RESULTS FROM 1 TO 20 OF 159

2016, Monografia o trattato scientifico, ENG

Fundamental Aspects of Plasma Chemical Physics Kinetics

Mario Capitelli, Roberto Celiberto, Gianpiero Colonna, Fabrizio Esposito, Claudine Gorse, Khaled Hassouni, Annarita Laricchiuta, Savino Longo

Describing non-equilibrium "cold" plasmas through a chemical physics approach, this book uses the state-to-state plasma kinetics, which considers each internal state as a new species with its own cross sections. Extended atomic and molecular master equations are coupled with Boltzmann and Monte Carlo methods to solve the electron energy distribution function. Selected examples in different applied fields, such as microelectronics, fusion, and aerospace, are presented and discussed including the self-consistent kinetics in RF parallel plate reactors, the optimization of negative ion sources and the expansion of high enthalpy flows through nozzles of different geometries. The book will cover the main aspects of the state-to-state kinetic approach for the description of nonequilibrium cold plasmas, illustrating the more recent achievements in the development of kinetic models including the self-consistent coupling of master equations and Boltzmann equation for electron dynamics. To give a complete portrayal, the book will assess fundamental concepts and theoretical formulations, based on a unified methodological approach, and explore the insight in related scientific problems still opened for the research community.

DOI: 10.1007/978-1-4419-8185-1

2015, Altro prodotto, ITA

Energia e vita: le infinite relazioni

Ferrazzoli Marco; Antoni Vanni; Longo Savino; Barbante Carlo; Galletta Giuseppe

Tavola Rotonda, 18 Maggio 2015, Sala Convegni Orto Botanico di Padova.

2015, Articolo in rivista, ENG

Theoretical determination of the microstructure of Cs covering of Mo in negative ion sources for nuclear fusion applications

Damone Angelo; Panarese Antonio; Coppola Carla Maria; Jansky J.; Coletti Cecilia; Chiodo Letizia; Serianni Gianluigi; Antoni Vanni; Longo Savino

Cs is the most well known catalyst used in negative ion sources for fast neutral beam generation employed in nuclear fusion, where the element is evaporated and deposited on Mo surfaces forming non permanent films. In this paper the interaction of Cs with Mo under conditions of interest for negative ion sources is studied using different methods. Cs-Mo potential has been characterized starting from high level electronic calculations for two atoms. Mo-Mo and Mo-Cs potentials are based on new fits of the literature data. Density functional theory calculations on a reduced cell are used to determine the adsorption energy of Cs on Mo for different sites. Good reproduction of experimental results, when available, is achieved (e.g. Mo crystal data, Cs-2 dissociation energy) and new results for the evaporation energy of Cs from Mo surfaces, CsMo dissociation energy, adatom geometry etc. are reported and tabulated. A functional expression of the Cs-Mo[0 0 1] interaction potential is proposed based on these ab-initio results. The use of this potential is illustrated by classical MD calculations for the morphology for Cs partial layers on Mo[0 0 1]. Calculations show that the interaction between Cs and the surface leads to peculiar morphology of Cs partial layers, to be considered in future studies of Cs role in negative ion sources as well as in the ongoing quest to alternative catalyzers.

Plasma physics and controlled fusion (Print) 57 (3), pp. 035005-1–035005-9

DOI: 10.1088/0741-3335/57/3/035005

2014, Articolo in rivista, ENG

Radio-frequency capacitively coupled plasmas in hydrogen excited by tailored voltage waveforms: comparison of simulations with experiments

Diomede, P.; Economou, D. J.; Lafleur, T.; Booth, J-P; Longo, S.

