High-precision Half-life Measurement Research Articles

High-precision measurements of half‐lives for 69Ge, 73Se, 83Sr, 85mSr, and 63Zn radionuclides relevant to the astrophysical p-process via photoactivation at the Madison Accelerator Laboratory

The ground state half-lives of 69Ge, 73Se, 83Sr, 63Zn, and the half-life of the 1/2− isomer in 85Sr have been measured with high precision using the photoactivation technique at an unconventional bremsstrahlung facility that features a repurposed medical electron linear accelerator. The γ-ray activity was counted over about 6 half-lives with a high-purity germanium detector, enclosed into an ultra low-background lead shield. The measured half-lives are: T1/2(69Ge) = 38.82 ± 0.07 (stat) ± 0.06 (sys) h; T1/2(73Se) = 7.18 ± 0.02 (stat) ± 0.004 (sys) h; T1/2(83Sr) = 31.87 ± 1.16 (stat) ± 0.42 (sys) h; T1/2(85mSr) = 68.24 ± 0.84 (stat) ± 0.11 (sys) min; T1/2(63Zn) = 38.71 ± 0.25 (stat) ± 0.10 (sys) min. These high-precision half-life measurements will contribute to a more accurate determination of corresponding ground-state photoneutron reaction rates, which are part of a broader effort of constraining statistical nuclear models needed to calculate stellar nuclear reaction rates relevant for the astrophysical p-process nucleosynthesis.

High-precision half-life measurement of 123Xe and 125Xe for fuel areal density diagnosing in inertial confinement fusion

The half-lives of 123Xe and 125Xe are important to diagnose deuterium-tritium (DT) fuel areal density in inertial confinement fusion (ICF). In this work, those two half-lives have been measured with HPGe γ-ray spectrometers using the reference source method. Data have been recorded over seven half-lives with three independent measurements for 123Xe and two for 125Xe. New values of 123Xe (2.040 ± 0.009) h and 125Xe (17.048 ± 0.032) h have been determined with significant reduction of the uncertainty compared to the currently recommended value of (2.08 ± 0.02) and (16.9 ± 0.2) h, respectively.

High precision half-life measurement of 125Cs and 125Xe with γ-spectroscopy

In order to provide data for the simulation of the astrophysical γ-process, the cross section measurement of the 124Xe(p,γ)125Cs reaction is in progress at MTA Atomki using the activation technique. Precise information on the decay characteristics of the reaction products is of crucial importance for measurements carried out using this method. The half-lives of the produced 125Cs and its daughter 125Xe are published in previous works, but with large uncertainties and ambiguous values. To make these nuclear parameters more precise, the half-lives have been re-measured with high precision using γ-spectroscopy. The obtained new half-life values are t1/2 = 44.35 ± 0.29 minutes for 125Cs and t1/2 = 16.87 ± 0.08 hours for 125Xe.

Resolving the discrepancy in the half-life of F20

We report a new precision half-life measurement of $^{20}\mathrm{F}$, performed using the $\ensuremath{\beta}$-counting station of the University of Notre Dame's Nuclear Science Laboratory. The measured half-life of $11.0160{(41)}_{\text{stat}}{(155)}_{\text{sys}}$ s resulting from this work will help resolve the longstanding discrepancy between two earlier sets of high-precision half-life measurements.

High-precision half-life measurement of the β+ decay of Na21

The ${\ensuremath{\beta}}^{+}$ decay of $^{21}\mathrm{Na}$ to $^{21}\mathrm{Ne}$ is one of the four cases currently being used to determine the value of ${V}_{\mathrm{ud}}$ from nuclear mirror ($T=1/2$) transitions. To date, published values for the half-life of $^{21}\mathrm{Na}$ have not been consistent with one another. We report here a new measurement of the half-life: $22.4615\ifmmode\pm\else\textpm\fi{}{0.0039}_{(\mathrm{stat})}\ifmmode\pm\else\textpm\fi{}{{}_{0.0015}^{0.0001}}_{(\mathrm{syst})}s$. This result increases the world average of the $^{21}\mathrm{Na}$ half-life by 0.0048 s and reduces the uncertainty by a factor of 1.5.

