E. Dumonteil

CEA Paris-Saclay

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Andrea Zoia

Université Paris-Saclay

Alain Mazzolo

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Fausto Malvagi

Institut de Radioprotection et de Sûreté Nucléaire

Loïc Thulliez

Institut de Recherche sur les Lois Fondamentales de l'Univers

Cheikh M’Backé Diop

Université Alioune Diop de Bambey

A. Letourneau

CEA Paris-Saclay

Odile Petit

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Cyril Dieudonné

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Henri Louvin

CEA Paris-Saclay

A. Wex

Technical University of Munich

Cooperative Institutions

A. Alikhanyan National Laboratory

605

European Organization for Nuclear Research

595

Centre National de la Recherche Scientifique

289

Universidad Nacional Autónoma de México

217

Istituto Nazionale di Fisica Nucleare, Sezione di Torino

212

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

196

Istituto Nazionale di Fisica Nucleare, Sezione di Bologna

189

Institut National de Physique Nucléaire et de Physique des Particules

180

Istituto Nazionale di Fisica Nucleare

170

CEA Paris-Saclay

151

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Implementation of an approximate Zero-variance scheme in TRIPOLI Monte Carlo Code

S Christoforou J.E. Hoogenboom E. Dumonteil Odile Petit Cheikh M’Backé Diop

In an accompanying paper it is shown that theoretically a zero-variance Monte Carlo scheme can be devised for criticality calculations if the space, energy and direction dependent adjoint function is exactly known. This requires biasing of the transition and collision kernels with the appropriate adjoint function. In this paper it is discussed how an existing general purpose Monte Carlo code like TRIPOLI can be modified to approach the zero-variance scheme. This requires modifications for reading in the adjoint function obtained from a separate deterministic calculation for a number of space intervals, energy groups and discrete directions. Furthermore, a function has to be added to supply the direction dependent and the averaged adjoint function at a specific position in the system by interpolation. The initial particle weights of a certain batch must be set inversely proportional to the averaged adjoint function and proper normalization of the initial weights must be secured. The sampling of the biased transition kernel requires cumulative integrals of the biased kernel along the flight path until a certain value, depending on a selected random number is reached to determine a new collision site. The weight of the particle must be adapted accordingly. The sampling of the biased collision kernel (in a multigroup treatment) is much more like the normal sampling procedure. A numerical example is given for a 3-group calculation with a simplified transport model (two-direction model), demonstrating that the zero-variance scheme can be approximated quite well for this simplified case.

Kernel (algebra)

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Simulation and design of an IPHI-based neutron source, first steps toward SONATE

Journal of Neutron Research (2022)

Borana Mom Loïc Thulliez E. Dumonteil Mickaël Binois Yann Richet

Facilities providing bright thermal neutron beams are of primary importance for various research topics. At CEA-Saclay, a compact accelerator driven neutron source, SONATE, is investigated in taking advantage of the IPHI accelerator able to deliver a 3 MeV proton beam with an intensity up to 100 mA. To optimize the performances of such a neutron source, it is necessary to maximize the thermal neutron flux while minimizing the contribution of other particles. In this work, optimization has been performed using the Monte Carlo code TOUCANS, a neutron transport code based on Geant4 developed at CEA-Saclay. This latter has been coupled to PROMETHEE, a software allowing multi-objective optimization for many simulation software. In this work the Kriging metamodel based approach is used to optimize a neutron beamdump. To take into account the various constraints, noise on the detection system and radiation protection issues, several beamdump configurations are evaluated. The variation of beamdump parameters makes it possible to identify the set of optimal solutions, the Pareto front. It allows to focus on the set of best choices and to choose wisely the best configurations. After describing the validation of TOUCANS on experimental tests performed from 2016 to 2022, the capability of such an approach will be presented.

Neutron Transport

10.3233/jnr-220027

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Citations (1)

Some considerations on exponential flights

arXiv (Cornell University) (2010)

Andrea Zoia E. Dumonteil Alain Mazzolo

In this paper we elucidate the relation between the Boltzmann equation, which governs the evolution of many random transport phenomena in Physics (such as the propagation of neutrons, or the migration of chemical and biological species), and the underlying stochastic process, the so-called {\em exponential flights}. After introducing a general framework for $d$-dimensional setups, we analyze in detail the case $d=1$, 2, 3, and 4. In particular, we derive a number of exact or asymptotic results, providing a link between the space and time evolution of the transported particles, and the statistics of collisions each particle undergoes in a given bounded or unbounded, as well as scattering or absorbing domain. Monte Carlo simulations are performed so as to support our findings.

Boltzmann constant

Source

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Counting statistics: A Feynman-Kac perspective

Physical Review E (2012)

Andrea Zoia E. Dumonteil Alain Mazzolo

By building upon a Feynman-Kac formalism, we assess the distribution of the number of collisions in a given region for a broad class of discrete-time random walks in absorbing and nonabsorbing media. We derive the evolution equation for the generating function of the number of collisions, and we complete our analysis by examining the moments of the distribution and their relation to the walker equilibrium density. Some significant applications are discussed in detail: in particular, we revisit the gambler's ruin problem and generalize to random walks with absorption the arcsine law for the number of collisions on the half-line.

