Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

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Study of the mechanical behaviour of Li-ion cell electrodes

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

Laboratoire Modélisation multi-échelle et suivi Performance

01-09-2020

SL-DRT-20-1035

benoit.mathieu@cea.fr

Electrochemical energy storage incl. batteries for energy transition (.pdf)

In Li-ion cells, the negative electrode is currently mainly made of graphite particles. Using silicon could lead to significant improvements of the Energy Density but silicon suffers from very large volume changes upon cycling. This leads to fragmentation of particles, accelerated cell capacity loss, and possible safety issues. During this thésis, the student will investigate the mechanical behaviour of the particles in the electrode, especially the thickness changes during cycling and the stress/strain relations. He will build a numerical model to predict the mechanical properties of the electrode depending on the composition and particles morphology. The main target numerical method is the "descrete elements model" (DEM) but the student will also use other methods to bridge the gap between the electrode scale and the cell scale (homogenization methods) and the particles scale (finite elements). Input data will be obtained from dedicated experiments that will be conducted in the thesis: measurements on mechanical test Bench, morphological characterization by tomography or FIB-SEM 3D for example.

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Modular device for automated and reliable mapping of indoor installations

Département Métrologie Instrumentation et Information (LIST)

Laboratoire Capteurs et Architectures Electroniques

01-10-2020

SL-DRT-20-1036

maugan.michel@cea.fr

Factory of the future incl. robotics and non destructive testing (.pdf)

The proposed research subject will be focused on the 3D positioning of indoor measurements, where satellite-based positioning (such as the GPS) is ineffective. Different solutions already exist, but are either embedded into a specific equipment, or lack reliability and traceability. SLAM-based algorithms (Simultaneous Localization And Mapping) are of particular interest for these kind of use, allowing for simultaneous reconstruction of the surroundings and real-time localization of the sensor in the reconstructed environment, using low-cost visible cameras, possibly coupled with other sensors (e.g. inertial measurement unit) in order to increase its robustness. The research aims at developing a compact and cross-device mountable device based on these simultaneous localization and mapping solutions that are SLAM algorithms, in order to get a real-time 3D mapping of the surroundings that would include data from any measuring device (including radiological). This module would thus guarantee reliability of the 3D location of the measured value and enable traceability of the resulting mapping in an interoperable format. The device should be embeddable on off-the-shelf hand-held meters (e.g. radiation or contamination meters, gamma-ray spectrometer?) and should thus be both lightweight and compact and result in limited pre- or post-processing.

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Transportable neutron spectro-imager with high detection sensitivity

Département Métrologie Instrumentation et Information (LIST)

Laboratoire Capteurs et Architectures Electroniques

01-09-2020

SL-DRT-20-1040

clement.lynde@cea.fr

Factory of the future incl. robotics and non destructive testing (.pdf)

Mapping of the radiological situation and waste characterization are important issues for the management of the clean-up and the decommissioning of nuclear facilities. Imaging tools offer a solution of interest for remote detection and localization of irradiating hot spots, by superimposing an image of radioactivity on a visible image. Gamma imaging is the most mature technique at present, due to numerous developments carried out over the last thirty years by several research teams around the world, particularly those at CEA. However, the location and spectrometric measurement of neutron emission is also of great interest to allow the characterization of a wider range of nuclear materials as well as to confirm the presence of particular isotopes, such as plutonium or uranium. Prototypes of neutron spectro-imagers are under development, but significant improvements in terms of sensitivity or portability still need to be made to achieve the performance required to meet the needs of the nuclear industry, particularly those of decommissioning. The proposed thesis topic aims at developing a transportable neutron imager with high sensitivity and capable of measuring the neutron energy spectrum. The developments will rely on the coupling of the two methods of neutron imaging: emission encoding and the use of the elastic scattering phenomenon. This association can be achieved by setting up a measurement system composed of three elements: a coded mask and two pixelated neutron detectors. For reasons of sensitivity and compactness, the pixelated neutron detectors will be based on the coupling of neutron/gamma discriminating plastic scintillators with an array of silicon photomultipliers. The energy signature of the neutrons may be obtained by a spatial and kinetic analysis of the interactions.