A combined computational-experimental study was performed of a geometrically symmetric capacitively coupled plasma in hydrogen sustained by tailored voltage waveforms consisting of the sum of up to three harmonics. Predictions of a particle-in-cell with Monte Carlo collisions/fluid hybrid model were in reasonably good agreement compared to data from an array of experimental plasma diagnostics. The plasma was electrically asymmetric, with a dc self-bias developed, for all but a sinusoidal voltage waveform. Hydrogen ions (H+, H-2(+), H-3(+)) bombarding the electrodes exhibited different ion flux-distribution functions due to their different masses and collisionality in the sheath. Plasma density, ion flux and absolute value of the dc self-bias all increased with increasing the number of harmonics. The energy of ions bombarding the substrate electrode may be controlled by switching the applied voltage waveform from (positive) 'peaks' to (negative) 'valleys'.

Plasma sources science & technology (Print) 23 (6)

DOI: 10.1088/0963-0252/23/6/065049

2014, Abstract in atti di convegno, ENG

Laser ablation plasmas produced from metals and silicates in meteorite samples

M. Dell'Aglio (a), A. De Giacomo (a,b), R. Gaudiuso (a,b), O. De Pascale (b), S. Longo (a,b)

41st EPS conference, Berlino, 23.- 27.6.2014

2014, Articolo in rivista, ENG

Particle Methods for Nonequilibrium Hypersonic and Plasma Flows

D. Bruno, A. Panarese, P. Diomede, S. Longo, F. Taccogna, P. Minelli, S.T. Surzhikov, A.S. Dikaljuk, P. De Palma and M.D. de Tullio

Kinetic modelling of nonequilibrium flows is described as it applies to hypersonic phenomenology. A Monte Carlo method is described for the study of species separation on shock wave fronts; a Particle in Cell with Monte Carlo Collisions (PIC/MCC) technique is described for the simulation of dust in plasma flows; modelling of nonequilibrium radiation in shock heated gases; implementation of slip models for the description of separation zones occurring in shock- boudary layer interactions.

The Open plasma physics journal 7, pp. 88–100

DOI: 10.2174/1876534301407010088

2014, Articolo in rivista, ENG

Laser Induced Breakdown Spectroscopy of meteorites as a probe of the early solar system

Dell'Aglio M.; De Giacomo A.; Gaudiuso R.; De Pascale O.; Longo S.

This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis. © 2014 Elsevier B.V. All rights reserved.

Spectrochimica acta. Part B, Atomic spectroscopy 101, pp. 68–75

DOI: 10.1016/j.sab.2014.07.011

2013, Articolo in rivista

Stochastic models of chiral symmetry breaking in autocatalytic networks with anomalous fluctuations

Longo, Savino; Coppola, Carla Maria

Many mechanisms and related models concerning chiral symmetry breaking in extended reacting and ecological systems have been formulated in the last years. One common feature of most of these proposals is the important role played by autocatalysis and diffusion. In this paper, a classical model of simulated evolution is discussed in terms of chiral symmetry breaking, and the role played by anomalous fluctuations induced by autocatalysis is shown by a simple stochastic approach. The importance of the kinetics of the loss reactions is also discussed.

Rendiconti lincei. Scienze fisiche e naturali 24 (3), pp. 277–281

DOI: 10.1007/s12210-013-0234-4

2013, Articolo in rivista, ENG

Momentum transfer Cs+/H-2 cross section from an inversion of transport data

Diomede, Paola; Longo, Savino

Monte Carlo (MC) calculations of C-s(+) transport in H-2 are performed in order to establish a reliable transport cross section for momentum transfer. This system is important for plasma modeling in the context of the negative ion source design proposed for plasma heating in future nuclear fusion reactors. Two procedures are checked: use of the Langevin approximation based on realistic values of the physical parameters and a purely statistical, multi-parameter function allowing for shape variation at relative high energy. The two alternatives are discussed and final results provided to be used for negative source modeling.

The European physical journal. D, Atomic, molecular and optical physics (Print) 67 (5)

DOI: 10.1140/epjd/e2013-40043-4

2013, Articolo in rivista, ENG

Kinetic modelling of atom production and thermalization in CCRF discharges in H2

Panarese A.; Diomede P.; Longo S.

