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Sample records for kinetic ion particle

  1. Capacitively Coupled Radio Frequency Discharge Plasmas In Hydrogen: Particle Modeling and Negative Ion Kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2005-05-16

    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.

  2. Kinetic modeling of particle dynamics in H{sup −} negative ion sources (invited)

    SciTech Connect

    Hatayama, A. Shibata, T.; Nishioka, S.; Ohta, M.; Yasumoto, M.; Nishida, K.; Yamamoto, T.; Miyamoto, K.; Fukano, A.; Mizuno, T.

    2014-02-15

    Progress in the kinetic modeling of particle dynamics in H{sup −} negative ion source plasmas and their comparisons with experiments are reviewed, and discussed with some new results. Main focus is placed on the following two topics, which are important for the research and development of large negative ion sources and high power H{sup −} ion beams: (i) Effects of non-equilibrium features of EEDF (electron energy distribution function) on H{sup −} production, and (ii) extraction physics of H{sup −} ions and beam optics.

  3. Effects of dust particles in plasma kinetics: Ion dynamics time scales

    SciTech Connect

    Angelis, U. de; Tolias, P.; Ratynskaia, S.

    2012-07-15

    The self-consistent kinetic theory of dusty plasmas [V. N. Tsytovich and U. de Angelis, Phys. Plasmas 6, 1093 (1999)] is extended to frequency regimes relevant for ion dynamics, accounting for both constant and fluctuating plasma sources. In contrast to earlier models, binary plasma collisions are no longer neglected with respect to collisions with dust; hence, the model developed here is also valid for low dust densities. Expressions are found for the system's permittivity, the ion collision integral, and the spectral densities of ion density fluctuations. The structure of the ion kinetic equation is analyzed, and applications of the model for both astrophysical and laboratory environments are discussed.

  4. Effects of dust particles in plasma kinetics: Ion dynamics time scales

    NASA Astrophysics Data System (ADS)

    de Angelis, U.; Tolias, P.; Ratynskaia, S.

    2012-07-01

    The self-consistent kinetic theory of dusty plasmas [V. N. Tsytovich and U. de Angelis, Phys. Plasmas 6, 1093 (1999)] is extended to frequency regimes relevant for ion dynamics, accounting for both constant and fluctuating plasma sources. In contrast to earlier models, binary plasma collisions are no longer neglected with respect to collisions with dust; hence, the model developed here is also valid for low dust densities. Expressions are found for the system's permittivity, the ion collision integral, and the spectral densities of ion density fluctuations. The structure of the ion kinetic equation is analyzed, and applications of the model for both astrophysical and laboratory environments are discussed.

  5. Kinetics of positive ions and electrically neutral active particles in afterglow in neon at low pressure

    NASA Astrophysics Data System (ADS)

    Pejović, Milić M.; Nešić, Nikola T.; Pejović, Momčilo M.

    2014-04-01

    Kinetics of positive ions and electrically neutral active particles formed during breakdown and successive discharge in neon-filled tube at 6.6 millibars pressure had been analyzed. This analysis was performed on the basis of mean value of electrical breakdown time delay t¯d dependence on afterglow period τ (memory curve). It was shown that positive ions are present in the 1μs < τ < 30 ms interval, which is manifested through t ¯d slow increase with the increase of τ. A rapid t¯d increase in the 30 ms < τ < 3 s interval is a consequence of significant decrease of positive ions concentration and dominant role in breakdown initiation have ground state nitrogen atoms, which further release secondary electrons from the cathode by catalytic recombination process. These atoms are formed during discharge by dissociation of ground state nitrogen molecules that are present as impurities in neon. For τ > 3 s, breakdown is initiated by cosmic rays and natural radioactivity. The increase of discharge current leads to decrease of t¯d due to the increase of positive ions concentration in inter electrode gap. The increase of applied voltage also decreases t¯d for τ > 30 ms due to the increase of the probability for initial electron to initiate breakdown. The presence of UV radiation leads to the decrease of t¯d due to the increased electron yield caused by photoelectrons. The influence of photoelectrons on breakdown initiation can be noticed for τ > 0.1 ms, while they dominantly determine t¯d for τ > 30 ms.

  6. Kinetics of positive ions and electrically neutral active particles in afterglow in neon at low pressure

    SciTech Connect

    Pejović, Milić M. Nešić, Nikola T.; Pejović, Momčilo M.

    2014-04-15

    Kinetics of positive ions and electrically neutral active particles formed during breakdown and successive discharge in neon-filled tube at 6.6 millibars pressure had been analyzed. This analysis was performed on the basis of mean value of electrical breakdown time delay t{sup ¯}{sub d} dependence on afterglow period τ (memory curve). It was shown that positive ions are present in the 1μs < τ < 30 ms interval, which is manifested through t{sup ¯}{sub d} slow increase with the increase of τ. A rapid t{sup ¯}{sub d} increase in the 30 ms < τ < 3 s interval is a consequence of significant decrease of positive ions concentration and dominant role in breakdown initiation have ground state nitrogen atoms, which further release secondary electrons from the cathode by catalytic recombination process. These atoms are formed during discharge by dissociation of ground state nitrogen molecules that are present as impurities in neon. For τ > 3 s, breakdown is initiated by cosmic rays and natural radioactivity. The increase of discharge current leads to decrease of t{sup ¯}{sub d} due to the increase of positive ions concentration in inter electrode gap. The increase of applied voltage also decreases t{sup ¯}{sub d} for τ > 30 ms due to the increase of the probability for initial electron to initiate breakdown. The presence of UV radiation leads to the decrease of t{sup ¯}{sub d} due to the increased electron yield caused by photoelectrons. The influence of photoelectrons on breakdown initiation can be noticed for τ > 0.1 ms, while they dominantly determine t{sup ¯}{sub d} for τ > 30 ms.

  7. Effect of ions on sulfuric acid-water binary particle formation: 1. Theory for kinetic- and nucleation-type particle formation and atmospheric implications

    NASA Astrophysics Data System (ADS)

    Merikanto, Joonas; Duplissy, Jonathan; Määttänen, Anni; Henschel, Henning; Donahue, Neil M.; Brus, David; Schobesberger, Siegfried; Kulmala, Markku; Vehkamäki, Hanna

    2016-02-01

    We derive a version of Classical Nucleation Theory normalized by quantum chemical results on sulfuric acid-water hydration to describe neutral and ion-induced particle formation in the binary sulfuric acid-water system. The theory is extended to treat the kinetic regime where the nucleation free energy barrier vanishes at high sulfuric acid concentrations or low temperatures. In the kinetic regime particle formation rates become proportional to sulfuric acid concentration to second power in the neutral system or first power in the ion-induced system. We derive simple general expressions for the prefactors in kinetic-type and activation-type particle formation calculations applicable also to more complex systems stabilized by other species. The theory predicts that the binary water-sulfuric acid system can produce strong new particle formation in the free troposphere both through barrier crossing and through kinetic pathways. At cold stratospheric and upper free tropospheric temperatures neutral formation dominates the binary particle formation rates. At midtropospheric temperatures the ion-induced pathway becomes the dominant mechanism. However, even the ion-induced binary mechanism does not produce significant particle formation in warm boundary layer conditions, as it requires temperatures below 0°C to take place at atmospheric concentrations. The theory successfully reproduces the characteristics of measured charged and neutral binary particle formation in CERN CLOUD3 and CLOUD5 experiments, as discussed in a companion paper.

  8. Kinetic effects on the Kelvin–Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations

    PubMed Central

    Nakamura, T. K. M.; Hasegawa, H.; Shinohara, I.

    2010-01-01

    Ion-to-magnetohydrodynamic scale physics of the transverse velocity shear layer and associated Kelvin–Helmholtz instability (KHI) in a homogeneous, collisionless plasma are investigated by means of full particle simulations. The shear layer is broadened to reach a kinetic equilibrium when its initial thickness is close to the gyrodiameter of ions crossing the layer, namely, of ion-kinetic scale. The broadened thickness is larger in B⋅Ω<0 case than in B⋅Ω>0 case, where Ω is the vorticity at the layer. This is because the convective electric field, which points out of (into) the layer for B⋅Ω<0 (B⋅Ω>0), extends (reduces) the gyrodiameters. Since the kinetic equilibrium is established before the KHI onset, the KHI growth rate depends on the broadened thickness. In the saturation phase of the KHI, the ion vortex flow is strengthened (weakened) for B⋅Ω<0 (B⋅Ω>0), due to ion centrifugal drift along the rotational plasma flow. In ion inertial scale vortices, this drift effect is crucial in altering the ion vortex size. These results indicate that the KHI at Mercury-like ion-scale magnetospheric boundaries could show clear dawn-dusk asymmetries in both its linear and nonlinear growth. PMID:20838425

  9. Wave-particle resonance condition test for ion-kinetic waves in the solar wind

    NASA Astrophysics Data System (ADS)

    Narita, Y.; Marsch, E.; Perschke, C.; Glassmeier, K.-H.; Motschmann, U.; Comişel, H.

    2016-04-01

    Conditions for the Landau and cyclotron resonances are tested for 543 waves (identified as local peaks in the energy spectra) in the magnetic field fluctuations of the solar wind measured by the Cluster spacecraft on a tetrahedral scale of 100 km. The resonance parameters are evaluated using the frequencies in the plasma rest frame, the parallel components of the wavevectors, the ion cyclotron frequency, and the ion thermal speed. The observed waves show a character of the sideband waves associated with the ion Bernstein mode, and are in a weak agreement with the fundamental electron cyclotron resonance in spite of the ion-kinetic scales. The electron cyclotron resonance is likely taking place in solar wind turbulence near 1 AU (astronomical unit).

  10. Negative-ion yield in low-pressure radio frequency discharges in hydrogen: Particle modeling and vibrational kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2006-03-15

    A theoretical study of the complex interplay between the vibrational kinetics and the plasma dynamics in low-pressure hydrogen plasmas produced by radio frequency discharges is performed. The study is realized by means of a one-dimensional particle model with five species (e, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup -}) while the vibrational/dissociation kinetics is based on a continuum model and the two are self-consistently coupled. In particular, we analyze the influence of pressure.

  11. Spherical ion kinetic simulations of DT implosions

    SciTech Connect

    Vidal, F.; Matte, J.P.; Casanova, M.; Larroche, O.

    1995-10-01

    The implosion of the DT plasma in an ablatively driven glass microballoon was simulated with a spherical ion kinetic code. The ion velocity distribution functions were strongly non-Maxwellian, and mostly depleted of fast ions. A high viscosity contributed to fuel heating, while large ion heat fluxes towards the pusher strongly cooled the fuel. This latter kinetic effect may explain in part why hydrodynamic simulations usually predict higher neutron yields than are measured.

  12. Kinetic transport simulation of energetic particles

    NASA Astrophysics Data System (ADS)

    Sheng, He; Waltz, R. E.

    2016-05-01

    A kinetic transport code (EPtran) is developed for the transport of the energetic particles (EPs). The EPtran code evolves the EP distribution function in radius, energy, and pitch angle phase space (r, E, λ) to steady state with classical slowing down, pitch angle scattering, as well as radial and energy transport of the injected EPs (neutral beam injection (NBI) or fusion alpha). The EPtran code is illustrated by treating the transport of NBI fast ions from high-n ITG/TEM micro-turbulence and EP driven unstable low-n Alfvén eigenmodes (AEs) in a well-studied DIII-D NBI heated discharge with significant AE central core loss. The kinetic transport code results for this discharge are compared with previous study using a simple EP density moment transport code ALPHA (R.E. Waltz and E.M. Bass 2014 Nucl. Fusion 54 104006). The dominant EP-AE transport is treated with a local stiff critical EP density (or equivalent pressure) gradient radial transport model modified to include energy-dependence and the nonlocal effects EP drift orbits. All previous EP transport models assume that the EP velocity space distribution function is not significantly distorted from the classical ‘no transport’ slowing down distribution. Important transport distortions away from the slowing down EP spectrum are illustrated by a focus on the coefficient of convection: EP energy flux divided by the product of EP average energy and EP particle flux.

  13. Adsorption-Desorption Kinetics of Soft Particles

    NASA Astrophysics Data System (ADS)

    Osberg, Brendan; Nuebler, Johannes; Gerland, Ulrich

    2015-08-01

    Adsorption-desorption processes are ubiquitous in physics, chemistry, and biology. Models usually assume hard particles, but within the realm of soft matter physics the adsorbing particles are compressible. A minimal 1D model reveals that softness fundamentally changes the kinetics: Below the desorption time scale, a logarithmic increase of the particle density replaces the usual Rényi jamming plateau, and the subsequent relaxation to equilibrium can be nonmonotonic and much faster than for hard particles. These effects will impact the kinetics of self-assembly and reaction-diffusion processes.

  14. Stochastic Parallel PARticle Kinetic Simulator

    Energy Science and Technology Software Center (ESTSC)

    2008-07-01

    SPPARKS is a kinetic Monte Carlo simulator which implements kinetic and Metropolis Monte Carlo solvers in a general way so that they can be hooked to applications of various kinds. Specific applications are implemented in SPPARKS as physical models which generate events (e.g. a diffusive hop or chemical reaction) and execute them one-by-one. Applications can run in paralle so long as the simulation domain can be partitoned spatially so that multiple events can be invokedmore » simultaneously. SPPARKS is used to model various kinds of mesoscale materials science scenarios such as grain growth, surface deposition and growth, and reaction kinetics. It can also be used to develop new Monte Carlo models that hook to the existing solver and paralle infrastructure provided by the code.« less

  15. Macroscale particle simulation of kinetic Alfven waves

    NASA Technical Reports Server (NTRS)

    Tanaka, Motohiko; Sato, Tetsuya; Hasegawa, Akira

    1987-01-01

    Two types of simulations of the kinetic Alfven wave are presented using a macroscale particle simulation code (Tanaka and Sato, 1986) which enables individual particle dynamics to be followed in the MHD scales. In this code, low frequency electromagnetic fields are solved by eliminating high frequency oscillations such as the light modes, and the scalar potential electric field is solved by eliminating Lagrangian oscillations. The dependences of the frequency and the Landau damping on the perpendicular wavenumber were studied, and good agreement was found between simulation and theoretical predictions. Some fundamental nonlinear interactions of the kinetic Alfven wave with the particles (parallel acceleration of the electrons) were also noted.

