Decay Half-lives Research Articles

Uncertainty analysis of infinite multiplication factor and nuclide number density based on the UAM-PWR benchmark with respect to cross sections, fission yields and decay half-life

Uncertainty analysis is performed to qualify the uncertainty of the infinite multiplication factor (kinf) and nuclide number density induced by cross sections, fission yields and decay half-life in ENDF/B-VIII.0. The SUNDEW code, initially developed for burnup sensitivity and uncertainty analysis with respect to cross sections based on the generalized perturbation theory, is extended to consider fission yields and decay half-life. The Bayesian/general least-squares method is adopted to generate the covariance matrix of fission yields. TMI-1 PWR pin cell given in the UAM project is calculated by SUNDEW. In addition to kinf, the uncertainty of the number densities of various nuclides important for different aspects are calculated and analyzed, including nuclides involved in burnup credit, nuclides used for burnup measurement, and 135Xe. Main conclusions are that the cross section covariances in ENDF/B-VIII.0 can induce larger uncertainty to kinf than ENDF/B-VII.1; the fission yields and decay half-life have obvious contributions for the uncertainty of nuclide number density in some cases.

Cluster pre-formation probabilities and decay half-lives for trans-lead nuclei using modified generalised liquid drop model (MGLDM)

Cluster pre-formation probabilities and decay half-lives for trans-lead nuclei using modified generalised liquid drop model (MGLDM)

Cluster approach to spontaneous fission of even-even isotopes of U, Pu, Cm, Cf, Fm, No, Rf, Sg, and Hs

For even isotopes of nuclei U, Pu, Cm, Cf, Fm, No, Rf, Sg, and Hs, spontaneous fission and $\ensuremath{\alpha}$-decay half-lives are calculated within the dinuclear system model and compared with existing experimental data. Cluster radioactivity half-lives are also described for even U, Pu, and Cm isotopes. All these processes are considered for the evolution of a nucleus in the charge (mass) asymmetry coordinate and in the relative distance between the centers of clusters formed. The important roles of the driving potential and mass parameter in the charge asymmetry coordinate are shown for spontaneous fission. The global isotopic trends of spontaneous fission and $\ensuremath{\alpha}$-decay half-lives are studied. Drastic changes in the functional dependence of spontaneous fission half-life on the neutron number and in the absolute values of half-lives in the U--No and Rf--Hs nuclear groups are explained.

Automated Detection and Analysis of Exocytosis.

Timelapse TIRF microscopy of pH-sensitive GFP (pHluorin) attached to vesicle SNARE proteins is an effective method to visualize single vesicle exocytic events in cell culture. To perform an unbiased, efficient identification and analysis of such events, a computer-vision based approach was developed and implemented in MATLAB. The analysis pipeline consists of a cell segmentation and exocytic-event identification algorithm. The computer-vision approach includes tools for investigating multiple parameters of single events, including the half-life of fluorescence decay and peak ΔF/F, as well as whole-cell analysis of the frequency of exocytosis. These and other parameters of fusion are used in a classification approach to distinguish distinct fusion modes. Here a newly built GUI performs the analysis pipeline from start to finish. Further adaptation of Ripley's K function in R Studio is used to distinguish between clustered, dispersed, or random occurrence of fusion events in both space and time.

Neutrinoless Double Beta Decay with Germanium Detectors: 1026 yr and Beyond

In the global landscape of neutrinoless double beta (0νββ) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the 76Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive 0νββ decay search. The Majorana and Gerda experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of 2.53 ± 0.08 keV at the Qββ and an unprecedented low background level of 5.2×10−4 cts/(keV·kg·yr), respectively. In this paper, we will review the path of 0νββ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the Gerda experiment setting a limit on the half-life of 76Ge 0νββ decay at T1/2>1.8×1026 yr (90% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to 1028 yr and beyond, opening the way to the exploration of the normal ordering region.

Alpha decay study of Thorium isotopes using double folding model with NN interactions derived from relativistic mean field theory

The alpha decay half-lives of some Thorium isotopes have been calculated within the framework of the WKB semi-classical approximation, with the inclusion of the Bohr-Sommerfeld quantization condition. The effective potentials used are the double folding nuclear potential, Coulomb potential, and centrifugal potential. Apart from using the famous M3Y-Reid and M3Y-Paris nucleon-nucleon (NN) interactions, the microscopic NN interaction derived from relativistic mean field theory Lagrangian (R3Y), with different parametrizations, has also been used. The results obtained using the R3Y potentials are compared to the phenomenological M3Y-Reid and M3Y-Paris NN interactions. The R3Y based interactions are found to perform slightly better than the M3Y based interactions for density-independent double folding model. When density-dependence of the double folding model is used, the M3Y-Paris and R3Y-W give the best descriptions of the α−decay half-lives of the Thorium isotopes, while the M3Y-Reid gives the highest deviation from experimental data.

