Scientific direction Development of key enabling technologies
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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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Vegetal-voltaic: Solar approach for the design of a green district: Optimization of the coupling between photovoltaic solar and vegetation at different scales

Département des Technologies Solaires (LITEN)

Laboratoire enveloppe et Intégration du PhotoVoltaïque

01-10-2020

SL-DRT-20-1046

ya-brigitte.assoa@cea.fr

Solar energy for energy transition (.pdf)

Achieving European energy objectives requires the design of greener districts, therefore their revegetation, but also the integration of renewable energies such as solar photovoltaic. An optimal arrangement of these two elements is essential with urban densification according to their specific constraints, sometimes in conflict, for good energy efficiency and growth (occupation of areas on the ground or on the building, weather conditions...). The purpose of this thesis is to conduct an in-depth analysis of the criteria for sizing solar installations and plants allowing their symbiosis in the urban landscape. The work will consist of the numerical and experimental studies at different scales (building and ground) of solutions optimizing the choice of photovoltaic technology according to the type of plants and the desired impact on their growth speed, their lifespan and their layout. An optimized approach for the system design based on the management of thermal (emissivity on the rear face) and optical (transmission and reflection of solar radiation) exchanges between the photovoltaic module and the surrounding plants will be defined. A thermal, electrical and optical model validated according to the defined solutions of arrangement of the system ?PV modules and plants? (on building, ground and support structure) will be proposed.

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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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Improvement and understanding of the performance of silicon cell-based solar generators in harsh environments

Département des Technologies Solaires (LITEN)

Laboratoire Photovoltaïque à Concentration

01-09-2020

SL-DRT-20-1061

philippe.voarino@cea.fr

Solar energy for energy transition (.pdf)

The thesis will be carried out at the interface of several laboratories of the Department of Solar Technologies (DTS) of the CEA located in Le Bourget du Lac on the campus of the National Institute for Solar Energy (INES). The objective of this thesis is to improve the resistance to environmental conditions (radiation, e/H+, UV, thermal cycling) of space solar generators based on silicon solar cells, and to better understand the degradation mechanisms of cells/materials associated. By finely controlling the manufacturing of cells (doping, impurity, architecture, etc.) and modules (materials, thickness, architecture, optical trapping, etc.), it is possible to improve the performance of silicon modules at the end of their lifetime while maintaining a competitive price (?/W), 1 to 3 orders of magnitude lower than space III-V modules.

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Modeling the energy consumption flexibility on several spatial and temporal scales

Département des Technologies Solaires (LITEN)

Laboratoire Systèmes Electriques Intelligents

01-10-2020

SL-DRT-20-1068

xavier.lepivert@cea.fr

Energy efficiency for smart buildings, electrical mobility and industrial processes (.pdf)

In a context of massive integration of non-dispatchable renewable production (wind and photovoltaic), the fullfilment of « production = consumption » will imply in the future to act more and more on the second term of this equality. Many questions arise about the real potential of consumption flexibility in a smartgrid, and this depending on the geographic level and also the time range of activation. The management of flexibilities as well as their valuation, will require various models, different depending on the markets (ancillary services, SPOT, intraday, balancing market) and the geographic level considered (house, building, district, city). The thesis will focus on developing: - Electrical consumption and flexibilities modelling - Learning algorithms / parameterization of these models. These will be oriented ?big data?. - Methodologies for getting one model from another To carry out this work, we will use existing simulation tools for the finest spatial scales as well as a consumption measurement database (« Linky » smart metering).

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