  16. Kinetics of particle wrapping by a vesicle

    NASA Astrophysics Data System (ADS)

    Mirigian, Stephen; Muthukumar, Murugappan

    2013-07-01

    We present theoretical results on kinetics for the passive wrapping of a single, rigid particle by a flexible membrane. Using a simple geometric ansatz for the shape of the membrane/particle complex we first compute free energy profiles as a function of the particle size, attraction strength between the particle and vesicle, and material properties of the vesicle—bending stiffness and stretching modulus. The free energy profiles thus computed are taken as input to a stochastic model of the wrapping process, described by a Fokker-Planck equation. We compute average uptake rates of the particle into the vesicle. We find that the rate of particle uptake falls to zero outside of a thermodynamically allowed range of particle sizes. Within the thermodynamically allowed range of particle size, the rate of uptake is variable and we compute the optimal particle size and maximal uptake rate as a function of the attraction strength, the vesicle size, and vesicle material properties.

  17. Kinetic interfaces of patchy particles

    NASA Astrophysics Data System (ADS)

    Araújo, N. A. M.; Dias, C. S.; Telo da Gama, M. M.

    2015-05-01

    We study the irreversible adsorption of patchy particles on substrates in the limit of advective mass transport. Recent numerical results show that the interface roughening depends strongly on the particle attributes, such as, patch-patch correlations, bond flexibility and strength of the interactions, uncovering new absorbing phase transitions. Here, we revisit these results and discuss in detail the transitions. In particular, we present new evidence that the tricritical point, observed in systems of particles with flexible patches, is in the tricritical directed percolation universality class. A scaling analysis of the time evolution of the correlation length for the aggregation of patchy particles with distinct bonding energies confirms that the critical regime is in the Kardar-Parisi-Zhang with quenched disorder universality class.

  18. Kinetic interfaces of patchy particles.

    PubMed

    Araújo, N A M; Dias, C S; Telo da Gama, M M

    2015-05-20

    We study the irreversible adsorption of patchy particles on substrates in the limit of advective mass transport. Recent numerical results show that the interface roughening depends strongly on the particle attributes, such as, patch-patch correlations, bond flexibility and strength of the interactions, uncovering new absorbing phase transitions. Here, we revisit these results and discuss in detail the transitions. In particular, we present new evidence that the tricritical point, observed in systems of particles with flexible patches, is in the tricritical directed percolation universality class. A scaling analysis of the time evolution of the correlation length for the aggregation of patchy particles with distinct bonding energies confirms that the critical regime is in the Kardar-Parisi-Zhang with quenched disorder universality class. PMID:25923051

  19. Kinetic ion thermometers for electron transfer dissociation.

    PubMed

    Pepin, Robert; Tureček, František

    2015-02-19

    Peptide fragment ions of the z-type were used as kinetic ion thermometers to gauge the internal energy of peptide cation-radicals produced by electron transfer in the gas-phase. Electron transfer dissociation (ETD)-produced z2 ions containing the leucine residue, z2(Leu-Lys) and z2(Leu-Arg), were found to undergo spontaneous dissociation by loss of C3H7 that was monitored by time-resolved kinetic measurements on the time scale of the linear ion trap mass spectrometer. Kinetic modeling of the dissociations, including collisional cooling and product loss by neutralization, provided unimolecular rate constants for dissociation that were converted to the z ion internal energies using RRKM theory. The internal energy of z2(Leu-Lys) and z2(Leu-Arg) fragment ions was found to decrease with the increasing size of the precursor peptide ion, indicating vibrational energy partitioning between the ion and neutral fragments and ergodic behavior. The experimentally determined excitation in the peptide cation-radicals upon electron transfer (285-327 kJ mol(-1)) was found to be lower than that theoretically calculated from the reaction exothermicity. The reasons for this missing energy are discussed. PMID:25594857

  20. Kinetic Simulations of Ion Beam Neutralization

    SciTech Connect

    Wang, Joseph

    2010-05-21

    Ion beam emission/neutralization is one of the most fundamental problems in spacecraft plasma interactions and electric propulsion. Although ion beam neutralization is readily achieved in experiments, the understanding of the underlying physical process remains at a rather primitive level. No theoretical or simulation models have convincingly explained the detailed neutralization mechanism, and no conclusions have been reached. This paper presents a fully kinetic simulation of ion beam neutralization and plasma beam propagation and discusses the physics of electron-ion coupling and the resulting propagation of a neutralized mesothermal plasma.

  1. Trapped particle stability for the kinetic stabilizer

    NASA Astrophysics Data System (ADS)

    Berk, H. L.; Pratt, J.

    2011-08-01

    A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favourable field-line curvature exists. The window of operation is determined for achieving magnetohydrodynamic (MHD) stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analysed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic-stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore, a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region.

  2. Nonlinear particle simulation of ion cyclotron waves in toroidal geometry

    SciTech Connect

    Kuley, A. Lin, Z.; Bao, J.; Wei, X. S.; Xiao, Y.

    2015-12-10

    Global particle simulation model has been developed in this work to provide a first-principles tool for studying the nonlinear interactions of radio frequency (RF) waves with plasmas in tokamak. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation with realistic electron-to-ion mass ratio. Boris push scheme for the ion motion has been developed in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron and ion Bernstein waves in global gyrokinetic toroidal code (GTC). The nonlinear simulation capability is applied to study the parametric decay instability of a pump wave into an ion Bernstein wave side band and a low frequency ion cyclotron quasi mode.

  3. Deterministic aggregation kinetics of superparamagnetic colloidal particles

    NASA Astrophysics Data System (ADS)

    Reynolds, Colin P.; Klop, Kira E.; Lavergne, François A.; Morrow, Sarah M.; Aarts, Dirk G. A. L.; Dullens, Roel P. A.

    2015-12-01

    We study the irreversible aggregation kinetics of superparamagnetic colloidal particles in two dimensions in the presence of an in-plane magnetic field at low packing fractions. Optical microscopy and image analysis techniques are used to follow the aggregation process and in particular study the packing fraction and field dependence of the mean cluster size. We compare these to the theoretically predicted scalings for diffusion limited and deterministic aggregation. It is shown that the aggregation kinetics for our experimental system is consistent with a deterministic mechanism, which thus shows that the contribution of diffusion is negligible.

  4. On a Kinetic Equation for Coalescing Particles

    NASA Astrophysics Data System (ADS)

    Escobedo, Miguel; Laurençot, Philippe; Mischler, Stéphane

    Existence of global weak solutions to a spatially inhomogeneous kinetic model for coalescing particles is proved, each particle being identified by its mass, momentum and position. The large time convergence to zero is also shown. The cornestone of our analysis is that, for any nonnegative and convex function, the associated Orlicz norm is a Liapunov functional. Existence and asymptotic behaviour then rely on weak and strong compactness methods in L1 in the spirit of the DiPerna-Lions theory for the Boltzmann equation.

  5. Kinetic Simulations of Particle Acceleration at Shocks

    SciTech Connect

    Caprioli, Damiano; Guo, Fan

    2015-07-16

    Collisionless shocks are mediated by collective electromagnetic interactions and are sources of non-thermal particles and emission. The full particle-in-cell approach and a hybrid approach are sketched, simulations of collisionless shocks are shown using a multicolor presentation. Results for SN 1006, a case involving ion acceleration and B field amplification where the shock is parallel, are shown. Electron acceleration takes place in planetary bow shocks and galaxy clusters. It is concluded that acceleration at shocks can be efficient: >15%; CRs amplify B field via streaming instability; ion DSA is efficient at parallel, strong shocks; ions are injected via reflection and shock drift acceleration; and electron DSA is efficient at oblique shocks.

  6. Optimal Estimation of Ion-Channel Kinetics from Macroscopic Currents

    PubMed Central

    Zeng, Xuhui; Yao, Jing; Yuchi, Ming; Ding, Jiuping

    2012-01-01

    Markov modeling provides an effective approach for modeling ion channel kinetics. There are several search algorithms for global fitting of macroscopic or single-channel currents across different experimental conditions. Here we present a particle swarm optimization(PSO)-based approach which, when used in combination with golden section search (GSS), can fit macroscopic voltage responses with a high degree of accuracy (errors within 1%) and reasonable amount of calculation time (less than 10 hours for 20 free parameters) on a desktop computer. We also describe a method for initial value estimation of the model parameters, which appears to favor identification of global optimum and can further reduce the computational cost. The PSO-GSS algorithm is applicable for kinetic models of arbitrary topology and size and compatible with common stimulation protocols, which provides a convenient approach for establishing kinetic models at the macroscopic level. PMID:22536358

  7. Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

    NASA Astrophysics Data System (ADS)

    Oboh, I.; Aluyor, E.; Audu, T.

    2015-03-01

    The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R2), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.

  8. Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

    SciTech Connect

    Oboh, I.; Aluyor, E.; Audu, T.

    2015-03-30

    The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R{sup 2}), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.

  9. Verification of electromagnetic fluid-kinetic hybrid electron model in global gyrokinetic particle simulation

    SciTech Connect

    Holod, I.; Lin, Z.

    2013-03-15

    The fluid-kinetic hybrid electron model is verified in global gyrokinetic particle simulation of linear electromagnetic drift-Alfvenic instabilities in tokamak. In particular, we have recovered the {beta}-stabilization of the ion temperature gradient mode, transition to collisionless trapped electron mode, and the onset of kinetic ballooning mode as {beta}{sub e} (ratio of electron kinetic pressure to magnetic pressure) increases.

  10. Maximizing Ion Current by Space Charge Neutralization using Negative Ions and Dust Particles

    SciTech Connect

    A. Smirnov; Y. Raitses; N.J. Fisch

    2005-01-25

    Ion current extracted from an ion source (ion thruster) can be increased above the Child-Langmuir limit if the ion space charge is neutralized. Similarly, the limiting kinetic energy density of the plasma flow in a Hall thruster might be exceeded if additional mechanisms of space charge neutralization are introduced. Space charge neutralization with high-mass negative ions or negatively charged dust particles seems, in principle, promising for the development of a high current or high energy density source of positive light ions. Several space charge neutralization schemes that employ heavy negatively charged particles are considered. It is shown that the proposed neutralization schemes can lead, at best, only to a moderate but nonetheless possibly important increase of the ion current in the ion thruster and the thrust density in the Hall thruster.

  11. Maximizing ion current by space-charge neutralization using negative ions and dust particles

    SciTech Connect

    Smirnov, A.; Raitses, Y.; Fisch, N.J.

    2005-05-15

    Ion current extracted from an ion source (ion thruster) can be increased above the Child-Langmuir limit if the ion space charge is neutralized. Similarly, the limiting kinetic energy density of the plasma flow in a Hall thruster might be exceeded if additional mechanisms of space-charge neutralization are introduced. Space-charge neutralization with high-mass negative ions or negatively charged dust particles seems, in principle, promising for the development of a high current or high energy density source of positive light ions. Several space-charge neutralization schemes that employ heavy negatively charged particles are considered. It is shown that the proposed neutralization schemes can lead, at best, only to a moderate but nonetheless possibly important increase of the ion current in the ion thruster and the thrust density in the Hall thruster.

  12. Maximizing ion current by space-charge neutralization using negative ions and dust particles

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Raitses, Y.; Fisch, N. J.

    2005-05-01

    Ion current extracted from an ion source (ion thruster) can be increased above the Child-Langmuir limit if the ion space charge is neutralized. Similarly, the limiting kinetic energy density of the plasma flow in a Hall thruster might be exceeded if additional mechanisms of space-charge neutralization are introduced. Space-charge neutralization with high-mass negative ions or negatively charged dust particles seems, in principle, promising for the development of a high current or high energy density source of positive light ions. Several space-charge neutralization schemes that employ heavy negatively charged particles are considered. It is shown that the proposed neutralization schemes can lead, at best, only to a moderate but nonetheless possibly important increase of the ion current in the ion thruster and the thrust density in the Hall thruster.

  13. Kinetic theory of magnetized dusty plasmas with dust particles charged by collisional processes and by photoionization

    SciTech Connect

    Galvao, R. A.; Ziebell, L. F.

    2012-09-15

    In this work, we detail the derivation of a plasma kinetic theory leading to the components of the dielectric tensor for a magnetized dusty plasma with variable charge on the dust particles, considering that the dust component of the plasma contains spherical dust particles with different sizes, which are charged both by inelastic collisions of electrons and ions and by photoionization.

  14. Kinetic Simulations of SNR Shocks- Prospects for Particle Acceleration

    NASA Astrophysics Data System (ADS)

    Chapman, Sandra

    2006-02-01

    Recent kinetic simulations of supercritical, quasi-perpendicular shocksyield time varying shock solutions that cyclically reform on thespatio-temporal scales of the incoming protons. Whether a shock solution isstationary or reforming depends upon the plasma parameters which, for SNRshocks are ill defined but believed to be within thetime-dependent regime. We will first review the structure and evolution ofthe time dependentsolutions, and the acceleration processes of the ions and electrons inthese time dependent fields, for a proton-electron plasma. We will thenpresent recent results for a three component plasma: backgroundprotons; electrons; and a second heavier ion population. These accelerationmechanisms may generate a suprathermalïnjection$quot; population - a seed population for subsequentacceleration at the shock, which can in turn generate particles at cosmicray energies.

  15. Simulating complex ion channel kinetics with IonChannelLab

    PubMed Central

    Covarrubias, Manuel; Sánchez-Rodríguez, Jorge E; Perez-Cornejo, Patricia; Arreola, Jorge

    2010-01-01

    In-silico simulation based on Markov chains is a powerful way to describe and predict the activity of many transport proteins including ion channels. However, modeling and simulation using realistic models of voltage- or ligand-gated ion channels exposed to a wide range of experimental conditions require building complex kinetic schemes and solving complicated differential equations. To circumvent these problems, we developed IonChannelLab a software tool that includes a user-friendly Graphical User Interface and a simulation library. This program supports channels with Ohmic or Goldman-Hodgkin-Katz behavior and can simulate the time-course of ionic and gating currents, single channel behavior and steady-state conditions. The program allows the simulation of experiments where voltage, ligand and ionic concentration are varied independently or simultaneously. PMID:20935453

  16. Trapped Particle Instability in Kinetic Stabilized Tandem Mirror

    NASA Astrophysics Data System (ADS)

    Berk, Herbert; Pratt, Jane

    2009-11-01

    The kinetic stabilizer tandem mirror (KSTM) devised by R. F. Post (J. Fus. Energy 2007) is an innovative concept devised to stabilize a symmetric tandem mirror machines using a concept devised by D. Ryutov (Proc. of Course and Workshop, Varenna, Italy, 1987) and empirically verified in the Gas Dynamic Trap (Ivanov, et. al. Trans. Fusion Technology 39, 127, 2001). The KSTM uses the momentum flux of unconfined particles that only sample the outer end regions of the mirror where there is very favorable field line curvature. Charged ion beams at relatively low energy are externally injected into the ends and reflected out from the ends. MHD stability with a power drain less than the fusion power production can be achieved. We examine the effect of fast growing trapped particle instability (Berk et. al. Sov J. Plasma Phys. 1983) on the overall stability. In this case stability is very sensitive to the electron connection between the stabilizer and end plug.

