Explainable observers and interpretable AI for superconducting accelerators and radioactive isotope identification
GANIL’s SPIRAL1 and SPIRAL2 facilities produce complex data that remain hard to interpret. SPIRAL2 faces instabilities in its superconducting cavities, while SPIRAL1 requires reliable isotope identification under noisy conditions.
This PhD will develop observer-based interpretable AI, combining physics models and machine learning to detect, explain, and predict anomalies. By embedding causal reasoning and explainability tools such as SHAP and LIME, it aims to improve the reliability and transparency of accelerator operations.
Methods for the Rapid Detection of Gravitational Events from LISA Data
The thesis focuses on the development of rapid analysis methods for the detection and characterization of gravitational waves, particularly in the context of the upcoming LISA (Laser Interferometer Space Antenna) space mission planned by ESA around 2035. Data analysis involves several stages, one of the first being the rapid analysis “pipeline,” whose role is to detect new events and to characterize them. The final aspect concerns the rapid estimation of the sky position of the gravitational wave source and their characteristic time, such as the coalescence time in the case of black hole mergers. These analysis tools constitute the low-latency analysis pipeline.
Beyond its value for LISA, this pipeline also plays a crucial role in the rapid follow-up of events detected by electromagnetic observations (ground or space-based observatories, from radio waves to gamma rays). While fast analysis methods have been developed for ground-based interferometers, the case of space-borne interferometers such as LISA remains an area to be explored. Thus, a tailored data processing method will have to consider the packet-based data transmission mode, requiring event detection from incomplete data. From data affected by artifacts such as glitches, these methods must enable the detection, discrimination, and analysis of various sources.
In this thesis, we propose to develop a robust and effective method for the early detection of massive black hole binaries (MBHBs). This method should accommodate the data flow expected for LISA, process potential artifacts (e.g., non-stationary noise and glitches), and allow the generation of alerts, including a detection confidence index and a first estimate of the source parameters (coalescence time, sky position, and binary mass); such a rapid initial estimate is essential for optimally initializing a more accurate and computationally expensive parameter estimation.
Unveiling the Universal Coupling Between Accretion and Ejection: From Microquasars to Extragalactic Transients
This PhD project investigates the universal coupling between accretion and ejection, the fundamental processes through which black holes and neutron stars grow and release energy. Using microquasars as nearby laboratories, the project will study how variations in accretion flows produce relativistic jets, and how these mechanisms scale up to supermassive black holes in tidal disruption events (TDEs).
Accretion–ejection coupling drives energy feedback that shapes galaxy formation and evolution, yet its physical origin remains poorly understood. The candidate will combine multi-wavelength observations—from SVOM (X-ray/optical) and new radio facilities (MeerKAT, SKA precursors)—to perform time-resolved analyses linking accretion states to jet emission.
Recent missions such as Einstein Probe and the Vera Rubin Observatory (LSST) will greatly expand the sample of transients, including jetted TDEs, enabling new tests of jet-launching physics across mass and time scales.
Working within the CEA/IRFU team, a major SVOM partner, the student will participate in real-time transient detection and multi-wavelength follow-up, while also exploiting archival data to provide long-term context. This project will train the candidate in high-energy astrophysics, radio astronomy, and data-driven discovery, contributing to a unified understanding of accretion, jet formation, and cosmic feedback.
Aurorae are well known optical phenomena in the Solar System planets. Aurorae have great diagnostic value, as their emissions reveal the planets’ atmospheric compositions, the occurrence of magnetic fields and the solar wind conditions at the planet’s orbit. Looking for aurorae on exoplanets and brown dwarfs is the next frontier. A first breakthrough in this direction has occurred recently, with the detection of a CH4 emission attributed to auroral excitation on the brown dwarf W1935. This detection, and the prospects of observing other auroral features with existent and upcoming telescopes, is what motivates this project. In particular, we will build the first model dedicated to investigate CH4 and H3+ auroral emission on exoplanets and brown dwarfs. The model will be used to investigate the conditions at W1935, and to predict the detectability of aurorae on other sub-stellar objects.
Beam dynamics for a multi-stage laser-plasma accelerator
Laser–plasma wakefield accelerators (LWFAs) can provide accelerating gradients exceeding 100 GV/m, providing a pathway to reduce the size and cost of future high-energy accelerators for applications in synchrotron radiation, free-electron lasers, and emerging medical and industrial uses.
Scaling this technology to higher beam energies and charges requires both technological maturity and innovative acceleration schemes. Multi-stage configurations — connecting several plasma acceleration stages — offer key advantages: increasing beam energy beyond single-cell limits and enhancing total charge and/or repetition rate. These systems aim to overcome single-stage limitations while maintaining or improving beam quality at higher energies.
Designing an accelerator delivering stable, reproducible, high-quality beams requires comprehensive understanding of plasma acceleration physics and beam transport between successive stages.
Building on expertise at CEA Paris–Saclay's DACM, this PhD will focus on physical and numerical studies to propose a fully integrated multi-stage LWFA design, with particular attention to optimizing all components — plasma accelerating section and transport lines — to preserve beam quality in terms of transverse size, divergence, emittance, and energy spread.
Exploring trends in rocky exoplanets observed with JWST
One of JWST’s major goals is to characterize, for the first time, the atmospheres of rocky, temperate exoplanets, a key milestone in the search for potentially habitable worlds. The temperate rocky exoplanets accessible to JWST are primarily those orbiting M-type stars. However, a major question remains regarding the ability of planets orbiting M-dwarfs to retain their atmospheres.
