Transcutaneous sampling of gaseous biomarkers

The development of wearable medical devices is a fundamental and essential in order to promote ambulatory medicine. Exhaled gases as transcutaneous gases (gases that diffuse through the skin) are known to carry molecules ("biomarkers") representative of pathologies or degradation of the physiological state, the ambulatory monitoring of which would be a real diagnostic and monitoring tool. However, the personal equipment associated to the continuous monitoring of exhaled gases is inappropriate for intensive sports activities, unlike the transcutaneous gases monitoring which could be carried out without losing mobility and discreetly (social impact), for example with a device placed on the forearm. Apart from oxygen and carbon dioxide, most of the biomarkers present are in very low concentrations and are therefore difficult to detect. One way of getting around this low concentration is to carry out a pre-concentration step, i.e. to accumulate over time, and therefore to concentrate enough molecules so that they are more easily detectable and measurable.
The objective of this thesis is therefore to develop and optimise a transcutaneous gas collector and pre-concentrator. The work will consist in particular in modelling the gas exchanges between the skin and the device in order to optimize the efficiency of the pre-concentration. The model will be compared with experimental results on a gas test bench for validation with two biomarkers of interest.
This subject requires a highly motivated person with skills in modelling and instrumentation. Skills in mechanical design of medical devices would be a plus.

Study and optimization of a blast wave generated by a pulsed electric generator

Design of a new light-sheet microscope for the temporal monitoring of organoids-on-chip

The subject of the thesis is the development of a fluorescence light-sheet microscope for the optical characterization of organoids-on-chips and 3D organoids. The thesis will focus on the conception of a compact multi-color 3D system, to allow time-lapse imaging of multi-scattering 3D samples directly in a cell culture incubator. The work will begin with a clear understanding of the miniaturization process on the quality of the images. The excitation will be correctly model to avoid optical artefacts and to allow the deepest penetration into the biological tissue. The candidate will be responsible to test different optical strategies as well as different excitation wavelengths. As a final step, the system will be characterized in a cell culture incubator for the morphological and functional monitoring of organs-on-a-chip and 3D organoids using specific fluorescent markers. If needed, novel modifications of the microfluidic chamber with integrated optical functions will be proposed. The research program will mainly focus on the morphological and functional monitoring of two samples: pancreatic organoids on a microfluidic chip and 3D brain organoids.

Contribution of Artificial Intelligence in Establishing Three-Dimensional Contamination Mapping within Civil Engineering Structures of Nuclear Facilities using Gamma Spectrometry Measurements

Understanding the radiological inventory of a nuclear installation is paramount to ensure the control of safety and criticality risks throughout the facility's lifespan, as well as to manage the radiological impact on both human health and the environment. Managing the radiological condition of the processes and equipment within an installation enables the definition of safe intervention scenarios to optimize maintenance operations or decontamination/dismantling activities in hostile environments and enhance waste management. During the dismantling of a nuclear facility, decontamination operations are necessary to reclassify areas from nuclear waste zones to conventional waste zones. This step necessitates the prior creation of an accurate map of artificial radioactivity within the concrete civil engineering structures.

To address the limitations of existing methodologies and in accordance with the directives of the Nuclear Safety Authority (ASN), the proposed doctoral research aims to develop an innovative and efficient non-destructive radiological characterization methodology using machine learning algorithms (artificial intelligence) for automated analysis of in-situ gamma spectrometry measurements with a highly resolved Germanium detector. The ultimate goal is to establish real-time three-dimensional maps of contaminant distribution within contaminated civil engineering structures of nuclear facilities.

The characterization methodology developed as a result of this project holds significant potential for industrial applications, particularly in the field of nuclear facility decontamination and dismantling.

The doctoral candidate will work within a team with extensive experience in the development and in situ implementation of non-destructive radiological characterization techniques (alpha and gamma imaging techniques, alpha, beta, and gamma spectrometry techniques). The candidate will have the opportunity to evaluate the proposed solutions on some of the world's largest dismantling sites.

