CIFRE thesis in the field of non-destructive testing using magnetic sensors in collaboration with 3 partners:
Laboratoire de Nanomagnétisme et Oxyde (SPEC/LNO) du CEA Paris-Saclay
Laboratoire de Génie Electrique et Ferroélectricité (LGEF) de l’INSA Lyon
Entreprise CmPhy
Research objectives:
Use numerical modelling to optimize the properties of laser-plasma accelerators in the 50 MeV-200 MeV range for VHEE radiotherapy:
(i) optimize the properties of a laser-plasma accelerator (energy spread, divergence) with electron beams injected from a plasma-mirror injector using the WarpX and HiPACE++ codes.
(ii) Study the impact of such electron beams on DNA using Geant4DNA.
This numerical modelling will then be used to guide/design/interpret experiments of radiobiology on in-vitro biological samples that are planned at our in-house 100 TW laser facility at CEA during the project. This will be carried out in the context of research project FemtoDose funded by the French National Research Agency.
The researcher will benefit from a large variety of training available at CEA on HPC and computer programming as well as training at our industrial partners (ARM, Eviden) and Université Paris Saclay, which has MSc courses in radiobiology and also hosts a research centre (INanoTherad) dedicated to novel radiotherapy treatments, gathering physicists, radiobiologists and medical doctors. The activities will be carried out in the framework of the Marie Sklodowska Curie Action Doctoral Network EPACE (European compact accelerators, their applications, and entrepreneurship)
The solid-state systems, presently considered for quantum computation, are built from localized two-level systems, prime examples are superconducting qubits or semiconducting
quantum dots. Due to the fact that they are localized, they require a fixed amount of hardware per qubit.
Propagating or “flying” qubits have distinct advantages with respect to localised ones: the hardware footprint depends only on the gates and the qubits themselves (photons) can be created on demand making these systems easily scalable. A qubit that would combine the advantages of localised two-level systems and flying qubits would provide a paradigm shift in quantum technology. In the long term, the availability of these objects would unlock the possibility to build a universal quantum computer that combines a small, fixed hardware footprint and an arbitrarily large number of qubits with long-range interactions. A promising approach in this direction is to use electrons rather than
photons to realise such flying qubits. The advantage of electronic excitations is the Coulomb interaction, which allows the implementation of a two-qubit gate.
The aim of the present Phd will be the development of the first quantum-nanoelectronic platform for the creation, manipulation and detection of flying electrons on time scales down to the picosecond and to exploit them for quantum technologies.
N-doped oxides and/or oxinitrides constitute a booming class of compounds with a broad spectrum of useable properties and in particular for novel technologies of carbon-free energy production, surface coatings for improving the mechanical strength of steels or protection against corrosion and multifunctional sensors. In this research field the search for new materials is particularly desirable because of unsatisfactory properties of current materials. The insertion of nitrogen in the crystal lattice of an oxide semiconductor allows in principle to modulate its electronic structure and transport properties enabling new functionalities. A detailed understanding of these aspects requires materials that are as perfect as possible. The production of corresponding single crystalline thin films is however highly challenging. In this thesis work, single crystalline oxynitride heterostructures will be grown by atomic plasma-assisted molecular beam epitaxy. The heterostructure will combine two N doped layers: a N doped BaTiO3 will provide ferroelectricity and a heavily doped ferrimagnetic ferrite whose magnetic properties can be modulated using N doping to obtain new artificial multiferroic materials better suited to applications. The resulting structures will be investigated with respect to their ferroelectric and magnetic characteristics as well as their magnetoelectric coupling, as a function of the N doping. These observations will be correlated with a detailed understanding of crystalline and electronic structures. The later will be modelled thanks to electronic structure calculation to reach a comprehensive description of this new class of materials.
The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, ferroelectric and magnetic characterizations as well as in state-of-the-art synchrotron radiation techniques. X-ray magnetic dichroism is particularly suited to this study and the project will give rise to close collaboration and/or co-supervision with the DEIMOS beamline of SOLEIL synchrotron.
Our ability to manufacture metal oxide nanoparticles (NPs) with well-defined composition, morphology and properties is a key to accessing new materials that can have a revolutionary technological impact, for example for photocatalysis or storage of energy. Among the different nanopowders production technologies, Flame Spray Pyrolysis (FSP) constitutes a promising option for the industrial synthesis of NPs. This synthesis route is based on the rapid evaporation of a solution - solvent plus precursors - atomized in the form of droplets in a pilot flame to obtain nanoparticles. Unfortunately, mastery of the FSP process is currently limited due to too much variability in operating conditions to explore for the multitude of target nanoparticles. In this context, the objective of this thesis is to develop the experimental and numerical framework required by the future deployment of artificial intelligence for the control of FSP systems. To do this, the different phenomena taking place in the synthesis flames during the formation of the nanoparticles will be simulated, in particular by means of fluid dynamics calculations. Ultimately, the creation of a digital twin of the process is expected, which will provide a predictive approach for the choice of the synthesis parameters to be used to arrive at the desired material. This will drastically reduce the number of experiments to be carried out and in consequence the time to develop new grades of materials
Thermoelectricity, a materials’ capability to convert heat in to electric energy has been known to exist in liquids for many decades. Unlike in solids, this conversion process liquids take several forms including the thermogalvanic reactions between the redox ions and the electrodes, the thermodiffusion of charged species and the temperature dependent formation of electrical double layer at the electrodes. The observed values of Seebeck coefficient (Se = - DV/DT, the ratio between the induced voltage (DV) and the applied temperature difference (DT)) are generally above 1 mV/K, an order of magnitude higher than those found in the solid (semiconductor) counterpart. The first working example of a liquid-based thermoelectric (TE) generator was reported in 1986 using Ferro/ferricyanide redox salts in water.