In 2024, an exceptional 500-hour Director’s Discretionary Time (DDT) program, entitled Rocky Worlds, was dedicated to this topic, underlining its strategic importance at the highest level (NASA, STScI).
The main objective of this PhD project is to: 1) Analyze all available JWST/MIRI eclipse data for rocky exoplanets from Rocky Worlds and other public programs using a consistent and homogeneous framework; 2)Search for population-level trends in the observations and interpret them using 3D atmospheric simulations.
Through this work, we aim to identify the physical processes that control the presence and composition of atmospheres on temperate rocky exoplanets.
Stochastic Neutron Noise Estimation Using a Rare-Event Simulation Approach. Application to the Monitoring of Nuclear System Reactivity
This PhD project aims to develop an innovative method to characterize the reactivity of fissile systems by analyzing their stochastic fluctuations, known as zero-power neutron noise. In a subcritical fissile medium, neutrons originating from spontaneous fission can initiate short and random chain reactions, generating a fluctuating signal. This noise carries essential information on the distance of the system to criticality, a key parameter both for the safety of nuclear installations (prevention of criticality accidents) and for the detection of undeclared fissile materials (nuclear security and non-proliferation).
Existing theoretical approaches to infer system reactivity from neutron noise are limited to idealized situations and become unsuitable in realistic configurations, particularly when the system is strongly subcritical or when significant uncertainties exist regarding its geometry or composition (as in the case of the Fukushima Daiichi corium or spent fuel storage). Monte Carlo simulations then appear as a natural alternative, but current simulations rely on variance reduction techniques that fail to correctly preserve stochastic fluctuations.
This thesis proposes to address this scientific challenge by adapting a relatively recent variance reduction method known as Adaptive Multilevel Splitting (AMS), originally developed to efficiently sample rare events while preserving their statistical properties. The goal is to extend this method to neutron transport in multiplying media and to make it a tool capable of faithfully simulating the temporal correlations characteristic of neutron noise. Following the theoretical developments, the algorithm will be implemented in Geant4, compared to analytical benchmark solutions, and experimentally validated through in situ measurements (using neutron sources or research reactors). In the long term, this work may lead to direct applications in nuclear monitoring, safety diagnostics, and detector physics, while also opening perspectives in fundamental physics and medical physics.
Magnetar formation: from amplification to relaxation of the most extreme magnetic fields
Magnetars are neutron stars with the strongest magnetic fields known in the Universe, observed as high-energy galactic sources. The formation of these objects is one of the most studied scenarios to explain some of the most violent explosions: superluminous supernovae, hypernovae, and gamma-ray bursts. In recent years, our team has succeeded in numerically reproducing magnetic fields of magnetar-like intensities by simulating dynamo amplification mechanisms that develop in the proto-neutron star during the first seconds after the collapse of the progenitor core. However, most observational manifestations of magnetars require the magnetic field to survive over much longer timescales (from a few weeks for super-luminous supernovae to thousands of years for Galactic magnetars). This thesis will consist of developing 3D numerical simulations of magnetic field relaxation initialized from different dynamo states previously calculated by the team, extending them to later stages after the birth of the neutron star when the dynamo is no longer active. The student will thus determine how the turbulent magnetic field generated in the first few seconds will evolve to eventually reach a stable equilibrium state, whose topology will be characterized and compared with observations.
Understanding the origin of the remarkable efficiency of distant galaxy formation
The James Webb Space Telescope is revolutionizing our understanding of the distant universe. A result has emerged that challenges our models: the extremely high efficiency of star formation in distant galaxies. However, this finding is derived indirectly: we measure the mass of stars in galaxies, not their star formation rate. This is the main weakness of the James Webb. The aim of this thesis is to remedy this weakness by using its angular resolution capacity, which has not been taken into account until now, in order to obtain a more robust measurement of the SFR of distant galaxies. We will deduce a law that will improve the robustness of SFR determination using morphological properties and combining data from the James Webb Space Telescope with data from ALMA (z=1-3). We will then apply it to the distant universe (z=3-6, part 2) and use it as a benchmark for numerical simulations (part 3).
Spectro-temporal analysis of Gamma-Ray Burst afterglows detected with SVOM
Gamma-Ray Bursts (GRB) are the most powerful explosions in the Universe. They last a few tens of seconds and emit the same amount of energy as the Sun during its entire lifetime. They gamma-ray emission is followed by a long lasting (hours to days) emission from the X-rays to the radio band. This "afterglow" emission is rich on information about the GRB nearby environnent and host galaxy. SVOM (Space based astronomical Variable Object Monitor) is a Sino-French mission, dedicated to GRB studies, and has been successfully launched in June 2024. It carries a multi-wavelength payload covering gamma-rays/X-rays/optical and includes two dedicated ground based robotic telescopes in Mexico and China.
The PHD project is focussed on the exploitation of the SVOM data for GRBs. The successful candidate will join the MXT science Teal at DAp. MXT is a new type of X-ray telescope, for which the DAp is responsible and its Instrument Centre is also hosted at DAp.
The PHD student will participate actively to the spectral and temporal analysis of MXT data. These data will be compared
to the other data acquired by the SVOM collaboration, especially in the optical an infrared domains.
This dataset will be used as a support to the physical interpretation of GRBs. More specifically, the aspects related to the modeling of the energy injection in the first phases of the afterglow will be used to determine the nature of the compact object at the origin of the relativistic flux, generating the electromagnetic emission observed.