Determination of the elemental composition of micrometric and submicrometric particles levitating in a low pressure Radio-Frequency plasma discharge using Laser-Induced Breakdown Spectroscopy

International audienceThe LIBS (Laser-Induced Breakdown Spectroscopy) technique has shown its potential in many fields of applications including that of aerosol analysis. The latter is usually carried out on the particle flow, thereby allowing quantitative detection in various experimental conditions such as ambient air analysis or exhaust stack monitoring, to name but a few. A possible alternative method for particle analysis has been experimented combining a low pressure RF (Radio-Frequency) plasma discharge with the LIBS technique. Such approach has two peculiar features in comparison to the usual LIBS analysis. First, the particles injected in the RF plasma discharge are trapped in levitation. Second, the analysis is performed at a reduced pressure of around 1 mbar. LIBS detection at such low pressure has this peculiarity that particle vaporization is assumed to be achieved through direct laser particle interaction whereas it is caused by laser-induced plasma ignited in the gas at atmospheric pressure. The use of such particle trap could allow improving particle sampling, making organic particle analysis possible (by using an inert gas for RF plasma ignition) and even (depending on the pressure) obtaining a better signal to noise ratio. Detection of the elements of nanoparticle agglomerates made following their injection in the RF discharge has demonstrated the feasibility of such approach. Future experiments are intended to explore its potentialities when tackling issues such as process control or ambient air monitoring

Mutual Impedance Probe in Collisionless Unmagnetized Plasmas With Suprathermal Electrons—Application to BepiColombo

Context: Mutual impedance experiments are active electric probes providing in-situ space plasma measurements. Such active experiments consist of a set of electric antennas used as transmitter(s) and receivers(s) through which various dielectric properties of the plasma can be probed, giving therefore access to key plasma parameters such as, for instance, the electron density or the electron temperature. Since the beginning of the space exploration, such active probes have been launched and operated in Earth's ionospheric and magnetospheric plasmas. More recently and in the coming years, mutual impedance probes have been and will be operated onboard exploratory planetary missions, such as Rosetta, BepiColombo and JUICE, to probe the cometary plasma of 67P/Churyumov-Gerasimenko, the Hermean and the Jovian magnetospheres, respectively.Aims: Some analytic modeling is necessary to calibrate and analyse mutual impedance observations in order to access to macroscopic bulk plasma quantities. In situ particle observations from various space missions have confirmed that space plasmas are out of local thermodynamic equilibrium. This means that particle velocity distributions can be far from a Maxwellian distribution, exhibiting for instance temperature anisotropies, beams or a suprathermal population. The goal of this paper is to characterize the effect of suprathermal electrons on the instrumental response in order to assess the robustness of plasma diagnostics based on mutual impedance measurements in plasmas characterized by a significant amount of suprathermal particles.Methods: The instrumental response directly depends on the electron velocity distribution function (evdf). In this work, we choose to model suprathermal electrons by considering different approaches using: (i) a kappa evdf, (ii) a double-Maxwellian evdf or (iii) a mix of a Maxwellian evdf and a kappa evdf. For each case, we compute the spatial distribution of the electrostatic potential induced by the transmitters, discretized and modeled here as an ensemble of pulsating point charges.Results: We apply our modeling by building synthetic mutual impedance spectra of the PWI/AM2P probe, lauched in October 2018 onboard the Mercury Magnetospheric Orbiter (MIO/MMO) spacecraft of the BepiColombo exploratory space mission, in order to calibrate and analyse the future electron observations in the plasma environment of Mercury

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Detection and metrology of nanoparticles trapped inside a low pressure cold plasma

Face au développement actuel des nanotechnologies il apparaît important de pouvoir contrôler la taille des nano-objets mis en oeuvre par les industriels aussi bien pour la qualité des produits manufacturés que pour la sécurité des personnes et la protection de l'environnement. Le travail qui a été accompli au cours de cette thèse concernait la recherche de solutions innovantes pour mesurer la taille de nanoparticules en voie sèche. Pour cela nous nous sommes plus particulièrement concentrés sur la physique des plasmas poudreux. En effet l'utilisation d'un plasma permet de favoriser la désagglomération de l'échantillon de poudre que l'on souhaite caractériser et la présence de poussières dans un plasma modifie sensiblement les caractéristiques électriques de ce dernier. Nous avons montré dans un premier temps qu'il est possible de déterminer la taille moyenne de poussières piégées dans une décharge capacitive RF à basse pression à partir de la mesure de la variation des paramètres électriques de cette dernière quand de la poudre s'y forme ou y est injectée. Nous avons également développé une nouvelle technique de granulométrie par sédimentation à basse pression et assistée par plasma. Cette technique consiste à disperser l'échantillon de poudre en l'injectant dans un plasma puis à en déduire sa taille à partir de la mesure de sa vitesse de sédimentation après l'extinction du plasma. Ainsi, il est possible de déterminer la fonction de distribution en taille de l'échantillon de poudre que l'on analyse. Le système que nous avons conçu a été utilisé avec succès pour contrôler en temps réel une ligne de production de nanopoudres au CEA Saclay.The recent development of nanotechnology has made nanoparticle sizing more and more important for the quality of manufactured products as well as for human health and environmental protection. The aim of this thesis was to look for innovative solutions to measure the size and the concentration of nanoparticles in dry environnement. To meet this requirement we focused on the physics of dusty plasmas because the desagglomeration of a powder sample is enhanced when it is exposed to a plasma and the dusts modify signifcantly the electrical properties of the plasma where they are trapped. The first result of this work is the determination of the mean size of dusts that are injected or formed in a RF low pressure capacitive discharge from the variations of the electrical parameters of the plasma and of the discharge. A new particle sizing technique has also been developed. It consists of determining the powder size distribution from the measurement of its sedimentation speed following the extinction of the discharge. The system that has been designed was successfully used to monitor in real time a nanopowder production line based at the CEA Saclay

