•A setup to perform In-Gas Laser Ionization and Spectroscopy experiments at the Super Separator Spectrometer is presented.•The reported studies address important aspects necessary to applied the ...IGLIS technique to short-lived isotopes.•An R&D phase required to reach an enhanced spectral resolution will be carried out at KU Leuven.•High-sensitivity and enhanced-resolution laser spectroscopy studies will be possible with the IGLIS setup at S3.
The results of preparatory experiments and the preliminary designs of a new in-gas laser ionization and spectroscopy setup, to be coupled to the Super Separator Spectrometer S3 of SPIRAL2-GANIL, are reported. Special attention is given to the development and tests to carry out a full implementation of the in-gas jet laser spectroscopy technique. Application of this novel technique to radioactive species will allow high-sensitivity and enhanced-resolution laser spectroscopy studies of ground- and excited-state properties of exotic nuclei.
In literature quite a lot of data is available on uptake of radioactive caesium in mushrooms. There is less available on the evolution of concentration in fruitbodies after several years and on ...“outbound” transfer of radiocaesium from fruitbodies to their direct environment, i.e. dilution according to cooking techniques. The recent event at Fukushima has put the question of radionuclides in food, and the following exposure of consumers, high on the agenda. The purpose of this paper is twofold: (1) in order to investigate the variation in time of caesium uptake by fungi, analyses of the same species having grown on the same spot at different intervals during the last 25 years have been performed and (2) in terms of radiation protection the most important thing is the activity taken in by the consumer and not the contamination of raw products. Preparation can have a great impact on activity concentration. Various species of mushrooms frequently eaten have been sampled in Europe and contaminated areas in Japan. Different preparation techniques that can break the walls of the hyphae (drying, deepfreezing etc.) have been applied as well as different treatments: boiling or macerating in water with salt, in acid and basic media. The pH of different media was adjusted and measured. The samples and the medium were analysed separately in gamma spectrometry.
À la recherche de l’ultime atome Stodel, Christelle; Boilley, David; Piot, Julien ...
Reflets de la Physique,
07/2017, Letnik:
54, Številka:
54
Journal Article
Recenzirano
Odprti dostop
La dernière ligne du tableau périodique de Mendeleïev est maintenant complète et l’élément le plus lourd, l’oganesson, compte 118 protons. Il s’agit là de la limite atteinte avec les technologies ...actuelles, mais pas la limite d’existence des éléments chimiques.Une nouvelle génération d’instruments est en construction pour aller plus loin et pour synthétiser en plus grand nombre les derniers éléments découverts, afin de pouvoir étudier leurs propriétés.
The present work investigates the uncertainties in a nuclear liquid-drop model. The model parameters, their uncertainties and correlations, are determined through standard regression analysis that ...includes a statistical treatment of the errors of the model. The adjustment of the model is based on experimental binding energies corrected by the Thomas-Fermi shell corrections. The uncertainties are then propagated onto observables to reveal the reliability of the predictions and insight is provided to guide further research. Standard regression analysis is further extended to encompass experimental uncertainties as well as correlations. Strong support for such an extension can be found in Bayesian inference. The uncertainties and the correlations regarding microscopic corrections are not currently known, however, when available, these contributions may be included through this extended formalism.
Background: Synthesis of super-heavy elements is performed by heavy-ion fusion-evaporation reactions. However , fusion is known to be hindered with respect to what can be observed with lighter ions. ...Thus some delicate ambiguities remain on the fusion mechanism that eventually lead to severe discrepancies in the calculated formation probabilities coming from different fusion models. Purpose: In the present work, we propose a general framework based upon uncertainty analysis in the hope of constraining fusion models. Method: To quantify uncertainty associated with the formation probability, we propose to propagate uncertainties in data and parameters using the Monte-Carlo method in combination with a cascade code called KEWPIE2, with the aim of determining the associated uncertainty, namely the 95% confidence interval. We also investigate the impact of different models or options, which cannot be modeled by continuous probability distributions, on the final results. An illustrative example is presented in detail and then a systematic study is carried out for a selected set of cold-fusion reactions. Results: It has been rigorously shown that, at the 95% confidence level, the total uncertainty of the empirical formation probability appears comparable to the discrepancy between calculated values. Conclusions: The results obtained from the present study provide a direct evidence for predictive limitations of the existing fusion-evaporation models. It is thus necessary to find other ways to assess such models for the purpose of establishing a more reliable reaction theory, which is expected to guide future experiments on the production of super-heavy elements.