High-precision half-life measurement for the superallowed Fermi β+ emitter Mg22

A high-precision half-life measurement for the superallowed Fermi $\beta^+$ emitter $^{22}$Mg was performed at the TRIUMF-ISAC facility using a 4$\pi$ proportional gas counter. The result of $T_{1/2} = 3.87400 \pm 0.00079$ s is a factor of 3 more precise than the previously adopted world average and resolves a discrepancy between the two previously published $^{22}$Mg half-life measurements.

High-precision half-life determination for Na21 using a 4π gas-proportional counter

A high-precision half-life measurement for the superallowed ${\ensuremath{\beta}}^{+}$ transition between the isospin $T=1/2$ mirror nuclei $^{21}\mathrm{Na}$ and $^{21}\mathrm{Ne}$ has been performed at the TRIUMF-ISAC radioactive ion beam facility yielding ${T}_{1/2}=22.4506(33)$ s, a result that is a factor of 4 more precise than the previous world-average half-life for $^{21}\mathrm{Na}$ and represents the single most precisely determined half-life for a transition between mirror nuclei to date. The contribution to the uncertainty in the $^{21}\mathrm{Na} \mathcal{F}{t}^{\mathrm{mirror}}$ value due to the half-life is now reduced to the level of the nuclear-structure-dependent theoretical corrections, leaving the branching ratio as the dominant experimental uncertainty.

The GRIFFIN data acquisition system

Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new experimental facility for radioactive decay studies at the TRIUMF-ISAC laboratory. This article describes the details of the custom designed GRIFFIN digital data acquisition system. The features of the system that will enable high-precision half-life and branching ratio measurements with levels of uncertainty better than 0.05% are described. The system has demonstrated the ability to effectively collect signals from High-purity germanium crystals at counting rates up to 50kHz while maintaining good energy resolution, detection efficiency and spectral quality.

High-Precision Half-Life Measurements for the Superallowed β^{+} Emitter ^{10}C: Implications for Weak Scalar Currents.

Precision measurements of superallowed Fermi β-decay transitions, particularly for the lightest superallowed emitters ^{10}C and ^{14}O, set stringent limits on possible scalar current contributions to the weak interaction. In the present work, a discrepancy between recent measurements of the ^{10}C half-life is addressed through two high-precision half-life measurements, via γ-ray photopeak and β counting, that yield consistent results for the ^{10}C half-life of T_{1/2}=19.2969±0.0074 s and T_{1/2}=19.3009±0.0017 s, respectively. The latter is the most precise superallowed β-decay half-life measurement reported to date and the first to achieve a relative precision below 10^{-4}. A fit to the world superallowed β-decay data including the ^{10}C half-life measurements reported here yields b_{F}=-0.0018±0.0021 (68%C.L.) for the Fierz interference term and C_{S}/C_{V}=+0.0009±0.0011 for the ratio of the weak scalar to vector couplings assuming left-handed neutrinos.

High-precision half-life and branching-ratio measurements for superallowed Fermiβ+emitters at TRIUMF – ISAC

A program of high-precision half-life and branching-ratio measurements for superallowed Fermi emitters is being carried out at TRIUMF's Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. Recent half-life measurements for the superallowed decays of 14 O, 18 Ne, and 26 Al m , as well as branching-ratio measurements for 26 Al m and 74 Rb are reported. These results provide demanding tests of the Standard Model and the theoretical isospin symmetry breaking (ISB) corrections in superallowed Fermi decays.

Upgrade of the SPIRAL identification station for high-precision measurements of nuclear β decay

The low-energy identification station at SPIRAL (Système de Production d'Ions Radioactifs Accélérés en Ligne) has been upgraded for studying the β decays of short-lived radioactive isotopes and to perform high-precision half-life and branching-ratio measurements for superallowed Fermi and isospin T=1/2 mirror β decays. These new capabilities, combined with an existing Paul trap setup for measurements of β–ν angular-correlation coefficients, provide a powerful facility for investigating fundamental properties of the electroweak interaction through nuclear β decays. A detailed description of the design study, construction, and first results obtained from an in-beam commissioning experiment on the β+ decays 14 O and 17F are presented.

