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Electron capture properties are crucial to establish the decay schemes of numerous radionuclides. The present modelling aims at improving the theoretical estimates of these decays, which are needed when no measurement is available. Allowed and forbidden unique transitions are calculated on the basis of precise relativistic wave functions of the atomic electrons, determined in previous work. In this context, correcting for atomic effects is of high importance. The two common approaches from Bahcall and Vatai to correct for the overlap and exchange effects have been extended to every subshell in a unified formulation, with the electron occupation precisely taken into account. The shake-up and shake-off effects, which create secondary vacancies, and the influence of the hole due to the capture process, have been considered. Uncertainties are also estimated. Relative capture probabilities and their ratios, including capture-to-positron ratios, have been found to be in good agreement with a selection of precise measurements. This modelling was then applied to the third forbidden unique transition of 40 K decay, with an update of the recommended values for the branching ratios and the total decay half-life. [ABSTRACT FROM AUTHOR]

From a review of the available literature, a database of experimental shape factors from measured beta spectra was created in previous work. Classical assumptions applied in beta spectra calculations which avoid the determination of the electron and nuclear wave functions were tested by comparison with each measured spectrum present in the database. From this systematic comparison, it was demonstrated that the typical assumption λ k =1 is inappropriate for all forbidden unique transitions. Moreover, the equally common ξ -approximation was also proved to be incorrect for about half of the listed first forbidden non-unique transitions and for all second non-unique ones. In present work, this study has been performed once again using an improved analytical screening correction. General results from previous study still remain the same. Except for allowed transitions, the mean energies in current nuclear databases are expected to be erroneous. Some selected beta spectra are also given to illustrate these results. [ABSTRACT FROM AUTHOR]

Abstract: The low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction with the 8He beam delivered by the SPIRAL facility at . The light charged particles produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known state, two new resonances were observed: at (width ) and at with . Through the analysis of the angular distributions, they correspond to a state and to an state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects. [Copyright &y& Elsevier]

Based on previous study, the calculation of electron capture decays has been improved by considering a more accurate atomic model with precise atomic energies, and different radiative corrections have been tested. The computer code has been revised in order to greatly speed-up the calculation and has then been coupled with the BetaShape code. The influence of the nuclear component has also been explored using a simple nuclear model. All the calculations are compared with precise measurements available in the literature. • An improved theoretical model for electron captures is presented. • Influence of precise atomic energies is explored. • Influence of radiative correction is explored. • Influence of the nuclear component is explored. • Calculations are compared with available precise measurements. [ABSTRACT FROM AUTHOR]

The accurate measurement of beta spectra is highly important in numerous fields such as nuclear energy, nuclear medicine, ionizing radiation metrology and fundamental physics. We have developed a beta spectrometer close to 4π configuration based on silicon detectors. The influence of self-absorption has been studied by means of Monte Carlo simulations and the source preparation technique has been optimized consequently. The measured spectra from 133Ba and 36Cl decays have been compared with PENELOPE simulations. • A beta spectrometer based on Si detectors. • Monte Carlo simulations with PENELOPE. • Influence of radioactive sources. • Preliminary beta spectrum of 36Cl decay. [ABSTRACT FROM AUTHOR]

We measured with unprecedented accuracy key features of the 138 La radioactive decays as β particle energy distribution from 0.5 keV to the end-point and ratios of electron capture probabilities P L / P K , P M / P K and P M / P L . This was achieved by making use of LaBr 3 :Ce and CeBr 3 scintillator detectors. The advantage of the presented technique relies on the double role of LaBr 3 :Ce as source of 138 La and detector medium resulting in a relatively efficient counting statistics and unaltered β energy detection. The experimental results are compared to advanced computational techniques and significant deviation is found below 20 keV with the computational spectrum showing a 5% excess of β particle relative to the experimental spectrum at 10 keV. [ABSTRACT FROM AUTHOR]

We measured with unprecedented accuracy key features of the 138 La radioactive decays as β particle energy distribution from 0.5 keV to the end-point and ratios of electron capture probabilities P L / P K , P M / P K and P M / P L . This was achieved by making use of LaBr 3 :Ce and CeBr 3 scintillator detectors. The advantage of the presented technique relies on the double role of LaBr 3 :Ce as source of 138 La and detector medium resulting in a relatively efficient counting statistics and unaltered β energy detection. The experimental results are compared to advanced computational techniques and significant deviation is found below 20 keV with the computational spectrum showing a 5% excess of β particle relative to the experimental spectrum at 10 keV. [ABSTRACT FROM AUTHOR]

