1. NAME AND TITLE

HYPERMET: Gamma-Ray Spectra Analyzer Germanium Detector

2. CONTRIBUTOR

Naval Research Laboratory, Washington, D. C.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; CDC 3800 (A), T. I. ASC-7 IBM COMPATIBLE (B), FACOM M190 (C).

4. NATURE OF PROBLEM SOLVED

HYPERMET performs an automatic analysis of a multichannel gamma-ray pulse-height spectrum taken with a germanium detector. It has a number of options including an energy calibration, correction for radioactive decay, and a CALCOMP plot of each fit.

5. METHOD OF SOLUTION

A peak search is done by using a zero-area sliding transform on the data. A peak is indicated by a rise above a preset threshold. A fitting subregion is then defined about the peak and initial values are determined for the parameters of a semi-empirical peak-shape function plus background. Within this subregion, initial estimates are made for the parameters such as background level.

An iterative non-linear least-squares fit is done for the optimum values of the parameters. If programmed criteria for a good fit are not satisfied, the residuals (data minus fit) are searched for indication of an additional peak in the data. If found, the fit is repeated with the additional peak included.

6. RESTRICTIONS OR LIMITATIONS

HYPERMET is dimensioned for up to 8192 channel spectra with up to 100 peaks per spectrum.

7. TYPICAL RUNNING TIME

Running time varies linearly with peak width and quadratically with the number of multiplet peaks which must be fit simultaneously. Spectra with poor statistics are fit more rapidly than those with good statistics for which the statistical criteria for a good fit are more stringent.

For a typical spectrum with peak widths from 3 to 5 channels FWHM, moderate statistics, and mostly well separated peaks, running time on the CDC 3800 computer is on the order of one minute for every ten peaks in the spectrum.

8. COMPUTER HARDWARE REQUIREMENTS

HYPERMET is operable on the CDC 3800 (A), T. I. ASC-7 (B), or the FACOM M190 computers. Except for a few system input-output routines, it will fit into one 32 K word bank on a CDC 3800 computer.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCES

G. W. Phillips, "Guide to Program HYPERMET Version 2.7," (August 1976).

G. W. Phillips and K. W. Marlow, "Program HYPERMET for Automatic Analysis of Gamma-Ray Spectra from Germanium Detectors," NRL-MR-3198 (January 1976).

G. W. Phillips, "Guide to Program HYPERMET Version A.1," (February 1977).

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.