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Features

• Quantify peak energy and net area for asymmetric peaks commonly found in alpha spectroscopy
• Multiplet deconvolution using spectrum stripping technique
• Alpha-specific FWHM and efficiency calibration and calculation
• Performs recalibration using a tracer on a per sample basis to account for variability during sample preparation
• The peak search is best suited for locating and quantifying peaks significantly larger than normal background

Description

The Alpha Spectroscopy Software provides the ability to process alpha spectra collected using ion-implanted PIPS or other charged particle detectors. It includes specialized processing algorithms primarily designed for handling multiplets, and for compensation of low-energy tail functions primarily due to self absorption within the samples.

The primary functions included with this package are:

PEAK SEARCH	An alpha-specific peak search program designed to identify peaks without prior knowledge of the isotopes present.
CALIBRATION	FWHM and efficiency algorithms specific to alpha analysis.
PROCESSING	Support of tracer methodology by providing FWHM and geometry/chemistry efficiency computation on an individual sample basis.

PEAK SHAPE AND EFFICIENCY DETERMINATION

Alpha spectral analysis presents a problem not found in gamma spectroscopy. There is no prior knowledge of the full-width half-maximum (FWHM) behavior of the peaks because the FWHM of an alpha peak is dependent on the reproducibility of the sample mounting technique. Information can only be obtained from the spectrum itself (i.e. tracer), due to the unavoidable differences between materials and the self-absorption of alpha particles by the sample.

Information about the tracer isotope is entered into a certificate file. Once defined, the software can be set up to compute not only the constant FWHM for the spectra, but also the overall efficiency (geometry plus chemical yield). Once computed, the activity computation process (optional) can then accurately compute isotope specific activity.

The software can analyze samples whether a tracer is introduced in the sample or not. In the case of no tracer, the software relies upon previous FWHM and efficiency calibrations derived from standard samples and the laboratory must ensure that the sample mounting technique guarantees consistent peak shapes.

PEAK PROCESSING

The Alpha Peak Search Program locates and determines the area of peaks within the spectrum. Since alpha spectra often have asymmetric peak shapes which are difficult to fit with empirical line-forms, the peak search program employs a spectrum stripping method to determine peak areas. The program first smooths the data to reduce the number of spurious peaks found in the spectrum, then searches the spectrum for maxima using a correlator function. Once the peak maxima and peak valleys (points D and B in the adjacent figure) are located, the tail for the highest energy peak is determined (points C to D and E to F) and the peak is stripped from the spectrum. This process of stripping peaks from the spectrum is repeated until all peaks are analyzed. As each peak is analyzed, relevant quantities, area, centroid, FWHM, etc. are calculated. The peak search report lists the area, centroid, FWHM, energy and counts per second for each alpha peak.

Tail Construction with Three Overlapping Peaks

ACTIVITY CALCULATIONS

Isotope identification, activity calculation and related reporting is provided through Model 480201 Nuclide Identification Software.