A new dynamical cascade code for decaying hot nuclei is proposed and specially adapted to the synthesis of super-heavy nuclei. For such a case, the interesting channel is of the tiny fraction that ...will decay through particles emission, thus the code avoids classical Monte-Carlo methods and proposes a new numerical scheme. The time dependence is explicitely taken into account in order to cope with the fact that fission decay rate might not be constant. The code allows to evaluate both statistical and dynamical observables. Results are successfully compared to experimental data.
.
The existence of super-heavy nuclei can only be explained by the introduction of stabilizing ground state shell effects. The macroscopic-microscopic masses are constructed from the sum of a ...macroscopic, liquid-drop, energy contribution and a microscopic, shell correction energy. In the present study, shell correction energies are inferred by subtracting the liquid-drop contributions to their corresponding experimental masses. As most super-heavy nuclei masses are not precisely known, they are deduced from measured
Q
α
values. Furthermore, a detailed uncertainty analysis regarding experimental masses and more importantly the liquid-drop masses delivers decisive theoretical constraints on shell correction energies. The current work focuses on two
α
decay chains, the first following from a hot fusion reaction leading to the synthesis of
291
Lv , and the second following from a cold fusion reaction leading to the synthesis of
277
Cn . Contrasting the outcomes obtained for these two decay chains demonstrates that mass measurement precisions of about 50keV are required in order to efficiently constrain the shell correction energies of super-heavy nuclei.
KEWPIE–a cascade code devoted to investigating the dynamical decay of excited nuclei, specially designed for treating very low probability events related to the synthesis of super-heavy nuclei formed ...in fusion–evaporation reactions–has been improved and rewritten in C++ programming language to become KEWPIE2. The current version of the code comprises various nuclear models concerning the light-particle emission, fission process and statistical properties of excited nuclei. General features of the code, such as the numerical scheme and the main physical ingredients, are described in detail. Some typical calculations having been performed in the present paper clearly show that theoretical predictions are generally in accordance with experimental data. Furthermore, since the values of some input parameters cannot be determined neither theoretically nor experimentally, a sensibility analysis is presented. To this end, we systematically investigate the effects of using different parameter values and reaction models on the final results. As expected, in the case of heavy nuclei, the fission process has the most crucial role to play in theoretical predictions. This work would be essential for numerical modeling of fusion–evaporation reactions.
Program title: KEWPIE2
Catalogue identifier: AEZB_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEZB_v1_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: GNU General Public License, version 3
No. of lines in distributed program, including test data, etc.: 41230
No. of bytes in distributed program, including test data, etc.: 259652
Distribution format: tar.gz
Programming language: C++.
Computer: All Linux based workstations, Apple machines.
Operating system: Linux, OS X.
RAM: Depending on the size of system and calculated quantities.
Classification: 17.8, 17.10, 17.23.
External routines: The latest version of the GSL library, available on http://www.gnu.org/software/gsl/
Nature of problem: Estimating evaporation-residue cross-sections and average fission times related to the synthesis of super-heavy elements.
Solution method: A specific algorithm based on the Bateman equations and the spectral discretization method.
Restrictions: The main area of application is the study of the de-excitation of heavy or super-heavy nuclei.
Running time: A few seconds up to several hours, depending on the calculated quantities (evaporation-residue cross-section or average fission time).
The real-time path-integral propagator approach is used to study the fusion probability of massive nuclei including of quantum effect. An analytical expression of the probability to pass over barrier ...of an inverted harmonic potential is obtained, in which both height and curvature of the barrier are controlled by the neck degree of freedom. The fusion probabilities of three systems in central collision as functions of the center-of-mass energy are calculated and in agreement with the experimental results. It is shown that the quantum fluctuation enhances the fusion probability at low energies, and the neck fluctuation makes the slope of the fusion probability curve become flatter.
PDF