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Design, fabrication and characterization of subwavelength nanostructured Si photonics devices enabled by advanced immersion lithography

Département d'Optronique (LETI)

Laboratoire d'Intégration Photonique sur Silicium

01-10-2020

SL-DRT-20-1042

cecilia.dupre@cea.fr

Photonics, Imaging and displays (.pdf)

The demand for telecommunications capacity has increased rapidly in recent years. To satisfy this demand, optical transceivers, previously used only for long distance data transfer, are now used for the shorter distances found in datacenters. Photonic integrated circuits based on silicon are particularly relevant for this application as they use establish CMOS technology to achieve high performance and yield at a low cost. Previous work has shown that integrated components based on sub-wavelength structures allow the possibility of new optical functionalities and improved performance, such as reduced insertion losses and significantly increased spectral bandwidth. The CEA-LETI has its own Si photonics platform including an immersion lithography tool that allows reproducible and precise patterning with dimensions as low as 50nm. The objective of this PhD are to design new high spectral bandwidth/low-loss photonic components using sub-wavelength structures, to develop the fabrication technology for this type of component on the CEA-LETI Si photonics platform and to characterise their optical properties. This PhD, based at CEA-LETI (Grenoble), will be in close collaboration with the C2N-CNRS (Paris-Saclay).

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New generation of coded aperture collimators for imaging ionising radiations

Département Métrologie Instrumentation et Information (LIST)

Laboratoire Capteurs et Architectures Electroniques

01-10-2020

SL-DRT-20-1056

vincent.schoepff@cea.fr

Factory of the future incl. robotics and non destructive testing (.pdf)

The localization of radioactive hot spots is a major issue for the initial characterization of an installation to be decommissioned. International research teams, in order to detect, localize and quantify the emitted radiations of radiological materials, developed specific tools for a long time. Miniaturized gamma imaging systems, equipped with coded masks (multi-pinhole collimators arranged according to a specific mathematical pattern) and pixelated semi-conductor detectors have been developed over the past twenty years, including by CEA List and CEA Irfu who are proposing the research project. Nevertheless, due to their nature, imaging high-energy radiations (from 10 keV to 2 MeV) still is challenging, and we propose to address those challenges in the frame of this subject. Aiming at developing a new generation of large field of view coded masks, the research program will lead to prototypes manufactured by sophisticated techniques of machining and/or by 3D metal printing processes, allowing the optimization of performances in the field of gamma and neutron imaging. Expected research paths will focus on two different encoding methods : non linear spatial encoding with 3D masks (hemispherical, conical or polyhedral) and temporal encoding (setting the mask in motion to allow temporal modulation of signals, a route generally considered risky in systems and rarely studied). The two encoding approaches will be studied independently and successively then coupled, in order to optimize performance.

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Development of uniform surface sources by functionalization for decommissioning & dismantling

Département Métrologie Instrumentation et Information (LIST)

Laboratoire de Métrologie de l'Activité

01-10-2020

SL-DRT-20-1058

valerie.lourenco@cea.fr

The decommissioning of nuclear installations and the management of the radioactive waste produced during this stage are major concerns for the future, especially with the ageing of the European nuclear plants. Improving the qualification of contamination assessment systems would make it possible to analyse more precisely and ideally identify more quickly the the appropriate waste management channel to help control the resulting costs. The thesis topic focuses on widespread cases where the activity is present on/in surfaces, flat or curved, as well as in pipes. The objective of the thesis is to realize uniform, traceable, flat or cylindrical surface sources, even deformable, with limited radiation attenuation (case of pure beta or alpha emitters). The added value associated with the traceability of these sources lies in the control of the deposited activity level, whatever the radionuclide considered. The approach adopted is the functionalization of a substrate to immobilise and distribute the radionuclides uniformly without excessive attenuation of the radiation emitted, while ensuring that the surface remains non-contaminating. The formation of strong chemical bonds with the surface will guarantee the stability of the layer formed and the chemical affinity with the grafted complexing molecules aims to permanently immobilise the activity. The choice of the functionalization method depends on the substrate on which the bonding takes place (metallic, polymeric, conductive or non-conductive, flexible or rigid). The other end of these molecules can be functionalized to make them specific to the target radionuclides. The tests of surface sources will be carried out first with Am-241, both alpha and low energy gamma emitter and pure beta or not emitters of interest for the elaboration of typical waste spectra. The problem of large surfaces and especially the criterion of source uniformity (variability of surface activity < 10 %, including uncertainties), constrain the method to be used for the functionalization of the surface. The evaluation of the uniformity of the activity distribution over the source surface will be carried out by autoradiography (imaging technique whose signal is proportional to the activity).

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