THE EGS5 CODE SYSTEM

PREFACE
In the nineteen years since EGS4 was released, it has been used in a wide variety of applications,
particularly in medical physics, radiation measurement studies, and industrial development. Every
new user and every new application bring new challenges for Monte Carlo code designers, and
code refinements and bug fixes eventually result in a code that becomes difficult to maintain.
Several of the code modifications represented significant advances in electron and photon transport
physics, and required a more substantial invocation than code patching. Moreover, the arcane
MORTRAN3[48] computer language of EGS4, was highest on the complaint list of the users of
EGS4. The size of the EGS4 user base is difficult to measure, as there never existed a formal user
registration process. However, some idea of the numbers may be gleaned from the number of EGS4
manuals that were produced and distributed at SLAC: almost three thousand. Consequently, the
EGS5 project was undertaken. It was decided to employ the FORTRAN 77 compiler, yet include
as much as possible, the structural beauty and power of MORTRAN3.
We wish to acknowledge Patrick Lui (Technology Transfer Office at SLAC) for administrating
the business end of this project and securing sufficient funds to enable its completion. We wish to
acknowledge Dr. Ray Cowan (MIT/SLAC BaBar) for converting the SLAC-265 document, written
in TEX/Psizzl to L A TEX. SLAC 265 served as the foundation upon which this document is built.
Finally, we wish to acknowledge Prof. David W. O. Rogers, co-author of EGS4, for his many
years of EGS4 development and Monte Carlo leadership. We also wish to thank Dr. James Liu
(SLAC Radiation Physics Group) for helping to create and run the suite of benchmarking codes
for EGS5. Dr. Francesc Salvat’s assistance in developing the sampling methods for the multiple
elastic scattering distributions is most gratefully acknowledged.
This report consists of four chapters and several appendices. Chapter 1 is an introduction to
EGS5 and to this report in general. We suggest that you read it. Chapter 2 is a major update of
similar chapters in the old EGS4 report[126] (SLAC-265) and the old EGS3 report[61] (SLAC-210),
in which all the details of the old physics (i.e., models which were carried over from EGS4) and
the new physics are gathered together. The descriptions of the new physics are extensive, and not
for the faint of heart! Detailed knowledge of the contents of Chapter 2 is not essential in order
to use EGS, but sophisticated users should be aware of its contents. In particular, details of the
restrictions on the range of applicability of EGS are dispersed throughout the chapter. First-time
users of EGS should skip Chapter 2 and come back to it later if necessary.
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