Détection et métrologie de nanoparticules en suspension dans un plasma froid basse pression

Face au développement actuel des nanotechnologies il apparaît important de pouvoir contrôler la taille des nano-objets mis en oeuvre par les industriels aussi bien pour la qualité des produits manufacturés que pour la sécurité des personnes et la protection de l'environnement. Le travail qui a été accompli au cours de cette thèse concernait la recherche de solutions innovantes pour mesurer la taille de nanoparticules en voie sèche. Pour cela nous nous sommes plus particulièrement concentrés sur la physique des plasmas poudreux. En effet l'utilisation d'un plasma permet de favoriser la désagglomération de l'échantillon de poudre que l'on souhaite caractériser et la présence de poussières dans un plasma modifie sensiblement les caractéristiques électriques de ce dernier. Nous avons montré dans un premier temps qu'il est possible de déterminer la taille moyenne de poussières piégées dans une décharge capacitive RF à basse pression à partir de la mesure de la variation des paramètres électriques de cette dernière quand de la poudre s'y forme ou y est injectée. Nous avons également développé une nouvelle technique de granulométrie par sédimentation à basse pression et assistée par plasma. Cette technique consiste à disperser l'échantillon de poudre en l'injectant dans un plasma puis à en déduire sa taille à partir de la mesure de sa vitesse de sédimentation après l'extinction du plasma. Ainsi, il est possible de déterminer la fonction de distribution en taille de l'échantillon de poudre que l'on analyse. Le système que nous avons conçu a été utilisé avec succès pour contrôler en temps réel une ligne de production de nanopoudres au CEA Saclay.The recent development of nanotechnology has made nanoparticle sizing more and more important for the quality of manufactured products as well as for human health and environmental protection. The aim of this thesis was to look for innovative solutions to measure the size and the concentration of nanoparticles in dry environnement. To meet this requirement we focused on the physics of dusty plasmas because the desagglomeration of a powder sample is enhanced when it is exposed to a plasma and the dusts modify signifcantly the electrical properties of the plasma where they are trapped. The first result of this work is the determination of the mean size of dusts that are injected or formed in a RF low pressure capacitive discharge from the variations of the electrical parameters of the plasma and of the discharge. A new particle sizing technique has also been developed. It consists of determining the powder size distribution from the measurement of its sedimentation speed following the extinction of the discharge. The system that has been designed was successfully used to monitor in real time a nanopowder production line based at the CEA Saclay.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

Discharge impedance evolution, stray capacitance effect, and correlation with the particles size in a dusty plasma

International audienceDust particles growing or injected in a plasma modify significantly the impedance of capacitively coupled radio frequency discharges. The principal modifications are the increase of the plasma bulk resistance and of the plasma sheath capacitance. In this work, we propose a method to evaluate the impedance of the discharge (sheath+plasma bulk) during the growth of dust particles in a plasma. This method does not require the measurement of any current/voltage phase shift. Then, the evolution of the power coupled into the plasma as well as the voltage drop across the plasma bulk are derived. It follows that the plasma coupled power increases by a factor of five during the dust growth. The effect of the reactor stray capacitance on the power coupled to the plasma is underlined. Finally, a perfect correlation between the evolution of the size of the dust particles in the plasma and the increase of the plasma/electrode sheath capacitance suggests that charged dust particles induce an electrostatic force on the plasma sheath. An analytical model is proposed in order to take this phenomenon into account in future dusty plasma electrical modelling

Electrical time resolved metrology of dust particles growing in low pressure cold plasmas