α -cluster formation and decay: The role of shell structure

Shell structure effects on $\ensuremath{\alpha}$-cluster formation and decay are studied by using the quartetting wave function approach (QWFA). Both the intrinsic and center-of-mass (c.o.m.) motions of an $\ensuremath{\alpha}$ cluster inside a core nucleus are investigated with different contributing shell model wave functions. The overlap between intrinsic wave functions of four nucleons in the $\ensuremath{\alpha}$-like quartet state and in a free $\ensuremath{\alpha}$ particle is analyzed in detail. The change of the effective potential describing the c.o.m. motion of the quartet is explicitly shown for the major shell closures $Z=82$ and $N=126$. It is found that both the $\ensuremath{\alpha}$-cluster formation probability and the half-life are sensitive to the quartet shell model states. By extending the QWFA calculations from $^{212}\mathrm{Po}$ to $\ensuremath{\alpha}$ emitters with one or two extra nucleons, we show that the bound state and scattering wave functions of the $\ensuremath{\alpha}$ cluster are changed accordingly. The calculated $\ensuremath{\alpha}$-decay half-lives agree nicely with the experimental data.

Production and measurement of fission product noble gases

Gaseous fission products have been produced via thermal neutron irradiation of a highly-enriched uranium target and extracted using a custom gas processing system for measurement on a prototype, high-resolution β − γ coincidence detection system. The gas was extracted and measured in two stages in order to measure the prompt and β−–delayed fission products. This paper presents an overview of the system used to produce gaseous fission products, and the results of the advanced coincidence spectrometry techniques used to identify and quantify decays from the radionuclides produced, including the noble gases 85Kr, 85mKr, 88Kr, 133Xe, 135Xe, 133mXe and 135mXe, as well as 133I and 88Rb. The measurements were validated by determination of the nuclear decay half-lives, specifically for the ground state decay of 135Xe, which was found to be 9.15(49) hours and consistent with the literature value. This work demonstrates the UK capability to produce gaseous radionuclides for quality assurance and calibration purposes in Radionuclide Laboratories supporting the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

Studying the $$\alpha$$-Decay Half-Lives of Nuclei in the Range $${68\leqslant Z\leqslant 118}$$ by Double-Folding and Cluster Formation Formalisms

Studying the $$\alpha$$-Decay Half-Lives of Nuclei in the Range $${68\leqslant Z\leqslant 118}$$ by Double-Folding and Cluster Formation Formalisms

Novel formula for decay half-life of charged particle from the resonance of $$\delta $$-well decorated Coulomb barrier

Novel formula for decay half-life of charged particle from the resonance of $$\delta $$-well decorated Coulomb barrier

Description of magnetic moments within the Gogny Hartree-Fock-Bogolyubov framework: Application to Hg isotopes

While the ground state configuration is classically determined by the variational principle minimizing the binding energy of the system, we propose here a different procedure to identify the configuration of the ground state in odd-$A$ nuclei. This procedure is based on the Hartree-Fock-Bogolyubov (HFB) framework with a self-consistent blocking of the unpaired nucleon and identifies the ground state as the blocked quasiparticle configuration compatible with the observed spin and parity and, most importantly, the measured magnetic moment. The magnetic moments are calculated within the HFB framework for all odd Hg isotopes for which experimental data is available. To validate the method, a systematic comparison between the predicted and measured electric quadrupole moments and isotopic shifts is performed. For even-even isotopes, we show that the ground state deformation, and more particularly the competition between the prolate and oblate shapes, can hardly be determined through a comparison of the QRPA $\ensuremath{\beta}$-decay half-life with experiment, though this approach also calls for an observable similar to the one used for odd-$A$ isotopes, namely the spin-flip component of the isovector part of the magnetic moment operator. For even isotopes with shape coexistence, no adequate constraint could be identified, except though the charge radius. Assuming light even-even Hg isotopes to have an oblate shape, the resulting charge radii staggering observed in the Hg chain by laser spectroscopy can through this identification procedure be reproduced.

