**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.

**KEYWORDS: ** GAMMA-RAY; MOMENTS METHOD; INFINITE MEDIUM; ONE-DIMENSION