1. NAME AND TITLE

GAMMOM-I: Gamma-Ray Moments Method Code System.

AUXILIARY ROUTINES

NPOINT: Data Fitter.

NSLANT: Data Fitter.

GAMMOM-I is a descendant of the GRMM portion of CCC-135/GAMMOM.

2. CONTRIBUTOR

Center for Radiation Research, National Bureau of Standards, Washington, D. C.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; UNIVAC 1108 (A) and IBM 360/370 (B).

4. NATURE OF PROBLEM SOLVED

GAMMOM-I calculates the moments of the energy fluence from a plane source of gamma rays in an infinite medium.

5. METHOD OF SOLUTION

Each moments equation is an integral equation involving the function Ephi_nl(E) of energy for a particular spatial index n and angular index 1. The equation is solved by numerical procedures. The source term is completely specified for n = 0; for n not equal to 0, it may be regarded as known if the equations are solved in an appropriate succession of increasing n. Gaussian integration is used over part of the scattering integral term.

The auxiliary routines fit moments for point, plane isotropic, and plane slant sources. GAMMOM-I is concerned only with the calculation of moments. The SPENCER portion of CCC-135/GAMMOM may be used for constructing functions from the moments. However, some manipulation of the output from GAMMOM-I is necessary before using it as input to SPENCER. The auxiliary routines NPOINT and NSLANT are designed to be compatible with the output from GAMMOM-I.

6. RESTRICTIONS OR LIMITATIONS

For routine use on the UNIVAC 1108 (55 K words available storage) the number of energies for which moments are calculated is limited to 200 and the number of (n,l) combinations is limited to 121.

7. TYPICAL RUNNING TIME

On the UNIVAC 1108, the running time for a single source energy, 150 solution energies and 78 (n,l) combinations is about 2 minutes. The running time is roughly proportional to the number of solution energies. It is approximately proportional to the maximum number LS of Legendre coefficients of the cross section required for the calculation.

The sample problem executed on the IBM 360/91 computer in 2 minutes.

8. COMPUTER HARDWARE REQUIREMENTS

GAMMOM-I is operable on the UNIVAC 1108 (A) or IBM 360/370 (B) computers. At least 3 additional storage devices are required.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required. The overlay feature is required for the UNIVAC version only.

10. REFERENCE

C. M. Eisenhauer, G. L. Simmons, and L. V. Spencer, "A Gamma Ray Moments Computer Code, GAMMOM-I," NBS Technical Note 766 (April 1973).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

November 1973; updated July 1975.