RSIC COMPUTER CODE PSR-095

1. NAME AND TITLE

GAMMA: Monte Carlo Code System for Calculating Efficiencies and Response Functions of NaI(Tl) Crystals for Gamma Rays from Thick Disk Sources.

2. CONTRIBUTOR

Istituto Nazionale de Fisica Nucleare, Sezione di Bari, Bari, Italy.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

GAMMA evaluates the efficiencies and the response functions of NaI(Tl) crystals for gamma rays from thick disk sources. It considers the effective contribution of the secondary electrons with their possible bremsstrahlung radiation; the secondary electrons are followed in the source and in the detector.

5. METHOD OF SOLUTION

The calculation is performed using Monte Carlo methods. A primary photon is followed both in the source and in the detector. The electrons produced in photoelectric, Compton, and pair-production events are also followed with their possible bremsstrahlung or annihilation radiation, and the electron energy deposit in the detector is stored. In order to save computation time, the path of the electrons is assumed to be straight. A more realistic and costly simulation of the electron path gives improvements masked by statistic uncertainties with the commonly used gamma ray energies and detector dimensions. This becomes necessary for secondary electron ranges which are much greater than the source and detector dimensions.

6. RESTRICTIONS OR LIMITATIONS

Reliable results are obtained even for high energy gamma rays, provided the dimensions of the source and/or the detector are not too much smaller than the range of the secondary electron within.

7. TYPICAL RUNNING TIME

No study has been made by RSIC of typical running times for GAMMA.

8. COMPUTER HARDWARE REQUIREMENTS

GAMMA is operable on the IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCES

"GAMMA Code Input-Output Instructions," Informal Note.

M. Belluscio, R. de Leo, A. Pantaleo and A. Vox, "Efficiencies and Response Functions of NaI(Tl) Crystals for Gamma Rays from Thick Disk Sources," Nucl. Instr. Meth. 118 (1974) 553-563.

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

March 1984.