  17. Fokker–Planck kinetic modeling of suprathermal α-particles in a fusion plasma

    SciTech Connect

    Peigney, B.E.

    2014-12-01

    We present an ion kinetic model describing the transport of suprathermal α-particles in inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (α-particles) at a kinetic level. The model assumes spherical symmetry in configuration space and axial symmetry in velocity space around the mean flow velocity. A two-energy-scale approach leads to a self-consistent modeling of the coupling between suprathermal α-particles and the thermal bulk of the imploding plasma. This method provides an accurate numerical treatment of energy deposition and transport processes involving suprathermal particles. The numerical tools presented here are then validated against known analytical results. This enables us to investigate the potential role of ion kinetic effects on the physics of ignition and thermonuclear burn in inertial confinement fusion schemes.

  18. Cancellation of drift kinetic effects between thermal and energetic particles on the resistive wall mode stabilization

    NASA Astrophysics Data System (ADS)

    Guo, S. C.; Liu, Y. Q.; Xu, X. Y.; Wang, Z. R.

    2016-07-01

    Drift kinetic stabilization of the resistive wall mode (RWM) is computationally investigated using MHD-kinetic hybrid code MARS-K following the non-perturbative approach (Liu et al 2008 Phys. Plasmas 15 112503), for both reversed field pinch (RFP) and tokamak plasmas. Toroidal precessional drift resonance effects from trapped energetic ions (EIs) and various kinetic resonances between the mode and the guiding center drift motions of thermal particles are included into the self-consistent toroidal computations. The results show cancellation effects of the drift kinetic damping on the RWM between the thermal particles and EIs contributions, in both RFP and tokamak plasmas, even though each species alone can provide damping and stabilize RWM instability by respective kinetic resonances. The degree of cancellation generally depends on the EIs equilibrium distribution, the particle birth energy, as well as the toroidal flow speed of the plasma.

  19. Effects of Ion-Ion Collisions and Inhomogeneity in Two-Dimensional Kinetic Ion Simulations of Stimulated Brillouin Backscattering

    SciTech Connect

    Cohen, B I; Divol, L; Langdon, A B; Williams, E A

    2005-10-17

    Two-dimensional simulations with the BZOHAR [B.I. Cohen, B.F. Lasinski, A.B. Langdon, and E.A. Williams, Phys. Plasmas 4, 956 (1997)] hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability including the effects of ion-ion collisions and inhomogeneity. Ion-ion collisions tend to increase ion-wave dissipation, which decreases the gain exponent for stimulated Brillouin backscattering; and the peak Brillouin backscatter reflectivities tend to decrease with increasing collisionality in the simulations. Two types of Langevin-operator, ion-ion collision models were implemented in the simulations. In both models used the collisions are functions of the local ion temperature and density, but the collisions have no velocity dependence in the first model. In the second model, the collisions are also functions of the energy of the ion that is being scattered so as to represent a Fokker-Planck collision operator. Collisions decorrelate the ions from the acoustic waves in SBS, which disrupts ion trapping in the acoustic wave. Nevertheless, ion trapping leading to a hot ion tail and two-dimensional physics that allows the SBS ion waves to nonlinearly scatter remain robust saturation mechanisms for SBBS in a high-gain limit over a range of ion collisionality. SBS backscatter in the presence of a spatially nonuniform plasma flow is also investigated. Simulations show that depending on the sign of the spatial gradient of the flow relative to the backscatter, ion trapping effects that produce a nonlinear frequency shift can enhance (auto-resonance) or decrease (anti-auto-resonance) reflectivities in agreement with theoretical arguments.

  20. Comparison of solar wind driving mechanisms: ion cyclotron resonance versus kinetic suprathermal electron effects

    NASA Astrophysics Data System (ADS)

    Tam, Sunny W. Y.; Chang, Tom

    2003-09-01

    The combined kinetic effects of two possible solar wind driving mechanisms, ion cyclotron resonance and suprathermal electrons, have been studied in the literature [1]. However, the individual contribution by these two mechanisms was unclear. We compare the two effects in the fast solar wind. Our basic model follows the global kinetic evolution of the solar wind under the influence of ion cyclotron resonance, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects associated with the suprathermal electrons can be included in the model as an option. By comparing our results with and without this option, we conclude that, without considering any wave-particle interactions involving the electrons, the kinetic effects of the suprathermal electrons are relative insignificant in the presence of ion cyclotron resonance in terms of driving the solar wind.

  1. Merging for Particle-Mesh Complex Particle Kinetic Modeling of the Multiple Plasma Beams

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.

    2011-01-01

    We suggest a merging procedure for the Particle-Mesh Complex Particle Kinetic (PMCPK) method in case of inter-penetrating flow (multiple plasma beams). We examine the standard particle-in-cell (PIC) and the PMCPK methods in the case of particle acceleration by shock surfing for a wide range of the control numerical parameters. The plasma dynamics is described by a hybrid (particle-ion-fluid-electron) model. Note that one may need a mesh if modeling with the computation of an electromagnetic field. Our calculations use specified, time-independent electromagnetic fields for the shock, rather than self-consistently generated fields. While a particle-mesh method is a well-verified approach, the CPK method seems to be a good approach for multiscale modeling that includes multiple regions with various particle/fluid plasma behavior. However, the CPK method is still in need of a verification for studying the basic plasma phenomena: particle heating and acceleration by collisionless shocks, magnetic field reconnection, beam dynamics, etc.

  2. Ion-specific aggregation of hydrophobic particles.

    PubMed

    López-León, Teresa; Ortega-Vinuesa, Juan Luis; Bastos-González, Delfina

    2012-06-18

    This work shows that colloidal stability and aggregation kinetics of hydrophobic polystyrene (PS) nanospheres are extremely sensitive to the nature of the salt used to coagulate them. Three PS latices and four aggregating electrolytes, which all share the same cation (Na(+)) but have various anions located at different positions in the classical Hofmeister series depending on their kosmotropic or chaotropic character, are used. The present study focuses on analyzing different aggregating parameters, such as critical coagulation concentrations (CCC), cluster size distributions (CSD), initial kinetic constants K(11), and fractal dimensions of the aggregates d(f). While aggregation induced by SO(4)(2-) and Cl(-) behaved according to the predictions of the classical Derjaguin-Landau-Verwey-Overbeek theory, important discrepancies are found with NO(3)(-), which become dramatic when using SCN(-). These discrepancies among the anions were far more significant when they acted as counterions rather than as co-ions. While SO(4)(2-) and Cl(-) trigger fast diffusion-limited aggregation, SCN(-) gives rise to a stationary cluster size distribution in a few aggregation times when working with cationic PS particles. Clear differences are found among all analyzed parameters (CCC, CSD, K(11), and d(f)), and the experimental findings show that particles aggregate in potential wells whose depth is controlled by the chaotropic character of the anion. This paper presents new experimental evidence that may help to understand the microscopic origin of Hofmeister effects, as the observations are consistent with appealing theoretical models developed in the last few years. PMID:22556130

  3. Structure of kinetic/non-kinetic scale velocity shear layers and associated Kelvin-Helmholtz vortices: particle simulations

    NASA Astrophysics Data System (ADS)

    Nakamura, T.; Hasegawa, H.; Shinohara, I.

    2009-12-01

    Recent in-situ observations have revealed that Kelvin-Helmholtz (KH) vortices can roll-up not only at the Earth's magnetopause but also at the Mercury's magnetopause. Since kinetic effects cannot be neglected in Mercury-like small-scale situations, to universally understand the structure of the KH vortex the kinetic effects should be considered. Thus, in this study, we have performed 2D full particle (EM-PIC) simulations of KH vortices arising from kinetic and non-kinetic scale velocity shear layers. In this study, we focus on the basic situation in which the initial density, temperature and magnetic field are uniform and the magnetic field is perpendicular to the k-vector of KH instability. First, we investigated the kinetic equilibrium of velocity shear layers. In our simulation settings, particles are initialized with shifted Maxwellian velocity distributions having a bulk flow Vx0=±V0*tanh(Y/D0), where D0 is the initial half thickness of the velocity shear layer and V0 is the initial velocity jump across the shear layer. The +V0 (-V0) case corresponds to the dawn (dusk) case of the Earth’s and Mercury's situations. The Maxwellian loading of the particles, however, is only an approximation of equilibrium conditions, and past kinetic studies have shown that the true equilibrium condition is affected by the ion gyro-motion especially when D0<ρi, where ρi is the ion gyro radius. In this study, to exactly understand ion kinetic effects to the true equilibrium of various-scale velocity shear layer, we performed a parameter survey of D0 and V0. As a result, we found that in all cases until about 10 ion gyro-cycles the shear layer reaches the kinetic equilibrium, and further that when D0<ρi the thickness of the shear layer in the kinetic equilibrium always becomes 2ρi. It means there is a low threshold of the velocity shear layer which is determined by ρi. Moreover, we also found that the low threshold of the thickness in the dawn (dusk) case becomes thicker

  4. Twenty Five Years of Vibrational Kinetics and Negative Ion Production in H2 Plasmas: Modelling Aspects

    SciTech Connect

    Capitelli, M.; De Pascale, O.; Diomede, P.; Gorse, C.; Longo, S.; Pagano, D.; Gicquel, A.; Hassouni, K.

    2005-04-06

    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.

  5. Ion-acoustic shocks with reflected ions: modelling and particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Liseykina, T. V.; Dudnikova, G. I.; Vshivkov, V. A.; Malkov, M. A.

    2015-10-01

    > Non-relativistic collisionless shock waves are widespread in space and astrophysical plasmas and are known as efficient particle accelerators. However, our understanding of collisionless shocks, including their structure and the mechanisms whereby they accelerate particles, remains incomplete. We present here the results of numerical modelling of an ion-acoustic collisionless shock based on the one-dimensional kinetic approximation for both electrons and ions with a real mass ratio. Special emphasis is paid to the shock-reflected ions as the main driver of shock dissipation. The reflection efficiency, the velocity distribution of reflected particles and the shock electrostatic structure are studied in terms of the shock parameters. Applications to particle acceleration in geophysical and astrophysical shocks are discussed.

  6. Kinetic Simulations of Ion Beam Neutralization

    SciTech Connect

    Chang, O.; Wang, J.

    2011-05-20

    Full particle PIC simulations are performed to study the neutralization of an ion beam in the cohesionless, mesothermal regime. Simulations further confirmed that neutralization is achieved through interactions between the trapped electrons and the potential well established by the propagation of the beam front along the beam direction and is not through plasma instabilities as previous studies suggested. In the transverse direction, the process is similar to that of the expansion of mesothermal plasma into vacuum. Parametric simulations are also performed to investigate the effects of beam radius and domain boundary condition on the neutralization process. The results suggests that, while the qualitative behavior may be similar in ground tests, quantitative parameters such as the beam potential will be affected significantly by the vacuum chamber because of the limits imposed on the expansion process by the finite chamber space.

  7. Ion beam generation at the plasma sheet boundary layer by kinetic Alfven waves

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.; Smith, R. A.

    1989-01-01

    A two-dimensional quasi-linear numerical code was developed for studying ion beam generation at the plasma sheet boundary layer by kinetic Alfven waves. The model assumes that the central plasma sheet is the particle source, and that the last magnetic field lines on which kinetic Alfven waves exist and diffusion occurs can be either open or closed. As the possible source for the excitement of the kinetic Alfven waves responsible for ion diffusion, the resonant mode conversion of the surface waves to kinetic Alfven waves is considered. It is shown that, depending on the topology of the magnetic field at the lobe side of the simulation system, i.e., on whether field lines are open or closed, the ion distribution function may or may not reach a steady state.

  8. Trapped Particle Instabilities in the Kinetically Stabilized Tandem Mirror

    NASA Astrophysics Data System (ADS)

    Pratt, J.; Berk, H. L.; Horton, W.

    2009-05-01

    The kinetically stabilized tandem mirror (KSTM) is an innovative design to stabilize MHD modes in an axially symmetric tandem mirror machine (Post, J. Fus. Energy 2007). Originally proposed by Ryutov (Ryutov, Proc. of Course and Workshop, Varenna, Italy, 1987), this stabilizer has been empirically verified in the Gas Dynamic Trap (Ivanov, Anakeev et.al. Trans. Fusion Technology. 39, 127, 2001). The KSTM uses the momentum flux of escaping particles that sample good magnetic-field-line-curvature region outside the central confinement region. Charged ion beams at relatively low energy are externally injected from the ends into the expander region at an energy that is consistent with a stable MHD prediction and acceptable power loss for fusion. If stable, the KSTM would be extremely useful for limiting radial diffusion since the chaotic step size is minimized. We confirm that MHD stability is achieved in the KSTM. We examine the effect of the trapped particle instability discussed in Berk, Rosenbluth, et al. Sov. J. Plasma Phys. 1983 on overall stability. In this case stability is very sensitive to the electron connection between the stabilizer and the end plug.

  9. Laser ion sources for particle accelerators

    NASA Astrophysics Data System (ADS)

    Sherwood, T. R.

    1996-05-01

    There is an interest in accelerating atomic nuclei to produce particle beams for medical therapy, atomic and nuclear physics, inertial confinement fusion and particle physics. Laser Ion Sources, in which ions are extracted from plasma created when a high power density laser beam pulse strikes a solid surface in a vacuum, are not in common use. However, some new developments in which heavy ions have been accelerated show that such sources have the potential to provide the beams required for high-energy accelerator systems.

  10. Kinetic theory of electromagnetic ion waves in relativistic plasmas

    SciTech Connect

    Marklund, Mattias; Shukla, Padma K.

    2006-09-15

    A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied.

  11. Surface-Induced Dissociation of Peptide Ions: Kinetics and Dynamics

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.; Shukla, Anil K.

    2003-12-01

    Kinetics and dynamics studies have been carried out for the surface-induced dissociation (SID) of a set of model peptides utilizing a specially designed electrospray ionization Fourier Transform ion cyclotron resonance mass spectrometer in which mass-selected and vibrationally relaxed ions are collided on a orthogonally-mounted fluorinated self-assembled monolayer on Au{l_brace}111{r_brace} crystal. The sampling time in this apparatus can be varied from hundreds of microseconds to tens of seconds, enabling the investigation of kinetics of ion decomposition over an extended range of decomposition rates. RRKM-based modeling of these reactions for a set of polyalanines demonstrates that SID kinetics of these simple peptides is very similar to slow, multiple-collision activation and that the distribution of internal energies following collisional activation is indistinguishable from a thermal distribution. For more complex peptides comprised of several amino acids and with internal degrees of freedom ( DOF) of the order of 350 there is a dramatic change in kinetics in which RRKM kinetics is no longer capable of describing the decomposition of these complex ions. A combination of RRKM kinetics and the sudden death approximation, according to which decomposition occurs instantaneously, is a satisfactory description. This implies that a population of ions-which is dependant on the nature of the peptide, kinetic energy and sampling time-decomposes on or very near the surface. The shattering transition is described quantitatively for the limited set of molecules examined to date

  12. Surface-Induced Dissociation of Peptide Ions: Kinetics and Dynamics

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.

