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Our Keep-in-Touch (KIT) meetings are a regular forum where our PhD students, Post-docs and researchers showcase their research work.
In special occasions we also invite Very Important Persons to deliver a seminar in KIT VIP-meetings.
The meetings take place at least once per month, during the academic year, and recently they are being held online via the zoom platform.
Chair for Experimental Physics V, Head; Ruhr University Bochum, Germany
Abstract
Some of the most important and fascinating phenomena in plasmas are related to kinetic effects, like e.g. collisonless heating or transport phenomena. Naturally, the distribution functions of the charged particles are at the heart of the problem. The distribution function is a result of the complex interaction of the particles with the gas atoms/molecules and the electric field structure. On the other hand, the electric field structure itself is usually resulting from the coupling to the electrons. Further, in low-temperature plasmas, the non-equilibrium conditions in these systems lead in general to distribution functions which deviate significantly from the standard Maxwellian distribution. While the common way of addressing kinetic effects is based on the use of the Boltzmann equation, an alternative approach for describing local Ohmic and non-local (stochastic) heating is provided by the Fokker-Planck equation supplemented by the Langevin equation. One advantage of this approach, as compared to the Boltzmann equation, is probably a more natural insight into the physics. Local and non-local interactions of electrons with fields are illustrated by selected examples. This includes the problem of self-consistent field structures, global distribution functions as well as tailored periodic field structures. Last not least, it will be shown that non-local effects can be important even under conditions of high collisionality. Finally, an outlook for further work on kinetic effects will be provided.
Professor Czarnetzky studied physics at the University of Essen in the 1980s and concluded the PhD (1991) and the Habilitation (1999) in experimental physics by the same University. He is full professor for physics at the Ruhr University Bochum (RUB) since 2001, and was dean / deputy dean of the Faculty for Physics and Astronomy of the (RUB) in 2008-2012 and 2014-2015. He is fellow of the Institute of Physics IOP since 2009, member of the External Advisory Board of the DOE Plasma Science Center since 2010, and appointed professor at Osaka University, Japan, since 2017. His research interests are well-balanced between experiments and theory. This requires well-designed plasma sources (some proposed by Czarnetzky, like INCA), advanced diagnostics (e.g. using and developing advanced laser diagnostic techniques, with lasers ranging from fs to cw operation and wavelengths from the UV to the IR), and the development of analytical models often combined with simulations (focusing on the kinetic description of plasmas). He received several prestigious awards, such as the Plasma Physics Innovation Prize of the European Physical Society (2010), the Jade-Award from the Japan-Deutschland Foundation for outstanding merits on German-Japanese scientific and cultural Exchange (2015), the von Engel & Franklin Prize of the International Conference on Phenomena in Ionized Gases (administered by the Board of Physical Sciences, University of Oxford) (2017), the ISPlasma Prize for outstanding achievements in the field of Plasma Science and its Applications (2018), and the the Plasma Materials Science Hall of Fame Prize (2024) "for the excellent achievements in many years of outstanding research on physical analysis of phenomena related to low-temperature plasma materials processing, and proposals for original plasma processing equipment".
Applied Physics and Science Education, Eindhoven University of Technology (TU/e), The Netherlands
Abstract
The semiconductor industry is moving towards ever increasing densities and ever decreasing feature sizes. This was kicked of 40 years ago, by two international initiatives: Sematech in the USA and JESSI in the European Union. Those initiatives have lasted for around 10 years. After that, the technology was mature, and industry hardly needed the input of academia for solving their technical challenges in the plasma domain. In recent years, since the moment that feature sizes came below 10 nm, a revival of the field has been taking place. For example: vertical etching angle specifications ask for side wall angles between 89.6 and 90 degrees, anisotropy has been approaching and now exceeds 100, etc. This has evoked a new need of industry for input from plasma physics, sheath physics, fluid dynamics and surface physics and chemistry in these size regimes (Knudsen flow, single atom reactions, etc). Recently, the USA launched the CHIPS act, a package of 45 G$ for semiconductor processing technology. Europe has a similar CHIPS-package. In the presentation the needs of modern-day semiconductor processing will be highlighted, and we will also try to show how we, as people in academia, can cater to that need while at the meantime performing cutting edge fundamental science.
