3 sujets /DPhN/LEARN

Dernière mise à jour :


 

MODELLING LIGHT ANTI-ION REACTIONS ON ATOMIC NUCLEI

SL-DRF-24-0347

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 : 01-10-2024

Contact :

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

0169087277

Thesis supervisor :

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

0169087277

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

The anti-(p, n, d, t, 3He, 4He)-nucleus reactions are both instructive and complicated to study. In addition to knowledge of the products of the antinuclon-nucleon reaction, they require the- nuclear environment to be taken into account, in particular the interactions in the final state.
Antiproton-nucleon reactions are/will be used/studied in particular at Cern's antiproton decelerator (AD) ring and at the FAIR facility in Germany to understand the behaviour oft antimatter. Reactions with light anti-ions (dbar, 3He-bar, for example) are of more recent interest, in particular with the GAPS (General AntiParticle Spectrometer) experiment, which aims to measure the fluxes of these particles in cosmic rays. The idea is to identify dark maJer, of which these particles are decay products, and whose measured quantities could 'easily' emerge from the cosmic background noise.
Recently, antiproton-nucleus reactions have been added to the INCL (IntraNuclear Cascade Liège) nuclear reaction code developed at the CEA (Irfu/DPhN) and this code is currently being implemented in the Geant4 transport code. The aim of the proposed thesis is to now include the reactions anti-(d, t, 3He, 4He)-nucleus in the INCL code.
Uncertainty propagation in a Monte-Carlo transport code

SL-DRF-24-0367

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 : 01-10-2024

Contact :

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

0169087277

Thesis supervisor :

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

0169087277

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

Nuclear reaction modeling has been continuously being improved for many decades now. That's especially the case for our nuclear cascade code INCL. An ANR project has been funded for the next four years (2024-2027) to work on the issue of uncertainty and error estimate. Since this code is implemented in the particle transport code Geant4, the next step is to propagate these uncertainties from INCL to Geant4. There was a recent study on uncertainty propagation, called Transport Monte Carlo (TMC). However, this study only addresses the propagation of uncertainties related to model parameters, there was no propagation of model biases (related to hypotheses) and their uncertainties, which are both outside the physical model. Therefore, the propagation of biases and their uncertainties, which are coming from Monte Carlo collision models, is unexplored territory. The aim of the proposed PhD project is then to develop methods for this kind of propagation and to study the functioning and features of the developed methods in schematic scenarios. The full implementation of the developed methods into a transport code, such as GEANT4, however, is not within the core scope of the thesis, but it might be possible if time permits.
High-precision measurements of nuclear recoil on the 100 eV scale for cryogenic detectors

SL-DRF-24-0274

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

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

Saclay

Contact :

Loïc THULLIEZ

David LHUILLIER

Starting date : 01-10-2024

Contact :

Loïc THULLIEZ
CEA - DRF/IRFU/DPhN/LEARN

0169087453

Thesis supervisor :

David LHUILLIER
CEA - DRF/IRFU/DPHN/LEARN

01 69 08 94 97

The CRAB method aims to provide an absolute calibration of cryogenic detectors used in dark matter and coherent neutrino scattering experiments. These experiments have in common the fact that the signal they are looking for is a very low-energy nuclear recoil (around 100 eV), requiring detectors with a resolution of a few eV and a threshold of O(10eV). Until now, however, it has been very difficult to produce nuclear recoils of known energy to characterize the response of these detectors. The main idea of the CRAB method, detailed here [1, 2], is to induce a nuclear capture reaction with thermal neutrons (25 meV energy) on the nuclei constituent the cryogenic detector. The resulting compound nucleus has a well-known excitation energy, the neutron separation energy, being between 5 and 8 MeV, depending on the isotope. If it de-excites by emitting a single gamma ray, the nucleus will recoil with an energy that is perfectly known, given by the two-body kinematics. A calibration peak, in the desired range of some 100 eV, then appears in the energy spectrum of the cryogenic detector. A first measurement performed in 2022 with a CaWO4 cryogenic detector from the NUCLEUS experiment (a coherent neutrino scattering experiment supported by TU-Munich, in which CEA is heavily involved) has validated the method [3].

This thesis comes within the scope of the second phase of the project, which involves high precision measurements using a thermal neutron beam from the TRIGA-Mark-II reactor in Vienna (TU-Wien, Austria). Two complementary approaches will be used simultaneously to achieve a high precision: 1/ the configuration of the cryogenic detector will be optimized for very good energy resolution, 2/ large crystals of BaF2 and BGO will be placed around the cryostat for a coincident detection of the nuclear recoil in the cryogenic detector and the gamma ray that induced this recoil. This coincidence method will significantly reduce the background noise and will enable the CRAB method to be extended to a wider energy range and to the constituent materials of most cryogenic detectors. We expect these measurements to provide a unique characterization of the response of cryogenic detectors, in an energy range of interest for the search for light dark matter and coherent neutrino scattering. High precision will also open up a window of sensitivity to fine effects coupling nuclear physics (nucleus de-excitation time) and solid-state physics (nucleus recoil time in matter, creation of crystal defects during nucleus recoil) [4].

The PhD student will be heavily involved in all aspects of the experiment: simulation, on-site installation, analysis and interpretation of the results.

• Nuclear physics

• Particle physics

 

Retour en haut