1. NAME AND TITLE

GAMX1: A Computer Code System for Evaluating Spectra Peak Areas.

2. CONTRIBUTOR

Atomic Energy Board, Pelindaba, Pretoria, Republic of South Africa, through the NEA Data Bank, Gif-sur-Yvette, France.

3. CODING LANGUAGE AND COMPUTER

Fortran; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

GAMX1 evaluates accurate peak areas of gamma-ray and X-ray spectra generated by Ge(Li) and Si(Li) spectrometers. It renders accurate estimates of peak heights, position of centroids, and the backgrounds in the vicinity of the photopeaks being analyzed. However, it is intended to analyze spectra containing isolated peaks of known energy only; no facilities for peak location, energy calibration, or the analysis of doublets are included.

5. METHOD OF SOLUTION

Photopeaks are analytically represented by a function composed of two Gaussians and an arc tangent superimposed upon a cubic polynomial background, thus ensuring the flexibility required for an authentic reproduction of X-ray and gamma-ray line shapes. This analytic peak function is applied to experimental spectra by virtue of the iterative Newton-Raphson non-linear least-squares fitting technique and the resulting set of equations is solved by pivotal condensation with back substitution. The empirical energy dependence of certain peak parameters is derived to enable the characteristics of the detection and measuring system to be quantified in terms of the energy dependence of the detector response before general spectra are analyzed. The quality of the fit to the photopeaks allows the uncertainty in each parameter and in the peak area to be computed. The error computed for the area of each individual peak is typically of the order of twice the uncertainty to be expected purely from statistics.

6. RESTRICTIONS OR LIMITATIONS

Twelve previously analyzed GAMX1 peaks are employed in the present study, the energy of each photopeak (MeV) is 10F7.3, the parametric data pertaining to each photopeak is a set format, and the number of constants in each empirical equation is 411. The coefficients of the empirical parametric energy equations is a set format, the energy dependence of each parametric function in the sequence is 411, the number of peaks to be analyzed is 13, and a maximum of 200 data points exist for each spectrum.

7. TYPICAL RUNNING TIME

No study has been made by RSIC of typical running times for GAMX1.

8. COMPUTER HARDWARE REQUIREMENTS

GAMX1 is operable on the IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran compiler is required.

10. REFERENCE

J. White, "GAMX--A Computer Program for the Evaluation of Gamma-Ray and X-Ray Peak Areas from Spectra Generated by Semiconductor Detectors," PEL-255 (November 1976).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

November 1984.

KEYWORDS: GAMMA-RAY SPECTRUM ANALYSIS; DETECTOR RESPONSE