One of the needs of the industry, but also of academia, is diversity. We need a well-trained workforce with a diverse composition. TU/e has embarked on a course of increasing the diversity in the academic population. With that strategy, for instance, the fraction of female staff in tenured academia increased from 2 % to 35 % in 6 years in the physics department. We will describe the vital steps that have contributed to this spectacular shift.
Gerrit Kroesen studied Applied Physics at Eindhoven University of Technology from 1977 to 1983. He completed his PhD on plasma physics in 1988 and was appointed Assistant Professor in the Elementary Processes in Gas Discharges (EPG) group in 1985. He took a sabbatical at IBM in New York (USA) in 1990, and another one at the University of Kyoto (Japan) in 1997. Kroesen still works in the EPG group, since 1996 as Associate Professor and since 2000 as Full Professor, focusing on experimental plasma physics. He became Dean of Applied Physics in 2012.
Gerrit Kroesen has constantly strived to push the boundaries of plasma physics, by following a combined effort of experiments, diagnostics, theory and modeling. His research focuses on the internal elementary processes in the plasma, but also touches upon phenomena induced at surfaces that are in contact with the plasma. Different application areas have captured his interest over the years. Starting in plasma etching and plasma deposition, he moved on to environmental applications, plasma displays, dusty plasmas, EUV producing plasmas, EUV produced plasmas, to medical applications. He coauthored 200+ papers and 10 patents, and supervised 150+ PhD and MSc theses. Gerrit Kroesen was awarded the Von Engel and Franklin Prize in 2015 for “his pioneering work on plasma deposition and etching where he improved the understanding of plasma and sheath dynamics, plasma and sheath chemistry” and for “his leading contributions to dusty plasma physics, lighting and EUV sources, and his pioneering work in plasma medicine”.
The Pioneer database on plasma-catalytic CO2 conversion
Maik Budde, Eindhoven University of Technology (TU/e PMP)
This presentation introduces the Pioneer database on CO2 conversion through plasma and plasma-assisted catalysis, utilizing literature data. Open to users and contributors, the tool aims to enhance performance comparisons and improve CO2 conversion efficiency via plasma-catalysis. With plasma-catalysis rapidly growing in various processes, the need for standardized assessments is evident. The "PIONEER DataBase," initiated within an H2020 European project, compiles extensive CO2 conversion data.
Production of Graphene, Graphene Derivatives and other carbon-based hybrid structures using atmospheric surface-wave plasmas
Edgar Felizardo, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, 1049,
Portugal
The wide adoption of graphene and derivatives has been hindered by the low quality of commercially available products sold as such. Furthermore, the development of new consistent and repeatable methods for the synthesis of large quantities of high quality customizable carbon-based nanostructures remains a major challenge. In this KIT meeting, a disruptive plasma technology and a corresponding laboratory prototype of a versatile microwave plasma-based machine for gram-scale fabrication of highquality graphene and derivatives (N-graphene, Graphene/N-graphene-metal oxides) are presented.
Microwave N2 plasmas at intermediate pressures: modeling of excitation and transport
Margherita Altin, Faculty of Science and Engineering, Maastricht University, 6211 KH Maastricht, The Netherlands
In a N2-O2 plasma for NOx production, N2 molecules are the toughest species. Their high dissociation energy makes out-of-equilibrium vibrational and electronic excitation desirable to lower the dissociation energy. A vortex-stabilized microwave (MW) discharge in pure N2 is used to test the viability of these non-equilibrium conditions at intermediate pressures.
Reflectrometry Diagnostics for atmospheric entry applications: state-ofthe-art and new developments
Ricardo Ferreira, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Insight into the plasma properties of high-speed ionized flows is key for the validation of predictive aerothermodynamic tools for atmospheric entry applications. Plasma radiation will namely be highly dependent on the flow electron densities, which accordingly need to be accurately estimated. We performed an extensive review on past re-entry microwave diagnostics, including both in-flight and ground-test experiments.
CO2 conversion by plasma: Towards a systematic approach to kinetic model validation
Olivier Guaitella, LPP, Ecole Polytechnique, UPMC, Université Paris Sud-11, CNRS, Palaiseau, France
CO2 conversion by Non Thermal Plasma (and molecule synthesis in general) can be highly efficient when the formation processes rely on the use of short-lived species, whether radicals, or vibrationally and electronically excited states. In order to design efficient processes, we must first identify the precise role of these short-lived species, which are difficult to measure experimentally.
