Conversion electron spectrometry of Pu isotopes with a silicon drift detector

An electron spectrometry set-up was built at IRMM consisting of a vacuum chamber with a moveable source holder and windowless Peltier-cooled silicon drift detector (SDD). The SDD is well suited for measuring low-energy x rays and electrons emitted from thin radioactive sources with low self-absorption. The attainable energy resolution is better than 0.5 keV for electrons of 30 keV. It has been used to measure the conversion electron spectra of three plutonium isotopes, i.e. ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, as well as ²⁴¹Am (being a decay product of ²⁴¹Pu). The obtained mixed x-ray and electron spectra are compared with spectra obtained with a close-geometry set-up using another SDD in STUK and spectra measured with a Si(Li) detector at IRMM. The potential of conversion electron spectrometry for isotopic analysis of mixed plutonium samples is investigated. With respect to the ²⁴⁰Pu/²³⁹Pu isotopic ratio, the conversion electron peaks of both isotopes are more clearly separated than their largely overlapping peaks in alpha spectra. - Highlights: • Built set-up for conversion electron spectrometry with silicon drift detector. • Conversion electron spectra measured from ^238,239,240Pu and ²⁴¹Am. • Compared with other SDD set-up and Si(Li) detector.