The desired profile is a candidate with an engineering school or Master's degree (M2) background and strong knowledge in nuclear instrumentation and measurement, particularly in the physical phenomena related to the interactions of ionizing radiation with matter. An inclination towards, and preliminary proficiency in, statistical data processing methods and machine learning (computer programming in Python) are likewise highly valued.

Investigation and use of uranium glasses for optical neutron detection

The Dosimetry, Sensors and Instrumentation Laboratory of the CEA Cadarache, develops, manufactures and operates neutron flux detectors used in the vicinity of and inside nuclear reactor cores. In addition to conventional detectors (fission chambers, collectrons, etc.), the laboratory is working on innovative measurement methods such as optical detectors, semiconductors, fiber scintillators, etc. As part of this PhD thesis, the laboratory wants to explore the potential of Uranium-doped glasses. These glasses are known to show bright fluorescence under various types of radiations. The main idea of this thesis is to try to exploit this fluorescence to detect the fission reactions induced when the glass is exposed to a neutron flux. This could enable the development of a new generation of optical neutron detectors halfway between a fission chamber and a scintillator.
The thesis will focus on two main topics:
- firstly, a detailed understanding of fluorescence mechanisms, and the synthesis of uranium glass with properties optimized for our needs (sensitivity, emission spectrum, isotopic vector, etc.). Synthesis will be carried out in partner laboratories;
- secondly, the development of a dedicated instrumentation, probably in the form of optical fibers, to test these prototypes in a reactor.

Design and realization of a high-temperature optical neutron detector. Application to an experimental program in the JOYO reactor

As part of the development of fourth-generation sodium-cooled fast reactors, the CEA/IRESNE Dosimetry and Instrumentation Laboratory is working on innovative neutron measurement systems capable of operating at temperatures of the order of 600°C, and insensitive to the parasitic phenomena that occur under these conditions. Recently, a new type of optical signal neutron detector (ODN) has been developed at the laboratory. Despite a more complex signal interpretation, this instrument has several advantage: it can be miniaturized and it is intrinsically insensitive to problems of partial discharges and leakage currents that occur in ionization chambers at high temperature.
We propose to pursue the theoretical and experimental development of ODNs to adapt them to high temperatures. The PhD student will further develop the modelling tools already available in the laboratory for simulating the detector response. The work will investigate heavy ion-noble gas interaction cross sections, also a radiative collisional model to predict emission spectra and their temporal dynamics. Part of the work will involve dimensioning a high-temperature prototype and testing it in the JSI TRIGA reactor. Ultimately, the detector will be qualified in the JOYO research reactor as part of a broader experimental program.

Development of methodologies for testing electronic systems in irradiating environments

Decontamination and dismantling (D&D) worksites, and more generally nuclear facilities, involve the use of electronic equipment (sensors, mobile vectors, robots, remotely operated arms, etc.) in harsh environments. Radiation is one of the main factors affecting the reliability of electronic components and systems. In this context, the evaluation of electronic components and systems makes it possible to identify which technologies are most tolerant to irradiating environments, and also to determine which sub-functions are the most sensitive.
To address this challenge, it is necessary to develop electronic qualification methodologies for the nuclear field, based on experience from the space field but taking into account certain specific features: the environment can be much more extreme, the use of commercial components is widespread, and a system-level approach must be considered (as it is not possible to develop everything from the component upwards). System-level testing and the use of COTS components in irradiating environments are emerging issues of interest to many stakeholders.
The thesis work will therefore begin with the study of specifically developed systems. We will then have a complete understanding of the system and, above all, of the elementary components that make it up. We'll be able to characterize each elementary component and the complete system under a single beam. The degradation synergy between the system and the elementary component will be studied to evaluate degradation rules, before moving on to the implementation of methodologies that can then be evaluated on commercial "black box" systems. The aim is to verify that the conclusions reached in the first stage are still valid, and to determine the observables needed to identify a failure. Innovative AI-based data analysis methods can also be implemented, depending on the type and quantity of data collected. Given the expected numbers of systems to be tested, it is also essential to complement this work with a rationalization of irradiation resources. To this end, tests will be carried out, notably on the filtering of X-ray photons in the photoelectric range to keep only the Compton range and thus have an equivalence to Cobalt60. Finally, a methodology will have to be implemented. This methodology will have to take into account system procurement, definition of observables, definition of irradiation and characterization conditions, as well as analysis of the elementary and functional failures observed.
Part of the thesis work will also involve defining the structure of a "radiation" database for listing radiation tests carried out on electronic components and systems.

