High precision half-life measurement of the extinct radio-lanthanide Dysprosium-154

Abstract

Sixty years after the discovery of 154Dy, the half-life of this pure alpha-emitter was re-measured. 154Dy was radiochemically separated from proton-irradiated tantalum samples. Sector field- and multicollector-inductively coupled plasma mass spectrometry were used to determine the amount of 154Dy retrieved. The disintegration rate of the radio-lanthanide was measured by means of α-spectrometry. The half-life value was determined as (1.40 ± 0.08)∙106 y, with an uncertainty reduced by a factor of ~ 10 compared to the currently adopted value of (3.0 ± 1.5)∙106 y. This precise half-life value is useful for the the correct testing and evaluation of p-process nucleosynthetic models using 154Dy as a seed nucleus or as a reaction product, as well as for the safe disposal of irradiated target material from accelerator driven facilities. As a first application of the half-life value determined in this work, the excitation functions for the production of 154Dy in proton-irradiated Ta, Pb, and W targets were re-evaluated, which are now in agreement with theoretical calculations.

Determination of the Half-Life of Gadolinium-148

“…Considering the decay of the 153 Gd tracer between the two activity measurements (before deposition and the measurement after deposition, i.e., 210 days), a (3.18 ± 0.13)% plating yield was obtained. The uncertainty on the plating yield includes the 1.42% uncertainty on the geometry correction factor deduced in (Chiera et al, 2022) which allows a direct comparison of the count rate of the 153 Gd in solution and the count rate of the 153 Gd deposited on the graphite foil, as well as takes into account the 0.42% uncertainty on the half-life of the 153 Gd tracer (Nica, 2020). The amount of 148 Gd plated on the graphite foil corresponds hence to (3.778 ± 0.038) × 10 12 atoms.…”

“…For a reliable comparison of the activity of the 153 Gd contained in the Gd aliquot and the activity of the 153 Gd deposited in the thin Gd layer, both γ-ray measurements were performed in equal geometries by using the very same custom-made holder (see Fig. 1), following the method described in (Chiera et al, 2022). The γ-ray measurement of the 153 Gd contained in the aliquot before deposition (namely, "Measurement A") was performed for 28800 s. Successively, the plating solution was prepared.…”