**RSIC COMPUTER CODE PSR-086**

**1. NAME AND TITLE**

GAMLEG-75: Multigroup Cross Section Generator for Photon Transport Calculations.

**2. CONTRIBUTORS**

Los Alamos National Laboratory, Los Alamos, New Mexico.

Imperial College of London, London, England.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; CDC-7600 (GAMLEG), CDC-6400 (SUMMAT).

**4. NATURE OF PROBLEM SOLVED**

GAMLEG is a numerical code system designed to produce multigroup photon cross sections. It
prepares group averages of Legendre moments of the Klein-Nishina differential scattering cross section
for scattering transfers from energy E' to energy E. It also accepts the following as input: absorption,
coherent scattering, source, and flux data and provides group averages of this data. Isotropic coherent
scattering can be included in scattering cross section averages.

**5. METHOD OF SOLUTION**

GAMLEG-75 begins by reading input control integers describing the number of group energy
bounds, the number of integration points per group, the number of Legendre transfer moments to be
prepared, and an integer describing what type of weighting function is to be used. Cross sections may
be weighted with an input flux distribution or with a source energy distribution, or cross sections may
be formed without a weighting function. If an input flux is used as a weighting function, the energies
(in Mev) at which it is specified are read and then the values of the flux are read. Next, a source
energy distribution is read, first the energies (Mev) at which the source is specified and then the values
of the source distribution. Values of the group energy (Mev) bounds are then read. After printing the
input thus far read, GAMLEG-75 prepares integers needed in the calculation and translates energies
to electron rest mass units. Thus, all integrations are computed over intervals expressed in terms of
electron rest mass units.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for GAMLEG-75.

**8. COMPUTER HARDWARE REQUIREMENTS**

GAMLEG-75 is operable on the CDC-7600 computer but can be easily changed to the CDC-6600
computer by replacing the unit definition of the program card with those of the CDC-6600.
SUMMAT, which handles GAMLEG-produced cross sections, is operable on the CDC-6400 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCES**

K. D. Lathrop, "Computer Code Abstract," *Nucl. Sci. Eng.* 24 (1966) 218.

K. D. Lathrop, "GAMLEG -- A Fortran Code to Produce Multigroup Cross Sections for Photon Transport Calculations," LA-3267 (April 1965).

D. Lindstrom, "Description of Code Contents," Informal Note (September 1974).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source
code, sample problem and output, and library data input.

**12. DATE OF ABSTRACT**

March 1984.

**KEYWORDS: ** ANISN/DOT INPUT or DATA GENERATOR; GAMMA-RAY CROSS
SECTION PROCESSING; MULTIGROUP CROSS SECTION PROCESSING