11 sujets IRFU/DPhN

Dernière mise à jour : 31-03-2020


• Neutronics

• Nuclear Physics

• Nuclear physics

• Particle physics

 

Simulation and tests of a compact neutron source based on the IPHI accelerator

SL-DRF-20-0717

Research field : Neutronics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Loïc THULLIEZ

Antoine DROUART

Starting date : 01-10-2020

Contact :

Loïc THULLIEZ
CEA - DRF/IRFU/DPhN/LEARN

0169087453

Thesis supervisor :

Antoine DROUART
CEA - DSM/IRFU/SPhN/Structure Noyau

01 69 08 73 52

Neutron beams are used for many applications in materials science, engineering, archaeology or the study of works of art, where they complement other non-destructive analyses, such as X-ray imaging. These beams are traditionally supplied by nuclear research reactors or spallation sources.

The choice of the source depends on the characteristics of the desired neutron beam (energy spectrum, frequency of neutron pulses, etc.). Today a large proportion of reactors are reaching the end of their life cycle. For example, the Orphée research reactor will be closed in October 2019. To compensate for the reduction in the available neutron beam time (limiting the number of experiments that can be carried out), new alternative sources are being developed. These, called CANS (Compact Accelerator Neutron Sources) produce neutrons through nuclear reactions of charged particles (proton, deutons) on a target, the material of which depends on the type and energy of the incident particles. A CANS is being developed at CEA-Saclay (tests and measurements are under way) at the IPHI-neutrons facility with the longer-term objective of developing the SONATE source. IPHI-neutrons uses high intensity (>10mA) and low energy (3MeV) proton beams on a beryllium or lithium target. The neutrons generated with energies above > 100 keV are then moderated to energies below 50 meV. These new facilities have the advantage of being cheaper and more flexible than nuclear reactors or spallation sources. However, due to their lower power compared to reactors, neutron fluxes are less important. This is why it is necessary to optimise these installations as much as possible and therefore to be able to model their operation from the production of primary neutrons to their final use.

This thesis topic proposes to carry out a full simulation of a CANS, within the framework of the IPHI-neutrons project. This simulation will integrate the production of primary neutrons in the target, the propagation of these neutrons and their slowing down by a cold moderator as well as their transport to the measurement point by an optimized collimator, allowing the minimization of the background noise on the experimental device. Finally, the use of the neutron beam for a radiography application will also be modelled. These simulations will be based on tests and measurements performed on the IPHI-neutrons facility. These will aim at the characterization the neutron beam (energy, spatial distribution, flux) as well as the gamma background noise at the point of detection. The student will actively participate in the installation of equipment, tests and data analysis.

Pushing ab initio calculations of atomic nuclei throughout the nuclear chart

SL-DRF-20-0439

Research field : Nuclear Physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Vittorio SOMA

Thomas DUGUET

Starting date : 01-10-2020

Contact :

Vittorio SOMA
CEA - DRF/IRFU/DPhN/LENA

0169083236

Thesis supervisor :

Thomas DUGUET
CEA - DRF/IRFU/DPhN/LENA

0169082338

Laboratory link : http://irfu.cea.fr/dphn/index.php

The theoretical description from first principles, i.e. in a so-called ab initio fashion, of atomic nuclei containing more than ~12 nucleons has become possible only recently thanks to crucial developments in many-body theory and the availability of increasingly powerful high-performance computers. Such ab initio techniques are being successfully applied to study the structure of nuclei starting from the lighter isotopes and reaching today mid-mass nuclei containing up to about 80 nucleons. The extension to even heavier systems requires decisive breakthroughs regarding the storage and running time induced by any of the available many-body methods. In this context, the goal of the thesis is to formulate and apply the recently proposed Importance Truncation (IT) techniques within the frame of Gorkov Self-consistent Green’s function calculations, a specific ab initio technique devised at CEA Saclay over the last 9 years, as a way to select a priori and systematically many-body basis states that do contribute significantly to many-body correlations. The project will exploit the latest advances in nuclear theory, including the use of nuclear interactions from chiral effective field theory and renormalisation group techniques, as well as high-performance computing codes and resources. The work will consist in formal developments, computational tasks and application of the new technology to cases of experimental interest. International collaborations constitute an integral part of the project.
Continuum QCD approaches and 3D structure of the nucleon

