High-resolution alpha-particle spectrometry of 238U

The alpha-particle emission probabilities associated with the three main alpha transitions of 238U were measured by high-resolution alpha-particle spectrometry. Highly enriched 238U material was used and its isotopic composition characterised by mass spectrometry. Source production through electrodeposition was optimised to reconcile conflicting demands for good spectral resolution and statistical precision. Measurements were performed at IRMM and CIEMAT for 1–2 years in three different set-ups. A new magnet system was put into use to largely eliminate true coincidence effects with low-energy conversion electrons. Finally the accuracy and precision of the relative emission probabilities for the three transitions – 77.01 (10)%, 22.92 (10)% and 0.068 (10)%, respectively – have been improved significantly. •Measured alpha-particle emission probabilities in the decay of 238U.•Used high-resolution alpha-particle spectrometry on electrodeposited sources.•Improved accuracy and precision significantly.•Results are Pα,0=77.01 (10)%, Pα,1=22.92 (10)% and Pα,2=0.068 (10)%.