The properties of wave propagation in moving media differ from those in non-moving media. The rotation of an isotropic dielectric medium is for instance known to lead to polarisation rotation, which corresponds to a phase shift between the spin angular momentum (SAM) components of the wave, and image rotation, which corresponds to a phase shift between the orbital angular momentum (OAM) components of the wave. Compared to typical dielectrics, a rotating magnetised plasma stands out in that polarisation rotation can arise from two different contributions: Faraday rotation, which stems from the intrinsic gyrotropy of plasmas, and mechanical polarisation rotation, which stems from the medium's rotation. A rotating magnetised plasma could also provide new means to transform SAM into OAM. Understanding the implications of rotation effects on propagation is anticipated to be of importance for basic plasma physics, but also for applications including pulsars physics and light manipulation. The first part of this project will be mostly theoretical and fundamental. We will seek here to derive dispersion relations for electromagnetic wave propagation in a rotating plasma. Practically, we will build on our recent results, notably the simple case of propagation without OAM in an aligned rotator, and progressively add complexity with the goal of producing the most general model possible. We will in particular aim to include both SAM and OAM, as well as different geometrical effects. These fundamental results will then provide us with the necessary tools to examine two practical applications. The first applied problem considered here will be to examine how these effects of rotation on wave propagation could be observed in laboratory experiments. Our preliminary results indeed suggest that the effect of mechanical rotation on wave polarisation in a plasma could in principle be separated from Faraday rotation in the presence of strong magnetic fields (tens to hundreds of Teslas). Such fields have recently been achieved using capacitor-coil targets in laser driven high energy density plasma (HEDP) experiments, and we will here seek to confirm in collaboration with HEDP specialists the possibility of using these unique conditions to measure polarisation drag. Concurrently with this work on polarisation rotation in laboratory experiments, a second applied problem we will consider is the possible effects of the mechanical rotation of the magnetosphere surrounding pulsars on the polarisation of pulsars's signal received on Earth. We will notably study here, in collaboration with pulsar polarimetry specialists, how the inclusion of pulsars inclination - which is essential to pulsars' emission - in propagation model derived in the presence of rotation could explain certain experimental polarimetric observations, and in turn confirm our theoretical conjecture that polarisation could be uniquely used to determine the rotation direction in pulsars.

DECAIR aims to demonstrate the scientific and technological feasibility of a roll-to-roll plasma process at atmospheric pressure in air applied to the deposition of a thin and homogeneous layer. To keep the substrate intact and to realize a homogeneous coating on a large-scale surface, we will use a Dielectric Barrier Discharge (DBD). DBDs have been studied since the beginning of the century to realize thin layer coatings in nitrogen or rare gas atmosphere. In both cases, the quality of the coating is influenced by the regime of the discharge. When the discharge is filamentary, the coating is porous and fails to become dense. It consists of a large number of nanoparticles stacked together. By contrast, when the discharge is homogenous, the energy is uniformly transferred on the surface, then the coating is thick and consists on a homogeneous layer. Working in the homogenous mode will therefore be essential in the context of this project. To obtain a homogeneous discharge in a DBD, different pre-ionization mechanisms are required in order to create seed electrons prior to the ionization. These seed electrons result from a memory effect of the previous discharge. In rare gases or in nitrogen, the memory effect mainly depends on gas mechanisms. For a long time, it was considered impossible to obtain a diffuse discharge in air. However, recent studies as well as our preliminary results prove the opposite. Unlike in the other gases, the memory effect in air seems restricted to mechanisms occurring on the dielectric surface. Up to date, this process has not been precisely characterized. To fill this gap in knowledge, it is urgent to measure the electric charge dynamics on the dielectric during the discharge process. An interesting technique to quantify these electric charges in-situ is based on the electro-optic Pockels effects. This technic coupled to a systematic analysis of the dielectric material and the working conditions of homogeneous discharges will help understand the memory effect in air at atmospheric pressure. Simultaneously, the optimal working conditions will be established. Moreover, an optimization of the power transferred to the discharge will be carried out through a careful design of the power supply. After this optimization, it will then be possible to work at higher frequencies and at higher applied voltages, while remaining in diffuse discharge. With the increase of the excitation frequency, gas phase mechanisms are susceptible to play a non-negligible role. These mechanisms will be studied with a 1D Kinetic model and advanced optical diagnostic (OES, LIF). We will then realize SiOx coatings from the organosilicon precursor HMDSO. The choice of this precursor is due to its well-known dissociation mechanisms and our expertise working with it. We will first study the influence of the coating on the memory effect, before analyzing the coating properties and the deposition speed. The analysis of all the realized coatings will bring out the optimal conditions to obtain a dense coatings in air. These coatings will be compared to reference deposits made in atmospheric N2 homogeneous discharge. We will then demonstrate the feasibility to performing a dense and homogeneous coating of SIOx using a DBD at atmospheric pressure in air. From a scientific point of view, this project is designed to address fundamental questions, which critically limit our current understanding of the mechanisms behind homogenous DBD in air. Moreover, this process will be transferable to an industrial process through a slight modification of an existing Corona reactor treatment. The current atmospheric pressure processes use nitrogen or rare gas. By using only dry and filtered air, the financial and energetic costs of the process will be drastically reduced, which will make the coating of thin films more respectful of the environment.