Structural and decay properties of nuclei appearing in the α-decay chains of 296,298,300,302,304120 within the relativistic mean field formalism

An extensive study of [Formula: see text]-decay half-lives for various decay chains of isotopes of [Formula: see text] is performed within the axially deformed relativistic mean-field (RMF) formalism by employing the NL3, NL3[Formula: see text], and DD-ME2 parameter set. The structural properties of the nuclei appearing in the decay chains are explored. The binding energy, quadrupole deformation parameter, root-mean-square charge radius, and pairing energy are calculated for the even–even isotopes of [Formula: see text], which are produced in five different [Formula: see text]-decay chains, namely, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. A superdeformed prolate ground state is observed for the heavier nuclei, and gradually the deformation decreases towards the lighter nuclei in the considered decay chains. The RMF results are compared with various theoretical predictions and experimental data. The [Formula: see text]-decay energies are calculated for each decay chain. To determine the relative numerical dependency of the half-life for a specific [Formula: see text]-decay energy, the decay half-lives are calculated using four different formulas, namely, Viola–Seaborg, Alex–Brown, Parkhomenko–Sobiczewski and Royer for the above said five [Formula: see text]-decay chain. We notice a firm dependency of the half-life on the [Formula: see text]-decay formula in terms of [Formula: see text]-values for all decay chains. Further, this study also strengthens the prediction for the island of stability in terms of magic number at the superheavy valley in the laboratories.

Investigation of bound state β− decay half-lives of bare atoms

We investigate the bound state ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of highly ionized atoms, in which the decay electron remains in a bound atomic state rather than being emitted into the continuum. A survey of 3344 nuclei is performed in order to search possible bound state ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay nuclei. We find that, for candidates $^{163}\mathrm{Dy}$, $^{193}\mathrm{Ir}$, $^{194}\mathrm{Au}$, $^{202}\mathrm{Tl}$, $^{205}\mathrm{Tl}$, $^{215}\mathrm{At}$, $^{222}\mathrm{Rn}$, $^{243}\mathrm{Am}$, and $^{246}\mathrm{Bk}$, the channel of ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay is completely forbidden in the neutral case but can be opened in the bare case. The corresponding bound-state ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay half-lives of these nuclei are predicted by using the Takahashi-Yokoi model, which are found to be significantly different from those in the neutral case.

Alpha decay half-lives of superheavy nuclei 104 ≤ Z ≤ 125

In order to describe scattering, fusion, fission and ground state masses, Krappe and collaborators developed unified nuclear potential, by generalizing liquid drop model. They have incorporated phenomenological parameters accounting for the attractive force between two separated fragments. One of the phenomenological parameters involved in this model is the range of folded Yukawa function, which accounts for surface diffuseness of the potential and short range attractive interaction. The role of range of folding function of Yukawa-plus-exponential potential is analyzed for alpha decay of heavy and superheavy nuclei. Significant effect of this function is noted in preformation probability which improves the accuracy of half-lives of alpha decay. Half-lives for alpha decay are better obtained for two values of the range of folding function 0.54 and 0.8[Formula: see text]fm for heavy and superheavy mass regions, respectively. The study confirms the associated shell structure [Formula: see text] in heavy nuclei and [Formula: see text] and [Formula: see text] in superheavy nuclei. The calculations are extended to predict the half-lives of superheavy nuclei with [Formula: see text] and [Formula: see text] which are not yet synthesized experimentally.

Correlations of α -decay properties and isospin-asymmetry

The isospin-asymmetry nuclear chains with $N\ensuremath{-}Z$ from 2 to 60 are investigated to find the correlations of $\ensuremath{\alpha}$-decay properties and isospin asymmetry. Both the proton- and neutron-skin thicknesses of $\ensuremath{\alpha}$ emitters belonging to different $N\ensuremath{-}Z$ chains are tightly aligned along straight lines, the slope of which depends on the shell closure. For even-even $\ensuremath{\alpha}$ emitters, the neutron-skin thickness ${\mathrm{\ensuremath{\Delta}}}_{n}$ multiplied by $N\ensuremath{-}Z$ is a parabolic function of the isospin-asymmetry parameter $I=(N\ensuremath{-}Z)/A$. For the nuclei of incomplete neutron shells, the $\ensuremath{\alpha}$-decay half-life ${T}_{\ensuremath{\alpha}}$ exponentially increases with ${\mathrm{\ensuremath{\Delta}}}_{n}$ in the isospin chain. In the nuclei with valence neutrons and/or protons outside the magic core, ${T}_{\ensuremath{\alpha}}$ exponentially decreases with increasing ${\mathrm{\ensuremath{\Delta}}}_{n}$. The values of ${T}_{\ensuremath{\alpha}}$ and ${Q}_{\ensuremath{\alpha}}$ are almost exponential functions of isospin asymmetry.

