High precision measurements ofNa26β−decay

Abstract

High-precision measurements of the half-life and β-branching ratios for the β − decay of 26 Na to 26 Mg have been measured in β-counting and γ -decay experiments, respectively. A 4π proportional counter and fast tape transport system were employed for the half-life measurement, whereas the γ rays emitted by the daughter nucleus 26 Mg were detected with the 8π γ-ray spectrometer, both located at TRIUMF's isotope separator and accelerator radioactive beam facility. The half-life of 26 Na was determined to be T 1/2 = 1.07128 ± 0.00013 ± 0.00021 s, where the first error is statistical and the second systematic. The logf t values derived from these experiments are compared with theoretical values from a full sd-shell model calculation.

High-precision branching-ratio measurement for the superallowedβ+emitter26Alm

“…Full list-mode event data, including energies and times relative to the start of the cycle, were recorded during the first 6.4 s and the last 44 s of each cycle, but these were vetoed between cycle times of 6.4 and 30 s when the activity was dominated by the short-lived 26 Na (T 1 2 = 1.07128 s [15]) contaminant. For the list-mode data, triggers were generated by γ singles, γ γ coincidences, βγ coincidences, and scaleddown β singles (with a scale down factor of 100) events.…”

“…3). Both curves were fit using a maximum-likelihood routine [15,20] [15]) were fixed to their previously measured values, while the activities of both species, as well as the constant background activity, were free parameters. The resulting fit to the SCEPTAR β data is shown in Fig.…”

“…For completeness, experimental limits were placed on all possible decay paths open to 26 Al m by fitting the expected locations of γ rays that would be emitted following 26 Al m nonsuperallowed decay. In each case the peak shape parameters and centroid were constrained to the values determined from the fits to the large number of γ rays from 26 Na decay [15] in the full projection of the matrix, with only the background shape and peak area left free when fitting the time-gated γ -ray spectra. This analysis is complicated for the 1780-keV transition that would arise from EC decay to the 0 + 1 state of 26 Mg, due to the presence of a background γ ray at 1779 keV [see Fig.…”

Precision half-life measurement of Al25

“…A thin carbon foil at the center of the tandem high voltage terminal broke up the molecules while stripping multiple electrons from the Mg beam. A mass analyzing magnet downstream of the tandem was used to select only 24 Mg 8+ ions, which were then sent to the RIB production target.…”

“…The weighted average of all these values yields a half-life of 7.1651(23) s, with a Birge ratio [12,24] of 0.88. Since this Birge ratio is close to one it implies that the fluctuations in the data set are statistical in nature.…”