International audienceThe electrical parameters of a capacitively coupled radiofrequency (CCRF) discharge change significantly when dust arises in the discharge. This work demonstrates the ability to follow in real time the evolution of the size and of the concentration of dust particles forming in a CCRF discharge from the variation of the electron density and of the self-bias voltage of the active electrode. According to experimental findings, it appears that the variation of this self-bias voltage depends on the surface of the dust particles. This trend is confirmed by an analytical modelling considering the low frequency behaviour of the phenomenon

Instrumental modeling of Mutual Impedance experiments and validation tests in plasma chamber

International audienceMutual impedance experiments are in situ space plasma diagnostic techniques for the determination of characteristic plasma parameters, such as the plasma density and the electron temperature. These electric experiments rely on the coupling between two emitting and two receiving antennas embedded in the plasma to be diagnosed.Different versions of mutual impedance instruments are included in the scientific payload of past, present and future exploratory planetary space missions, such as the RPC-MIP instrument onboard the Rosetta spacecraft that explored the cometary environment of comet 67P/CG, the PWI/AM2P experiment onboard the Mio spacecraft of the BepiColombo mission that will investigate the Hermean environment, the RPWI/MIME experiment onboard the JUICE spacecraft that will characterize the magnetosphere and ionosphere of Ganymede, and the DFP/COMPLIMENT instrument onboard the Comet Interceptor spacecraft that will map the ionized environment of a pristine comet and its interaction with the solar wind.The next step in planetary exploration shall rely on small satellite platforms and the concept of multi-point measurements missions. In particular, by mapping the investigated plasma environment, multi-point measurements shall improve our understanding of the investigated physical phenomena by enabling the distinction between spatial and time dependent variations, a distinction that is not possible with current single-point measurements configurations.In this context, mutual impedance instruments are now being adapted to better fit small satellite platforms. Instrumental development efforts are put into various and complementary directions. First, we are increasing the signal emission amplitude of the mutual impedance instrument in order to improve the signal-to-noise ratio of the measurements and to relax EMC (i.e. electromagnetic compatibility) constraints on the small satellite platform while maintaining robust plasma density and electron temperature diagnostic performances. Second, we are optimizing the time-resolution of the instrument to facilitate the coupling of mutual impedance experiments with different plasma experiments, such as the Quasi-Thermal Noise and the Langmuir Probe experiments, all using the same electric sensors to perform their measurements. Indeed, coupling between different experiments and sharing of sensors is crucial for nanosatellite applications, where the limited mass and volume strongly constrain the design of the payload instrumentation.To reach such goals, we use two complementary tools. Our first tool is a numerical 1D-1V full-kinetic electrostatic Vlasov-Poisson model that enables to simulate the propagation of electric perturbations generated in the plasma by mutual impedance experiments and address both the effect of nonlinearities and inhomogeneities in the instrumental response. Our second tool is the plasma chamber of CNRS-LPC2E space laboratory (Orléans, France) that enables experimental tests of space plasma instruments and nanosatellites in typical plasma conditions encountered in planetary ionospheres. We use this plasma chamber to test both mutual impedance miniaturized instrument prototypes and new mutual impedance instrumental modes.The results of our investigation are the following.First, using our new instrumental model in both linear and non-linear regimes, we identify for the first time the maximum emission amplitude that can be used in mutual impedance experiments without introducing spurious nonlinear perturbations in the plasma and show the robustness of both plasma density and electron temperature diagnostics even when non-linear effects such as wave-wave and wave-particle interactions are triggered in the plasma. We find on optimal threshold of the electric energy injected in the plasma to be smaller than 10% of the electron thermal energy, to be applied to the design of future mutual impedance experiments.Second, using both our numerical model and the plasma chamber facility, we show that the sensor occupation can be drastically reduced without loss of plasma density diagnostic, thus potentially enabling a significant increase of time resolution for future mutual impedance experiments. This result enables the design of a new mutual impedance instrumental mode, called "chirp mode", for which the measurement time duration is reduce by a factor 10-100 compared to typical space applications such as the RPC/MIP onboard the Rosetta spacecraft.These new instrumental developments will be at the basis of significant improvements in the design of future mutual impedance experiments for planetology exploration

Detection of nanoparticle agglomerates trapped in a low pressure RF (Radio-Frequency) plasma discharge using LIBS (Laser-induced Breakdown spectroscopy)

Nanotechnology is often said to be the industry of the 21st century. In most cases, the designing of nanostructured materials implies utilizing engineered nanoparticles as basic building blocks. Such materials often have new functionalities and enhanced properties which make them of great interest for many industrial applications. The apparent limitless possibilities offered by nanotechnologies in terms of applications and economic gain are to lead to a dramatic increase of engineered nanoparticle production. The need for nanoparticle-based materials is therefore expected to grow along with that for nanometrology allowing characterization of nanoparticles in-situ and in real time if possible. Workplace surveillance and process control are among many others issues where such instrumental development is required

Quantitative Determination of Density of Ground State Atomic Oxygen from Both TALIF and Emission Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

International audienc