In situ and real-time characterization of nanomaterials by plasma spectroscopy
The objective of this Phd is to develop an experimental device to perform in situ and real time elemental analysis of nanoparticles during their synthesis (by laser pyrolysis or flame spray pyrolysis). Laser-Induced Breakdown Spectroscopy (LIBS) will be used to identify the different elements present and their stoichiometry.
Preliminary experiments conducted at LEDNA have shown the feasibility of such a project and in particular the acquisition of a LIBS spectrum of a single nanoparticle. Nevertheless, the experimental device must be developed and improved in order to obtain a better signal to noise ratio, to increase the detection limit, to take into account the different effects on the spectrum (effect of nanoparticle size, complex composition or structure), to automatically identify and quantify the elements present.
In parallel, other information can be sought (via other optical techniques) such as the density of nanoparticles, the size or shape distribution.
Differential phase contrast imaging based on quad-pixel image sensor
Biopharmaceutical production is booming and consists of using cells to produce molecules of interest. To achieve this, monitoring the culture and the state of the cells is essential. Quantitative phase imaging by holography is a label-free optical method that has already demonstrated its ability to measure the concentration and viability of cultured cells. However, implementing this technique in a bioreactor faces several challenges related to the high cell density. It is therefore necessary to develop new quantitative phase imaging methods, such as differential phase contrast imaging.
The objective of the PhD is to develop this technique using a specific image sensor for which a prototype has been designed at CEA-LETI. The PhD candidate will use this new sensor and develop the reconstruction and image-processing algorithms. They will also identify the limitations of the current prototype and define the specifications for a second prototype that will be developed at CEA-LETI. Finally, they will consider the design of an inline probe to be immersed in the bioreactor.
Investigation of Fuel Damage under Reactivity-Initiated Accident Conditions Using Laser Heating: Correlation with Fission Gas Release
High-power laser heating is an experimental technique developed within the Fuel Study Department that allows the induction of thermal transients on nuclear ceramic samples. It notably makes it possible to reproduce, at the laboratory scale, the thermomechanical conditions representative of an incidental or accidental sequence, in order to study fundamental mechanisms such as fuel cracking or fragmentation.
Indeed, in certain situations, such as a thermal transient of the Reactivity-Initiated Accident (RIA) type, fuel fragmentation (or over-fragmentation) can lead to the release of fission gases and ultimately result in the rupture of the fuel rod cladding.
This type of transient is particularly characterized by a complex spatiotemporal evolution of temperature within the fuel, which is difficult to reproduce at the laboratory scale. To date, only high-power laser heating techniques make it possible to replicate the heating rates reached during such transients and to reproduce the thermomechanical conditions of an RIA at the scale of a manipulable sample in the laboratory.
In this context, the PhD project aims to provide experimental data related to fuel fragmentation and over-fragmentation under Reactivity-Initiated Accident conditions. To achieve this, the student will be required to improve and develop the existing experimental setup and perform experiments aimed at reproducing the thermomechanical conditions leading to fuel fragmentation. A combined experimental/modeling approach will be necessary to optimally design and interpret the experiments. The data obtained will be used to validate the fragmentation models developed at CEA and should also allow projections for integrating these experimental techniques into shielded cells.
The PhD will be conducted within a collaborative framework (CHAIRE MATLASE) between LAMIR (Laboratory for the Analysis of Radionuclide Migration) within the Institute for Research on Nuclear Systems for Low-Carbon Energy Production (IRESNE) at CEA Cadarache, and the ILM team (Laser-Matter Interaction) at the Institut Fresnel in Marseille. The latter will provide expertise in high-power laser/material interactions and optical instrumentation for the development of the system and complex optical diagnostics.
This environment will allow the doctoral student to work in a stimulating scientific setting and to disseminate their research both in France and internationally, through conferences and publications in peer-reviewed journals.
[1]M. Reymond, J. Sercombe, L. Gallais, T. Doualle, and Y. Pontillon, ‘Thermo-mechanical simulations of laser heating experiments on UO2’, Journal of Nuclear Materials, vol. 557, 2021, doi: 10.1016/J.JNUCMAT.2021.153220.
[2]M. Reymond et al., ‘High power laser heating of nuclear ceramics for the generation of controlled spatiotemporal gradients’, J Appl Phys, vol. 134, no. 3, p. 33101, Jul. 2023, doi: 10.1063/5.0146541.
[3]Hugo Fuentes et al., ‘Numerical and experimental simulation of nuclear fuel fragmentation via laser heating of ceramics’, TopFuel 2024. Accessed: Oct. 02, 2025. [Online]. Available: https://www.researchgate.net/publication/386167297_Numerical and experimental simulation of nuclear fuel via laser heating of ceramics
Optical intradermal sensing via instrumented microneedles
Cortisol plays a central role in regulating the circadian cycle and in many essential physiological processes such as energy metabolism and immune response. Conventional monitoring of cortisol relies on single blood or saliva samples, which do not accurately reflect the temporal dynamics of its secretion. It is therefore necessary to develop innovative approaches that enable continuous, minimally invasive, and reliable measurement of cortisol concentration in patients.
The doctoral project aims to develop an original optical instrumentation system coupled with microneedles functionalized with fluorescent aptamers for continuous, minimally invasive intradermal monitoring of cortisol without the need for sampling. Within this framework, the PhD candidate will be responsible for designing and sizing the future optical microneedles intended for cortisol detection. They will set up the experimental systems required to characterize the optical microneedles fabricated within the department and test their performance in a representative environment. Finally, the PhD candidate will develop a comprehensive data processing and analysis methodology to identify the key parameters that establish a quantitative relationship between the collected signals and cortisol concentration. Altogether, this work will contribute to the development of an innovative measurement device based on cutting-edge optical emission and detection technologies available at CEA Leti, combining precision, sensitivity, compactness, and thus compatibility with in situ use.