SL-DRF-20-0457

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Cédric Mezrag

Hervé Moutarde

Starting date : 01-10-2019

Contact :

Cédric Mezrag
CEA - DRF/IRFU/DPhN/LSN


Thesis supervisor :

Hervé Moutarde
CEA - DRF/IRFU/SPhN/Théorie Hadronique

33 1 69 08 73 88

Laboratory link : http://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=4189

Most of the visible mass of the universe is contained in nucleons. However, the origin of this mass remains mysterious, with the portion from the Higgs mechanism in standard renormalization schemes corresponding to only a few percent of the total mass. The answer is to be found in the dynamics of strong interaction, described by the theory of quantum chromodynamics (QCD) in terms of quarks and gluons. Thus, the interaction between quarks and gluons is responsible for the emergence of known and measured properties of hadrons such as their masses or spins.

There is now a strong theoretical and experimental dynamic to determine the 3D structure of hadrons in terms of quarks and gluons. From a theoretical point of view, the classical tools of quantum field theory, namely perturbative expansion, do not allow the study of the emerging properties of hadrons. The latter are inherently non- disruptive.

The aim of this thesis is to develop and use a non-perturbative formalism based on the Dyson-Schwinger and Bethe-Salpeter equations to determine the 3D structure of hadrons, in particular the nucleon. Different dynamic assumptions will be used to obtain a 3D mapping of the charge, mass and orbital angular momentum effects. A comparison of the results obtained with the experimental data will be carried out in collaboration with the other LSN members.
SHAPE EVOLUTION IN NEUTRON-RICH EXOTIC NUCLEI

SL-DRF-20-0011

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Magdalena Zielinska

Wolfram KORTEN

Starting date : 01-10-2020

Contact :

Magdalena Zielinska
CEA - DSM/IRFU/SPhN/Structure Noyau

01 69 08 74 86

Thesis supervisor :

Wolfram KORTEN
CEA - DRF/IRFU/DPhN/LENA

+33169084272

Personal web page : https://www.researchgate.net/profile/Wolfram_Korten

Laboratory link : http://irfu.cea.fr/Sphn/Phocea/Vie_des_labos/Ast/ast_sstheme.php?id_ast=293

More : https://www.phy.anl.gov/atlas/

One of the most fundamental properties of the atomic nucleus is its shape, which is governed by the interplay of macroscopic, liquid-drop like properties of the nuclear matter and microscopic shell effects, which reflect the underlying nuclear interaction. In some cases, configurations corresponding to different shapes may coexist at similar excitation energies, which results in the wave functions of these states mixing. Experimental observables such as quadrupole moments and the electromagnetic transition rates between states are closely related to the nuclear shape. The experimental determination of these observables, therefore, represents a stringent test for theoretical models. This thesis is integrated in our ongoing programme to study nuclear shapes by means of Coulomb excitation and more specifically such an experiment is planned on 100Zr. This method allows to extract the excitation probability for each excited state and to extract a set of electro magnetic matrix elements, and in particular the quadrupole moment which determines the shape of the nucleus. The radioactive 100Zr beam is provided by the ATLAS-CARIBU facility at Argonne National Laboratory (ANL), which is currently the only facility world-wide able to deliver beams of such refractory elements. The programme advisory committee has already accepted the experiment with high priority and we expect it to be scheduled in Q4/2020. The PhD student will participate in the preparation and setting-up of the experiment. It would be advantageous if he/she started already working on the subject already during the stage M2. He/she will be responsible for the data analysis, the presentation of the scientific results (at conferences or workshops) and their publication in a scientific journal. During the thesis work the PhD student may also participate in other experiments of the research group. All experiment(s) take place in international collaborations and may require prolonged stays at foreign laboratories (e.g. 4-6 weeks at ANL, USA).
The nuclear fission process in the light of prompt gamma-rays

SL-DRF-20-0339

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Thomas MATERNA

Starting date : 01-10-2020

Contact :

Thomas MATERNA
CEA - DRF/IRFU/DPhN/LEARN

0169084091

Thesis supervisor :

Thomas MATERNA
CEA - DRF/IRFU/DPhN/LEARN

0169084091

Personal web page : https://www.researchgate.net/profile/Thomas_Materna

Laboratory link : http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=498

Although known and studied for more than 80 years, nuclear fission remains a very active research topic both for its fundamental aspect of the study of nuclear matter and for its applications, including nuclear energy.