Modelling of low-current quasi-stationary gas discharges
Pedro Almeida, Universidade da Madeira and Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
The seminar is concerned with the modelling of low-current quasi-stationary discharges, including the Townsend and corona discharges, as well as discharges along dielectric surfaces. An integrated approach suitable for the computation of the whole range of existence of a quasi-stationary discharge from its inception to a non-stationary transition to another discharge form, such as a transition from the Townsend discharge to a normal glow discharge, the corona-to-streamer transition, or the transition from stationary negative corona to selfpulsing regimes.
Determination of atomic oxygen density and reduced electric field in
oxygen-containing plasmas through OES methods
Lex Kuijpers, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Understanding of basic plasma parameters, such as gas temperature, vibrational temperature, dissociation fraction, etc. is often achieved through plasma diagnostics. Plasma diagnostics in CO2 and O2 plasmas are often expensive, active, complex and with high sensitivity to noise. In this work, the efforts were directed towards the investigation of two non-intrusive diagnostic approaches
Diagnostics and modeling of an atmospheric pressure argon microplasma jet
Duarte Gonçalves, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Atmospheric-pressure plasma jets provide an open and easily accessible way of producing excited and charged species. These unobtrusive sources are used in different applications, especially medical and biological [1]. Furthermore, the innate plasma-flow interaction provides a rich opportunity for different modeling and experimental studies [2].
Influence of N2 on the CO2 dissociation fraction and vibrational kinetics in low temperature CO2-N2 plasmas
Chloé Fromentin, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Fighting climate change is one of the greatest challenge Humanity has to tackle in the twentyfirst century and to achieve the goal of zero net emissions by 2050 the development of new technologies capable of reducing anthropogenic CO2 emissions is required [1]. The conversion of CO2 into chemicals and energy products via the Carbon Capture and Utilisation (CCU) method is a promising way to not only decrease the CO2 emissions, but also generate more economic value and reduce the dependence of fossil fuels while closing the carbon cycle [2].
The LisbOn Kinetics Monte Carlo solver
Tiago C. Dias, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
The modelling of low-temperature plasmas (LTP) is essential to understand the fundamental processes ruling the system and to find a configuration that maximizes the efficiency for a determined application. However, models should describe accurately the reality, which is not always the case.
Underlying mechanisms of discharge contraction in a CO2/CH4 microwave plasma
Omar Biondo, Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk B2610, Belgium
We study discharge contraction in a MW plasma at sub-atm pressure, operating in CO2 and CO2/CH4 mixtures, and compare our results against the different mechanisms proposed for this phenomenon. In particular, the addition of CH4 alters the thermodynamic properties of the mixture, especially the reactive component of the thermal conductivity.
Comparison of numerical and experimental results for validation of a kinetic scheme for CO2-CH4 plasmas
Edmond Baratte, Laboratoire de Physique des Plasmas (UMR 7648), CNRS-Univ.Paris Sud-Sorbonne Universite -Ecole polytechnique 91128 Palaiseau, France
The Dry Reforming of Methane (DRM) assisted by plasma, which aims at transforming CO2 and CH4 into value-added products (like CO and H2), has known a spike of interest over the last decade because of its potential to create high energy-density molecules. Though a vast literature is available for both pure CO2 plasmas and pure CH4 plasmas, the understanding of the base mechanisms controlling CO2 - CH4 plasmas is still challenging because of the large number of species and possible reaction pathways.
Electron-neutral scattering cross sections for H2O
Maik Budde, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Water is an omnipresent impurity that is frequently encountered in many applications. On the other hand, it is also an abundant source of hydrogen. For instance in CO2 plasma conversion, water addition might allow the direct production of hydrocarbons. Here, the interaction of water molecules with electrons is crucial. A common description of the electron kinetics is the solution of the electron Boltzmann equation in the two-term approximation yielding the electron energy distribution function.
Modelling chemistry and transport in microwave discharges for CO2
conversion
Pedro Viegas, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
The study of CO2 conversion by means of microwave (MW) plasma discharges involves a complex interplay of many effects, namely transport of reactive flows, chemistry with several species and degrees of freedom and electromagnetic fields. The interplay of these effects is not well known but is important for optimization of reactor performances. In this work, a steady-state 1D-radial plasma fluid model is developed to study the contraction of CO2 MW discharges.
