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Benchmark calculations for electron velocity distribution function obtained with Monte Carlo Flux simulations
Get PDFModern, multi-modular plasma modeling requires accurate and versatile methods for the determination of the electron velocity distribution function from which rate coefficients of electron impact processes as well as electron transport quantities are determined. In this paper we propose as a solution a modified version of a strongly overlooked method developed in the early 90\u27s, namely, Monte Carlo Flux (MCF). The improvement lies in a criterion for the otherwise somewhat empirical selection of the time-step used in the method. We show that an MCF based code highlights and overcomes the limitations of two-terms codes such as BOLSIG+ and it is much faster than a conventional Monte Carlo. Moreover, MCF is in excellent agreement with the multi-term method for a wide range of reduced electric fields, being at the same time much simpler to implement and to extend to more general cases than the latter. Explicit illustrations of the Markov matrices representing short-time kinetics are presented to gain insight into the method. The two-dimensional velocity distribution and its expansion into Legendre polynomials are discussed for electrons in argon.</p
In Situ Observation of Nanoparticle Exsolution from Perovskite Oxides: From Atomic Scale Mechanistic Insight to Nanostructure Tailoring
No full textUnderstanding and controlling the formation of nanoparticles at the surface of functional oxide supports is critical for tuning activity and stability for catalytic and energy conversion applications. Here, we use a latest generation environmental transmission electron microscope to follow the exsolution of individual nanoparticles at the surface of perovskite oxides, with ultrahigh spatial and temporal resolution. Qualitative and quantitative analysis of the data reveals the atomic scale processes that underpin the formation of the socketed, strain-inducing interface that confers exsolved particles their exceptional stability and reactivity. This insight also enabled us to discover that the shape of exsolved particles can be controlled by changing the atmosphere in which exsolution is carried out, and additionally, this could also produce intriguing heterostructures consisting of metal–metal oxide coupled nanoparticles. Our results not only provide insight into the in situ formation of nanoparticles but also demonstrate the tailoring of nanostructures and nanointerfaces
Ultrafast Dynamics of Non-equilibrium Organic Exciton-Polariton Condensates
No full textExciton–polariton condensation in organic materials, arising from the coupling of Frenkel excitons to the electromagnetic field in cavities, is a phenomenon resulting in low-threshold coherent light emission among other fascinating properties. The exact mechanisms leading to the thermalization of organic exciton–polaritons toward condensation are not yet understood, partly due to the complexity of organic molecules and partly to the canonical microcavities used in condensation studies, which limit broadband studies. Here, we exploit an entirely different cavity design, i.e., an array of plasmonic nanoparticles strongly coupled to organic molecules, to successfully measure the broadband ultrafast dynamics of the strongly coupled system. Sharp features emerge in the transient spectrum originating from the formation of a condensate with a well-defined molecular vibrational composition. These measurements represent the first direct experimental evidence that molecular vibrations drive condensation in organic systems and provide a benchmark for modeling the dynamics of organic-based exciton–polariton condensates
First electron temperature and density measurements of D-module plasma in GAMMA 10/PDX using Thomson scattering and microwave interferometer systems
No full textWe developed an yttrium aluminium garnet (YAG)-Thomson scattering (TS) system for measuring an electron temperature and density in the divertor simulation experimental module (D-module) plasma in GAMMA 10/PDX. We applied a frequency multiplied microwave interferometer (MIF) system for measuring a line integrated electron density in D-module. In D-module, there are many electrostatic probes on the V-shaped tungsten target plate. However, they cannot measure the upstream plasma parameters. By using the YAG-TS system and MIF system, we can obtain the upstream plasma parameters. In the argon gas puffing D-module plasma, we successfully obtained the electron temperature and density of upstream plasma for the first time.</p
Growth rates of ITG modes in the presence of flow shear
No full textPlasma microinstabilities in toroidal magnetic confinement devices can be driven unstable by a radial ion temperature gradient and stabilized by rotational flow shear. In this study, we argue that these nonlinear dynamics can be captured by the linear stabilization of Floquet modes. To that end, we propose a novel method (the τAC method) to calculate growth rates by averaging over linear Floquet modes. The τAC method is compared to nonlinear and other linear approaches and is shown to work well at low parallel velocity gradient drive. As such, the method provides a promising approach to explore the parameter dependencies of flow shear stabilization.</p
White paper on the future of plasma science in environment, for gas conversion and agriculture
No full textClimate change, environmental pollution control, and resource utilization efficiency, as well as food security, sustainable agriculture, and water supply are among the main challenges facing society today. Expertise across different academic fields, technologies, and disciplines is needed to generate new ideas to meet these challenges. This “white paper” aims to provide a written summary by describing the main aspects and possibilities of the technology. It shows that plasma science and technology can make significant contributions to address the mentioned issues. The paper also addresses to people in the scientific community (inside and outside plasma science) to give inspiration for further work in these fields
Super-resolution Mapping of Enhanced Emission by Collective Plasmonic Resonances
Get PDFPlasmonic particle arrays have remarkable optical properties originating from their collective behavior, which results in resonances with narrow line widths and enhanced electric fields extending far into the surrounding medium. Such resonances can be exploited for applications in strong light–matter coupling, sensing, light harvesting, nonlinear nanophotonics, lasing, and solid-state lighting. However, as the lattice constants associated with plasmonic particle arrays are on the order of their resonance wavelengths, mapping the interaction between point dipoles and plasmonic particle arrays cannot be done with diffraction-limited methods. Here, we map the enhanced emission of single fluorescent molecules coupled to a plasmonic particle array with ∼20 nm in-plane resolution by using stochastic super-resolution microscopy. We find that extended lattice resonances have minimal influence on the spontaneous decay rate of an emitter but instead can be exploited to enhance the outcoupling and directivity of the emission. Our results can guide the rational design of future optical devices based on plasmonic particle arrays.</p