Experimental techniques in alpha-particle spectrometry and alpha-gamma coincidence measurements. Application to the study of 242Pu and 243Am

Abstract

Actinides and their natural decay products play a major role in several fields such as the nuclear fuel cycle of fission reactor systems, nuclear medicine, quality control, environmental monitoring, nuclear forensics and safeguards. Extensive measurement and evaluation programmes have been undertaken over the past fifty years to address the need for accurate actinide decay data and recommendations have been issued for a re-evaluation of the actinide data such as a-particle and ?-ray energies and emission probabilities of selected nuclides. In this work, efforts have focused on the improvement of some techniques useful to the study of alpha-particle emitting nuclides. Three main aspects have been considered: alpha-particle spectrometry, alpha-gamma coincidence measurements and numerical analysis of spectroscopic data. Two spectrometric devices based on ion-implanted Si detectors have been used at the University of Extremadura and CIEMAT with the aim of obtaining high-quality alpha-particle spectra suited for accurate spectral analysis. An alpha-gamma coincidence chamber with semiconductor detectors in both channels was also designed and characterized at the University of Extremadura. To improve data treatment and analysis, a new code to fit alpha-particle spectra, called ALFITeX, and a decoding and analysis code, DIGDATA, were developed in this work. The experimental set-ups and the analysis tools developed in this work have been applied to obtain a new set of a -particle emission probabilities of 242Pu by alpha-particle spectrometry, and to study the decay scheme of 243Am, in particular with the determination of several ?-ray emission probabilities from this nuclide using advanced alpha-gamma coincidence measurements.