ralph Nelson at SLAC, and later Richard Ford at the Hanson High Energy Physics Laboratory on the Stanford University campus, decided to combine their programming efforts and produced the first version of EGS in 1978.
The Electron Gamma Shower (EGS) Code
System (or EGS3, as it was known at that time) was designed
to simulate the flow of electrons and photons through matter
at energies ranging from just below an MeV to several thousand
GeV. EGS uses a statistical game-playing approach to solve the
difficult mathematical problem posed by electron transport through
matter. The program uses Monte Carlo (game-playing) methods
to simulate the statistical outcome of each interaction. All
possible outcomes of an interaction are identified and assigned
to an imaginary roulette wheel and the wheel is weighted to
reflect predicted outcomes of an interaction. The wheel is spun
and particles are created and transported in a random-walk process.
This version of EGS proved valuable in detector design, radiation shielding analysis, determining accelerator component temperature rises, and other accelerator problems. EGS, which was well documented, user-friendly, versatile, upwardly-compatible and supported by technical experts, was licensed free of charge to the scientific community. The program soon became very popular and a large user community developed.