    2003-12-01

    Kinetics and dynamics studies have been carried out for the surface-induced dissociation (SID) of a set of model peptides utilizing a specially designed electro spray ionization Fourier Transform Ion cyclotron resonance mass spectrometer in which mass-selected and vibrationally relaxed ions are collided on an orthogonally-mounted fluorinated self-assembled monolayer on Au {111} crystal. The sampling time in this apparatus can be varied from hundreds of microseconds to tens of seconds, enabling the investigation of kinetics of ion decomposition over an extended range of decomposition rates. RRKM-based modeling of these reactions for a set of polyalanines demonstrates that kinetics of these simple peptides is very similar to slow, multiple-collision activation and that the distribution of internal energies following collisional activation is indistinguishable from a thermal distribution. For more complex peptides comprised of several amino acids and with internal degrees of freedom (DOF) of the order of 350 there is a dramatic change in kinetics in which RRKM kinetics is no longer capable of describing the decomposition of these complex ions. A combination of RRKM kinetics and the “sudden death” approximation, according to which decomposition occurs instantaneously, is a satisfactory description. This implies that a population of ions – which is dependant on the nature of the peptide, kinetic energy and sampling time – decomposes on or very near the surface. The shattering transition is described quantitatively for the limited set of molecules examined to date.

  13. Kinetic approach for the ion drag force in a collisional plasma

    SciTech Connect

    Ivlev, A.V.; Zhdanov, S.K.; Khrapak, S.A.; Morfill, G.E.

    2005-01-01

    The linear kinetic approach to calculate the ion drag force in a collisional plasma is generalized. The model collision integral (for ion-neutral collisions) is discussed and employed to calculate the plasma response for arbitrary velocity of the plasma flow and arbitrary frequency of the collisions. The derived plasma response is used to calculate the self-consistent force on the test charged particle. The obtained results are compared to those of the traditional pair collision approach, and the importance of the self-consistent kinetic consideration is highlighted. In conclusion, the applicability of the proposed approach is discussed.

  14. Plasma particle simulation of electrostatic ion thrusters

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Keefer, Dennis; Ruyten, Wilhelmus

    1990-01-01

    Charge exchange collisons between beam ions and neutral propellant gas can result in erosion of the accelerator grid surfaces of an ion engine. A particle in cell (PIC) is developed along with a Monte Carlo method to simulate the ion dynamics and charge exchange processes in the grid region of an ion thruster. The simulation is two-dimensional axisymmetric and uses three velocity components (2d3v) to investigate the influence of charge exchange collisions on the ion sputtering of the accelerator grid surfaces. An example calculation has been performed for an ion thruster operated on xenon propellant. The simulation shows that the greatest sputtering occurs on the downstream surface of the grid, but some sputtering can also occur on the upstream surface as well as on the interior of the grid aperture.

  15. Gravitationally induced particle production: Thermodynamics and kinetic theory

    NASA Astrophysics Data System (ADS)

    Lima, J. A. S.; Baranov, I.

    2014-08-01

    A relativistic kinetic description for the irreversible thermodynamic process of gravitationally induced particle production is proposed in the context of an expanding Friedmann-Robertson-Walker geometry. We show that the covariant thermodynamic treatment referred to as "adiabatic" particle production provoked by the cosmic time-varying gravitational field has a consistent kinetic counterpart. The variation of the distribution function is associated to a noncollisional kinetic term of quantum-gravitational origin which is proportional to the ratio Γ/H, where Γ is the gravitational particle production rate and H is the Hubble parameter. For Γ ≪H the process is negligible and as should be expected it also vanishes (regardless of the value of Γ) in the absence of gravitation. The resulting nonequilibrium distribution function has the same functional form of equilibrium with the evolution laws corrected by the particle production process. The macroscopic temperature evolution law is also kinetically derived for massive and massless particles. The present approach points to the possibility of an exact (semiclassical) quantum-gravitational kinetic treatment by incorporating backreaction effects in the cosmic background.

  16. Kinetic instability of ion acoustic mode in permeating plasmas

    SciTech Connect

    Vranjes, J.; Poedts, S.; Ehsan, Zahida

    2009-07-15

    In plasmas with electron drift (current) relative to static ions, the ion acoustic wave is subject to the kinetic instability which takes place if the directed electron speed exceeds the ion acoustic speed. The instability threshold becomes different in the case of one quasineutral electron-ion plasma propagating through another static quasineutral (target) plasma. The threshold velocity of the propagating plasma may be well below the ion acoustic speed of the static plasma. Such a currentless instability may frequently be expected in space and astrophysical plasmas.

  17. Particle transport and deposition: basic physics of particle kinetics

    PubMed Central

    Tsuda, Akira; Henry, Frank S.; Butler, James P.

    2015-01-01

    The human body interacts with the environment in many different ways. The lungs interact with the external environment through breathing. The enormously large surface area of the lung with its extremely thin air-blood barrier is exposed to particles suspended in the inhaled air. Whereas the particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drug. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental to understanding subsequent biological response, and the basic physics of particle motion and engineering knowledge needed to understand these subjects is the topic of this chapter. A large portion of this chapter deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: 1) the physical characteristics of particles, 2) particle behavior in gas flow, and 3) gas flow patterns in the respiratory tract. Other areas, such as particle transport in the developing lung and in the diseased lung are also considered. The chapter concludes with a summary and a brief discussion of areas of future research. PMID:24265235

  18. Adsorption-desorption kinetics of soft particles onto surfaces

    NASA Astrophysics Data System (ADS)

    Osberg, Brendan; Gerland, Ulrich

    A broad range of physical, chemical, and biological systems feature processes in which particles randomly adsorb on a substrate. Theoretical models usually assume ``hard'' (mutually impenetrable) particles, but in soft matter physics the adsorbing particles can be effectively compressible, implying ``soft'' interaction potentials. We recently studied the kinetics of such soft particles adsorbing onto one-dimensional substrates, identifying three novel phenomena: (i) a gradual density increase, or ''cramming'', replaces the usual jamming behavior of hard particles, (ii) a density overshoot, can occur (only for soft particles) on a time scale set by the desorption rate, and (iii) relaxation rates of soft particles increase with particle size (on a lattice), while hard particles show the opposite trend. The latter occurs since unjamming requires desorption and many-bodied reorganization to equilibrate -a process that is generally very slow. Here we extend this analysis to a two-dimensional substrate, focusing on the question of whether the adsorption-desorption kinetics of particles in two dimensions is similarly enriched by the introduction of soft interactions. Application to experiments, for example the adsorption of fibrinogen on two-dimensional surfaces, will be discussed.

  19. Test-particle method in kinetic theory of a plasma.

    NASA Technical Reports Server (NTRS)

    Matsuda, K.

    1971-01-01

    The introduction of a test particle into a system is considered. The system may be described by the Born-Bogoliubov-Green-Kirkwood-Yvon hierarchy. The field particles form a cloud which surrounds the test particle. The cloud is described by a conditional probability function which satisfies a certain equation. A generalization of the superposition principle reported by Rostoker (1964) to higher order correlation functions is discussed. Kinetic equations with the generalized Lenard-Balescu term are obtained, taking into account also diffusion by waves. The characteristics regarding the absorption or emission of waves by particles can be calculated.

  20. Finite-size particle simulations in the drift-kinetic approximation

    NASA Astrophysics Data System (ADS)

    Evstatiev, Evstati; Spencer, Andy; Kim, Jin-Soo; Shadwick, Bradley

    2013-10-01

    We extend previous variational formulations of finite-size particle plasma simulation methods to the drift-kinetic approximation. Such approximation is applicable to strongly magnetized plasmas, e.g., in tokamacs and magnetic mirrors. In our numerical examples we apply the drift-kinetic approximation to the electron population of the plasma in an electron cyclotron heating ion source (ECRIS) device. The electrons in an ECRIS device are strongly non-Maxwellian (due to the radio-frequency heating) and require kinetic treatment. The drift-kinetic approximation has allowed us to reduce the computational load associated with resolving the electron motion by about two orders of magnitude and to extend the simulation time to hundreds of microseconds. Details of the algorithms and some numerical results will be presented. Simulations are done with FAR-TECH's SIMulation of PLasmas code, SIMPL. Work supported by the DOE-SBIR office of Nuclear Physics.

  1. State to State and Charged Particle Kinetic Modeling of Time Filtering and Cs Addition

    SciTech Connect

    Capitelli, M.; Gorse, C.; Longo, S.; Diomede, P.; Pagano, D.

    2007-08-10

    We present here an account on the progress of kinetic simulation of non equilibrium plasmas in conditions of interest for negative ion production by using the 1D Bari code for hydrogen plasma simulation. The model includes the state to state kinetics of the vibrational level population of hydrogen molecules, plus a PIC/MCC module for the multispecies dynamics of charged particles. In particular we present new results for the modeling of two issues of great interest: the time filtering and the Cs addition via surface coverage.

  2. Integrating particle physical geometry into composting degradation kinetics.

    PubMed

    Wang, Yongjiang; Ai, Ping

    2016-01-01

    The study was carried out to integrate physical geometry of compost particle with degradation kinetics to model biological reactions, which revealing additional dynamic approaches. A sphere and its circumscribing cube were used to represent compost particles. An inner sphere, representing anaerobic zone, was introduced to describe variations of substrate volume without sufficient oxygen supply. Degradation of soluble substrates and hydrolysis of insoluble substrates were associated with the particle geometry. Transportation of soluble substrates produced from hydrolysis was expressed using Fick's law. Through the integration of degradation kinetics with geometry models, degradation models could describe varying volume of composting materials involving aerobic or anaerobic digestion and transportation of soluble substrates in a unit compost particle. PMID:26520491

  3. Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation

    SciTech Connect

    Manley, N.B.; Fabrikant, J.I.; Alpen, E.L.

    1988-12-01

    The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. This study concerns the cell population and cell cycle kinetics of the subependymal layer in the mouse brain, and the effects of charged particle irradiations on this cell population. Quantitative high resolution autoradiography was used to study the kinetic parameters in this cell layer. This study should help in understanding the effects of these high-energy heavy ions on normal mammalian brain tissue. The response of the mammalian brain exposure to charged particle ionizing radiation may be extremely variable. It varies from minimal physiological changes to overt tissue necrosis depending on a number of factors such as: the administered dose, dose-rate, the volume of the irradiated tissue, and the biological end-point being examined.

  4. Pulsed ion beam investigation of the kinetics of surface reactions

    NASA Technical Reports Server (NTRS)

    Horton, C. C.; Eck, T. G.; Hoffman, R. W.

    1989-01-01

    Pulsed ion beam measurements of the kinetics of surface reactions are discussed for the case where the width of the ion pulse is comparable to the measured reaction time, but short compared to the time between successive pulses. Theoretical expressions are derived for the time dependence of the ion-induced signals for linear surface reactions. Results are presented for CO emission from surface carbon and CF emission from Teflon induced by oxygen ion bombardment. The strengths and limitations of this technique are described.

  5. Kinetic model of particle-inhibited grain growth

    NASA Astrophysics Data System (ADS)

    Thompson, Gary Scott

    The effects of second phase particles on matrix grain growth kinetics were investigated using Al2O3-SiC as a model system. In particular, the validity of the conclusion drawn from a previous kinetic analysis that the kinetics of particle-inhibited grain growth in Al2 O3-SiC samples with an intermediate volume fraction of second phase could be well quantified by a modified-Zener model was investigated. A critical analysis of assumptions made during the previous kinetic analysis revealed oversimplifications which affect the validity of the conclusion. Specifically, the degree of interaction between particles and grain boundaries was assumed to be independent of the mean second phase particle size and size distribution. In contrast, current measurements indicate that the degree of interaction in Al2O3-SiC is dependent on these parameters. An improved kinetic model for particle-inhibited grain growth in Al 2O3-SiC was developed using a modified-Zener approach. The comparison of model predictions with experimental grain growth data indicated that significant discrepancies (as much as 4--5 orders of magnitude) existed. Based on this, it was concluded that particles had a much more significant effect on grain growth kinetics than that caused by a simple reduction of the boundary driving force due to the removal of boundary area. Consequently, it was also concluded that the conclusion drawn from the earlier kinetic analysis regarding the validity of a modified-Zener model was incorrect. Discrepancies between model and experiment were found to be the result of a significant decrease in experimental growth rate constant not predicted by the model. Possible physical mechanisms for such a decrease were investigated. The investigation of a small amount of SiO2 on grain growth in Al2O3 indicated that the decrease was not the result of a decrease in grain boundary mobility due to impurity contamination by particles. By process of elimination and based on previous observations

  6. Influence of particle/solid surface zeta potential on particle adsorption kinetics.

    PubMed

    Savaji, Kunal V; Niitsoo, Olivia; Couzis, Alexander

    2014-10-01

    In this paper we attempt to understand monolayer formation of spherical particles on a solid surface immersed in a suspension and driven by electrostatic interaction force. The study focuses on the theoretical aspects of the particle adsorption and modeling work based on the random sequential adsorption (RSA) approach is done in order to describe the particle adsorption kinetics and the saturation coverage. The theoretical model is then compared with experimental data obtained under conditions similar to those of the modeling work. Studying the adsorption of polystyrene particles on a silicon wafer in an aqueous system was employed to experimentally validate the theoretical framework. It has been shown both theoretically and experimentally that the particle and solid surface zeta potential values do influence the adsorption kinetics but the effect is too negligible to be of any use in accelerating the kinetics. We have shown that the electrostatically driven particle adsorption is a transport limited process and the rate of transport is not a major function of the zeta potential values of the particle and the solid surface. The faster kinetics seen when the ionic concentration of the suspension is increased is because of the blocking effects and not due to faster approach of particles towards the solid surface. Finally, we have made an important addition to the existing models by incorporating the variation in the flux as a function of particle/solid surface zeta potentials, surface coverage and the randomized position of incidence of an incoming particle on the solid surface. PMID:24996026

  7. CALCINATION KINETICS AND SURFACE AREA OF DISPERSED LIMESTONE PARTICLES

    EPA Science Inventory

    The paper gives results of measurements of the rates of calcination of two types of limestones, ranging in particle size from 1 to 90 micrometers, and over the temperature range of 516 to 1000 C. A kinetic model, based on the B.E.T. (Brunauer-Emmett-Teller) surface area of the Ca...