Plasma: Barriers for Space Exploration and Gifts for Human from the Universe - VIP-meeting
Minkwan Kim, Aeronautics and Astronautics Engineering Department, University of Southampton, Southampton SO16 7QF, United Kingdom
Plasma, which is an ionised gas, is the most common state of matters in the universe. On the space exploration missions such as planetary entry, plasma brings us technical challenges by causing harsh environment and interrupting communications, knows as ‘radio blackout’. However, the special type of plasmas, which is known as ‘non-thermal plasma’, brings us the innovative solution for urgent global problems on public health and environment. Dr Minkwan Kim (University of Southampton) will show you novel aerospace technologies to overcome the challenges of planetary entry caused by plasmas, and explore the next generation of medicine and environment remediation technologies using plasmas.
Overview of the newly funded scientific projects in the N-PRiME group
Tiago Silva, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
In this talk I will present an overview of recently funded scientific projects in the N-PRiME group. These projects include: (i) ROADMARS (funded by Portuguese National funds) to investigate the interest and feasibility of microwave discharges to decompose CO2 and produce oxygen under Martian conditions, (ii) PARADISE (funded by Portuguese National funds) to explore the potential of plasma technology to reform industrial emissions into solar fuels, (iii) PERFORMER (funded by ESA) to study the separation of oxygen in CO2 discharges, and (iv) IMPACT and CREATOR (funded by MIT Portugal Research seed Funds) to investigate elementary processes involved in CO2 plasma recycling, while fostering collaborative research between MIT and the N-PRiME group.
From Huygens to ESTHER
Lionel Marrafa, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Focusing on previous ESA missions and studies, the talk shall illustrate their link with basic research in the field of aerodynamics and plasmas and more specifically of nonequilibrium radiating flows. Huygens mainly, but also IRDT (Inflatable Reentry and Descent Technology Demonstrator), IRENE (Italian Reentry Nacelle Experiment, to test a deployable braking device) and PHOEBUS (a demonstrator for future sample return capsules) shall be presented.
Gas heating mechanisms in plasmas: an overview
Carlos Pintassilgo, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Faculdade de Engenharia, Universidade do Porto, Porto, Portugal
This talk reports a comprehensive picture of the main gas heating mechanisms in plasma discharges in different gases and mixtures, such as pure N2, N2-NO, N2 O2 (including air-like mixtures), and CO2. Modelling predictions, based on the numerical solutions of the time-dependent gas thermal balance equation, are systematically compared to experimental results.
Vibrational kinetics of CO2 in non-thermal plasma: a diagnostic study - VIP-meeting
Richard Engeln, Department of Applied Physics (PMP), Eindhoven University of Technology, Eindhoven, The Netherlands
Vibrational excitation is seen as the panacea for efficient CO2 dissociation in plasma. During the presentation I will discuss the development of diagnostic techniques to increase our current level of understanding of the vibrational kinetics within CO2 discharges, with the intention to ultimately contribute to a controlled and efficient dissociation process in plasma.
The quest for deterministic direct plasma synthesis of nanostructures - VIP-meeting
Uros Cvelbar, Jozef Stefan Institute, Ljubljana, Slovenia
Building 1D or 2D nanostructures like nanowires or nanowalls is important for numerous applications requiring large-scale nanomaterials production. Here, plasmas present a great opportunity since nanowires or nanowalls in plasmas are produced not only faster but in bulk quantities with high quality. These quantities are orders larger in quantity and time than any other comparing processing method available today. However, to master these processes in plasmas, understanding basic mechanisms underlying the growth of any nanostructure in plasma is extremely important. Here, we have selected the direct plasma synthesis to study these mechanisms, where nanostructures are grown directly on exposed materials to only gaseous discharges.
2021 update of the SPARK Line-by-Line "Libre" nonequilibrium radiation code
Mário Lino da Silva, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
This talk presents the recent release of the 3.0 version of the SPARK Line-by-Line (LbL) code. SPARK LbL (formerly called SPARTAN) is a Line-by-Line radiation code specifically tailored for the simulation of radiation from hot, nonequilibrium gases and plasmas. The code has been developed continuously for the last 15 years and applied to solve radiative transfer problems in aerospace applications (namely atmospheric entry spacecraft).
