arXiv subjects

E. Dumonteil

Publications and source records attributed to E. Dumonteil.

9 recordsLinked to original sources

arXiv2025

Neutron production with a 10 kW HiCANS based on SATELIT, a CEA-Saclay target with liquid lithium

High-Current Accelerator-driven Neutron Sources (HiCANS) are currently under development across Europe to address the shortage of medium-scale neutron sources, as many research nuclear reactors have been decommissioned over the past several years. At CEA-Saclay, a HiCANS has been developed utilizing the IPHI accelerator, which delivers a 3 MeV proton beam with a current of up to 100 mA, and the CEA-Saclay liquid lithium target named SATELIT. In 2024-2025, a successful experimental campaign was conducted, during which a 10 kW proton beam was directed at the liquid lithium target for nearly 100 h to generate neutrons via the 7Li(p,n)7Be nuclear reaction. Throughout the experimental campaign, a total deposited beam power of 840~kW.h was accumulated, including two continuous operational days exceeding 11 h each. A polyethylene moderator coupled with SATELIT enabled the extraction of a thermal neutron beam, with a flux measured at 1.4 m from the extraction point exceeding $10^6$ n.cm$^{-2}$.s$^{-1}$, which is sufficient for numerous neutron applications. The next step for the long-term operation of this facility involves developing strategies to mitigate the radiological concerns associated with the accumulation of 7Be within the system. Overall, this work demonstrates that such facilities can play a significant role in the future of medium-scale neutron sources in Europe.

physics.acc-ph↗

arXiv2024

Improvement of Geant4 Neutron-HP package: Unresolved Resonance Region description with Probability Tables

Whether for shielding applications or for criticality safety studies, solving the neutron transport equation with good accuracy requires to take into account the resonant structure of cross sections in part of the Unresolved Resonance Region (URR). In this energy range even if the resonances can no longer be resolved experimentally, neglecting them can lead to significant numerical biases, namely in flux-based quantities. In Geant4, low energy neutrons are transported using evaluated nuclear data libraries handled by the Neutron High-Precision (Neutron-HP) package. In the version 11.01.p02 of the code, the URR can only be described by average smooth cross sections that do not take into account the statistical resonant structure of the cross sections. To overcome this shortcoming, the treatment of the URR with the use of the probability table method has been implemented in Geant4 and successfully validated with the reference Monte Carlo neutron transport codes MCNP6 (version 6.2) and Tripoli-4 (version 12). These developments will be taken into account in the next release of Geant4. All the validations of Geant4 have been performed with probability tables generated from both the NJOY and CALENDF pre-processing tools. Therefore Geant4 now has this unique feature to study the relative impact of the strategies involved during the production of probability table by the two pre-processing codes. This has been used to show that self-shielding is important also for inelastic cross sections in the example of 238U. The tool to generate probability tables usable by Geant4 either from NJOY or from CALENDF is made available on a dedicated GitLab repository and will be included in Geant4.

physics.comp-ph↗

arXiv2023

Observation of a nuclear recoil peak at the 100 eV scale induced by neutron capture

Coherent elastic neutrino-nucleus scattering and low-mass Dark Matter detectors rely crucially on the understanding of their response to nuclear recoils. We report the first observation of a nuclear recoil peak at around 112 eV induced by neutron capture. The measurement was performed with a CaWO$_4$ cryogenic detector from the NUCLEUS experiment exposed to a $^{252}$Cf source placed in a compact moderator. The measured spectrum is found in agreement with simulations and the expected peak structure from the single-$γ$ de-excitation of $^{183}$W is identified with 3 $σ$ significance. This result demonstrates a new method for precise, in-situ, and non-intrusive calibration of low-threshold experiments.

nucl-ex↗

arXiv2023

Study of collision and $γ$-cascade times following neutron-capture processes in cryogenic detectors

The emission of $γ$-rays after a neutron capture in a cryogenic detector can generate mono-energetic nuclear recoils in the sub-keV regime, of direct interest for the calibration of Dark Matter and Coherent Elastic Neutrino Nucleus Scattering experiments. Here we show that accurate predictions of the nuclear recoil spectra induced by neutron captures require taking into account the interplay between the development in time of the de-excitation $γ$-cascade of the target nucleus and that of the associated atomic collisions in matter. We present detailed simulations coupling the FIFRELIN code for the description of the $γ$-cascades and the IRADINA code for the modelling of the fast atomic movements in matter. Nuclear recoil spectra are predicted, and made available to the community, for concrete cases of Al$_2$O$_3$, Si, Ge and CaWO$_4$ crystals exposed to a low intensity beam of thermal neutrons. We find that timing effects cause new calibration peaks to emerge in the recoil spectra and also impact the shape of the continuous recoil distribution. We discuss how they could give access to a rich physics program, spanning the accurate study of the response of cryogenic detectors in the sub-keV range, tests of solid state physics simulations and tests of nuclear models.

physics.ins-det↗

arXiv2023

Improvement of Geant4 Neutron-HP package: Doppler broadening of the neutron elastic scattering kernel and cross sections

