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By means of a self-consistent three-dimensional particle model of the sourceextraction 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. [ABSTRACT FROM AUTHOR]

In this work we study in detail the kinetics of H- ion swarms in velocity space: this provides a useful contrast to the usual literature in the field, where device features in configuration space are often included in detail but kinetic distributions are only marginally considered. To this aim a Monte Carlo model is applied, which includes several collision processes of H- ions with neutral particles as well as Coulomb collisions with positive ions. We characterize the full velocity distribution i.e. including its anisotropy, for different values of E/N, the atomic fraction and the H+ mole fraction, which makes our results of interest for both source modeling and beam formation. A simple analytical theory, for highly dissociated hydrogen is formulated and checked by Monte Carlo calculations. [ABSTRACT FROM AUTHOR]

Space-time correlation function of density and pressure for equilibrium Argon gas in the hydrodynamic regime have been calculated by the DSMC particle simulation method. The results agree well with the predictions of a linear hydrodynamic theory and look promising in view of the possible application of the method to the study of systems for which a theoretical description is more problematic. It is the case of the equilibrium fluctuations in molecular gases, fluctuations in the kinetic regime and fluctuations in non-equilibrium conditions. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present a 1D(r)2D(v) particle code for capacitively coupled radio frequency discharge plasmas in hydrogen, which includes a rigorous kinetic modeling of ion transport and several solutions to speed up the convergence. In a test case the effect of surface atom recombination and molecule vibrational deactivation on H- concentration is investigated. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the present work, starting from classical MHD scheme, based on Maxwell equations, Euler fluid dynamic equations and generalised Ohm law, a critical study of fluid dynamics, electromagnetism, chemical and physical behaviour of plasma is carried out, and then a aircraft re-entry MHD numerical scheme is implemented. This scheme is used for MHD calculations in different conditions, in the range of low magnetic force and intermediate electrical conductivity. Initial imposed magnetic fields are uniform, but also some cases with coil generated magnetic fields are considered. Calculations of magnetic field and induced currents are extended also inside the blunt body. Results show interesting physical and electromagnetic effects. Comparison with other methods shows possible development in keeping into account other physical and chemical effects. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Different approaches to study vibrational kinetics coupled to electron one for modeling different kinds of negative ion sources are presented. In particular two types of sources are investigated. The first one is a classical negative ion source in which the plasma is generated by thermoemitted electrons; in the second one, electrons already present in the mixture are accelerated by an RF field to sufficiently high energy to ionize the gas molecules. For the first kind of ion source a new computational scheme is presented to couple heavy particle and electron kinetics. Moreover models developed for an RF inductive discharge and for a parallel plate discharge are described. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We study the dynamics of a steady overdriven detonation wave in planar geometry by means of DSMC simulation. The exothermic reaction is modeled as a single step, irreversible, threshold reaction with Arrhenius kinetics. Results show that the nonequilibrium character of the velocity distribution function in the shock front modifies substantially the kinetics of the reaction and the overall profile of the reaction zone. [ABSTRACT FROM AUTHOR]