Simulation of effects of magnetic field using a Monte Carlo framework
Kryštof Mrózek, Department of Physical Electronics, Faculty of Science, Masaryk University, Czech republic
Electron energy distribution function (EEDF) is important characteristic of almost every discharge. Its knowledge can help greatly plasma diagnostics and also if it often necessary to know EEDF in order to be able to accurately model plasma discharge. At the moment there are several freely available tools (Bolsig+, LoKI-B) which calculates EEDF by solving Boltzmann kinetic equation using so-called two-term approximation. These frameworks are quite fast but two-term approximation might not be sufficient for certain types of plasma or for calculating swarm parameters like diffusion coefficient of electrons or reaction rate coefficients. One possible alternative to two-term approximation is to use more robust, albeit slower, Monte-Carlo based solvers.
A few notes on the solution of the electron Boltzmann equation for
swarms and the fitting of cross sections
Nuno Pinhão, Instituto de Plasmas e Fusão Nuclear, Campus Tecnológico e Nuclear/ Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
In this talk we discuss a few problems on the interpretation of electron swarm data and the fitting of electron collision cross sections.
Graphene-Based Hybrid Nanostructures Production
Using Plasma-Based Methods
Ana Dias, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
One of the main challenges in the materials nanoscience research area lies in the sensitivity and complexity of the synthesis processes. Plasmas are an alternative and sustainable strategy to synthesize disruptive nanostructures since they allow the effective control over the nucleation and assembling mechanisms at atomic scale level. In the present work a microwave plasma-based method [1][2] at atmospheric pressure conditions is used to produce multiple free-standing carbon nanostructures, i.e., N-graphene and N-graphene-metal-based composites (NGMCs), possessing unique features that make them valuable in a wide range of applications.
Towards a detailed reaction mechanism set for CO2-H2O low
temperature plasmas
Tiago Silva, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
The vision of using plasmas to transform CO2 into valuable products has become well recognized by the scientific plasma community. This is motivated by the potential of plasmas to activate CO2 at reduced energy cost and excite CO2 vibrations that efficiently contribute to overcome the dissociation barrier. Therefore, investigation of the steps involved in plasma decomposition of CO2 is a key issue to move from the laboratory level towards industrial sector. This contribution is devoted to the modeling of CO2-H2O discharges, operating at pressures ranging from 1 to 5 torr.
Non-equilibrium kinetics in CO2-N2 plasmas
Chloé Fromentin, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
The aim of this work is precisely to investigate the kinetics of CO2-N2 plasmas. A zerodimensional kinetic model for glow-type discharges in CO2, CO2-O2 and CO2-N2 is being developed. The model couples the electron kinetics, described by the electron Boltzmann equation, to a system of rate balance equations describing the creation and loss of vibrational and electronic excited states, different radicals and ions.
ESTHER qualification campaign and first experimental results
Ricardo Ferreira, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
This presentation will focus on the ESTHER qualification activities that have been carried over the last 6 months, namely mechanical design, the laser ignition system and the first experimental shots in the isochoric combustion chamber. The shots are analysed and compared to the test scale combustion chamber “Bombe”. A Fourier Transform analysis of the pressure signal is carried out to infer on the acoustic pressure waves and sound speed inside the chamber. Furthermore, a qualitative analysis of the influence different combustion parameters is presented as well as a discussion on the upcoming test campaign.
Aerodynamic study of atmospheric-pressure plasma jets
Duarte Gonçalves, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
Atmospheric-Pressure Plasma Jets (APPJs) have been used for scientific and industrial applications due to their ability to generate reactive species at high pressure while providing means to carry them into a target. An imposed flow assumes a jet structure, repetitive discharges generate the plasma, and the plasma itself affects the flow. APPJs present also an opportunity for new modelling strategies to explain the underlying mechanisms of the aeroelectro-dynamic interactions controlling these jets. We engage on this challenge by exploring the aerodynamics of APPJs using both modelling and experimental approaches.
Kinetic Monte Carlo models to study the heavy-species and electron
kinetics
Tiago Dias, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
In this presentation, we discuss our recent efforts towards a unified KMC formulation of complex plasma-chemistry models. We start by presenting and validating an innovative KMC approach to solve the chemical kinetics. Then, we show our first steps to study the electron kinetics through well-stablished MC techniques. Finally, we discuss on how we will selfconsistently couple these formulations in the near future.
A compact FMCW reflectometer/interferometer design for the monitoring of atmospheric entry flows
Ricardo Ferreira, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
On the next experimental fusion reactors, the number of suitable diagnostics to measure relevant plasma quantities is very limited. Millimetre wave diagnostics are one of the obvious choice due to the limited in-vessel access requirements and front-end robustness. Frequency-Modulated Continuous-Wave (FMCW) reflectometry is a wellestablished technique to measure electron density profiles and to provide feedback for plasma position and shape control in such applications. This work presents the reflectometer architecture, discussing the main key design features and the prototype expected performance and valid test regions. Also, it compares its expected performance to previous similar experiments.