Prompt gamma rays allow probing the structure and properties of fragments emitted during the fission process. Their use therefore offers a new perspective for its study. In particular, it makes it possible to explore effects that have not yet been studied experimentally, such as the influence of the shape of the fragments on the fission process or the sharing of excitation energy between the fragments. On the other hand, the measurement of fission-prompt gamma rays also provides valuable data for the simulation of gamma heating in nuclear reactors.

The thesis work will consist in the analysis of the data from the new gamma spectrometer, FIPPS, installed at the Grenoble research reactor. This spectrometer is composed of an array of Germanium detectors arranged around a fissile target placed in an intense flux of thermal neutrons. Experimental results will allow the student to test recent models on the fission and fragment de-excitation processes.

Neutron-Proton interaction and spectroscopy of neutron-rich chlorine isotopes

SL-DRF-20-0472

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Alain GILLIBERT

Starting date : 01-10-2020

Contact :

Alain GILLIBERT
CEA - DRF/IRFU/DPhN/LENA

0169082584

Thesis supervisor :

Alain GILLIBERT
CEA - DRF/IRFU/DPhN/LENA

0169082584

In nuclear physics, atomic nuclei are described in the framework of shell models, with formal analogies to atomic physics. Orbitals characterized with angular momentum are successively filled from the bottom of the nuclear well. « Magic nuclei » correspond to to the full filling of orbitals before a major energy gap is crossed, with a net gain of stability. Not only stable nuclei were successfully described this way, but it also provides a framework for the evolution of nuclear properties versus the neutron/proton asymmetry parameter. Evolution of orbitals and associated magic numbers is under study with increasing neutron number for exotic nuclei far from stability. For calcium isotopes with a magic proton number Z=20, the relative ordering of proton orbitals 0d3/2 and 1s1/2 evolves from 40Ca (N=20) to 48Ca (N=28) and filling the neutron 0f7/2 orbital as an effect of the neutron-proton interaction in nuclei [1]. It was evidenced by the measurement of energies and spins of ground states and first excited states of potassium isotopes Z=19, which can be described as a proton hole in a calcium core. We propose to extend this study of low-energy spectroscopy to the neighbor chlorine isotopes Z=17 and a valence proton in 0d3/2 and 1s1/2 orbitals.

This study will be the aim of an experiment to be done in 2020 at the RIBF facility (Tokyo). An intense secondary beam including 46,48Ar isotopes will be obtained from fragmentation of a primary 70Zn beam at 345 MeV/u. In beam spectroscopy will be studied from one proton removal reaction in inverse kinematics 46,48Ar (p,2p) 45,47Cl and a cryogenic thick liquid hydrogen target surrounded by a time-projection chamber used for proton tracking and reconstruction of the reaction vertex in the target [2]. In flight emitted photons from 45,47Cl at target will be detected with the high resolution HiCARI array of Ge detectors, dedicated to this 2020 experimental campaign. We will measure the momentum distribution of 45,47Cl fragments to determine the angular momentum (s or d wave) of the knocked proton, giving access to the spin of the final state.

The experiment will be examined in 2019 December for an expected realization in 2020. A close collaboration with nuclear structure theoreticians will be an opportunity to analyze the results and develop the theoretical skills of the student.

Search for pear-shaped nuclei in actinides: study of a new reaction mechanism for the production of neutron-deficient actinides and development of a detector dedicated to the laser spectroscopy of actinides

SL-DRF-20-0270

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Marine VANDEBROUCK

Starting date : 01-10-2020

Contact :

Marine VANDEBROUCK
CEA - DRF/IRFU/DPhN/LENA


Thesis supervisor :

Marine VANDEBROUCK
CEA - DRF/IRFU/DPhN/LENA


Understanding the limits of the nucleus cohesion, and in particular its mass limit, is currently one of the major areas of research in nuclear physics. The study of heavy nuclei, located in the upper part of the nuclear chart, has recently benefited from a new experimental approach: the laser spectroscopy. This is a method from atomic physics, allowing the properties of the nucleus to be deduced through the study of atomic levels, independent of nuclear models.