This article describes the Nuclide++ module developed at LNE-LNHB to simulate the decay schemes related to single or multiple radionuclides, by randomly selecting decay pathways. Written in C++, with respect of the Geant4 coding style, this module can be used transparently in Geant4-based simulation applications as an alternative to the existing Radioactive Decay Module (RDM). Nuclide++ takes advantage of the DDEP recommended data, accurate β-emitting spectra calculation and detailed description of the atomic rearrangement. This module can be useful in many applications, especially those involving radioactive sources. The reliability of the module was verified through comparisons with a while chosen radionuclides. • A C++ module to generate decay schemes of radionuclides with DDEP recommended data is presented. • The module permits to efficiently simulate radioactive sources with single or multiple radionuclides. • Efficiently process complete decay chains, including metastable levels and time dependence of detectors. • The reliability is demonstrated through comparisons with chosen radionuclides. • The module can be used transparently in Geant4-based simulation applications, alternatively to existing Geant4-RDM. [ABSTRACT FROM AUTHOR]

Atomic and nuclear data represent an important input for the accuracy of primary activity measurements based on liquid scintillation. In particular, the reliability of β-spectrum computation has been investigated for several years through experimental and theoretical studies providing solid evidence for the need to consider the atomic effects. In the present study, the activity standardization of two β-emitting radionuclides (60Co, 106Ru/106Rh) was carried out by means of the 4πβ−γ coincidence and Triple-to-Double Coincidence Ratio (TDCR) methods. The comparison between the activity concentrations given by both primary techniques presents new evidence that a better agreement is obtained when the exchange and screening effects are included in the β-spectra implemented in the model of light emission for TDCR measurements. A new development of a stochastic model based on Geant4 simulations for TDCR calculations is also presented. • Primary activity measurements of 60Co and 106Ru/106Rh are presented. • Activity assessment with the TDCR method depends on β-spectra computation. • For both radionuclides, the TDCR and 4πβ−γ coincidence results are compared. • Good agreement is obtained when the atomic effects are considered in the β-spectra calculation. [ABSTRACT FROM AUTHOR]

The present paper addresses the calibration of well-type ionization chambers (ICs) used at LNE-LNHB as standard transfer instruments to calibrate hospitals in the case of SIR-Spheres ® 90 Y resin microspheres (Sirtex, Australia). Developed for interventional oncology, this radiopharmaceutical is directly injected in the liver for cancer treatment via a selective internal radiation therapy. The present work was carried out in the framework of the European project “Metrology for molecular radiotherapy” (MetroMRT). As commonly performed in radionuclide metrology for radiopharmaceuticals, the objective is to ensure the metrological traceability of SIR-Spheres ® to hospitals. Preceding studies were focused on primary measurements of SIR-Spheres ® based on the TDCR (Triple to Double Coincidence Ratio) method, applied after the dissolution of the 90 Y-labeled resin microspheres. As 90 Y is a high-energy β - -emitter, the IC response strongly depends on the transport of electrons in the radioactive solution and surroundings (vial, chamber liners and materials). The variability of the IC-response due to the geometry dependence is investigated by means of measurements and Monte Carlo simulations in the case of a Vinten IC. The aim of the present study was also to propose a reliable uncertainty for ICs calibrations for the standard transfer of SIR-Spheres ® to hospitals. [ABSTRACT FROM AUTHOR]

Abstract: Xenon-127 was standardized by internal gas counting using three proportional counters in a differential arrangement to eliminate edge effects. The detection efficiency of the proportional counters was calculated by considering the cascade of events following the electron capture and associated gamma transitions. Activity per unit volume was measured with 0.7% relative standard uncertainty. Gamma-ray spectrometry was performed and absolute photon emission intensities were derived. This study shows that 127Xe could be a surrogate for 133Xe for the calibration of remote radio–xenon monitoring stations. [Copyright &y& Elsevier]

Abstract: Metallic magnetic calorimeters are a specific type of cryogenic detectors that have been shown to enable precise measurement of the shape of low energy beta spectra. The aim of their use at LNHB is the determination of the shape factors of beta spectra. The beta source is enclosed in the detector absorber, allowing for very high detection efficiency. It has turned out that the type of source is of crucial importance for the correctness of the measured spectrum. Spectra of 63Ni measured with several sources prepared by drying a NiCl2 solution differ from one another and from theory, whereas spectra measured with electroplated sources are reproducible and agree with theory. With these latter measurements we could confirm the atomic exchange effect down to very low energy (200eV). [Copyright &y& Elsevier]

Abstract: The LNE-LNHB is developing metallic magnetic calorimeters, a specific type of cryogenic detectors, for beta spectrometry. The aim is the determination of the shape factors of beta spectra. Our latest detector has been designed to measure the spectrum of 241Pu, a pure beta emitter with an endpoint energy of 20.8keV. In this paper, the detection principle of metallic magnetic calorimeters is explained and a detailed description is given of the realization of the detector enclosing a 241Pu source inside the detector absorber. A spectrum resulting from our first measurement is shown and compared with a theoretical spectrum. [Copyright &y& Elsevier]