Calibration of the new High-Angle Time Projection Chambers of the T2K Experiment and Measurement of CP Violation in Neutrino Oscillations
The proposed thesis project focuses on studying neutrino oscillations, a key quantum phenomenon for exploring New Physics beyond the Standard Model. These oscillations, compared between neutrinos and antineutrinos, could shed light on one of the most fundamental questions in particle physics: the origin of the matter-antimatter asymmetry in the Universe.
The T2K experiment, located in Japan, studies these oscillations by generating an intense beam of muon neutrinos (and antineutrinos). This beam is measured at two points: a near detector, used to reduce systematic uncertainties related to the neutrino flux and interaction models, and a far detector (Super-Kamiokande), responsible for measuring the disappearance of muon neutrinos and the appearance of electron neutrinos after oscillations.
The thesis project is divided into two parts. The first part will involve calibrating the new detectors (new time projection chambers using resistive MicroMegas technology) to measure the neutrino energy spectrum and assess the associated systematic uncertainties. The second part will focus on analyzing the newly collected data, allowing for more precise measurements of oscillation parameters, improving the understanding of neutrino-nucleus interactions, and measuring CP violation in neutrino oscillations with 3 sigma significance in the case of maximal violation, as indicated by the latest T2K results, and ultimately 5 sigma in the future Hyper-Kamiokande experiment, which will use the same beam and near detector as T2K.
Measurement of charm elliptic flow in semi-central Pb-Pb collisions at 5 TeV at CERN with LHCb.
Heavy-ion collisions provide a unique opportunity to study the quark-gluon plasma (QGP), an exotic state of matter where quarks and gluons are no longer confined within hadrons and believed to have existed just a few microseconds after the Big Bang. Charm quarks are among the key probes for investigating the QGP. Indeed, they retain information about their interactions with the QGP, making them essential for understanding the properties of the plasma. The production of charm quarks and their interactions with the QGP is studied through the measurements of hadrons, mesons and baryons, containing at least one charm quark or antiquark, like D0 mesons or Lambda_c baryons. However, the hadronization process—how charm quarks become confined within colorless baryons or mesons—remains poorly understood.
A promising approach to gaining deeper insights into charm hadronization is to measure the elliptic flow of charm hadrons, which refers to long-range angular correlations and is a signature of collective effects due to thermalization. By comparing the elliptic flow of D0 mesons and Lambda_c baryons, researchers can better understand the charm hadronization mechanism, which is sensitive to the properties of the created medium.
To measure elliptic flow, the selected student will develop an innovative method that leverages the full capabilities of the detector. This method, which has never been applied before, provides a more intuitive and theoretically sound interpretation of the results. The candidate will adapt this technique for use with the LHCb detector to measure, compare, and interpret the elliptic flow of Lambda_c charm baryons and D0 mesons with the PbPb samples collected by LHCb in 2024.
Sensitivity calculation in deterministic neutronics: development of methodologies for the lattice phase.
Deterministic neutronics calculations usually rely on a two-step approach, called lattice and core steps. In the first one, the multigroup cross-sections are reduced (condensed over a few energy groups and homogenized over assembly-size regions) using a small subset of the whole system geometrical model (typically, a single subassembly representative of a repeated pattern) in order to reduce the dimensionality of the core calculation step. When those reduced cross-section sets are used for core sensitivity analyses, the impact of the lattice step is usually neglected. For some quantities of interest, this can lead to important discrepancies between the computed sensitivities and the actual ones, since lattice transport calculations are key for carrying the fine-energy local neutron spectrum information and resonance self-shielding effects. There can be an additional concern when those sensitivity calculations are used to provide feedback on nuclear data evaluations, or in the case of similarity studies. In order to address this issue, several approaches are available, such as direct calculations or perturbation theory studies, each representing different trade-offs in terms of cost or complexity.
The goal of this PhD is therefore to explore the state of the art of the domain, ranging from the most brute force approach to the ones based on perturbation theory, with the possibility to propose new methodologies. The implementation of the chosen methodologies in new generation codes (such APOLLO3) will allow eventually to improve the accuracy of sensitivity calculation.
The doctoral student will be based in a reactor physics research unit at CEA/IRESNE in Cadarache, which hosts many students and interns. Post-graduation perspectives include research in nuclear R&D labs and industry.