This project aims to a better fundamental knowledge of discharge development and structure for low cost thin film deposition processes using low temperature plasmas at atmospheric pressure. Plasma technology is a key technology for the modification of surfaces by deposition of thin protective or functional layers. It is usually done by means of low-pressure plasmas, which require extensive vacuum equipment, require batch processing and disable in-line treatment of objects. Plasmas operated at atmospheric pressure, such as Dielectric Barrier Discharges (DBDs) can overcome these disadvantages as it could already be demonstrated for silicon containing films. However DBDs are usually strongly non-uniform and thus deposition of layers will be inhomogeneous. A full understanding of the underlying physics of discharge formation is still missing, in particular for conditions for layer deposition. For example the control of discharge uniformity in gas mixtures containing precursor molecules (deposit monomers) is rarely studied. Furthermore, layer deposition on surfaces can influence the discharge characteristics as the charging and emission of charge carriers is crucial for the operation of DBDs. Furthermore, the control of such discharges is still poor as an increase of the frequency, and consequently of the power dissipated in the gas, can drastically change the flow and the energy of the plasma species created in the gas phase and interacting with the surface. To study such processes and give experimental benchmarks for numerical simulation special dedicated DBD arrangement will be studied by means of electrical and optical diagnostics. Based on these results the correlation with layer deposition studies will result in a better understanding of the control of such processes. In detail it will be studied, how distinct discharge modes (filamentary DBD, homogenous DBD, patterned and self-organized DBD) can be controlled by means of operation parameters and discharge geometry. On one hand the discharge development of monofilaments in the filamentary mode will be investigated with special attention on the surface processes. Therefore systematic variation of the dielectrics (nature, thickness) as well as a quantitative measurement of the surface charges on the dielectrics by means of electro-optical effects are foreseen. In order to study the role of surface charging studies with liquid dielectrics, where deposited charges can be moved from the active discharge zone are also foreseen. On the other hand utilizing a novel DBD arrangement with structured electrode the collective effects between discharge channels and columns as well as the radial dynamics of discharge formation will be studied. Both teams in Toulouse and Greifswald have a long-term experience on DBDs and their diagnostics (including advanced diagnostics like cross correlation spectroscopy or Laser induced fluroescence). Two PhD students will be involved in the project. Each of them will have two co-supervisors from both countries and will spend a few months in the partner laboratory each year (total 9 months). This is an additional guarantee of efficient communication between the two partners, and of sharing of their specific expertise.

The present project makes use of recent Monte Carlo advances to design a numerical tool addressing a quite extreme climate-science calculation: evaluating the radiative forcing of an ensemble of greenhouse gases, at the global scale, integrated over climatic durations, using a reference radiative transfer model with high-resolution spectral data and 4D atmospheric fields (space and time). Starting from the null-collision concept, the feasibility was recently established and the present challenge consists in defining an efficient strategy for sampling the space of molecular transitions combined with all the geometrical and temporal complexity of atmospheric variables. For this purpose, we gather climatologists, spectroscopists, specialists in the statistical-engineering of complex systems and specialists in geometry-modelling for computer graphics applications. MCG-Rad benefits of a prototype-algorithm available and already tested for clear-sky atmospheres. This algorithm will be implemented at the launching of the project, allowing first climatic evaluations, in particular within the Radiative Forcing Model Intercomparison Project. But outside this first practicability level, a major issue is convergence-enhancement: the size of the community interested by such reference radiative-transfer computations at the climatic scale will be highly dependent on the required computational-resource. We therefore concentrate an essential part of the present research on the theoretical exploration of all means to reduce the variance of the Monte Carlo estimate, i.e. using the most advanced propositions of both the transport-physics and computer-graphics communities to reduce the computational-resources. These theoretical considerations extend widely the objective of the original algorithm (that was restricted to clear-sky single atmospheric columns). The question is scalability when thinking of: - the 4D fields produced by climate General Circulation Models (GCM), including multiple-scattering in 3D clouds below the column-scale (clouds reconstructed from the GCM outputs); - the set of all radiative-observables of interest, as elaborated by the climate-change community, i.e. with an accuracy-requirement formulated in terms of integrated radiative-forcing (a quantity that is small compared to the involved infrared and shortwave fluxes which makes it difficult to evaluate) and including sensitivities to the concentration of absorption gases. Three neighbor communities will be connected to the project as they face similar challenges: heat-transfer/combustion engineering, planet atmospheric-studies, cloud dynamics. A second circle of scientific expertise will therefore join the project via annual meetings and workshops. They will contribute to our software-design choices, structuring the libraries so that the present work addresses a broader audience as an example of jointly sampling large spectroscopic databases and complex 3D/4D fields for accurate radiative-transfer objectives.

With the recent evolution of metallic 3D printing techniques and considering all the freedom it offers in terms of mechanical design, the idea is to develop a computerized method that will be liberated from the usual manufacturing constraints capable of creating optimal electromechanical converter shapes that would break away from traditional shapes. This method will consist of a topological optimization code, currently inexistent for electrodynamics problems, and another code allowing the interface with the 3D printing realization by taking into account certain mechanical constraints (printability, stress while working). The results from this method will allow to improve the efficiency of electromechanical converters offering a substantial gain in terms of energy converted (electrical generation) or consumed (electrical motorization).