However, due to the low electrical conductivity of liquids, its conversion efficiency was very low, preventing their use in low-temperature waste-heat recovery applications. The outlook of liquid TE generators brightened in the last decade with the development of ionic liquids (ILs). ILs are molten salts that are liquid below 100 °C. Compared to classical liquids, they exhibit many favorable features such as high boiling points, low vapour pressure, high ionic conductivity and low thermal conductivity accompanied by higher Se values. More recently, an experimental study by IJCLab and SPEC revealed that the complexation of transition metal redox couples in ionic liquids can lead to enhancing their Se coefficient by more than a three-fold from -1.6 to -5.7 mV/K, one of the highest values reported in IL-based thermoelectric cells. A clear understanding and the precise control of the speciation of metal ions therefore is a gateway to the rational design of future thermoelectrochemical technology.
Based on these recent findings, we proposes to further study the coordination chemistry of transition metal redox ions in ILs and mixtures. A long-term goal associated to the present project is to demonstrate the application potential of liquid thermoelectrochemical cells based on affordable, abundant and environmentally safe materials for thermal energy harvesting as an energy efficiency tool.
The objective of the thesis project is to analyze the physicochemical processes resulting from the extreme dose rates that can now be obtained in water with the ultra-short (fs) pulses of relativistic electrons produced by laser-plasma acceleration. Indeed, first measurements show that these processes are probably not equivalent to those obtained with longer pulses (µs) in the FLASH effect used in radiotherapy. To achieve this, we propose to analyze the dynamics of formation/recombination of the hydrated electron, an emblematic species of water radiolysis, to qualify and quantify the dose rate effect over increasingly shorter times. This will be done in three stages in support of the necessary and now accessible technological progress, to have a dose per pulse sufficient to directly detect the hydrated electron. First, with the existing UHI100 facility, using the scavenging of the hydrated electron by producing a stable species; then producing a less stable but detectable species in real time and increasing the repetition rate of the electron source. Finally, by using an innovative concept named a “hybrid target”, based on a plasma mirror as an electron injector coupled to a laser-plasma accelerator, delivering larger doses with a narrower energy spectrum, we will be able to develop pump-probe detection allowing access to the shortest times, and to the formation in clusters of ionization, of the hydrated electron and measuring its initial yield.
Optical pumping of xenon, giving rise to an intense NMR signal, is a specialty of the LSDRM team. Xenon, which is soluble in biological media, has a wide range of chemical shifts, which we use here to study the properties of cell barriers. Numerous pathologies stem from an alteration of these barriers.
In this thesis, we aim to develop a specific methodology using hyperpolarized xenon to study the functionality (integrity, permeability, selectivity) of biological barriers, using in vitro and in vivo spectroscopy and imaging. The thesis will be divided into two parts: in vitro, the aim will be to develop a device and NMR protocols for studying model cell assemblies; in vivo, studies on rodents will enable us to assess xenon's ability to reach organs more or less close to the lungs while maintaining its polarization, and to measure kinetics across barriers. This topic will enable major instrumental and methodological advances, as well as a deepening of our knowledge of selective transport processes at different biological barriers.
Due to the increasing energy demand, developing efficient storage systems, both stationary and portable, is crucial. Among these, lithium-ion batteries stand out as the most advanced, capable of being manufactured using liquid or solid electrolytes. All-solid-state batteries have a bright future thanks to their non-flammable electrolytes and their ability to use metallic lithium to increase energy density. Although research on these batteries is dynamic, their commercialization is not yet a reality. Indeed, two significant obstacles to their development remain: the low intrinsic ionic conductivity of solids and the difficulty of obtaining good solid/solid interfaces within the composite electrodes and the complete system.
This thesis explores the potential of pyrochlore oxyfluoride as a new class of superionic material for all-solid-state batteries, which are more stable in air and have higher ionic conductivity than current solid oxide electrolytes. The electrochemical properties of all-solid-state batteries will be carefully examined using a combination of in situ and operando techniques, such as XRD, Raman, ion beam/synchrotron analysis, solid-state NMR, X-ray tomography, etc.
Keywords :
Solid electrolyte, All-solid battery, Nuclear magnetic resonance, Electrochemistry, Pyrochlore Oxyfluoride, in situ/operando, Spectroscopy, Synchrotron
Graphene as a constituent of graphite was close to us for almost 500 years. However, it is only in 2005 that A. Geim and K. Novoselov (Nobel Prize in 2010) reported for the first time the obtaining of a nanostructure composed by a single layer of carbon atom. The exceptional electronic properties of graphene make it a very promising material for applications in electronic and renewable energies.
For many applications, one should be able to modify and control precisely the electronic properties of graphene. In this context, we propose to synthesize chemically graphene nanoparticles and study their absorption and photoluminescence properties. We will focus on families of elongated nanoparticles, with the aim of studying how size can enable us to observe and control multiexcitonic processes in these materials. This project will be developed in collaboration with Physicists so the candidate will work in a multidisciplinary environment.