  8. Linear kinetic theory and particle transport in stochastic mixtures

    SciTech Connect

    Pomraning, G.C.

    1995-12-31

    We consider the formulation of linear transport and kinetic theory describing energy and particle flow in a random mixture of two or more immiscible materials. Following an introduction, we summarize early and fundamental work in this area, and we conclude with a brief discussion of recent results.

  9. Mass, Momentum and Kinetic Energy of a Relativistic Particle

    ERIC Educational Resources Information Center

    Zanchini, Enzo

    2010-01-01

    A rigorous definition of mass in special relativity, proposed in a recent paper, is recalled and employed to obtain simple and rigorous deductions of the expressions of momentum and kinetic energy for a relativistic particle. The whole logical framework appears as the natural extension of the classical one. Only the first, second and third laws of…

  10. Ion and electron kinetic physics associated with magnetotail dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Eastwood, Jonathan; Goldman, Martin; Newman, David; Zhang, Xiao-Jia; Hietala, Heli; Krupar, Vratislav; Mistry, Rishi; Lapenta, Giovanni; Angelopoulos, Vassilis

    2016-04-01

    Magnetic reconnection plays an important role in controlling the dynamics of the Earth's magnetotail. In particular, a dipolarization front (DF) may form at the leading edge of the reconnection exhaust as a consequence of its interaction with the pre-existing plasma sheet. Earthward moving DFs typically exhibit a rapid increase in the northward component of the magnetic field which divides the pre-existing plasma sheet from the hotter, high speed and lower density reconnection exhaust. Extensive observations have been made of DFs at Earth with multi-point missions such as Cluster, THEMIS/ARTEMIS and now Magnetospheric Multi-Scale (MMS). In this invited contribution we will first review previous work showing that DFs are often relatively thin and locations where significant particle acceleration and heating can occur in a variety of ways. The dynamics and kinematics of ions and electrons at DFs are very different, as a result of their different particle masses. The reflection of ions by DFs leads to acceleration and heating, and we show that via kinetic effects, some part of the pre-existing plasma sheet ion population is entrained and accelerated into the exhaust. This interaction in fact occurs over a macroscopic region, rather than simply being limited to the thin DF interface. This leads to a more general consequence which is that reconnection exhausts are not necessarily simply fed by plasma inflow across the separatrices, but also by plasma from the region into which the jet is propagating; the implications of this finding are discussed. In contrast, electron acceleration and thermalisation is more related to the presence of instabilities in particular associated with temperature anisotropy and the growth of whistler waves. We discuss the observational evidence and also explore the possibility of the role that Cherenkov emission of whistlers by electron holes could play in this process. Finally we will briefly highlight recent new work in this area, and

  11. Versatile gas/particle ion chromatograph.

    PubMed

    Ullah, S M Rahmat; Takeuchi, Masaki; Dasgupta, Purnendu K

    2006-02-01

    A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv. PMID:16509343

  12. 3D hybrid simulations with gyrokinetic particle ions and fluid electrons

    SciTech Connect

    Belova, E.V.; Park, W.; Fu, G.Y.; Strauss, H.R.; Sugiyama, L.E.

    1998-12-31

    The previous hybrid MHD/particle model (MH3D-K code) represented energetic ions as gyrokinetic (or drift-kinetic) particles coupled to MHD equations using the pressure or current coupling scheme. A small energetic to bulk ion density ratio was assumed, n{sub h}/n{sub b} {much_lt} 1, allowing the neglect of the energetic ion perpendicular inertia in the momentum equation and the use of MHD Ohm`s law E = {minus}v{sub b} {times} B. A generalization of this model in which all ions are treated as gyrokinetic/drift-kinetic particles and fluid description is used for the electron dynamics is considered in this paper.

  13. Kinetic-energy transfer in highly-charged-ion collisions with carbon

    NASA Astrophysics Data System (ADS)

    Lake, R. E.; Arista, N. R.

    2015-11-01

    We present an accurate theoretical model for the charge dependence of kinetic energy transferred in collisions between slow highly charged ions (HCIs) and the atoms in a carbon solid. The model is in excellent agreement with experimental kinetic-energy-loss data for carbon nanomembrane and thin carbon foil targets. This study fills a notable gap in the literature of charged-particle energy loss in the regime of low incident velocity (vp≲2.188 ×106 m/s) where charge states greatly exceed the equilibrium values.

  14. Towards a unified linear kinetic transport model with the trace ion module for EIRENE

    NASA Astrophysics Data System (ADS)

    Seebacher, J.; Kendl, A.

    2012-04-01

    Linear kinetic Monte Carlo particle transport models are frequently employed in fusion plasma simulations to quantify atomic and surface effects on the main plasma flow dynamics. Separate codes are used for transport of neutral particles (incl. radiation) and charged particles (trace impurity ions). Integration of both modules into main plasma fluid solvers provides then self-consistent solutions, in principle. The required interfaces are far from trivial, because rapid atomic processes in particular in the edge region of fusion plasmas require either smoothing and resampling, or frequent transfer of particles from one into the other Monte Carlo code. We propose a different scheme here, in which despite the inherently different mathematical form of kinetic equations for ions and neutrals (e.g. Fokker-Planck vs. Boltzmann collision integrals) both types of particle orbits can be integrated into one single code. We show that the approximations and shortcomings of this “single sourcing” concept (e.g., restriction to explicit ion drift orbit integration) can be fully tolerable in a wide range of typical fusion edge plasma conditions, and be overcompensated by the code-system simplicity, as well as by inherently ensured consistency in geometry (one single numerical grid only) and (the common) atomic and surface process modules.

  15. Towards a unified linear kinetic transport model with the trace ion module for EIRENE

    PubMed Central

    Seebacher, J.; Kendl, A.

    2012-01-01

    Linear kinetic Monte Carlo particle transport models are frequently employed in fusion plasma simulations to quantify atomic and surface effects on the main plasma flow dynamics. Separate codes are used for transport of neutral particles (incl. radiation) and charged particles (trace impurity ions). Integration of both modules into main plasma fluid solvers provides then self-consistent solutions, in principle. The required interfaces are far from trivial, because rapid atomic processes in particular in the edge region of fusion plasmas require either smoothing and resampling, or frequent transfer of particles from one into the other Monte Carlo code. We propose a different scheme here, in which despite the inherently different mathematical form of kinetic equations for ions and neutrals (e.g. Fokker–Planck vs. Boltzmann collision integrals) both types of particle orbits can be integrated into one single code. We show that the approximations and shortcomings of this “single sourcing” concept (e.g., restriction to explicit ion drift orbit integration) can be fully tolerable in a wide range of typical fusion edge plasma conditions, and be overcompensated by the code-system simplicity, as well as by inherently ensured consistency in geometry (one single numerical grid only) and (the common) atomic and surface process modules. PMID:22474397

  16. Kinetics of small particle activation in supersaturated vapors

    SciTech Connect

    McGraw, R.; Wang, J.

    2010-08-29

    We examine the nucleated (with barrier) activation of perfectly wetting (zero contact angle) particles ranging from bulk size down to one nanometer. Thermodynamic properties of the particles, coated with liquid layers of varying thickness and surrounded by vapor, are analyzed. Nano-size particles are predicted to activate at relative humidity below the Kelvin curve on crossing a nucleation barrier, located at a critical liquid layer thickness such that the total particle size (core + liquid layer) equals the Kelvin radius (Fig. 1). This barrier vanishes precisely as the critical layer thickness approaches the thin layer limit and the Kelvin radius equals the radius of the particle itself. These considerations are similar to those included in Fletcher's theory (Fletcher, 1958) however the present analysis differs in several important respects. Firstly, where Fletcher used the classical prefactor-exponent form for the nucleation rate, requiring separate estimation of the kinetic prefactor, we solve a diffusion-drift equation that is equivalent to including the full Becker-Doering (BD) multi-state kinetics of condensation/evaporation along the growth coordinate. We also determine the mean first passage time (MFPT) for barrier crossing (Wedekind et al., 2007), which is shown to provide a generalization of BD nucleation kinetics especially useful for barrier heights that are considerably lower than those typically encountered in homogeneous vapor-liquid nucleation, and make explicit comparisons between the MFPT and BD kinetic models. Barrier heights for heterogeneous nucleation are computed by a thermo-dynamic area construction introduced recently to model deliquescence and efflorescence of small particles (McGraw and Lewis, 2009). In addition to providing a graphical representation of the activation process that offers new insights, the area construction provides a molecular approach that avoids explicit use of the interfacial tension. Typical barrier profiles for

  17. Excitation of dust kinetic Alfven waves by semi-relativistic ion beams

    NASA Astrophysics Data System (ADS)

    Rubab, N.; Jaffer, G.

    2016-05-01

    The growth rates for dust kinetic Alfvén wave (DKAW) based on semi-relativistic Maxwellian distribution function are investigated in a hot and magnetized plasma. The dispersion relation of DKAW is obtained on a dust acoustic velocity branch, and the kinetic instability due to cross-field semi-relativistic ion flow is examined by the effect of dust parameters. Analytical expressions are derived for various modes as a natural consequence of the form of the solution, and is shown through graphical representation that the presence of dust particles and the cross-field semi-relativistic ions sensibly modify the dispersion characteristics of low-frequency DKAW. The results are valid for a frequency regime well below the dust cyclotron frequency. We suggest that semi-relativistic particles are an important factor in the growth/damping of DKAWs. It is also found that relativistic effects appear with the dust lower hybrid frequency are more effective for dust kinetic Alfvén waves in the perpendicular component as compared to the parallel one. In particular, the relativistic effects associated with electrons suppress the instability while ions enhance the growth rates. The growth rates are significantly modified with dust parameters and streaming velocity of cross-field ions.

  18. Grain boundary curvature and grain growth kinetics with particle pinning

    NASA Astrophysics Data System (ADS)

    Shahandeh, Sina; Militzer, Matthias

    2013-08-01

    Second-phase particles are used extensively in design of polycrystalline materials to control the grain size. According to Zener's theory, a distribution of particles creates a pinning pressure on a moving grain boundary. As a result, a limiting grain size is observed, but the effect of pinning on the detail of grain growth kinetics is less known. The influence of the particles on the microstructure occurs in multiple length scales, established by particle radius and the grain size. In this article, we use a meso-scale phase-field model that simulates grain growth in the presence of a uniform pinning pressure. The curvature of the grain boundary network is measured to determine the driving pressure of grain growth in 2D and 3D systems. It was observed that the grain growth continues, even under conditions where the average driving pressure is smaller than the pinning pressure. The limiting grain size is reached when the maximum of driving pressure distribution in the structure is equal to the pinning pressure. This results in a limiting grain size, larger than the one predicted by conventional models, and further analysis shows consistency with experimental observations. A physical model is proposed for the kinetics of grain growth using parameters based on the curvature analysis of the grain boundaries. This model can describe the simulated grain growth kinetics.

  19. Charged particle dynamics and molecular kinetics in the hydrogen postdischarge plasma

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2006-11-15

    The afterglow of a parallel plate radio frequency discharge in hydrogen is studied by numerical modelling to compare ion dynamics and chemical effects on the behavior of negative ions. While the ion dynamics requires a kinetic description of space dependent plasma relaxation (at least 1D), chemical effects require a vibrational kinetics of hydrogen molecules. Since previous models did not include both features it has not been possible until now to realize both effects in a single simulation. We apply an updated version of the 1D Bari model which includes a 1.5D (1Dr2Dv) Particle in Cell/Monte Carlo (PIC/MC) multispecies module coupled to the space and time dependent master equation for H{sub 2}(X{sup 1}{sigma}{sub g}{sup +},v=0,...,14) vibrational level population. Negative ion fronts are described in hydrogen for the first time and their impact on the plasma limiting surfaces produces a negative ion current evolution compatible with experimental findings. In the same conditions, the attachment rate overshoot is found to contribute about 7% to the average ion density in the plasma.

  20. Kinetic electron and ion instability of the lunar wake simulated at physical mass ratio

    NASA Astrophysics Data System (ADS)

    Haakonsen, Christian Bernt; Hutchinson, Ian H.; Zhou, Chuteng

    2015-03-01

    The solar wind wake behind the moon is studied with 1D electrostatic particle-in-cell (PIC) simulations using a physical ion to electron mass ratio (unlike prior investigations); the simulations also apply more generally to supersonic flow of dense magnetized plasma past non-magnetic objects. A hybrid electrostatic Boltzmann electron treatment is first used to investigate the ion stability in the absence of kinetic electron effects, showing that the ions are two-stream unstable for downstream wake distances (in lunar radii) greater than about three times the solar wind Mach number. Simulations with PIC electrons are then used to show that kinetic electron effects can lead to disruption of the ion beams at least three times closer to the moon than in the hybrid simulations. This disruption occurs as the result of a novel wake phenomenon: the non-linear growth of electron holes spawned from a narrow dimple in the electron velocity distribution. Most of the holes arising from the dimple are small and quickly leave the wake, approximately following the unperturbed electron phase-space trajectories, but some holes originating near the center of the wake remain and grow large enough to trigger disruption of the ion beams. Non-linear kinetic-electron effects are therefore essential to a comprehensive understanding of the 1D electrostatic stability of such wakes, and possible observational signatures in ARTEMIS data from the lunar wake are discussed.

  1. Kinetic electron and ion instability of the lunar wake simulated at physical mass ratio

    SciTech Connect

    Haakonsen, Christian Bernt Hutchinson, Ian H. Zhou, Chuteng

    2015-03-15

    The solar wind wake behind the moon is studied with 1D electrostatic particle-in-cell (PIC) simulations using a physical ion to electron mass ratio (unlike prior investigations); the simulations also apply more generally to supersonic flow of dense magnetized plasma past non-magnetic objects. A hybrid electrostatic Boltzmann electron treatment is first used to investigate the ion stability in the absence of kinetic electron effects, showing that the ions are two-stream unstable for downstream wake distances (in lunar radii) greater than about three times the solar wind Mach number. Simulations with PIC electrons are then used to show that kinetic electron effects can lead to disruption of the ion beams at least three times closer to the moon than in the hybrid simulations. This disruption occurs as the result of a novel wake phenomenon: the non-linear growth of electron holes spawned from a narrow dimple in the electron velocity distribution. Most of the holes arising from the dimple are small and quickly leave the wake, approximately following the unperturbed electron phase-space trajectories, but some holes originating near the center of the wake remain and grow large enough to trigger disruption of the ion beams. Non-linear kinetic-electron effects are therefore essential to a comprehensive understanding of the 1D electrostatic stability of such wakes, and possible observational signatures in ARTEMIS data from the lunar wake are discussed.