In this region of heavy nuclei, neutron-deficient actinides are of particular interest. Indeed, several theoretical calculations predict strong octupole deformations (pear shape).

The objective of the thesis is to study octupole deformations in neutron-deficient actinides. It will be done in collaboration with the University of Jyväskylä. The thesis is divided into two parts: i) an experiment at Jyväskylä to study the production of neutron-deficient actinides by a new reaction mechanism, ii) the development of a detector that will couple laser spectroscopy and delayed spectroscopy at S3/LEB at GANIL-Spiral2.
The measurement of beauty quark production in PbPb collisions at the LHC with the MFT detector

SL-DRF-20-0244

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire plasma de quarks et gluons (LQGP) (LQGP)

Saclay

Contact :

Andry Rakotozafindrabe

Stefano PANEBIANCO

Starting date : 01-10-2020

Contact :

Andry Rakotozafindrabe
CEA - DRF/IRFU/DPhN/ALICE

0169087482

Thesis supervisor :

Stefano PANEBIANCO
CEA - DRF/IRFU/SPhN/ALICE

0169087357

Personal web page : http://irfu.cea.fr/Phocea/Membres/Annuaire/index.php?uid=mwinn

Laboratory link : http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=500

More : https://home.cern/science/experiments/alice

The Quark Gluon Plasma is a state of matter created under extreme conditions at temperatures of the few hundreds MeV where nucleon constituants are deconfined long enough to produce sizeable effects when interacting with the plasma.

Thermodynamical conditions required to form this plasma can be reproduced in ultra relativistic heavy-ion collisions at the LHC (CERN).

The goal of the proposed thesis is the first measurement in the ALICE experiment of hadrons made of bottom quarks down to zero transverse momentum in Pb-Pb collisions from their decay into J/psi resonances. This measurement adds a very important constraint in the understanding of the initial state of heavy-ion collisions and in the heavy-quarks transport within the plasma, in particular their hadronisation.

The proposed thesis will be initially concentrated on the commissioning of a new high-precision silicon detector, called Muon Forward Tracker, necessary for the detection at forward rapidities of muon pairs coming from the J/psi decay. In a second stage, the analysis of the first Pb-Pb data that will be taken in 2021 with this new detector will allow studying the separation between prompt J/psi produced during the collisions from those coming from the B-mesons decay. This study, novel within the ALICE experiment, represents a very important test of heavy quarks properties inside the Quark Gluon Plasma.
Antimatter, hypernuclei: need to know the antiproton-nucleus interaction

SL-DRF-20-0229

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Jean-Christophe DAVID

Starting date : 01-10-2020

Contact :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Thesis supervisor :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Laboratory link : http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2105

Antiproton-nucleus reactions can occur at rest or in flight. The reactions at rest, or almost (~100 eV - 1 keV), are notably used at the Antiproton Decelerator (AD) at Cern by different experiments (GBAR, ASACUSA, AEgIS, ALPHA, ATRAP,). At FAIR, the PANDA project (antiProton ANnihilation at DArmstadt) aims to study hypernuclei with in-flight reactions (~GeV). In both cases, reliable simulations are necessary for a good analysis of the results. This is where we propose to make our contribution.



The INCL calculation code (IntraNuclear Cascade Liège) developed at the CEA (Irfu/DPhN) processes hadron-nucleus reactions for energies up to 20 GeV. Recognized for its reliability, it has recently been extended to the production of strange particles and hypernuclei (with the help of the ABLA de-excitation code), and can also be used within the Geant4 transport code. The extension to antiproton-nucleus reactions will therefore make it possible to participate in PANDA’s studies on hypernuclei, with a first step of tests on data already available (obtained at LEAR), as well as in the experiments of the Antiproton Decelerator where the behaviour of anti-hydrogen atoms is studied.



In addition, INCL is able to treat nucleus-nucleus reactions when one of the nuclei is light (A <= 18). This could also be used to treat by extension reactions with anti-deuteron and anti-helium. The GAPS experiment (General Anti-Particle Spectrometer) aims precisely to measure the fluxes of these particles in cosmic radiation. Simulations are obviously necessary in this case and INCL could thus contribute to this.