High-precision half-life measurements for the superallowed Fermiβ+emitter14O

The half-life of the superallowed Fermi ${\ensuremath{\beta}}^{+}$ emitter $^{18}\mathrm{Ne}$ has been determined via two high-precision $\ensuremath{\beta}$ counting experiments at TRIUMF's Isotope Separator and Accelerator facility. Using two different $4\ensuremath{\pi}$ continuous-flow gas-proportional counters, two independent measurements were made, yielding a weighted average of ${T}_{1/2}=1.{66400}_{\ensuremath{-}0.00048}^{+0.00057}$ s, which is consistent with but approximately 2 times more precise than a previous high-precision measurement based on $\ensuremath{\gamma}$-ray counting. The present work achieves $\ifmmode\pm\else\textpm\fi{}0.034%$ precision for the $^{18}\mathrm{Ne}$ half-life and will enable the inclusion of $^{18}\mathrm{Ne}$ among the set of precisely measured superallowed Fermi $\ensuremath{\beta}$-decay $ft$ values once improved measurements are made for its $Q$ value and superallowed branching ratio. As a test of systematic uncertainties, the half-life of $^{23}\mathrm{Ne}$ was measured and the world average has been improved, by a factor of 1.7, to $37.148\ifmmode\pm\else\textpm\fi{}0.032$ s.

High-precision half-life measurements of atomic nuclei

In a series of measurements performed at the IGISOL facility at the Accelerator Laboratory of the University of Jyvaskyla, the half-lives of 26Si, 29P, 30,31S, 42Ti and 62Ga were measured with high precision. These half-lives are important ingredients for tests of the weak-interaction standard model and allow, together with other experimental inputs and theoretical correction terms, the determination of the vector coupling constant of the weak interaction. The IGISOL method used in Jyvakyla is an ideal tool for these measurements as it allows to access all elements without distinction of their chemical properties.

High-Precision Half-Life Measurement for the Superallowedβ+EmitterAlm26

A high-precision half-life measurement for the superallowed β+ emitter 26Al(m) was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T 1/2 6346.54 ± 0.46(stat) ± 0.60 (syst) ms, consistent with, but 2.5 times more precise than, the previous world average. The 26Al(m) half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed β decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for (26)Al(m), 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi β-decay studies used to test the conserved vector current hypothesis and determine the V(ud) element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

Half-life of the superallowedβ+emitterNe18

The half-life of $^{18}\mathrm{Ne}$ has been determined by detecting 1042-keV \ensuremath{\gamma} rays in the daughter $^{18}\mathrm{F}$ following the superallowed-Fermi ${\ensuremath{\beta}}^{+}$ decay of samples implanted at the center of the $8\ensuremath{\pi}\ensuremath{\gamma}$-ray spectrometer, a spherical array of 20 HPGe detectors. Radioactive $^{18}\mathrm{Ne}$ beams were produced on-line, mass-separated, and ionized using an electron-cyclotron-resonance ionization source at the ISAC facility at TRIUMF in Vancouver, Canada. This is the first high-precision half-life measurement of a superallowed Fermi \ensuremath{\beta} decay to utilize both a large-scale HPGe spectrometer and the isotope separation on-line technique. The half-life of $^{18}\mathrm{Ne}$, 1.6656 \ifmmode\pm\else\textpm\fi{} 0.0019 s, deduced following a 1.4\ensuremath{\sigma} correction for detector pulse pile-up, is four times more precise than the previous world average. As part of an investigation into potential systematic effects, the half-life of the heavier isotope $^{23}\mathrm{Ne}$ was determined to be 37.11 \ifmmode\pm\else\textpm\fi{} 0.06 s, a factor of 2 improvement over the previous precision.