Half-life determination and comparison of activity standards of Pa.

The results of an international comparison of activity measurements of a solution of Pa are reported and analysed. Prior to this, no known standardisation of Pa by activity measurement had been carried out. The comparison was run in 2017-2018 involving eight laboratories, and returned results with no identifiable inconsistencies between methods or laboratories.

Alpha-particle emission probabilities of Pa derived from first semiconductor spectrometric measurements.

The nuclide Pa is a member of the U decay chain. It is a complex alpha emitter with 25 identified alpha emissions. Formerly published alpha-particle emission probabilities were derived from measurements taken with magnetic spectrometers.

Conversion electron spectroscopy of the 59.54 keV transition in Am alpha decay.

A windowless Peltier-cooled silicon drift detector (SDD) was used to measure internal conversion electron (ICE) spectra of thin Am sources. The ICE peaks associated with the 59.54 keV gamma transition in Np were deconvoluted and relative ICE intensities were derived from the fitted peak areas.

Automated optical distance measurements for counting at a defined solid angle.

Two optical distance measurement devices have been compared for accurately defining the source-detector geometry of alpha-particle counters. The first consists of a travelling microscope with unifocal lens, to which a linear distance gauge is attached. The focusing is done by human eye.

Measurement of absolute γ-ray emission probabilities in the decay of Ac in equilibrium with its progeny.

The emission probabilities of γ rays produced in the Ac decay series were determined by high-resolution γ-ray spectrometry of sources with standardised activity. The sources were prepared quantitatively on glass discs by drop deposition of a solution with Ac in radioactive equilibrium with its daughter nuclides. Their activity was measured by a primary standardisation technique based on alpha-particle counting at a defined low solid angle.