Probability and statistics

10.1103/physreve.85.011132

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Citations (8)

Analog Neutron Transport for Nuclear Instrumentation Applications with the Monte Carlo Code TRIPOLI-4

Nuclear Technology (2015)

Odile Petit E. Dumonteil

Monte Carlo simulations of nuclear instrumentation configurations generally need to be run in a full analog transport mode. Up to Version 9 of the Monte Carlo code TRIPOLI-4®, the transport between two consecutive neutron collisions is analog if no variance reduction technique is requested by the user, but the collision itself is sampled in a nonanalog way. This paper presents the first implementation of a full analog neutron transport mode in TRIPOLI-4. This option concerns only fixed-source simulations.Details on the modifications implemented in the code are provided: The analog sampling of neutron interactions and the particular cases of fission and scattering reactions with multiple outgoing neutrons are addressed.Preliminary verification tests are provided, and results from nonanalog and analog neutron transport in a simple configuration of a pressurized water reactor fuel assembly are compared. An example of application to the simulation of the NUCIFER detector is also provided. This experiment, located in Saclay, France, next to the OSIRIS experimental reactor, is dedicated to reactor antineutrino detection, addressing both nonproliferation considerations and fundamental physics concerns. Antineutrinos emitted by fission reactions in OSIRIS are detected through the inverse beta decay reaction, producing a positron and a neutron. An analog TRIPOLI-4 simulation allowed us to calculate the distribution of neutron capture times on gadolinium nuclei.

Neutron Transport

Instrumentation

Nuclear data

10.13182/nt14-128

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Citations (7)

Source convergence diagnostics using Boltzmann entropy criterion application to different OECD/NEA criticality benchmarks with the 3-D Monte Carlo code Tripoli-4

E. Dumonteil A. Le Peillet Y. K. Lee Odile Petit Cédric Jouanne

The measurement of the stationarity of Monte Carlo fission source distributions in k{sub eff} calculations plays a central role in the ability to discriminate between fake and 'true' convergence (in the case of a high dominant ratio or in case of loosely coupled systems). Recent theoretical developments have been made in the study of source convergence diagnostics, using Shannon entropy. We will first recall those results, and we will then generalize them using the expression of Boltzmann entropy, highlighting the gain in terms of the various physical problems that we can treat. Finally we will present the results of several OECD/NEA benchmarks using the Tripoli-4 Monte Carlo code, enhanced with this new criterion. (authors)

Boltzmann constant

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Subcritical Copper-Reflected α-phase Plutonium (SCRαP) Measurements and Simulations

Jesson Hutchinson Wilfried Monange Rian Bahran Theresa Cutler Jennifer Arthur

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Residence times of branching diffusion processes

Physical review. E (2016)

E. Dumonteil Alain Mazzolo

The residence time of a branching Brownian process is the amount of time that the mother particle and all its descendants spend inside a domain. Using the Feynman-Kac formalism, we derive the residence-time equation as well as the equations for its moments for a branching diffusion process with an arbitrary number of descendants. This general approach is illustrated with simple examples in free space and in confined geometries where explicit formulas for the moments are obtained within the long time limit. In particular, we study in detail the influence of the branching mechanism on those moments. The present approach can also be applied to investigate other additive functionals of branching Brownian process.

Branching (polymer chemistry)

Formalism (music)

Branching process

10.1103/physreve.94.012131

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Citations (8)

Collision densities and mean residence times ford-dimensional exponential flights

Physical Review E (2011)

Andrea Zoia E. Dumonteil Alain Mazzolo

In this paper we analyze some aspects of exponential flights, a stochastic process that governs the evolution of many random transport phenomena, such as neutron propagation, chemical or biological species migration, and electron motion. We introduce a general framework for d-dimensional setups and emphasize that exponential flights represent a deceivingly simple system, where in most cases closed-form formulas can hardly be obtained. We derive a number of exact (where possible) or asymptotic results, among which are the stationary probability density for two-dimensional systems, a long-standing issue in physics, and the mean residence time in a given volume. Bounded or unbounded domains as well as scattering or absorbing domains are examined, and Monte Carlo simulations are performed so as to support our findings.

10.1103/physreve.83.041137

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Citations (30)

Observation of a Nuclear Recoil Peak at the 100 eV Scale Induced by Neutron Capture

Physical Review Letters (2023)

H. Abele G. Angloher A. Bento L. Canonica F. Cappella

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. We identify the expected peak structure from the single-γ de-excitation of ^{183}W with 3σ and its origin by neutron capture with 6σ significance. This result demonstrates a new method for precise, in situ, and nonintrusive calibration of low-threshold experiments.

Recoil

Neutron capture

10.1103/physrevlett.130.211802

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Citations (10)