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Plasma sources science & technology (Online) 22 (4)

DOI: 10.1088/0963-0252/22/4/045017

2013, Articolo in rivista, ENG

Non-thermal photons and H2 formation in the early universe

Coppola C.M.; Galli D.; Palla F.; Longo S.; Chluba J.

Monthly notices of the Royal Astronomical Society (Print) 434 (1), pp. 114–122

DOI: 10.1093/mnras/stt1007

2013, Abstract in atti di convegno, ENG

High-power laser probing of meteorite surfaces

M. Dell'Aglio (a), A. De Giacomo (a,b), R.Gaudiuso (a,b), O. De Pascale (a), S. Longo (a,b)

EMSLIBS 2013, Bari, 16-20 Settembre 2013

2013, Articolo in rivista, ENG

Three-dimensional structure of the extraction region of a hybrid negative ion source

Taccogna, F. and Minelli, P. and Longo, S.

A self-consistent three-dimensional particle-based model of the source extraction-acceleration transition region of a surface-produced negative ion source is developed. Some considerations are advanced on the characteristic of negative ion transport: it is purely electrostatic while collision-induced (charge exchange with atoms) and magnetic-induced (ion gyration around the filter field) transport contributions play no relevant role in H-extraction. In fact, the calculations presented here indicate that the key point is the penetration of the extraction grid field inside the plasma grid collar and the source region, which helps in removing the negative ions produced on the surface. This study suggests that the best plasma grid shape is characterized so as to allow the extraction field to arrive directly on the surface-emitting H- ions and that the best aperture size is directly related to the particular shape used.

Plasma sources science & technology (Print) 22 (4)

DOI: 10.1088/0963-0252/22/4/045019

2013, Articolo in rivista, ENG

Plasma grid shape and size effects on the extraction of negative ions

Taccogna, F. and Minelli, P. and Capitelli, M. and Longo, S. and Schneider, R.

By means of a self-consistent three-dimensional particle model of the source-extraction transition region of a surface-produced negative ion source, the characteristics of negative ion transport have been revealed. It is purely electrostatic and collision-induced (charge exchange with atoms) and magnetic-induced (gyration around filter field) transport contributions play no relevant role for the H- transport. In fact, the key point is the penetration of the EG field inside the source, which helps removing negative ions produced on the surface. This study suggests that the best PG shape is characterized such to allow the extraction EG field from attaching the surface from where H- are produced and that the best aperture size is directly related to this particular shape.

AIP conference proceedings 1515, pp. 3–11

DOI: 10.1063/1.4792764

2012, Presentazione

High-power laser probing of meteorite surfaces

M. Dell'Aglio (a), A. De Giacomo (a,b), R. Gaudiuso (a,b), O. De Pascale (a), G.S. Senesi (b), S. Longo (a,b)

EWASS 2012, Rome Italy, at the Pontificia Università Lateranense, 2012, July 1-6

2012, Contributo in volume

The Role of Paradigms in Science: A Historical Perspective

Corinna Guerra, Mario Capitelli Savino Longo

2012, Articolo in rivista

Hybrid simulation of a dc-enhanced radio-frequency capacitive discharge in hydrogen

P Diomede, S Longo, D J Economou and M Capitelli

Journal of physics. D, Applied physics (Online) 45, pp. 175204

2012, Articolo in rivista

Monte Carlo Calculation of the Translational Relaxation of Superthermal H Atoms in Thermal H2 Gas

Panarese A, Longo S

The Astrophysical journal 749, pp. 23

2012, Articolo in rivista, ENG

Non-equilibrium H2 Formation in the Early Universe: Energy Exchanges, Rate Coefficients, and Spectral Distortions

Coppola, C. M., D'Introno, R., Galli, D., Tennyson, J., & Longo, S.

The Astrophysical journal. Supplement series 199, pp. 16

2012, Contributo in volume, ENG

Chapter 1: Thermodynamic Properties of Gases behind Shock Waves

M. Capitelli, D. Bruno, G. Colonna, G. d'Ammando, A. D'Angola, D. Giordano, C. Gorse, A. Laricchiuta, S. Longo

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