Resolution of Alpha-Particle Spectra by Ionization Pulse Analysis of Collimated Samples

Abstract

A high‐resolution ion pulse analyzer has been developed for the study of alpha‐decay fine structure. Alpha‐particle spectra are distorted in conventional high geometry measurements by addition of ionization from excited‐state radiations of the daughter atom. Covering the sample foil with electroformed nickel mesh of a few mils thickness proved to be an effective technique for collimating the alpha particles and absorbing coincident excited‐state radiations. The resolution of the instrument was tested with samples of Bi²¹², Th²³⁰, and Pu²³⁸. The measured intensities and particle energies are in satisfactory agreement with magnetic deflection data. Alpha peak standard deviations of 12–13 kev were obtained at a detection efficiency of 0.04 count per disintegration. The standard deviation due to amplifier noise alone amounted to 10 kev.