Search for double-beta decay of mathrm {^{130}Te} to the 0^+ states of mathrm {^{130}Xe} with CUORE

The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay (0nu beta beta ) in the isotope mathrm {^{130}Te}. In this work we present the latest results on two searches for the double beta decay (DBD) of mathrm {^{130}Te} to the first 0^{+}_2 excited state of mathrm {^{130}Xe}: the 0nu beta beta decay and the Standard Model-allowed two-neutrinos double beta decay (2nu beta beta ). Both searches are based on a 372.5 kgtimes yr TeO_2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as mathrm {S^{0nu }_{1/2} = 5.6 times 10^{24} , mathrm {yr}} for the {0nu beta beta } decay and mathrm {S^{2nu }_{1/2} = 2.1 times 10^{24} , mathrm {yr}} for the {2nu beta beta } decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at 90% C.I. on the decay half lives is obtained as: mathrm {(T_{1/2})^{0nu }_{0^+_2} > 5.9 times 10^{24} , mathrm {yr}} for the 0nu beta beta mode and mathrm {(T_{1/2})^{2nu }_{0^+_2} > 1.3 times 10^{24} , mathrm {yr}} for the 2nu beta beta mode. These represent the most stringent limits on the DBD of ^{130}Te to excited states and improve by a factor sim 5 the previous results on this process.

Enhancing immunogenicity of HPV16 E7 DNA vaccine by conjugating codon-optimized GM-CSF to HPV16 E7 DNA

ObjectiveTo generate immunity against human papillomavirus (HPV), the use of a recombinant DNA vaccine to carry an appropriate target gene is a promising and cost-effective approach. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent immunomodulatory cytokine that enhances the efficacy of vaccines by promoting the development and prolongation of humoral and cellular immunity. In this study, we linked codon-optimized GM-CSF (cGM-CSF) to the HPV16 E7 sequence as fused protein and evaluated the immunogenic potential of this DNA vaccine. Materials and methodsWe have demonstrated that cGM-CSF enhanced immunity against tumor challenges by generating and promoting the proliferation of HPV16 E7-specific CD8+ T cells, which secrete IFN-γ in the murine model. In this study, we aimed to evaluate the immunogenic potential of DNA vaccine that constructed by linking codon-optimized GM-CSF to HPV16 E7 sequence in the animal model. We study the half-life of RNA decay and cellular location of HPV16 E7 by Q-PCR and Western blot. We also assess immune response in the animal model by flow cytometry and ELISA. ResultsThe cGM–CSF–E7 sequence increased and extended the expression of E7 mRNA, in comparison with the E7 sequence alone. Mice vaccinated with the cGM–CSF–E7 DNA vaccine exhibited a slower rate of tumor growth than those vaccinated with the unconjugated E7 DNA vaccine. We also found that the CD4 and CD8+ T cells from these mice showed strong secretion of IFN-γ. ConclusionThrough in vivo antibody depletion experiments, we demonstrated that both CD4+ and CD8+ T cells play an important role in the suppression of tumor growth.

Spontaneous double alpha decay: First experimental limit and prospects of investigation

Nuclear decays with simultaneous emission of two alpha particles are energetically possible for a number of nuclides. Prospects of searching for such kind of decay for nuclides present in the natural isotopic composition of elements are discussed here. The first experimental limit on half-life for 2α decay is set for 209Bi as T1/2 > 2.9·1020 y at 90 % C.L., using the data of work [P. de Marcillac et al. Nature 422 (2003) 876]. Theoretical T1/2 estimations for the process are also given. Using these values, which are on the level of 1033 y or more, one can conclude that the prospects of experimental observation of 2α decay are very pessimistic.

New experimental limits on double-beta decay of osmium

Double-beta processes in 184Os and 192Os were searched for over 15 851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm3 ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in 184Os were set at the level of lim T 1/2 ∼ 1016–1017 years. In particular the 2ν2K and 2ν KL decays of 184Os to the ground state of 184W are restricted as T 1/2 ⩾ 3.0 × 1016 years and T 1/2 ⩾ 2.0 × 1016 years, respectively. A lower limit on the half-life for the double-beta decay of 192Os to the first excited level of 192Pt was set as lim T 1/2 = 2.0 × 1020 years at 90% confidence level

Improvement of the 241Pu/239Pu isotope ratio measurement by thermal ionisation mass spectrometry - An approach to account for the 241Am in-growth after plutonium purification

Reliable determinations of plutonium isotope ratios are required in the nuclear field. Thermal ionisation mass spectrometry (TIMS) is used for this purpose. Commercially available TIMS instruments cannot distinguish between 241Am and 241Pu. A purification step before measurement to remove americium from plutonium solutions is required. Nevertheless, the amount of 241Am in-growth due to 241Pu decay (half-life 14.3 years) in the time between plutonium purification and TIMS measurements can be significant for an accurate determination of the 241Pu/239Pu isotope ratio. This paper presents a method, with a focus on nuclear safeguards, to correct for the 241Am in-growth after plutonium purification. In addition, the method provides an estimate for the americium ionisation efficiency to allow an even more accurate determination of the 241Pu/239Pu isotope ratio.