  2. Scaling of Kinetic Instability Induced Fast Ion Losses in NSTX

    SciTech Connect

    E.D. Fredrickson; D. Darrow; S. Medley; J. Menard; H. Park; L. Roquemore; D. Stutman; K. Tritz; S. Kubota; K.C. Lee

    2005-06-24

    During neutral beam injection (NBI) in the National Spherical Torus Experiment (NSTX), a wide variety of fast ion driven instabilities is excited by the large ratio of fast ion velocity to Alfven velocity, together with the relatively high fast ion beta, beta(sub)f. The fast ion instabilities have frequencies ranging from a few kilohertz to the ion cyclotron frequency. The modes can be divided roughly into three categories, starting with Energetic Particle Modes (EPM) in the lowest frequency range (0 to 120 kHz), the Toroidal Alfven Eigenmodes (TAE) in the intermediate frequency range (50 to 200 kHz) and the Compressional and Global Alfven Eigenmodes (CAE and GAE, respectively) from approximately equal to 300 kHz up to the ion cyclotron frequency. Each of these categories of modes exhibits a wide range of behavior, including quasi-continuous oscillation, bursting, chirping and, except for the lower frequency range, turbulence.

  3. A fully kinetic, self-consistent particle simulation model of the collisionless plasma--sheath region

    SciTech Connect

    Procassini, R.J.; Birdsall, C.K.; Morse, E.C. )

    1990-12-01

    A fully kinetic particle-in-cell (PIC) model is used to self-consistently determine the steady-state potential profile in a collisionless plasma that contacts a floating, absorbing boundary. To balance the flow of particles to the wall, a distributed source region is used to inject particles into the one-dimensional system. The effect of the particle source distribution function on the source region and collector sheath potential drops, and particle velocity distributions is investigated. The ion source functions proposed by Emmert {ital et} {ital al}. (Phys. Fluids {bold 23}, 803 (1980)) and Bissell and Johnson (Phys. Fluids {bold 30}, 779 (1987)) (and various combinations of these) are used for the injection of both ions {ital and} electrons. The values of the potential drops obtained from the PIC simulations are compared to those from the theories of Emmert {ital et} {ital al}., Bissell and Johnson, and Scheuer and Emmert (Phys. Fluids {bold 31}, 3645 (1988)), all of which assume that the electron density is related to the plasma potential via the Boltzmann relation. The values of the source region and total potential drop are found to depend on the choice of the electron source function, as well as the ion source function. The question of an infinite electric field at the plasma--sheath interface, which arises in the analyses of Bissell and Johnson and Scheuer and Emmert, is also addressed.

  4. A gyro-kinetic model for trapped electron and ion modes

    NASA Astrophysics Data System (ADS)

    Drouot, Thomas; Gravier, Etienne; Reveille, Thierry; Ghizzo, Alain; Bertrand, Pierre; Garbet, Xavier; Sarazin, Yanick; Cartier-Michaud, Thomas

    2014-10-01

    In tokamak plasmas, it is recognized that ITG (ion temperature gradient instability) and trapped electron modes (TEM) are held responsible for turbulence giving rise to anomalous transport. The present work focuses on the building of a model including trapped kinetic ions and trapped kinetic electrons. For this purpose, the dimensionality is reduced by averaging the motion over the cyclotron motion and the "banana" orbits, according to the fact that the instabilities are characterized by frequencies of the order of the low trapped particle precession frequency. Moreover, a set of action-angle variables is used. The final model is 4D (two-dimensional phase space parametrized by the two first adiabatic invariants namely the particle energy and the trapping parameter). In this paper, the trapped ion and electron modes (TIM and TEM) are studied by using a linear analysis of the model. This work is currently performed in order to include trapped electrons in an existing semi lagrangian code for which TIM modes are already taken into account. This study can be considered as a first step in order to include kinetic trapped electrons in the 5D gyrokinetic code GYSELA [J. Abiteboul et al., ESAIM Proc. 32, 103 (2011)]. Contribution to the Topical Issue "Theory and Applications of the Vlasov Equation", edited by Francesco Pegoraro, Francesco Califano, Giovanni Manfredi and Philip J. Morrison.

  5. Semi-aerobic stabilized landfill leachate treatment by ion exchange resin: isotherm and kinetic study

    NASA Astrophysics Data System (ADS)

    Zamri, Mohd Faiz Muaz Ahmad; Kamaruddin, Mohamad Anuar; Yusoff, Mohd Suffian; Aziz, Hamidi Abdul; Foo, Keng Yuen

    2015-03-01

    This study was carried out to investigate the treatability of ion exchange resin (Indion MB 6 SR) for the removal of chromium (VI), aluminium (III), zinc (II), copper (II), iron (II), and phosphate (PO4)3-, chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and colour from semi-aerobic stabilized leachate by batch test. A range of ion exchange resin dosage was tested towards the removal efficiency of leachate parameters. It was observed that equilibrium data were best represented by the Langmuir model for metal ions and Freundlich was ideally fit for COD, NH3-N and colour. Intra particle diffusion model, pseudo first-order and pseudo second-order isotherm models were found ideally fit with correlation of the experimental data. The findings revealed that the models could describe the ion exchange kinetic behaviour efficiently, which further suggests comprehensive outlook for the future research in this field.

  6. Kinetic study of ion-acoustic plasma vortices

    SciTech Connect

    Khan, S. A.; Aman-ur-Rehman; Mendonca, J. T.

    2014-09-15

    The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.

  7. Diffusion kinetics of the ion exchange of benzocaine on sulfocationites

    NASA Astrophysics Data System (ADS)

    Al'tshuler, O. G.; Shkurenko, G. Yu.; Gorlov, A. A.; Al'tshuler, G. N.

    2016-06-01

    The theory of the ion exchange kinetics on strong acid cationites with the participation of weak electrolytes is discussed. The kinetics of desorption of benzocaine in the protonated and molecular forms from strong acid cationites, sulfonated polycalixarene, and KU-23 30/100 sulfocationite, is studied experimentally. It is shown that the flow of protonated benzocaine from cationite upon desorption proceeding by the ion-exchange mechanism is more intense than upon desorption of nonionized benzocaine molecules. It is established that the diffusion coefficient of benzocaine cations is (1.21 ± 0.23) × 10-12 m2/s in KU-23 30/100 sulfocation and (0.65 ± 0.06) × 10-13 m2/s in sulfonated polycalixarene, while the diffusion coefficient of benzocaine molecules is (0.65 ± 0.15) × 10-14 m2/s in sulfonated polycalixarene.

  8. Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

    SciTech Connect

    Peng, Ivy Bo Markidis, Stefano; Laure, Erwin; Johlander, Andreas; Vaivads, Andris; Khotyaintsev, Yuri; Henri, Pierre; Lapenta, Giovanni

    2015-09-15

    We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration.

  9. Ion beam generation at the plasma sheet boundary layer by kinetic Alfven waves

    SciTech Connect

    Moghaddam-Taaheri, E.; Goertz, C.K.; Smith, R.A. )

    1989-08-01

    The kinetic Alfven wave, an Alfven wave with a perpendicular wavelength comparable to the ion gyroradius, can diffuse ions both in velocity and coordinate spaces with comparable transport rates. This may lead to the generation of ion beams in the plasma sheet boundary layer (PSBL). To investigate the ion beam generation process numerically, a two-dimensional quasi-linear code was constructed. Assuming that the plasma {beta} (the ratio of plasma pressure to the magnetic pressure) varies from {beta} = 1 to {beta} << 1 across the magnetic field, the dynamics of the ion beam generation in the PSBL was studied. It was found that if your start with an ion distribution function which monotonically decreases with velocity along the magnetic field and a density gradient across the magnetic field, ions diffuse in velocity-coordinate space until nearly a plateau is established along the diffusion path. Depending on the topology of the magnetic field at the lobe side of the simulation system, i.e., open or closed field lines, the ion distribution function may or may not reach a steady state. If the field lines are open there, i.e., if the diffusion extends into the lobe, the double diffusion process may provide a mechanism for continuously transferring the ions from the central plasma sheet to the lobe. The authors comment on the effect of the particle loss on the establishment of the pressure balance in the plasma sheet.

  10. Gyrokinetic particle simulations of reversed shear Alfven eigenmode excited by antenna and fast ions

    SciTech Connect

    Deng Wenjun; Holod, Ihor; Xiao Yong; Lin Zhihong; Wang Xin; Zhang Wenlu

    2010-11-15

    Global gyrokinetic particle simulations of reversed shear Alfven eigenmode (RSAE) have been successfully performed and verified. We have excited the RSAE by initial perturbation, by external antenna, and by energetic ions. The RSAE excitation by antenna provides verifications of the mode structure, the frequency, and the damping rate. When the kinetic effects of the background plasma are artificially suppressed, the mode amplitude shows a near-linear growth. With kinetic thermal ions, the mode amplitude eventually saturates due to the thermal ion damping. The damping rates measured from the antenna excitation and from the initial perturbation simulation agree very well. The RSAE excited by fast ions shows an exponential growth. The finite Larmor radius effects of the fast ions are found to significantly reduce the growth rate. With kinetic thermal ions and electron pressure, the mode frequency increases due to the elevation of the Alfven continuum by the geodesic compressibility. The nonperturbative contributions from the fast ions and kinetic thermal ions modify the mode structure relative to the ideal magnetohydrodynamic (MHD) theory. The gyrokinetic simulations have been benchmarked with extended hybrid MHD-gyrokinetic simulations.

  11. Kinetic models for the adsorption of lead ions by steel slag.

    PubMed

    Liu, Sheng-Yu; Gao, Jin; Qu, Bin; Yang, Yi-Jin; Xin, Xin

    2010-08-01

    Batch experiments were carried out to investigate the kinetics of adsorption of lead ions by steel slag on the basis of the external diffusion, intraparticle diffusion and adsorption reaction model (pseudo-first-order, pseudo-second-order). The results showed that the controlling step for the adsorption kinetics changed with experimental parameters varied. When the particle size of steel slag was larger than 120 mesh, intraparticle diffusion of Pb(2+) was the controlling step; when the initial concentration of Pb(2+) was less than 150 mg L(-1) or the shaking rate was lower than 150 rpm, external diffusion of Pb(2+) was promoted. Contrary to the former experimental conditions, the adsorption reaction was the controlling step, and the adsorption followed second-order kinetics, with an adsorption rate constant of 13.26 g mg(-1) min(- 1). The adsorption isotherm of Pb(2+) with steel slag followed the Langmuir model, with a correlation coefficient of 0.99. PMID:19808736

  12. Characterizing the kinetics of suspended cylindrical particles by polarization measurements

    NASA Astrophysics Data System (ADS)

    Liao, Ran; Ou, Xueheng; Ma, Hui

    2015-09-01

    Polarization has promising potential to retrieve the information of the steady samples, such as tissues. However, for the fast changing sample such as the suspended algae in the water, the kinetics of the particles also influence the scattered polarization. The present paper will show our recent results to extract the information about the kinetics of the suspended cylindrical particles by polarization measurements. The sample is the aqueous suspension of the glass fibers stirred by a magnetic stirrer. We measure the scattered polarization of the fibers by use of a simultaneous polarization measurement system and obtain the time series of two orthogonal polarization components. By use of correlation analysis, we obtain the time parameters from the auto-correlation functions of the polarization components, and observe the changes with the stirring speeds. Results show that these time parameters indicate the immigration of the fibers. After discussion, we find that they may further characterize the kinetics, including the translation and rotation, of the glass fibers in the fluid field.

  13. Kinetic theory of a longitudinally expanding system of scalar particles

    NASA Astrophysics Data System (ADS)

    Epelbaum, Thomas; Gelis, François; Jeon, Sangyong; Moore, Guy; Wu, Bin

    2015-09-01

    A simple kinematical argument suggests that the classical approximation may be inadequate to describe the evolution of a system with an anisotropic particle distribution. In order to verify this quantitatively, we study the Boltzmann equation for a longitudinally expanding system of scalar particles interacting with a ϕ 4 coupling, that mimics the kinematics of a heavy ion collision at very high energy. We consider only elastic 2 → 2 scatterings, and we allow the formation of a Bose-Einstein condensate in overpopulated situations by solving the coupled equations for the particle distribution and the particle density in the zero mode. For generic CGC-like initial conditions with a large occupation number, the solutions of the full Boltzmann equation cease to display the classical attractor behavior sooner than expected; for moderate coupling, the solutions appear never to follow a classical attractor solution.

  14. Interfacial/free radical polymerization microencapsulation: kinetics of particle formation.

    PubMed

    Mahabadi, H K; Ng, T H; Tan, H S

    1996-01-01

    Microcapsules containing pigment and polymer were prepared by dispersing a viscous mixture of pigment, core monomers, initiators and oil-soluble shell monomer in an aqueous solution of surfactants, forming oil-in-water droplets. Subsequently, a water-soluble shell monomer was added to these droplets, encapsulating them via interfacial (IF) polycondensation. These microcapsules were then heated for free radical (FR) polymerization of the core monomers. Effects of primary variables, such as the shearing time during particle formation, surfactant concentration, organic phase concentration, and mode of water-soluble shell monomer addition, were studied. The results indicated that polyvinylalcohol (PVOH), used as the surfactant/stabilizer, reacted with the oil-soluble shell monomers. The depletion of PVOH, especially when PVOH concentration was low, resulted in rapid growth of particle size and, eventually, suspension failure. The kinetic data revealed a particle formation mechanism which consists of two processes. The first process is the formation of an equilibrium particle size by the equilibrium process of particle breakage due to the mechanical shearing force and coalescence due to collisions among particles and surface tension forces. The second process is the reaction between PVOH and oil-soluble shell monomer which leads to the depletion of PVOH and consequently causes more coalescence of particles and a significant increase in the equilibrium particle size. The net effect of these two processes shows an optimum shearing time where the smallest particle size can be attained, and this optimum time is a function of several primary variables. Methods to prevent the reaction and therefore the depletion of PVOH are proposed. PMID:8864993

  15. Method for ion implantation induced embedded particle formation via reduction

    DOEpatents

    Hampikian, Janet M; Hunt, Eden M

    2001-01-01

    A method for ion implantation induced embedded particle formation via reduction with the steps of ion implantation with an ion/element that will chemically reduce the chosen substrate material, implantation of the ion/element to a sufficient concentration and at a sufficient energy for particle formation, and control of the temperature of the substrate during implantation. A preferred embodiment includes the formation of particles which are nano-dimensional (<100 m-n in size). The phase of the particles may be affected by control of the substrate temperature during and/or after the ion implantation process.

