PHOTOPEAK METHOD FOR COMPUTER ANALYSIS OF GAMMA-RAY SPECTRA FROM SEMICONDUCTOR DETECTORS

A method is presented for computer analysis of γ-ray spectra from semiconductor detector systems. We describe a mathematical formalism for the representation of photopeaks and the continua in their vicinity which is applicable to analysis of spectra measured under widely varying conditions. With this formalism the line shape is defined for each peak in the spectrum. The region of data about a single peak or multiple peaks is then fitted with the shape functions and a function representing the background continuum. The line-shape calculations and the fitting are performed by using a least-squares procedure with an iterative gradient minimization method with variable metric. For an automatic analysis an algorithm is developed to search the raw data for statistically significant peaks. The method has been incorporated into a general-purpose Fortran computer program. In addition to searching and fitting single and multiple peaks, the code performs the energy, efficiency, and line-shape calibrations and makes complete statistical and calibration-error estimates. For establishing the goodness of fit for each peak the output also includes numerical and graphical representation of the fit. Optionally, an on-line cathode-ray- tube display system may be used to assure the completeness of the results even with very complex spectra. The code has been used with a variety of spectra from Ge(Li) detectors of varying resolution and active volume. The performance is evaluated with test cases and by comparing the results of complete computer and careful hand analysis of 177mLu and 72As spectra. Applications to spectroscopic measurements and routine data analysis are discussed. © 1969.