Plasma reforming for oxygen production on Mars
Polina Ogloblina, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
In this seminar the results of experimental investigation of plasmas created in a simple and reproducible DC glow discharge, are going to be presented. The plasma under study is a mixture of CO2 with 2% of Ar and 2% of N2, for pressures in range 1–6 Torr and currents from 10 to 50 mA, both with gas at room (300 K) and Mars-like (220 K) temperatures. The CO2 and CO vibrational temperatures, the conversion factor and the reduced electric field are measured in these conditions. Experimental results and modelling predictions are compared for pure CO2 plasma at Earth and Mars-like temperatures.
Optimization methods for cross section fitting of swarm data
Nuno Pinhão, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
The use of numerical optimization methods is tempting but conventional algorithms fail in this type of problem. On this talk we discuss the application of evolutionary computing methods to automatic fitting of cross sections. After briefly introducing the formalism adopted in this work for a) the analysis of swarm experiments and b) the evolutionary methods, we apply these concepts to cross section fitting. We start with a simple model gas and a genetic algorithm allowing to introduce the basic concepts of this field. Then we study the evolution of a population of cross sections and see how good fitting parameters are obtained as well as a statistical estimation of the uncertainty of the cross sections. The statistical analysis of the optimized solutions also show the presence of correlations between different cross sections. Finally we apply these algorithms to real gases.
Influence of N2 on the asymmetric vibrating mode of CO2
Loann Terraz, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal
The effect of nitrogen addition in CO2 cold plasmas is explored in this presentation, and more specifically, the influence of N2 on the asymmetric population CO2(000v3), in order to reach an energy-efficient dissociation involving non-equilibrium processes. Experimental results show a greater conversion rate of CO2 into CO when N2 gas at room temperature is added to the plasma. Experiments are performed in non-thermal plasmas sustained by DC pulsed discharges, for pressure and current ranges of [1; 5] Torr and [20; 50] mA, respectively. A self-consistent model, previously validated for pure CO2 discharges, is further extended to take into account e-V, V-T and V-V reactions involving N2. The presentation focuses on the validation of the model, as well as the choice of the databases, by comparing the time-resolved densities of CO2(0v2l20) and CO2(000v3) between experimental results and modelling ones.
Modelling the vibrational kinetics of CO2 through the Fokker-Planck
approach - VIP-meeting
Pedro Viegas, Dutch Institute for Fundamental Energy Research, Computational Plasma Physics and Chemistry group, 5600 HH Eindhoven, The Netherlands
Low-temperature plasmas allow to convert greenhouse CO2 into new carbon-neutral fuels or useful chemicals with high energy efficiency. In order to understand and optimize these systems, reactor models that also take into account vibrational nonequilibrium have to be developed. However, the calculation of the vibrational distribution function (VDF) through the usual state-to-state (STS) approach compromises the computational efficiency of multidimensional models. In this presentation, a new approach is presented, more computationally efficient than the STS method, to calculate the VDF of the asymmetric stretching mode of CO2, based on the drift-diffusion Fokker-Planck (FP) equation. It is shown that the FP approach to vibrational kinetics can be self-consistently used in plasma models and the validation of this method is discussed, by comparing VDFs calculated through FP and STS simulations.
Kinetic and fluid modeling of non-equilibrium electron and ion transport
in gaseous and liquid matter - VIP-meeting
Ron White, College of Science & Engineering, James Cook University, Townsville, 4810, QLD, Australia
Accurate modelling of electron and ion transport in plasmas, plasma-liquid and plasmatissue interactions is dependent on (amongst other things) (i) the existence of accurate and complete sets of cross-sections, (ii) an accurate treatment of electron/ion transport in these phases, (iii) accurate description of other processes present e.g. localization (trapping), bubbles, etc. and (iv) understanding of the electron transport across the gas-liquid interface. The accuracy and completeness of electron-biomolecule cross-section sets can be assessed by comparison of calculated transport coefficients with those measured using a pulsed-Townsend swarm experiment of de Urquijo and co-workers. In this presentation we will present results from our recent studies of electrons in water, as the natural surrogate for human tissue.