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P. Carpentier

Publications and source records attributed to P. Carpentier.

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Microscopic description of the fission process including intrinsic excitations. Part I: 240Pu adiabatic and asymmetric fission path within the Schrodinger Collective Intrinsic Model

This article is the first in a trilogy aimed at presenting the first practical implementation of the Schrodinger Collective-Intrinsic Model (SCIM) applied to nuclear fission. Within the SCIM framework, the many-body wave function explicitly couples collective motion to intrinsic excitations, necessitating sets of Hartree-Fock-Bogoliubov (HFB) configurations that remain continuous and regular across a broad deformation range, from the ground state to scission and beyond. This paper focuses on constructing adiabatic HFB paths suitable for subsequent SCIM dynamical calculations. Standard constrained adiabatic paths often suffer from discontinuities and irregularities, which prevent the direct application of the formalism. To address these challenges, we implement two recently proposed overlap-based protocols, the Link and Drop methods, and combine them into a new numerical procedure.A comparison with the exact Gaussian Overlap Approximation confirms that the resulting adiabatic kernels exhibit properties consistent with the assumptions of the SCIM formalism. The regularized path is then analyzed in the scission region. We identify characteristic structures in the proton and neutron chemical potentials, a pronounced neutron enrichment of the neck at scission, and fragment particle-number distributions displaying a strong odd-even staggering in the proton sector. Finally, using a microscopic fragment-separation procedure formulated in the canonical basis, we extract static scission properties including fragment deformation energies and both Coulomb and nuclear contributions to the fragment interaction energy. These results establish the adiabatic foundations required for future SCIM calculations with intrinsic excitations and provide a microscopic characterization of the scission region in 240Pu.

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Microscopic description of the fission process including intrinsic excitations. Part II: 240Pu excited and asymmetric fission paths within the Schrodinger Collective

This second article of the trilogy presents the implementation of a third protocol, referred to as Continuous Deflation, designed to construct continuous and regular excited paths within the Schrodinger Collective-Intrinsic Model (SCIM), with applications to nuclear fission. We show that the use of standard 2QP excitations, even when combined with particle-number projection, prevents a consistent application of the SCIM framework. Motivated by the central role of pair breaking in low-energy fission, we explore how to construct intrinsic excited states that incorporate this mechanism while satisfying the continuity and regularity state requirements of the SCIM. To this end, we first analyze the Deflation procedure alone, which constructs excited states through orthogonality constraints. We then extend this construction along a deformation path by introducing an additional continuity constraint, thereby defining the Continuous Deflation method, which generates continuous paths based on excited states. In particular, we construct ten such continuous paths built on top of the adiabatic and asymmetric fission path of 240Pu. The resulting excited states are systematically analyzed in terms of their microscopic structure. We then investigate several fragment properties near scission, including neutron and proton chemical potentials, neutron necking as well as fragment particle-number distributions, and compare them with their adiabatic counterparts.

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Microscopic description of the fission process including intrinsic excitations. Part III: 240Pu fission dynamics along 1D asymmetric paths within the Schrodinger Collective Intrinsic Model

This last article of the trilogy focuses on the dynamical equation of the Schrodinger Collective-Intrinsic Model (SCIM). First, we motivate and discuss the need to regularize the adiabatic and excited dynamical ingredients entering the collective-intrinsic Hamiltonian, namely the collective potential, the collective inertia tensor, and the collective dissipative tensor. In particular, we introduce a Savitzky-Golay low-pass filter to remove numerical fluctuations incompatible with the second-order truncation in the Symmetric Ordered Product of Operators used to derive the SCIM equations. The diagonal and off-diagonal properties of the three dynamical ingredients are then analyzed along the asymmetric fission path in 240Pu. This study highlights the dominant role of neutron and proton excitation channels, especially in the second well and scission regions, whereas proton-neutron couplings remain essentially negligible. Furthermore, in the adiabatic limit of the SCIM, we perform a comparison with the GOA which reveals very close predictions. Second, we discuss the construction of the initial wave packet and the numerical resolution of the collective-intrinsic Schrodinger equation. Using a continuity equation, we derive the probability fluxes associated with the different components of the wave function, which provide direct access to the contribution of the different excitations to the final observables for the fission problem. The excited states are found to account for more than 80% of the total flux at scission. Finally, we evaluate, the neutron and proton fragment distributions as well as the energy balance, including the total kinetic and excitation energies. The obtained results are found to be consistent with available experimental data and demonstrate the importance of explicitly including intrinsic excitations in the description of fission dynamics.

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Impact of finite-range spin-orbit and tensor terms in Gogny EDF

Energy Density Functionals are of major interest for the study of the atomic nucleus as, coupled with mean-field and beyond N-body approaches, they are applicable to the whole nuclear chart, including superheavy elements. On the one hand, the growing need for nuclear data and, on the other hand, the large amount of experimental data on exotic nuclei explain the work carried out on these phenomenological forms of the nucleon-nucleon interaction to analyze the richness of the nuclear phenomena. In this paper, we propose a fully finite-range extension of the Gogny EDF, including a short-range spin-orbit term and a long-range tensor term. The original fitting protocol of the Gogny interaction has been adapted to include both finite range spin-orbit and tensor terms, adding new constraints and filters linked to relevant data. Nuclear matter, spectroscopic and fission properties are discussed, highlighting ways of improving EDFs when all spin and isospin exchanges are introduced with finite-range terms.

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HFB3: an axial HFB solver with Gogny forces using a 2-center HO basis (C++/Python)

The HFB3 program solves the axial nuclear Hartree-Fock-Bogoliubov (HFB) equations using bases formed by either one or two sets of deformed Harmonic Oscillator (HO) solutions with D1-type and D2-type Gogny effective nucleon-nucleon interactions. Using two sets of HO solutions shifted along the z-axis (2-center basis) allows to accurately describe highly elongated nuclear systems while keeping a moderate basis size, making this type of basis very convenient for the description of the nuclear fission process. For the description of odd-even and odd-odd systems, the equal-filling-approximation is used. Several observables can be calculated by the program, including the mean values of the multipole moments, nuclear radii, inertia tensors following Adiabatic Time-Dependent Hartree-Fock-Bogoliubov (ATDHFB) or Generator Coordinate Method (GCM) prescriptions, local and non-local one-body densities, local and non-local pairing densities, some fission fragment properties, etc. The program can ensure that the mean values associated with some specific operators take pre-defined values (constraints). Such constraints can be set on the usual multipole moments (for protons, neutrons or total mass). This program can be used as a monoprocess and monothreaded CLI executable, or through full-featured Python bindings (available through the Python Package Index PyPI).

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