Impact of power histories on the decay heat of spent nuclear fuel
Decay heat is the energy released by the disintegration of radionuclides present in spent fuel. Precise knowledge of its average value and range of variations is important for the design and safety of spent fuel transport and storage systems. Since this information cannot be measured exhaustively, numerical simulation tools are used to estimate the nominal value of decay heat and quantify its variations due to uncertainties in nuclear data.
In this PhD, the aim is to quantify the variations in decay heat induced by reactor operating data, particularly power histories, which are the instantaneous power of fuel assemblies during their residence in the core. This task presents a particular challenge as the input data are no longer scalar quantities but time-dependent functions. Therefore, a surrogate model of the scientific computing tool will be developed to reduce computation time. The global modeling of the problem will be carried out within a Bayesian framework using model reduction approaches coupled with multifidelity methods. Bayesian inference will ultimately solve an inverse problem to quantify uncertainties induced by power histories.
The doctoral student will join the Nuclear Projects Laboratory of the IRESNE institute at CEA Cadarache. He/she will develop skills in neutron simulation, data science, and nuclear reactors. He/she will be given the opportunity to present his/her work to various audiences and publish it in peer-reviewed journals.
Development of an X-ray detection system for particle ID of superheavy nuclei
The synthesis and study of the superheavy nuclei (SHN) is still one of the major challenges of modern nuclear physics. Experimental studies of hitherto unknown nuclei depend crucially on their identification in terms of atomic charge Z and nuclear mass A. To complete particle ID capabilities of the separator-spectrometer set-up S3 at GANIL-SPIRAL2, already providing a mass resolution sufficient to resolve the A of SHN, its focal plane detection system SIRIUS will be provided with X-ray detection for Z identification of the species of interest. The development of an X-ray detection system array, employing thin germanium crystals with thin entrance windows (based on so-called Low-Energy Photon Spectrometers (LEPS)), its integration in the SIRIUS set-up as well as its in-beam test and use for SHN decay spectroscopy will be the main tasks of the Ph.D. thesis. The Ph.D. student will be involved in SHN spectroscopic studies at GANIL and international accelerator laboratories like ANL, which serve as efficient preparation of the experiment campaigns planned at S3 which is scheduled to come online in 2024. This Ph.D. thesis work is an important ingredient for the preparation of the detection instrumentation needed for the S3 operation.
Study of reaction mechanisms for the synthesis of super-heavy elements
One of the main activities in nuclear physics is the study of the properties of the exotic nuclei up to the limits of the nuclear chart, in regions with extreme proton-neutron ratios (proton/neutron driplines) and at the highest masses A and atomic numbers Z. The so-called super-heavy nuclei (SHN) are expected to exist beyond the liquid drop limit of existence defined by a vanishing fission barrier, thanks to the quantum mechanical shell effects. These nuclei are particularly interesting because they are at the limit between few-body and large n-body physics: the magic proton and neutron numbers, Z and N, are replaced by a magic region or island extended in Z and N.
The synthesis of these very and super-heavy nuclei by fusion-evaporation reactions is an experimental challenge due to the extremely low cross-sections. Modelling the complete reaction in order to guide the experiments is also a difficult challenge, as models developed for lighter nuclei cannot simply be extrapolated. Fusion reactions are hindered compared to what is observed with light nuclei, because the very strong Coulomb interaction is enhanced by the strong repulsion caused by the large number of positive charges (protons) in the system in competition with the attractive strong (nuclear) force in a highly dynamic regime. The predictive power of the models needs to be improved, although the origin of the hindrance phenomenon is qualitatively well understood. The quantitative ambiguities are large enough to observe a few orders of magnitude differences in the fusion probabilities calculated by different models. A small change in the cross-section could result in many months being required to perform successful experiments.
At GANIL, in collaboration with other institutes, we have developed a model that describes all the three steps of the reaction to synthesise super-heavy nuclei. Future developments will focus on finding ways to assess the models in order to improve their predictive power, including the design of dedicated experiments to constrain the so-called fusion hindrance. Of course, a careful uncertainty analysis, which is new in theoretical nuclear physics, will be necessary to assess the different ideas. Standard methods as well as state-of-the-art data analysis methods such as Bayesian analysis may be used.
This PhD work will be done in collaboration with the experimental group at GANIL and a research team in Warsaw (Poland). Depending on the skills of the student, the thesis will be more oriented towards formal developments or towards the experiments at the new S3 facility at Spiral2. Participation in experiments is possible.
