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Nuclear decay data measurements were performed in the frame of a EURAMET project. Two specific goals were addressed: (1) High-precision measurements of ^238U alpha-particle emission probabilities and (2) experimental characterization of the shape of beta spectra using cryogenic detectors. In the paper, specific lessons learned from the metrological work are highlighted. This includes effects of source preparation on the quality of alpha and beta spectrometry, the influence of exchange effects on beta spectra and the use of a magnet system to eliminate coincidence effects by conversion electrons in alpha-particle spectra. [ABSTRACT FROM PUBLISHER]

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. [Copyright &y& Elsevier]

Abstract: High-resolution alpha-particle spectrometry was performed on the 230U decay series. A 230U source was prepared on a stainless steel disc by electrodeposition in an ammonium nitrate solution. Spectrometry of the alpha-particle energy spectrum was performed with ion-implanted planar silicon detectors in vacuum. A set of alpha emission probabilities is presented for 230U and 226Th. The measured peak intensities were corrected mathematically for coincidental detection of alpha-particles and conversion electrons emitted in the same decay. A good agreement with literature data was observed. The uncertainty budget and the correlation matrix are presented. The validity of the alpha-particle energies was tested and could be confirmed for most peaks within a few keV, but discrepancies were found for the 2nd peak of 226Th and the main peak of 218Rn. [Copyright &y& Elsevier]

Abstract: High-resolution alpha-particle spectrometry was performed with an ion-implanted silicon detector in vacuum on a homogeneously electrodeposited 236U source. The source was measured at different solid angles subtended by the detector, varying between 0.8% and 2.4% of 4π sr, to assess the influence of coincidental detection of alpha-particles and conversion electrons on the measured alpha-particle emission probabilities. Additional measurements were performed using a bending magnet to eliminate conversion electrons, the results of which coincide with normal measurements extrapolated to an infinitely small solid angle. The measured alpha emission probabilities for the three main peaks – 74.20 (5)%, 25.68 (5)% and 0.123 (5)%, respectively – are consistent with literature data, but their precision has been improved by at least one order of magnitude in this work. [Copyright &y& Elsevier]

Abstract: In this work, 213Bi has been separated from an open 225Ac source by collecting recoil atoms onto a glass plate in vacuum. The activity of such recoil sources has been measured as a function of time, using an ion-implanted planar Si detector in quasi-2π geometry. From these measurements, a new half-life value of T 1/2(213Bi)=45.62 (6)min was derived. Additionally, high-resolution alpha-spectrometry measurements were performed at a solid angle of 0.4% of 4πsr, to verify the energies and emission probabilities of the α-emissions from 213Bi. Using 225Ac, 221Fr, 217At and 213Po peaks as reference peaks, the measured 213Bi α-peak energies at E α,0=5878 (4)keV and E α,1=5560 (4)keV were about 10keV higher than validated data. The relative α-particle emission probabilities of 213Bi, P α,0=0.9155 (11) and P α,1=0.0845 (11), and the 213Bi alpha branching factor, P α=1−P β=2.140 (10)%, are compatible with recommended values, but have a higher accuracy. [Copyright &y& Elsevier]