A magnet system for the suppression of conversion electrons in alpha spectrometry

Abstract

A new magnet system has been designed and constructed to reduce coincidence effects between alpha particles and conversion electrons in high-resolution alpha-particle spectrometry. By means of a magnetic field, the conversion electrons are deflected away from the PIPS detector. Compared to existing magnet systems, the new system is not restricted to point sources and can accommodate source diameters up to about 30mm. Two yokes were built, allowing for configurations with 20mm or 36mm distance between the magnets. The effectiveness of both configurations is demonstrated by measuring the conversion electron spectrum of a 237Np source.The magnet system effectively rejects 93 (7)% of electrons up to 85keV (36mm) and 90 (9)% of electrons up to 320keV (20mm). It has been successfully applied in the alpha-particle spectrometry of the long-lived nuclides 236U and 238U, resulting in significant improvement of the accuracy of alpha emission probabilities.