Nuno Pinhão

Technical University of Lisbon | UTL · Institute for Plasma Research and Nuclear Fusion (IPFN)

This work proposes a complete and consistent set of cross sections for electron collisions with water gas molecules to be published in the IST-Lisbon database on LXCat. The set is validated by the electron swarm analysis technique. The anisotropic angular distribution of electrons in rotational collisions is considered by means of the Born approxim...

We present scanning drift tube measurements of electron swarm transport coefficients in CO as a function of the reduced electric field E/N at room temperature under time-of-flight (TOF) conditions. The measurements are compared to modeling results and other available experimental data on swarm transport over the broad range of E/N from 2 Td to 1603...

This work proposes a complete and consistent set of cross sections for electron collisions with water molecules to be published in the IST-Lisbon database on LXCat. The set is validated from the comparison between experimental and computed electron swarm parameters. The former are collected from literature while the latter are calculated using a sp...

This work discusses the potential of combining non-thermal plasmas and conducting membranes for in situ resource utilization (ISRU) on Mars. By converting different molecules directly from the Martian atmosphere, plasmas can create the necessary feed-stock and base chemicals for processing fuels, breathing oxygen, building materials, and fertilizer...

This work analyzes the temporal evolution of the electron kinetics in dry-air plasmas(80%N2:20%O2), excited by electric-field pulses with typical rise-times of 10−9and 10−6s,applied to a stationary neutral gaseous background at pressures of 105, 133 Pa and temperatureof 300 K. The study is based on the solution of the electron Boltzmann equation (E...

This work presents swarm parameters of electrons (the bulk drift velocity, the bulk longitudinal component of the diffusion tensor, and the effective ionization frequency) in C2Hn, with n = 2, 4, and 6, measured in a scanning drift tube apparatus under time-of-flight conditions over a wide range of the reduced electric field, 1 Td ≤ E/N ≤ 1790 Td (...

This work presents swarm parameters of electrons (the bulk drift velocity, the bulk longitudinal component of the diffusion tensor, and the effective ionization frequency) in C$_2$H$_n$, with $n =$ 2, 4 and 6, measured in a scanning drift tube apparatus under time-of-flight conditions over a wide range of the reduced electric field, 1 Td $\leq\,E/N...

The LisbOn KInetics Boltzmann (LoKI-B) is an open-source simulation tool (https://github. com/IST-Lisbon/LoKI) that solves a time and space independent form of the two-term electron Boltzmann equation, for non-magnetised non-equilibrium low-temperature plasmas excited by DC/HF electric fields from different gases or gas mixtures. LoKI-B was develop...

Abstract In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a60Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both...

This work presents transport coefficients of electrons (bulk drift velocity, longitudinal diffusion coefficient, and effective ionization frequency) in CO2 measured under time-of-flight conditions over a wide range of the reduced electric field, 15Td <= E/N <= 2660Td in a scanning drift tube apparatus. The data obtained in the experiments are also...

This work presents transport coefficients of electrons (bulk drift velocity, longitudinal diffusion coefficient, and effective ionization frequency) in CO2 measured under time-of-flight conditions over a wide range of the reduced electric field, 15Td <= E/N <= 2660Td in a scanning drift tube apparatus. The data obtained in the experiments are also...

The chemical reactions that take place in non-thermal plasma plug-flow type reactors can change the number of particles, the volumetric flow rate and the concentration of species, even if they do not take part in chemical reactions themselves. These changes, however, are frequently neglected in the computation of parameters characterizing the chemi...

This work focus on the role of the rare gas component in He/CH4/CO2 mixtures used for plasma production of Syngas in dielectric barrier discharges. The model comprehends coupled avalanche and afterglow phases each with different time scales, electron and chemical kinetics. Rare gas processes include electron excitation and ionisation, radiative tra...

Many results found in the literature for conversion, selectivity, yield and specific energy in DBD plug-flow reactors neglect the gas expansion due to chemical reactions. We discuss the errors introduced by this approximation and propose a simple method to obtain correct values. The method is applied to study methane conversion in He/CH4/CO2 mixtur...

In this work the electron kinetics in He/CH4/CO2 mixtures used for CH4 conversion is studied, including the contribution of H-2 and CO formed in the discharge, as an initial step to model the reforming of natural gas for syngas production in a dielectric barrier discharge. The electron Boltzmann equation for a swarm in the hydrodynamic regime is so...

This work is devoted to the study of the electron kinetics in He/CH4/CO2 and He/CH4/CO2/H2/CO mixtures, as a necessary step to model DBDs for conversion of natural gas into syngas. The velocity distribution function of an electron swarm in hydrodynamic regime is obtained solving the Boltzmann equation resulting from an expansion on density gradient...

In this work we study the electron kinetics in He/CH4/CO2 mixtures with the objective of studying Syngas production in cold or warm plasmas. The electron Boltzmann equation is solved in a hydrodynamic regime in a density gradients expansion, using a discrete ordinates numerical method. The electron collision cross sections used are based on sets pu...

The electron drift velocity in argon with admixtures of up to 2\% of nitrogen, hydrogen or oxygen is measured in a pulsed Townsend system for reduced electric fields ranging from 0.1 Td to 2.5 Td. The results are compared with those obtained by Monte Carlo simulations and from the solution of the electron Boltzmann equation using two different solu...

We have studied the production of synthesis gas and other hydrocarbons in a dielectric barrier discharge using mixtures of helium, methane and carbon dioxide. It was found that helium has a significant influence on the discharge, decreasing the breakdown voltage and increasing the rate of conversion of CH4 and CO2. However it also decreases the sel...