Experimental and theoretical studies of the fission fragment excitation energy and angular momentum generation
The discovery of nuclear fission in 1939 profoundly changed our understanding of nuclear physics. The fission reaction is the splitting of heavy nuclei, such as uranium 235, into two lighter nuclei, together with the release of a large amount of energy. Many years of research have led to the development of nuclear fission models, from which evaluated nuclear data files are derived. These files are essential inputs to reactor simulations; yet, their quality needs to be improved.
This PhD thesis aims to study the generation of angular momentum and the excitation energy of fission fragments from both experimental and theoretical standpoints. These studies will not only improve our understanding of the underlying process and our models, but also enhance the predictive power of simulation tools, particularly those used to predict gamma heating in reactors. Part of the work will involve finalizing the analysis of data acquired as part of a recent thesis. The student will take part in complementary experimental campaigns at the nuclear reactor of the Institut Laue-Langevin (ILL), using the LOHENGRIN spectrometer to measure isomeric ratios and the kinetic energy distributions of fission fragments.
The doctoral student will be based in a nuclear and reactor physics unit. He/she will develop skills in nuclear physics, data analysis, and computer programming. The programming languages used will be C++ and Python. Professional perspectives include academic research, R&D organisations, nuclear industry, and possibly also data scientist positions.
Time reversal invariance test in nuclear beta decay: Analysis of the data of MORA at JYFL
The Matter’s Origin from RadioActivity (MORA) experiment searches for a sign of CP violation in nuclear beta decay, via the precise measurement of the so-called D correlation. An innovative technique of in-trap ion polarization for such a measurement enables attaining unprecedented sensitivity to New Physics, which could explain the matter-antimatter asymmetry observed in the universe. With a goal in sensitivity on a non-zero D of a few 10-4, the measurement that MORA is undertaking at Jyväskylä will be competitive with the best limit obtained so far on a non-zero D correlation in neutron decay [5]. To attain such precision regime several weeks of data taking are required along the coming years (2025-2027) at Jyväskylä, both for 23Mg+ and 39Ca+. The data analysis has to be undertaken in parallel. Crosschecks and adaptation of existing simulations of individual detectors of MORA, performed with GEANT4 and PENELOPE Monte Carlo codes, are required to pursue the investigation of systematics effects potentially affecting the final sensitivity on D. Dissemination of the results of the data analysis at national and international conferences will be asked to the PhD student.
Innovative modeling for multiphysics simulations with uncertainty estimates applied to sodium-cooled fast reactors
Multiphysics modeling is crucial for nuclear reactor analysis, yet uncertainty propagation across different physical domains—such as thermal, mechanical, and neutronic behavior—remains underexplored due to its complexity. This PhD project aims to address this challenge by developing innovative methods for integrating uncertainty quantification into multiphysics models.
The key objective is to propose optimal modeling approaches tailored to different precision requirements. The project will explore advanced techniques such as reduced-order modeling and polynomial chaos expansion to identify which input parameters most significantly impact reactor system outputs. A key aspect of the research is the comparison between "high-fidelity" models, developed using the CEA reference simulation tools, and "best-estimate" models designed for industrial use. This comparative analysis will highlight how these errors propagate through different models and simulation approaches.
The models will be validated using experimental data from SEFOR, a sodium-cooled fast reactor. These experiments provide valuable benchmarks for testing multiphysics models in realistic reactor conditions. This research directly addresses the growing need for reliable, efficient modeling tools in the nuclear industry, aiming to improve reactor safety and performance.
The candidate will work in a dynamic environment at the CEA, benefiting from access to advanced simulation resources and opportunities for collaboration with other researchers and PhD students. The project offers the possibility of presenting results at national and international conferences, with strong career prospects in nuclear reactor design, safety analysis, and advanced simulation.
Development of a dosimetry system to track alpha particles in in vitro assays for Targeted Alpha Therapy
Targeted Alpha Therapy (TAT) is a promising new method of treating cancer. It uses radioactive substances called alpha-emitting radioisotopes that are injected into the patient's body. These substances specifically target cancer cells, allowing the radiation to be concentrated where it is needed most, close to the tumors. Alpha particles are particularly effective because of their short range and ability to target and destroy cancer cells.
As with any new treatment, TAT must undergo preclinical studies to test its effectiveness and compare it to other existing treatments. Much of this research is done in laboratory, where cancer cells are exposed to these radioactive substances to observe their effects, such as cell survival. However, assessing the effects of alpha particles requires special methods because they behave differently than other types of radiation.
Recently, a method for measuring the radiation dose received by cells in laboratory experiments has been successfully tested. This method uses detecto