DECONVOLUTION OF ALPHA-PARTICLE SPECTRA TO OBTAIN PLUTONIUM ISOTOPIC-RATIOS

Pulse-height spectra using high-resolution silicon detectors have been obtained for alpha-particles emitted from very thin Plutonium sources. The isotopic composition of the Plutonium in these sources was measured independently by mass spectrometry. In order to deconvolve the spectra in the energy region where peaks overlap as is the case for emissions from Pu-239 and Pu-240, we have computed the least-squared best fit using a "Simplex" minimisation procedure. The fitted peak shapes are obtained by deconvolving two exponentials with a Gaussian function. The activity ratios derived are in good agreement with those calculated from the mass-spectrometry data. The intensities and energies of separate peaks were also obtained and provided further evidence for the validity of the procedure. This verification of the software is an indication of its utility to alpha-particle spectrometry in general.