Improvement of microfluidic tools for kinetic data measurement
The development and modeling chemical processes require the acquisition of many thermodynamic and kinetic data . Conventional methods for measuring these data generally involve significant amounts of reagents. In particular for the reactive crystallisation, where the stochastic nature of nucleation requires the realization of a large number of experiments . The subject is to continue the work already done on the development of a dedicated chip to measure rapid nucleation kinetics . Firstly , the validity of kinetic measurements obtained by microfluidics technique will be evaluated and optimized based on well known and non- radioactive chemical systems . The microfluidic tool will then be used to study the sensitivity of these reactions to various operating parameters ( supersaturation , impurities , additives, etc. . ), before considering its transposition to nuclear processes such as decontamination of radioactive effluents. Finally, a new chip design could be proposed for the measurement of kinetics of liquid-liquid extraction , in connection with the development of new hydrometallurgical processes.
Development of a compact XRF for online analysis dedicated to process monitoring.
X-ray fluorescence (XRF) spectrometry is a well-known analytical technique for elemental analysis in an industrial context. In a simplified way, this technique is based on the measurement of X-radiation characteristics that are emitted by the atoms rearranging their electron cloud following an external stimulus. This is a non-destructive measurement relevant for the determination of chemical elements within liquid and solid mixture. In the 90s, the work conducted by the CEA has shown the relevance of XRF for the measurement of heavy elements using L-edge, (U, Pu, Am, Np, Cm, Pb) as well as lighter ones (Zr, Mo, Sr) using K-edge. Low detection limits (few mg/l) have been reached and the method has been implemented industrially for monitoring several processes (for instance at La Hague plant). However, operating a XRF requires heavy and cumbersome equipment, especially a nitrogen-cooled detector and a large X-Ray generator.
Recently the technology has been significantly improved on two key issues:
• The X-rays sources, which were miniaturized,
• The detectors thanks to new type of semiconductor of small volumes, operating at room temperature with a convenient spectral resolution (CdZnTe crystals for instance).
In this framework, the proposed subject concerns new R&D studies on potentialities offered by these improvements, regarding two application fields:
• On-line monitoring in reprocessing process.
• Screening of the contaminant in the polluted soils before remediation in a decommissioning context
Multiscale Modelling of Radiation Induced Segregation
Irradiation produces in materials excess vacancies and self-interstials that eliminate by mutual recombination or by annihilation at sinks (surfaces, grain boudaries, dislocations).
It sustains permanent fluxes of point defects towards those sinks. In case of preferential transport of one componant of an alloy, the chemical composition is modified in the vicinity of the sinks: a Radiation Induced Segregation (RIS). Its modelling requires a good description of the alloy properties: its driving forces (derived from the thermodynamics) and its kinetic coefficients (the Onsager matrix). The objectif on this project is to combine (i) atomic models (Kinetic Monte Carlo simulations and Self-Consistent Mean Field), fitted on ab initio calculations, that provide the Onsager coeffcients and the driving forces and (ii) a Phase-Field modelling that will give a description of the evolution of the alloy under irradiation at much larger time- and space-scales. The approach will be applied to Fe-Cr and Fe-Cu alloys, already modelled at the atomic scale. RIS will be first modelled near grain boundaries, then near dislocation loops. Special attention will be paid to the effect of elastic stresses on the RIS.
Ge-on-Insulator (GeOI) substrates for photonics
The induction of tensile strain in intrinsic and doped Germanium (Ge) is one approach currently explored to transform the Ge indirect bandgap into a direct one. To take full advantage of Ge, we study the Ge CMOS photonics platform with Ge-on-Insulator (GeOI) structure, which enables strong 2D optical confinement in the Ge photonic-wire devices. One recent study in our lab showed the interest of a method of incorporation of mechanical stress into Ge, one of the essential ingredients of the laser. In particular, the method could be applied to the massive Ge, making compatible gap direct and crystalline quality.
Post-doc objectives : Development of GeOI substrates from massive Ge donors with tensile strain inside the Ge film. These developments will be realized from the existing Smart Cut / thinning processes, combined with technological steps to overcome their current limits (SAB bonding). The substrates obtained will be characterized to determine their state of deformation as well as their damage (Raman / XRD) and final GeOI substrates will be provided to the application laboratories for the production of photonic components.
Implementation of a software package for the simulation of the Infrared Thermography Non Destructive Testing method
The CEA LIST implements simulation tools for several Non Destructively Testing (NDT) techniques, integrated to the CIVA software platform. The different methods used, nowadays in the CIVA platform, concern the ultrasonics, eddy current and radiography techniques. The TREFLE is a reference lab in thermics and had developped some original modelling approachs for the control by Infrared Thermography (IR) method. In the frame of a project funded by the Aquitaine region, these two labs collabore to implement simulation tools for the NDT by the Infrared Thermography technique, dedicated to industrial applications and accesssible to a non-numericians public.