  16. Test particle study of minor ions in solar wind turbulence

    NASA Technical Reports Server (NTRS)

    Zurbuchen, Th.; Bochsler, P.; Politano, H.; Pouquet, A.

    1995-01-01

    We perform a parameter study of the temporal evolution of a test particle distribution function in MHD turbulence. The turbulent fields are calculated using a pseudo-spectral method and periodic boundary conditions on a regular grid of 180(exp 3) points, appropriate for incompressible, homogeneous and isotropic turbulence. Initially, the kinetic and the magnetic energy are equal on the average. Both, deterministic and random initial conditions are used, in the former case with zeros of the magnetic field located at grid points, in the latter case located by interpolation between grid points. The evolution of the minor ion distribution function is studied in detail as these turbulent fields evolve, developing strong current and vorticity sheets. Using the full collisionless equation of motion for the test particles, the efficiency of nonlinear interactions can be studied. The results are compared to theoretical predictions and are then discussed in connection with the observations of the dynamical properties of solar wind minor ions derived from in situ observations.

  17. Nonequilibrium statistical field theory for classical particles: Basic kinetic theory

    NASA Astrophysics Data System (ADS)

    Viermann, Celia; Fabis, Felix; Kozlikin, Elena; Lilow, Robert; Bartelmann, Matthias

    2015-06-01

    Recently Mazenko and Das and Mazenko [Phys. Rev. E 81, 061102 (2010), 10.1103/PhysRevE.81.061102; J. Stat. Phys. 149, 643 (2012), 10.1007/s10955-012-0610-y; J. Stat. Phys. 152, 159 (2013), 10.1007/s10955-013-0755-3; Phys. Rev. E 83, 041125 (2011), 10.1103/PhysRevE.83.041125] introduced a nonequilibrium field-theoretical approach to describe the statistical properties of a classical particle ensemble starting from the microscopic equations of motion of each individual particle. We use this theory to investigate the transition from those microscopic degrees of freedom to the evolution equations of the macroscopic observables of the ensemble. For the free theory, we recover the continuity and Jeans equations of a collisionless gas. For a theory containing two-particle interactions in a canonical perturbation series, we find the macroscopic evolution equations to be described by the Born-Bogoliubov-Green-Kirkwood-Yvon hierarchy with a truncation criterion depending on the order in perturbation theory. This establishes a direct link between the classical and the field-theoretical approaches to kinetic theory that might serve as a starting point to investigate kinetic theory beyond the classical limits.

  18. Ion-Molecule Reactions and Ion Kinetics in DC Townsend Discharges in Dielectric Gases

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Arnold, James O. (Technical Monitor)

    1998-01-01

    In gas discharges the identify, transport, relative intensities, and kinetic energy distributions (KEDs) of ions may be dominated by ion-molecule reactions. In order to understand these discharges, there is a need for cross section data for various ion-molecule reactions, including symmetric and asymmetric charge-transfer, collisional detachment, and ion conversion reactions, especially for low to intermediate ion-impact energies. In view of the importance of dielectric gases, we have recently measured the KEDs of various positive and negative ions produced in DC Townsend discharges in SF6, CF4, CHF3, O2, and CO2. The relative abundance and mean energies of ions are obtained from the measured KEDs. The effective cross sections (Qeff) describing the KEDs of various ions can be derived by using the mean ion energies and the electric field-to-gas density ratios (E/N). In the case of SF6 and O2 discharges, the determined cross sections (Qeff) for the negative-ion molecule reactions are consistent with previously measured cross section data obtained by crossed-beam experiment. The availability of these cross section values enabled us to understand the ion data reasonably well. However, the lack of adequate cross section data for positive ions in all of the above gases is a major obstacle in understanding ion transport in these gas discharges.

  19. Origin of energetic ions observed in the terrestrial ion foreshock : 2D full-particle simulations

    NASA Astrophysics Data System (ADS)

    Savoini, Philippe; Lembege, bertrand

    2016-04-01

    Collisionless shocks are well-known structures in astrophysical environments which dissipate bulk flow kinetic energy and accelerate large fraction of particle. Spacecrafts have firmly established the existence of the so-called terrestrial foreshock region magnetically connected to the shock and filled by two distinct populations in the quasi-perpendicular shock region (i.e. for 45r{ } ≤ quad θ Bn quad ≤ 90r{ }, where θ Bn is the angle between the shock normal and the upstream magnetic field) : (i) the field-aligned ion beams or `` FAB '' characterized by a gyrotropic distributionsout{,} and (ii) the gyro-phase bunched ions or `` GPB '' characterized by a NON gyrotropic distribution. The present work is based on the use of two dimensional PIC simulation of a curved shock and associated foreshock region where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described by a self consistent approach. Our previous analysis (Savoini et Lembège, 2015) has evidenced that these two types of backstreaming populations can originate from the shock front itself without invoking any local diffusion by ion beam instabilities. Present results are focussed on individual ion trajectories and evidence that "FAB" population is injected into the foreshock mainly along the shock front whereas the "GPB" population penetrates more deeply the shock front. Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". The impact of these different injection features on the energy gain for each ion population will be presented in détails. Savoini, P. and B. Lembège (2015), `` Production of nongyrotropic and gyrotropic backstreaming ion distributions in the quasi-perpendicular ion foreshock région '', J. Geophys. Res., 120, pp 7154-7171, doi = 10.1002/2015JA021018.

  20. Infrared and Mass Analyzed Ion Kinetic Energy Spectroscopy of Cluster Ions

    NASA Astrophysics Data System (ADS)

    Feinberg, Thomas Neal

    A new method for obtaining mass analyzed kinetic energy spectroscopy for the study of cluster ions was tested. The experiments utilized an MS/MS instrument (Quadrupole/Electric Sector Analyzer) coupled to a cluster beam source. The ion source consisted of a molecular beam excited by high energy electron impact. Experiments were conducted using argon and argon/ethene gas mixtures in the ion source. Kinetic energy spectra of collision induced dissociation products and carbon dioxide laser photodissociation products were analyzed. The results for argon dimers showed a laser polarization effect on the measurement of the kinetic energy of the fragment argon ions in the infrared photodissociation event. When ionization occurred within the supersonic expansion zone, the polarization effects were no longer observed. Ethene gas in the ion source produced a variety of ions; some of these showed photodissociation efficiencies within the region of the monomer nu_7 vibrational mode. The spectroscopy and collision induced dissociation data are consistent with a structure consisting of a central core ion surrounded by one or more ethene molecules.

  1. Kinetic Effects of Energetic Particles on Resistive MHD Stability

    SciTech Connect

    Takahashi, R.; Brennan, D. P.; Kim, C. C.

    2009-04-03

    We show that the kinetic effects of energetic particles can play a crucial role in the stability of the m/n=2/1 tearing mode in tokamaks (e.g., JET, JT-60U, and DIII-D), where the fraction of energetic particle {beta}{sub frac} is high. Using model equilibria based on DIII-D experimental reconstructions, the nonideal MHD linear stability of cases unstable to the 2/1 mode is investigated including a {delta}f particle-in-cell model for the energetic particles coupled to the nonlinear 3D resistive MHD code NIMROD[C. C. Kim et al., Phys. Plasmas 15, 072507 (2008)]. It is observed that energetic particles have significant damping and stabilizing effects at experimentally relevant {beta}, {beta}{sub frac}, and S, and excite a real frequency of the 2/1 mode. Extrapolation of the results is discussed for implications to JET and ITER, where the effects are projected to be significant.

  2. Kinetic behavior of solid particles in fluidized beds: Annual report

    SciTech Connect

    Kono, H.O.; Huang, C.C.

    1987-10-01

    This report summarizes technical accomplishments for the first year in a 3-year contract project for the Morgantown Energy Technology Center (METC) of the US Department of Energy (DOE) under contract number AC21-86MC23249. The objectives of the project are (1) to develop experimental techniques for measuring the forces of fluidized particles, and (2) to predict solid particle performance in fluidized beds using data analysis and mathematical modeling. During the first year, the fracture-sensitive tracer-particle method was developed and applied to investigate the effects of fluidized particle size, superficial gas velocity, bed height, bed diameter, and bed configuration on the kinetic behavior of solid particles in fluidized beds. Quantitative data and comprehensive information were obtained. A piezoresistive strain-gauge sensor and a PC data-acquisition system were also developed; these are being used to measure the force distribution in fluidized beds. The pressure fluctuation method will also be investigated in the near future. 12 refs., 24 figs., 2 tabs.

  3. The particle distributions of asymmetric kinetic electrostatic structures

    SciTech Connect

    Nocera, L.; Palumbo, L. J.

    2011-03-15

    We give the energy distributions of electrons and ions supporting a steady state electrostatic structure in a collisionless plasma. The electric potential of the structure is skew asymmetrically distributed in space. We show that the jump discontinuous, logarithmically singular electron and ion distributions may be reduced to elliptic integrals. We give the coefficients of the logarithmic terms and the jumps at the discontinuities and we show that they are reciprocally proportional. We calculate bounds for the potential skew asymmetry and show that these bounds are regulated by the boundary conditions of the particle distributions. Despite singularities, our treatment reproduces a smooth space distribution of the potential amplitude and electron and ion distributions that are smooth at one of the boundaries of the electrostatic structure.

  4. Adsorption kinetic character of copper ions onto a modified chitosan transparent thin membrane from aqueous solution.

    PubMed

    Cheng, Zihong; Liu, Xiaoshuai; Han, Mei; Ma, Wei

    2010-10-15

    A modified chitosan transparent thin membrane (MCTTM) was prepared and used as the adsorbent to investigate the adsorption kinetics due to excellent capacity of removing copper ions in water solution. The structure and morphology of MCTTM were characterized by SEM analysis and FTIR analysis. External mass transfer, intra particle diffusion, and pseudo-first and pseudo-second order models were used to describe the adsorption process. The results obtained from the study illustrated that the adsorption process could be described by the pseudo-second order model, which indicated adsorption process was a chemical adsorption behavior of chelation ion exchange proved by the FTIR and adsorption free energy analysis. External mass transfer and intra particle diffusion processes were the rate-controlling steps. PMID:20634000

  5. Ion kinetic instabilities and turbulence of a parallel shearing flow of a plasma with hot ions

    NASA Astrophysics Data System (ADS)

    Mykhaylenko, Volodymyr St.; Mykhaylenko, Volodymyr; Lee, Hae June

    2015-11-01

    The results of the analytical and numerical investigations of the shear flow driven ion kinetic instabilities, excited due to the inverse ion Landau damping in the parallel shearing flow of plasmas with comparable ion and electron temperatures, that is the case relevant to a tokamak and space plasma, are presented. The levels of turbulence and the turbulent heating rates of ions and ion turbulent viscosity, resulted from the development of the electrostatic ion-temperature gradient and electromagnetic drift-Alfven turbulence, are determined and their consequences are discussed. This work was funded by National R&D Program through the National Research Foundation of Korea.Grants NRF-2014M1A7A1A03029878, NRF-2013R1A1A2005758.

  6. Two-dimensional topological order of kinetically constrained quantum particles

    NASA Astrophysics Data System (ADS)

    Kourtis, Stefanos

    2015-03-01

    Motivated by recent experimental and theoretical work on driven optical lattices, we investigate how imposing kinetic restrictions on quantum particles that would otherwise hop freely on a two-dimensional lattice can lead to topologically ordered states. The kinetically constrained models introduced here are derived as an approximate generalization of strongly interacting particles hopping on Haldane and equivalent lattices and are pertinent to systems irradiated by circularly polarized light. After introducing a broad class of models, we focus on particular realizations and show numerically that they exhibit topological order, by observing topological ground-state degeneracies and the quantization of corresponding invariants. Apart from potentially being crucial for the interpretation of forthcoming cold-atom experiments, our results also hint at unexplored possibilities for the realization of topologically ordered matter. A further implication, relevant to fractional quantum Hall (FQH) physics, is that the correlations responsible for FQH-like states can arise from processes other than density-density interactions. Financial support from EPSRC (Grant No. EP/K028960/1) and ICAM Branch Contributions.

  7. Kinetic phenomena in charged particle transport in gases and plasmas

    SciTech Connect

    Petrovic, Zoran Lj.; Dujko, Sasa; Sasic, Olivera; Stojanovic, Vladimir; Malovic, Gordana

    2012-05-25

    The key difference between equilibrium (thermal) and non-equilibrium (low temperature - a.k.a. cold) plasmas is in the degree in which the shape of the cross sections influences the electron energy distribution function (EEDF). In this paper we will discuss the issue of kinetic phenomena from two different angles. The first will be how to take advantage of the strong influence and use low current data to obtain the cross sections. This is also known as the swarm technique and the product of a ''swarm analysis'' is a set of cross sections giving good number, momentum and energy balances of electrons or other charged particles. At the same time understanding the EEDF is based on the cross section data. Nevertheless sometimes the knowledge of the cross sections and even the behaviour of individual particles are insufficient to explain collective behaviour of the ensemble. The resulting ''kinetic'' effects may be used to favour certain properties of non-equilibrium plasmas and even may be used as the basis of some new plasma applications.

  8. Multicomponent kinetic simulation of Bernstein-Greene-Kruskal modes associated with ion acoustic and dust-ion acoustic excitations in electron-ion and dusty plasmas

    NASA Astrophysics Data System (ADS)

    Hosseini Jenab, S. M.; Kourakis, I.

    2014-04-01

    A series of numerical simulations based on a recurrence-free Vlasov kinetic algorithm presented earlier [Abbasi et al., Phys. Rev. E 84, 036702 (2011)] are reported. Electron-ion plasmas and three-component (electron-ion-dust) dusty, or complex, plasmas are considered, via independent simulations. Considering all plasma components modeled through a kinetic approach, the nonlinear behavior of ionic scale acoustic excitations is investigated. The focus is on Bernstein-Greene-Kruskal (BGK) modes generated during the simulations. In particular, we aim at investigating the parametric dependence of the characteristics of BGK structures, namely of their time periodicity (τtrap) and their amplitude, on the electron-to-ion temperature ratio and on the dust concentration. In electron-ion plasma, an exponential relation between τtrap and the amplitude of BGK modes and the electron-to-ion temperature ratio is observed. It is argued that both characteristics, namely, the periodicity τtrap and amplitude, are also related to the size of the phase-space vortex which is associated with BGK mode creation. In dusty plasmas, BGK modes characteristics appear to depend on the dust particle density linearly.

  9. ASPEN: A Fully Kinetic, Reduced-Description Particle-in-Cell Model for Modeling Parametric Instabilities

    NASA Astrophysics Data System (ADS)

    Vu, H. X.; Bezzerides, B.; Dubois, D. F.