The impact of adding helium to CH4/CO2 mixtures used for the production of Syngas in a dielectric barrier discharge is discussed. Helium was found to have a major impact on the value of breakdown voltage, conversion values for CH4 and CO2, on the rate of increase of conversion with the specific input energy but almost no impact on selectivities. Th...

PLASMAKIN is a user-friendly software package to handle physical and chemical data used in plasma physics modeling and to compute the production and destruction terms in fluid models equations. These terms account for the particle or energy production and loss rates due to gas-phase and gas-surface reactions. The package has been restructured and e...

Following ambiguous results of an intercomparison exercise in 2004, we have reevaluated the sample preparation, measurement procedures and data treatment for gross alpha and beta counting. It was found that the Portuguese standards NP 4332:1996 and NP 4330:1996 do not provide enough background for correct treatment of data. This paper describes the...

The presence of small amounts of gas impurities in argon glow discharges used for optical emission spectrometry (GDOES) has strong implications on the accurate calibration of GDOES. To circumvent these difficulties, the intentional admixture of controlled amounts of H2 or N2 to argon has been practiced [1]. The understanding of the electron kinetic...

We present a comparison between results for the electron velocity distribution function (evdf), and transport and rate coefficients of an electron swarm obtained under different assumptions for the space and angular dependence of the evdf. Several solution techniques for the Boltzmann equation as well as Monte Carlo simulations have been tested. Th...

We present a comparison between the solutions of Boltzmann equation obtained from four different representations of the evdf and a Monte Carlo particle model and applied to the description of a pulsed Townsend discharge in the hydrodynamic regime. The comparison is made in neon at a constant and homogeneous electric field bellow 500 Td. The importa...

We present a comparison between the solutions of Boltzmann equation obtained from four different representations of the evdf and a Monte Carlo particle model and applied to the description of a pulsed Townsend discharge in the hydrodynamic regime. The comparison is made in neon at a constant and homogeneous electric field bellow 500 Td. The importa...

A modular concept on high-voltage pulse generators, under development for future use in facilities for plasma immersion ion implantation, is presented. The generator proposed uses individual modules, each one consisting of a pulse circuit based on a step-up transformer; the secondary of each step-up transformer is connected in series. Each step-up...

A modular concept on high-voltage pulse generators, under development for future use in facilities for plasma immersion ion implantation, is presented. The generator proposed uses individual modules, each one consisting of a pulse circuit based on a step-up transformer; the secondary of each step-up transformer is connected in series. Each step-up...

PLASMAKIN is a software library to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces - particle generation and loss rates, photon emission rates and energy exchange rates. PLASMAKIN supports any number of chemical species and reactions, is ind...

PLASMAKIN is a software library to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces — particle generation and loss rates, photon emission rates and energy exchange rates. PLASMAKIN supports any number of chemical species and reactions, is ind...

Based on a collisional–radiative model for argon atoms and copper atoms and (Cu+) ions, which was developed as a part of a comprehensive simulation network, optical emission intensities have been calculated for argon and copper lines in a direct current argon glow discharge with copper cathode. Comparison with experimental data has been made, both...

The current paper extends the pioneer diffractometer optimisation studies of the sixties to a general type of source including narrow wavelength distribution sources, the so-called monochromatic sources. The performance requirements for a double-crystal X-ray diffractometer are formulated and expressions for the full width at half maximum and the i...

We have investigated the effect of constriction on the characteristics of low-pressure glow discharges in argon. In a series of experiments four discharge tubes with plane-parallel electrodes of different diameters (D = 31.4, 20, 10 and 5 mm) and same electrode separation (L0 = 45 mm) were studied. The discharges were surrounded by floating-potenti...

A method is described that accounts for the imprisonment of resonance radiation in the calculation of the time-dependent distribution of atoms in resonance states and of the radiation escape in a gas-filled enclosure with cylindrical symmetry. Constant line profile, complete redistribution and pure spectral broadening are assumed. This method is ba...

Discharge mechanisms and characteristic parameters of halogen-quenched GM counters are extensively dependent on the composition of the fill gas. To determine the partial pressures of the different gas species present in the counter's filling mixture, a sampling device with a molecular leak and a QMS was used. Molecular flow was tested and the syste...

This report discusses the electron kinetics in He/CH4/CO2 mixtures as a necessary step to model the production of Syngas in cold or warm plasmas. In particular the influence of helium concentration, gas and vibrational temperatures and product (CO and H2) concentration on the electron velocity distribution function (evdf), transport parameters, col...

Small admixtures of molecular gases are known to influence significantly the characteristics of noble gas glow discharges. The rotational and vibrational levels of the molecules having much lower excitation thresholds, compared to those of the electronic transitions of the noble gases, may drain the energy of electrons, especially at low reduced el...

PLASMAKIN is an OpenSource software package for modeling the gas-phase and gas-surface kinetics of gas discharges. It has now been expanded to simulate the atomic emission spectra taking into account line broadening processes, radiation trapping and the instrumental resolution. The results of test cases are compared with experimental results or wit...

PLASMAKIN [1] is a package to handle physical and chemical data used in plasma physics modeling and to compute gas-phase and gas-surface kinetics data: particle production and loss rates, photon emission spectra and energy exchange rates. It has no limits on the number of chemical species and reactions that can be handled, is independent of problem...

A témában eredeti célkitűzésünk lézerrel gerjesztett szénplazmák megfigyelése és analizise volt szén-nanocsövek lézeres szintézise során, különös tekintettel a C3 molekulagyökre. Ennek során a grafitkemence részbeni megépitése megtörtént,de a támogatás összege (amit az eredeti költségvetéshez képest 1 millió Ft-tal csökkentve kaptunk) a teljes konf...