The objective of this post-doc position is the implementation of physical modelling (in a matlab environment) for the resolution of transient thermal problems in multilayers configurations (like composite materials used in aeronautics), eventually anisotropic, for a flash or a periodic excitation with uniform or point irradtiation.
Optimal management of a tertiary energy system
In the solution concerning residential or tertiary sites that consume and produce electrical energy , the objective is to optimize the use of energy based on economic criteria or constraints networks (adaptation of the consumption) without introducing perturbations of user comfort. The purpose of this position is to develop a solution for "optimal management of the use of solar energy in a tertiary building integrating EV charging stations and storage." according to three objectives:
- Minimize the cost of consumption based on a dynamic tarif - Maximize the use of solar energy - Minimize the power demand of the network. Taking into account the LCOS (levelised Cost Of Storage) of battery . The Post- Doc will contribute and participate in: - Specification of tertiary system - Development of algorithms for managing a tertiary system - Deploy and test the proposed solution.
Contribution to the development of miniature antennas measuring devices
The generalization of RF links operating at VUHFfrequencies to equip an increasing number of communicating electronic devices helps to intensify research on miniaturization and integration of antennas. As a result, significant progress are regularly carried out to reduce the size of antennas and it is not uncommon to find work describing antenna structures of 1/30 of the wavelength maximum dimension. Increased sensitivity to the operating environment is observable with electrically small antennas. This feature is reflected by problems of measurement of electrical and radiation properties that may be altered with the standard techniques of connecting a measuring cable to the antenna. Accordingly, the subject seeks to develop techniques for electrically small antennas charterization using non-invasive methods, that is to say does not interfere (or few) under test antenna. Two techniques will be investigated based on the work already done in the laboratory. The first technique is based on the far field electromagnetic reflectometry. The second technique involves the use of an RF-optical transducer in the vicinity of the antenna under test for a particular design of miniature optic RF conversion reflectometer for measuring antenna impedance.
3D occupancy grid analysis with a deep learning approach
The context of this subject is the development of autonomous vehicles / drones / robots.
The vehicle environment is represented by a 3D occupancy grid, in which each cell contains the probability of presence of an object. This grid is refreshed over time, thanks to sensor data (Lidar, Radar, Camera).
Higher-level algorithms, like path planning or collision avoidance, think in terms of objects described by their path, speed, and nature. It is thus mandatory to get these objects from individual grid cells, with clustering, classification, and tracking.
Many previous publications on this topic comes from the context of vision processing, many of them using deep learning. They show a big computational complexity, and do not benefit from occupancy grids specific characteristics (lack of textures, a priori knowledge of areas of interest…). We want to explore new techniques, tailored to occupation grids, and more compatible with embedded and low cost implementation.
The objective of the subject is to determine, from a series of 3D occupation grids, the number and the nature of the different objects, their position and velocity vector, exploiting the recent advances of deep learning on unstrucured 3D data.
Construction of databases for radionuclide identification based on neural networks (NANTISTA project)
The project NANTISTA (Neuromorphic Architecture for Nuclear Threat Identification for SecuriTy Applications) deals with the prevention of illegal traffic of nuclear materials at international borders. The project aims at the development of a detection platform using plastic scintillators for fast radionuclide identification (such as fissile materials) based on neural networks. The post-doctoral subject consists in the development of the detection system and the construction of databases dedicated to the learning process and the optimization of the neural networks. The databases will be built with experimental measurements given by radioactive sources. Radiation-matter simulations (Monte-Carlo codes Geant4 and Penelope) will also be implemented for the construction of the databases.
Design and implementation of a bio-inspired sense, application to offshore teleoperation and to operator assistance
In recent years, the Bio-inspired Robotics Group of Robotics team IRCCyN has developed an artificial bio-inspired electric fish sense. To emulate the electrical sense, resistive probes were used for piloting the IRCCyN submarine autonomous robot.
For its part, within the Interactive Robotics Laboratory (LRI), the CEA LIST has been pursuing for several years a research activity in the field of force feedback telerobotics. The operator manipulates a slave robot located in hostile environments via a master arm located in a safe area and a computer system.
The candidate’s work will take place in a CEA- IRCCyN project running in parallel over a first project whose purpose is to demonstrate the concept of electro- haptic loop on a Cartesian arm carrying an electric probe with a fixed and known geometry. The postdoc will be in charge of implementing the loop on a "marinized" manipulator arm with a complex geometry. To do this, with the assistance of CEA and IRCCyN , he/she will support the preparation of this arm and adaptation of electrical sensor (emitter electrodes , receiver , electronic) architecture considered , as well as the adaptation of the monitoring / control of the haptic interface at the base of the electro-haptic loop. In addition to the technological challenges of this adaptation, the candidate must also consider different strategies to exploit the electric field on a multi-body system of variable geometry.
Experimental validation and proof of concept of this new offshore teleoperation system will be carried out on scenarios, to be defined, representative of the final application.