Whether it is for shielding applications or for safety criticality studies, numerically solving the neutron transport equation with a good accuracy requires to precisely estimate the Doppler broadened elastic scattering kernel in the thermal and epithermal energy range of neutrons travelling in a free gas. In Geant4, low energy neutrons are transported using evaluated data libraries handled by the Neutron High-Precision (Neutron-HP) package. Version 11.00.p03 of the code features in particular the Doppler broadened elastic scattering kernel, provided by the so-called 'Sampling of the Velocity of the Target' (SVT) method. However this latter fails for resonant heavy nuclei such as 238U and can severely impact the solving of the Boltzmann equation in fissile media. To overcome this shortcoming, the Doppler Broadened Rejection Correction (DBRC) method has been implemented in Geant4 and successfully validated with the reference Monte Carlo neutron transport code Tripoli4 (version 11). This development will be taken into account in the next release of the code. The cross section Doppler broadening process, which is performed on-the-fly, is also carefully investigated and ways to improve it on a simulation-by-simulation basis are presented. All the validations have been performed with an automated benchmark tool which has been designed to support the quality assurance of the Geant4 Neutron-HP package. This tool is currently available on an ad hoc Gitlab repository and will be included in Geant4.

physics.comp-ph↗

arXiv2023

TOUCANS: a versatile Monte Carlo neutron transport code based on Geant4

This paper reports the development of TOUCANS, a new Monte Carlo neutron transport code fully written using the Geant4 toolkit. It aims at modeling complex systems easily and rapidly, thanks to a simple key-value input file. While its main focus is the transport of low energy neutrons -- below 20 MeV -- using evaluated cross-section libraries, it also takes advantage of the state-of-the-art capabilities offered by Geant4 regarding the modeled cross-sections for practically all particles at all energies. Hence it gives access to non-specialists to a wide variety of applications involving different particles, such as for instance the simulation of compact accelerator based neutron sources (CANS) which initially motivated its development. It leverages on recent implementations performed within Geant4 to provide both shielding calculation capabilities (using Adaptive Multilevel Splitting, which is a fully automated variance reduction technique) and criticality calculation capabilities (to estimate the keff of a multiplicative system). It also benefits from a tight coupling with CADMesh to readily import CAD models, with NCrystal to extend the support of thermal neutron transport to crystals, with FIFRELIN to increase compound nucleus de-excitation accuracy, and with FUNZ to provide to the user parametric simulation capabilities (such as multi-objective algorithms, calculation of Pareto sets, etc). Thanks to recent improvements of the neutron physics within the Geant4 Neutron-HP package, the TOUCANS code can be considered on-par with industrial neutron transport codes such as Tripoli-4 or MCNP in term of neutron physics accuracy. Its sources should be released soon amongst Geant4 advanced examples.

physics.acc-ph↗

arXiv2021

Calibration of nuclear recoils at the 100 eV scale using neutron capture

The development of low-threshold detectors for the study of coherent elastic neutrino-nucleus scattering and for the search for light dark matter necessitates methods of low-energy calibration. We suggest this can be provided by the nuclear recoils resulting from the $γ$ emission following thermal neutron capture. In particular, several MeV-scale single-$γ$ transitions induce well-defined nuclear recoil peaks in the 100 eV range. Using the FIFRELIN code, complete schemes of $γ$-cascades for various isotopes can be predicted with high accuracy to determine the continuous background of nuclear recoils below the calibration peaks. We present a comprehensive experimental concept for the calibration of CaWO$_4$ and Ge cryogenic detectors at a research reactor. For CaWO$_4$ the simulations show that two nuclear recoil peaks at 112.5 eV and 160.3 eV should be visible above background simply in the spectrum of the cryogenic detector. Then we discuss how the additional tagging for the associated $γ$ increases the sensitivity of the method and extends its application to a wider energy range and to Ge cryogenic detectors.

physics.ins-det↗

arXiv2016

Online Monitoring of the Osiris Reactor with the Nucifer Neutrino Detector

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides an new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the Inter- national Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2m away from the compact Osiris research reactor core (70MW) operating at the Saclay research centre of the French Alternative Energies and Atomic Energy Commission (CEA), the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the 0.85m3 detector remotely operating at a shallow depth equivalent to 12m of water and under intense background radiation conditions. Based on 145 (106) days of data with reactor ON (OFF), leading to the detection of an estimated 40760 electron antineutrinos, the mean number of detected antineutrinos is 281 +- 7(stat) +- 18(syst) electron antineutrinos/day, in agreement with the prediction 277(23) electron antineutrinos/day. Due the the large background no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.

physics.ins-det↗

arXiv2015

Experimental Parameters for a Cerium 144 Based Intense Electron Antineutrino Generator Experiment at Very Short Baselines

The standard three-neutrino oscillation paradigm, associated with small squared mass splittings $\ll 0.1\ \mathrm{eV^2}$, has been successfully built up over the last 15 years using solar, atmospheric, long baseline accelerator and reactor neutrino experiments. However, this well-established picture might suffer from anomalous results reported at very short baselines in some of these experiments. If not experimental artifacts, such results could possibly be interpreted as the existence of at least an additional fourth sterile neutrino species, mixing with the known active flavors with an associated mass splitting $\ll 0.1\ \mathrm{eV^2}$, and being insensitive to standard weak interactions. Precision measurements at very short baselines (5 to 15 m) with intense MeV electronic antineutrino emitters can be used to probe these anomalies. In this article, the expected antineutrino signal and backgrounds of a generic experiment which consists of deploying an intense beta minus radioactive source inside or in the vicinity of a large liquid scintillator detector are studied. The technical challenges to perform such an experiment are identified, along with quantifying the possible source and detector induced systematics, and their impact on the sensitivity to the observation of neutrino oscillations at short baselines.

physics.ins-det↗