Toward high-precision measurements of neutrino oscillations in the futur long baseline experiments

SL-DRF-20-0424

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Alain LETOURNEAU

Starting date : 01-10-2020

Contact :

Alain LETOURNEAU
CEA - DRF/IRFU/DPhN/LEARN

33 (0)1 69 08 76 01

Thesis supervisor :

Alain LETOURNEAU
CEA - DRF/IRFU/DPhN/LEARN

33 (0)1 69 08 76 01

The neutrino is currently the only particle in the standard model whose description is not entirely contained in it. His study therefore opens the way to the exploration of a new physics and to addressing very fundamental questions such as the preponderance of matter over antimatter in the universe. Future experiments with accelerator neutrinos (DUNE and T2HK) will measure its oscillation properties with unprecedented accuracy, which will require a high degree of control of uncertainties at the percent level.

One of the dominant uncertainties today is the one associated with the modelling of the neutrino interaction inside the detector. A decrease of this uncertainty would immediately imply an increase in the sensitivity of those experiments.

In this thesis work, we propose to improve the description of the neutrino-nuclei interaction, mainly the modelling of the final state of the interaction, and to evaluate its impact on the sensitivity of current and future experiments. The work will be based on the use and development of a nuclear cascade code coupled with measurement results. The results, coupled with an improvement of the near detector, would be used in the ongoing T2K experiment to improve the measurement of neutrino oscillations.

This work will also benefit to define the characteristics of the near detector in the DUNE experiment, whose components will be tested and validated at IRFU.
The neutrino nature through the study of double-beta decays of the Xenon 136 on in the PandaX-III experiment

SL-DRF-20-0284

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Damien NEYRET

Starting date : 01-10-2020

Contact :

Damien NEYRET
CEA - DRF/IRFU/DPhN/LSN

01 69 08 75 52

Thesis supervisor :

Damien NEYRET
CEA - DRF/IRFU/DPhN/LSN

01 69 08 75 52

Laboratory link : http://irfu.cea.fr/dphn/index.php

More : https://pandax.sjtu.edu.cn/

The neutrino, as the only particle of mater (fermion) without electrical charge, could be a Majorana particle, i.e. identical to its antiparticle. In this case a new phenomenon should appear for a few radioactive atomic nuclei: the neutrinoless double beta decay. The violation of the leptonic number which follows, forbidden by the Standard Model, would be a major discovery and one of the required conditions to explain the mater-antimatter asymmetry in the Universe.



The PandaX-III experiment aims to measure the kinematics of double-beta decays of Xenon 136 in a large volume of 10 bar gaseous Xenon. This experiment could detect double-beta decays without emission of neutrinos and distinguish them from backgrounds like regular double-beta decays with neutrino emission, gammas from radioactive contamination, or cosmics. These rare processes will be detected in gaseous Xenon inside large Time Projection Chambers (TPC) with a detection of ionization electrons based on Micromegas Microbulk micro-pattern gaseous detectors. The TPC will operate under a pressure of up to 10 bar. An excellent resolution of electron energy measurement and a very good reconstruction of the event topology is required to separate neutrinoless double-beta decays from the various backgrounds. A high radiological purity of the experimental set-up is also necessary to limit the gamma background contamination. This experiment will take place in the Jinping underground laboratory (Sichuan province, China) which presents the lowest residual cosmics rate in the world. A first 145kg-Xenon TPC chamber will be installed in 2020, and 5 modules will be installed in the following years to reach a level of 1t of Xenon.



Associated with the PandaX-III team at IRFU the student will participate to the development of data reconstruction algorithms by taking into account and compensating detectors imperfections like missing channels, performance inhomogeneities, etc... The compensation methods will include calibration methods and interpolations of missing data, and neural network methods of data corrections will be also evaluated. As soon as the data of the first TPC module are available the student will participate in collaboration of the other PandaX-III members to the analysis and the extraction of the physics results. In parallel he will participate to the detector R&D conducted on several types of Micromegas detectors, in order to reach 1% energy resolution at 2.5 MeV. This work will include performance measurements of the different prototypes in high pressure gaseous environment.

 

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