Recommended standards for gamma ray intensities

International audienceGamma ray data are used in more and more areas of application, and so over the years the demand for recommended gamma ray energies and intensities has increased. This paper proposes a list of gamma rays whose intensity is sufficiently well-known and they can be used for the calibration of gamma ray spectrometers and other applications; it is based on studies carried out by an international group of evaluators: the Decay Data Evaluation Project. One goal of this paper is to gather this set of data together in order to facilitate and generalize their use. In the first part, a brief description of the methodology followed throughout the evaluations is given, different methods of gamma ray intensity evaluation are presented, some typical examples of evaluations are shown; in the second part, the list of chosen nuclides is given along with their applications, and finally a list of recommended gamma ray intensities is presented

Radioactive equilibrium: 99^{99}Mo/99m^{99m}Tc decay characteristics

International audienceWithin the Decay Data Evaluation Project, as an example of a radioactive equilibrium with isomer, the 99Mo/99m Tc equilibrium mixture decay characteristics are examined. The results of a new decay data evaluation are presented for 99Mo/99mTc decay to nuclear levels in 99Tc. These evaluated data have been obtained using information published up to 2013

Calculation of beta spectral shapes

International audienceClassical beta spectra calculations are briefly described, highlighting the usual assumptions and limitations. To go beyond these usual assumptions, the numerical resolution of the Dirac equation for the atomic and beta electrons is necessary. This allowed us to determine the parameters $\lambda_i$ involved in the theoretical shape factors exactly. A systematic comparison between theoretical and experimental shape factors led us to disqualify the usual $\lambda_i$ = 1 assumption for all forbidden transitions. The usual $\xi$-approximation was proved to be incorrect for numerous first forbidden non-unique transitions, and for all higherorder non-unique transitions. A more accurate screening correction was defined and the atomic exchange effect was taken into account, an effect which is always neglected in usual calculations. The beta spectra of $^{63}$Ni and $^{241}$Pu, recently measured down to very low energies, are well reproduced in our calculations. The exchange effect was demonstrated to have a great influence on the spectral shape within this energy range

Emissions X K du manganèse: comparaison entre les spectres du métal et d'une source de 55Fe

National audienceThe Mn K x-ray emission spectra in metal and 55Fe source have been analyzed and energies, shapes and intensities of the Kα and Kβ emissions as well as Kβ/Kα ratio have been determined. A good agreement is obtained between the experimental data and the simulated spectra from MCDF calculations for the free atom and ions. Then, the shape and the intensity ratio of the emissions and their variation as a function of the 3d electron number, i.e. of the Mn oxydation number, are well described from the calculations. It is deduced that, for the transition elements, the emissions between inner shells essentially depend on the interaction of the inner hole with the d sub-shell and are well described with the help of an atomic model.Les spectres XK du manganèse, émis par le métal et par une source de 55Fe, ont été analysés et les caractéristiques, énergie, forme et intensité, des émissions Kα et Kβ ainsi que le rapport Kβ/Kα ont été déterminés. Un bon accord est obtenu entre ces données expérimentales et les résultats des calculs MCDF que nous avons effectués pour l'atome et l'ion libre. Ainsi, nos calculs reproduisent bien la forme des émissions, la valeur des rapports d'intensité et l'évolution du spectre en fonction du nombre d'électrons 3d, donc du degré d'oxydation du manganèse. Il ressort de cette étude que, pour les éléments de transition, les émissions qui prennent place entre niveaux de cœur dépendent essentiellement de l'interaction entre la lacune de cœur et la sous-couche d et sont bien décrites à l'aide d'un modèle atomique

Corrections for Exchange and Screening Effects in Low-energy Beta Decays

International audienceThe beta spectra of 241Pu and 63Ni have been recently measured using metallic magnetic calorimeters. This powerful experimental technique allows theoretical beta spectra calculations to be tested at low energy with an accuracy never before achievable. Their comparison with classical beta calculations exhibits a significant deviation below 4 keV for 241Pu and 8 keV for 63Ni. The atomicexchange effect explains the main part of this deviation in the 63Ni beta spectrum. This effect has a significant contribution, equivalent to the magnitude of the screening, in the 241Pu beta spectrum

Evidence for the exchange effect in the β decay of 241^{241}Pu

International audienceThe exchange effect has been previously given as a possible explanation for a significant deviation from an allowed shape observed at low energy in the $^{241}$Pu β spectrum. Calculations set out here confirm that this atomic effect explains a large part of this deviation. The equations needed to calculate the exchange effect are detailed, as well as the evaluation of the confluent hypergeometric function for complex arguments of large magnitudes. After a review of the possible other effects that could explain the remaining discrepancy at low energy, the screening correction using effective nuclear charges seems to be the best explanation. For radionuclides with high Z, this work has demonstrated the necessity to take into account the spatial variation of the nuclear charge experienced by the ejected electron to accurately correct for the screening effect

Development of a System for Measuring the Shape of beta Spectra Using a Semiconductor Si Detector

International audienceA system for the measurement of beta energy spectra has been developed. It is based on a silicon semi-conductor detector operating at liquid nitrogen temperatures, under ultra high-vacuum. Monte-Carlo simulations were made to optimize the detection chamber and the source holder. Descriptions of the electronic and mechanical systems are included, as well as the first measured spectr

Construction of beta spectrum on the basis of experimental nuclear decay data

International audienceA computer code for $\beta$-spectrum construction of 1300$+$ radionuclei has been created. The tools use the experimental nuclear data adopted and compiled in the ENSDF file and experimental or estimated parameters of shape factors. The final uncertainty on the calculated $\beta$-spectrum branch tries to deal with uncertainties on the radiation probability, the endpoint energy, and the shape factor parameters

Determination of X- and gamma-ray emission intensities in the decay of 131 I

20th International Conference on Radionuclide Metrology and its Applications (ICRM), organized by TU Wien, 8-12 June 2015 ,Vienna, Austria.International audienceThe activity per unit mass of an iodine-131 solution was absolutely standardized by both the 4 pi beta-gamma coincidence method and the 4 pi gamma counting technique. The calibrated solution was used to prepare point sources after a preliminary deposit of AgNO3 to prevent the loss of volatile iodine. Relative and absolute photon emission intensities of 15 sgamma-rays and those of the two K X-rays of xenon were determined by gamma-ray spectrometry, with relative uncertainties of 0.8% for the three main emissions

Standardization of xenon-127 and measurement of photon emission intensities

International audienceXenon-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 (127)Xe could be a surrogate for (133)Xe for the calibration of remote radio-xenon monitoring stations