System-level testing and the use of commercial components (COTS) in irradiating environments are topical issues. At the end of the thesis, the student will be able to apply these skills to a wide range of applications in the nuclear field (A&D sites, reactors), as well as to large particle physics instruments and the space sector.

Candidate profile : Master's degree in electronics or engineering degree in electronics.

Taylor bubbles: experiments and modeling

This doctoral position focuses on the microscale phenomena that occur in the near-wall region at bubble motion in a capillary tube (also known as Taylor bubble). These are elongated bubbles of vapor having bullet-like shapes that are formed in compact heat exchangers used in a variety of industrial applications such as cooling of electronics and steam generators in nuclear reactors, for instance. The phenomena associated include dewetting dynamics, formation of micrometric thick liquid layers and heat transfer. The PhD candidate will conduct an experimental study at STMF/CEA and SPEC/CEA (Paris-Saclay, France) using advanced non-intrusive optical diagnostics to evaluate these phenomena, in particular the film profile. The student will use the experimental data to validate a numerical approach in the open-source software OpenFOAM that will be developed in partnership with the University of Nottingham (United Kingdom).

Critical metal enrichment of solid streams from used printed circuit boards by multi-spectral sorting and artificial intelligence

In this project, we propose to valorize the critical metals lost, as they are not currently retrieved, when recycling printed circuit boards. The focus will be on the key step of sorting the electronic components resulting from the dismantling of these boards. This project involves the study of a multispectral sorting prototype combined with the development of software for recognition by Artificial Intelligence.

This thesis is financed by the REVIWEEE and CYCLAMET projects of the PEPR (priority research programs and equipment) 'Recyclability, recycling and reincorporation of recycled materials' of the 4th Future Investment Program of the French government. During his or her Ph.D. thesis work, the student will be exposed to an international and multidisciplinary environment, with in particular the realization of experimental developments in various fields such as mechatronics, spectroscopy, physical chemistry, characterization and modelling in strength of materials, instrumentation; but also, to work in programming and algorithms with the Borelli Centre of the ENS Paris-Saclay, partner of the project (co-direction of the thesis).

This thesis is therefore an excellent opportunity for professional growth, both from the point of view of your knowledge, and your know-how and life skills in an international multi-cultural environment: the CEA group is bi-located in Saclay and Singapore. It will also be an opportunity to use your knowledge in a practical way to achieve a goal with a potentially high environmental impact.

Effect of substitution on the ferroelectric and photocatalytic properties of Barium Titanate nanoparticles

As part of the energy transition, the production of hydrogen from solar energy appears to be an extremely promising means of storing and then producing energy. To develop on a large scale, water photoelectrolysis requires materials with high catalytic efficiency. Among the candidates considered, materials derived from barium titanates appear promising because their ferro- and piezoelectric properties could increase their photocatalytic effect. Therefore, we propose to synthesize BaTiO3 nanoparticles by flame spray pyrolysis and to make substitutions on Ba and O in order to study the effect of these modifications on the ferroelectric properties of the material. The addition of noble metal inclusions to the surface of the particles, likely to improve catalysis, will also be addressed. Finally, photocatalysis and piezocatalysis tests will make it possible to establish the links between ferroelectric and catalytic phenomena in this family of materials. This subject will be carried out in collaboration between the LEEL of the CEA and the SPMS of Centrale – Supelec.