    1998-11-01

    A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal WKB envelopes in order to model low-frequency and high-frequency parametric instabilities. Because temporal WKB approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. Although RPIC is fully three dimensional, it has been implemented in only two dimensions on a CRAY-T3D with 512 processors and on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. Given the current computers available to the authors, one and two dimensional simulations are feasible to, and have been, performed. Three dimensional simulations are much more expensive, and are not feasible at this time. However, with rapidly advancing computer technologies, three dimensional simulations may be feasible in the near future. We believe this code is the first PIC code capable of simulating the interaction between low-frequency and high-frequency parametric instabilites in multiple dimensions. Test simulations of stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and Langmuir decay instability (LDI), are presented.

  10. Kinetic particle simulation of turbulence in an FRC geometry

    NASA Astrophysics Data System (ADS)

    Fulton, Daniel; Lau, Calvin; Holod, Ihor; Lin, Zhihong; Dettrick, Sean; Binderbauer, Michl; Tajima, Toshiki

    2014-10-01

    Core turbulence in a Field Reversed Configuration (FRC) is studied using the Gyrokinetic Toroidal Code with modified equilibrium geometry. The code solves the gyrokinetic equation for ions and the drift kinetic equation for electrons. The simulation region is an annulus which excludes plasma near the O-point to avoid breakdown of the gyrokinetic dynamics of ions. The C-2 FRC equilibrium is introduced to study similar conditions as found in the C-2 experiments, where the core is found to be relatively quiescent. In simulation, we find the C-2 plasma is stable to ion temperature gradient instabilities using realistic experimental parameters, consistent with experimental results obtained in C-2. When temperature and density gradients are enhanced beyond typical C-2 parameters, we observe a class of instabilities that appear as flute-like drift modes. These results shed light on a possible reason why transport temperature scaling in the C-2 core is radically different from that of typical turbulent transport scaling such as the Bohm-like regime. Progress is also reported on simulations of scrape off layer turbulence and electron driven turbulence.

  11. Fulfillment of the kinetic Bohm criterion in a quasineutral particle-in-cell model

    NASA Astrophysics Data System (ADS)

    Ahedo, Eduardo; Santos, Robert; Parra, Félix I.

    2010-07-01

    Quasineutral particle-in-cell models of ions must fulfill the kinetic Bohm criterion, in its inequality form, at the domain boundary in order to match correctly with solutions of the Debye sheaths tied to the walls. The simple, fluid form of the Bohm criterion is shown to be a bad approximation of the exact, kinetic form when the ion velocity distribution function has a significant dispersion and involves different charge numbers. The fulfillment of the Bohm criterion is measured by a weighting algorithm at the boundary, but linear weighting algorithms have difficulties to reproduce the nonlinear behavior around the sheath edge. A surface weighting algorithm with an extended temporal weighting is proposed and shown to behave better than the standard volumetric weighting. Still, this must be supplemented by a forcing algorithm of the kinetic Bohm criterion. This postulates a small potential fall in a supplementary, thin, transition layer. The electron-wall interaction is shown to be of little relevance in the fulfillment of the Bohm criterion.

  12. Fulfillment of the kinetic Bohm criterion in a quasineutral particle-in-cell model

    SciTech Connect

    Ahedo, Eduardo; Santos, Robert; Parra, Felix I.

    2010-07-15

    Quasineutral particle-in-cell models of ions must fulfill the kinetic Bohm criterion, in its inequality form, at the domain boundary in order to match correctly with solutions of the Debye sheaths tied to the walls. The simple, fluid form of the Bohm criterion is shown to be a bad approximation of the exact, kinetic form when the ion velocity distribution function has a significant dispersion and involves different charge numbers. The fulfillment of the Bohm criterion is measured by a weighting algorithm at the boundary, but linear weighting algorithms have difficulties to reproduce the nonlinear behavior around the sheath edge. A surface weighting algorithm with an extended temporal weighting is proposed and shown to behave better than the standard volumetric weighting. Still, this must be supplemented by a forcing algorithm of the kinetic Bohm criterion. This postulates a small potential fall in a supplementary, thin, transition layer. The electron-wall interaction is shown to be of little relevance in the fulfillment of the Bohm criterion.

  13. Spectator Ions ARE Important! A Kinetic Study of the Copper-Aluminum Displacement Reaction

    ERIC Educational Resources Information Center

    Sobel, Sabrina G.; Cohen, Skyler

    2010-01-01

    Surprisingly, spectator ions are responsible for unexpected kinetics in the biphasic copper(II)-aluminum displacement reaction, with the rate of reaction dependent on the identity of the otherwise ignored spectator ions. Application of a published kinetic analysis developed for a reaction between a rotating Al disk and a Cu(II) ion solution to the…

  14. Fluid electrons with kinetic closure for long wavelength energetic particles driven modes

    SciTech Connect

    Chen Yang; Parker, Scott E.

    2011-05-15

    A kinetic electron closure scheme is presented for the fluid electron model that has been implemented in the GEM code [J. Lang, Y. Chen, S. E. Parker, and G.-Y. Fu, Phys. Plasmas 16, 102101 (2009)]. The most important element of the closure scheme is a complete Ohm's law for the parallel electric field E{sub ||}, derived by combining the quasineutrality condition, the Ampere's equation and the v{sub ||} moment of the gyrokinetic equations. A discretization method for the closure scheme is presented and studied in detail for a three-dimensional shearless slab plasma. It is found that for long wavelength shear Alfven waves the kinetic closure scheme is both more accurate and more robust than the previous GEM algorithm [Y. Chen and S. E. Parker, J. Comput. Phys. 189, 463 (2003)], whereas for the ion-gradient-driven instability the previous algorithm is more efficient. The fluid electron model with kinetic electron closure is useful for studying energetic particles driven modes with electron kinetic damping effects.

  15. Voltammetric Ion Selectivity of Thin Ionophore-Based Polymeric Membranes: Kinetic Effect of Ion Hydrophilicity.

    PubMed

    Amemiya, Shigeru

    2016-09-01

    The high ion selectivity of potentiometric and optical sensors based on ionophore-based polymeric membranes is thermodynamically limited. Here, we report that the voltammetric selectivity of thin ionophore-based polymeric membranes can be kinetically improved by several orders of magnitude in comparison with their thermodynamic selectivity. The kinetic improvement of voltammetric selectivity is evaluated quantitatively by newly introducing a voltammetric selectivity coefficient in addition to a thermodynamic selectivity coefficient. Experimentally, both voltammetric and thermodynamic selectivity coefficients are determined from cyclic voltammograms of excess amounts of analyte and interfering ions with respect to the amount of a Na(+)- or Li(+)-selective ionophore in thin polymeric membranes. We reveal the slower ionophore-facilitated transfer of a smaller alkaline earth metal cation with higher hydrophilicity across the membrane/water interface, thereby kinetically improving voltammetric Na(+) selectivity against calcium, strontium, and barium ions by 3, 2, and 1 order of magnitude, respectively, in separate solutions. Remarkably, voltammetric Na(+) and Li(+) selectivity against calcium and magnesium ions in mixed solutions is improved by 4 and >7 orders of magnitude, respectively, owing to both thermodynamic and kinetic effects in comparison with thermodynamic selectivity in separate solutions. Advantageously, the simultaneous detection of sodium and calcium ions is enabled voltammetrically in contrast to the potentiometric and optical counterparts. Mechanistically, we propose a new hypothetical model that the slower transfer of a more hydrophilic ion is controlled by its partial dehydration during the formation of the adduct with a "water finger" prior to complexation with an ionophore at the membrane/water interface. PMID:27527590

  16. Bridging the fluid-kinetic gap with implicit particle methods

    NASA Astrophysics Data System (ADS)

    Amaya, Jorge; Bacchini, Fabio; Innocenti, Maria Elena; Jiang, Wei; Olshevsky, Vyacheslav; Lapenta, Giovanni

    2015-11-01

    Plasmas have intrinsic kinetic scales determined by the response of electrons and ions. The kinetic scales determine the finest scales that are to be expected in a plasma. However, the intrinsic scales are tiny compared with the system scales of interest in most situations where a fluid approach is more efficient. When computers will be able to resolve all scales for the problems of interest now, we will no longer be interested in them and we will be attempting much bigger and more challenging problems. There is now and there always will be a grand canyon between the scales we can resolve with the supercomputers available and the system sizes we want to consider. Mathematics needs to be called into action to lay a bridge over this grand canyon. We consider two pontifex methods: the implicit method and the multi level-multi domain method. Our most recent developments will be described and their properties of stability, accuracy and ability to resolve the different characteristics will be discussed. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  17. Emergence of ion channel modal gating from independent subunit kinetics.

    PubMed

    Bicknell, Brendan A; Goodhill, Geoffrey J

    2016-09-01

    Many ion channels exhibit a slow stochastic switching between distinct modes of gating activity. This feature of channel behavior has pronounced implications for the dynamics of ionic currents and the signaling pathways that they regulate. A canonical example is the inositol 1,4,5-trisphosphate receptor (IP3R) channel, whose regulation of intracellular Ca(2+) concentration is essential for numerous cellular processes. However, the underlying biophysical mechanisms that give rise to modal gating in this and most other channels remain unknown. Although ion channels are composed of protein subunits, previous mathematical models of modal gating are coarse grained at the level of whole-channel states, limiting further dialogue between theory and experiment. Here we propose an origin for modal gating, by modeling the kinetics of ligand binding and conformational change in the IP3R at the subunit level. We find good agreement with experimental data over a wide range of ligand concentrations, accounting for equilibrium channel properties, transient responses to changing ligand conditions, and modal gating statistics. We show how this can be understood within a simple analytical framework and confirm our results with stochastic simulations. The model assumes that channel subunits are independent, demonstrating that cooperative binding or concerted conformational changes are not required for modal gating. Moreover, the model embodies a generally applicable principle: If a timescale separation exists in the kinetics of individual subunits, then modal gating can arise as an emergent property of channel behavior. PMID:27551100

  18. Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Diamandis, E. P.; And Others

    1983-01-01

    The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

  19. Superconducting Kinetic Inductance Detectors for astronomy and particle physics

    NASA Astrophysics Data System (ADS)

    Calvo, M.; Goupy, J.; D`Addabbo, A.; Benoit, A.; Bourrion, O.; Catalano, A.; Monfardini, A.

    2016-07-01

    Kinetic Inductance Detectors (KID) represent a novel detector technology based on superconducting resonators. Since their first demonstration in 2003, they have been rapidly developed and are today a strong candidate for present and future experiments in the different bands of the electromagnetic spectrum. This has been possible thanks to the unique features of such devices: in particular, they couple a very high sensitivity to their intrinsic suitability for frequency domain multiplexed readout, making the fabrication of large arrays of ultrasensitive detectors possible. There are many fields of application that can profit of such detectors. Here, we will briefly review the principle of operation of a KID, and give two sample applications, to mm-wave astronomy and to particle physics.

  20. Gelation kinetics of gelatin using particle tracking microrheology

    NASA Astrophysics Data System (ADS)

    Hardcastle, Joseph; Bansil, Rama

    2012-02-01

    Previous studies with gelatin have observed four distinct stages during the physical gelation process [Normand et al. Macromolecules, 2000, 33, 1063]. In this presentation we report measurements of microrheology in an effort to examine the time evolution of the gel on short length scales and time scales. By tracking latex particles in gelatin solution at different temperatures we can follow the microrheological changes and kinetics of the gelation process. Using the generalized Stokes-Einstein relation viscoelastic properties of these quasi-static gel states the evolution of the storage and loss moduli, G' and G'', are examined as functions of both time and temperature. The data show that both G' and G'' exhibit power law scaling versus frequency with the same exponent. The temperature and concentration dependence of the frequency at which the system crosses over from viscous to elastic behavior will be presented.

  1. Verification of particle-in-cell simulations against exact solutions of kinetic equations

    NASA Astrophysics Data System (ADS)

    Turner, Miles

    2015-09-01

    Demonstrating correctness of computer simulations (or verification) has become a matter of increasing concern in recent years. The strongest type of verification is a demonstration that the simulation converges to an exact solution of the mathematical model that is supposed to be solved. Of course, this is possible only if such an exact solution is available. In this paper, we are interested in kinetic simulation using the particle-in-cell method, and consequently a relevant exact solution must be a solution of a kinetic equation. While we know of no such solutions that exercise all the features of a typical particle-in-cell simulation, in this paper we show that the mathematical literature contains several such solutions that involve a large fraction of the functionality of such a code, and which collectively exercise essentially all of the code functionality. These solutions include the plane diode, the neutron criticality problem, and the calculation of ion energy distribution functions in oscillating fields. In each of theses cases, we can show the the particle-in-cell simulation converges to the exact solution in the expected way. These demonstrations are strong evidence of correct implementation. Work supported by Science Foundation Ireland under grant 08/SRC/I1411.

  2. Solar wind acceleration obtained from kinetic models based on electron velocity distribution functions with suprathermal particles

    NASA Astrophysics Data System (ADS)

    Pierrard, V.; Pieters, M.; Lazar, M.; Voitenko, Y.; Lamy, H.; Echim, M.

    2014-12-01

    Astrophysical and space plasmas are commonly found to be out ofthermal equilibrium, i.e., the velocity distribution functions (VDF)of plasma particles cannot be described well enough by Maxwelliandistribution functions. The suprathermal populations are ubiquitousenhancing the high-energy tail of the distribution. A kinetic model has been developed to successfullydescribe such plasmas with tails decreasing as a power law of thevelocity. In the present work, we show that a natural heating ofsolar and stellar coronas automatically appears when an enhancedpopulation of suprathermal particles is present at low altitude inthe solar (or stellar) atmosphere. This is true not only forelectrons and protons, but also for the minor ions which exhibit atemperature increase proportional to their mass. Moreover,suprathermal electrons contribute to the acceleration of stellarwinds to high bulk velocities when Coulomb collisions are neglected.These results are illustrated by using a global model of the solarcorona and solar wind based on VDF with suprathermal tails for thedifferent particle species. The energetic particles are non-collisional (without Coulomb collisions) even when thermalparticles are submitted to collisions. In the presence of long-rangecorrelations supplied by the fields and plasma instabilities,turbulence can play a role in the generation of such suprathermaltails. Solar wind observations are used as boundary conditions to determine the VDF in the other regions of the heliosphere. Consequences of suprathermal particles are also illustratedfor other space plasmas like the plasmasphere and the polar wind ofthe Earth and other planets.

  3. Microfluidic rheology of active particle suspensions: Kinetic theory.

    PubMed

    Alonso-Matilla, Roberto; Ezhilan, Barath; Saintillan, David

    2016-07-01

    We analyze the effective rheology of a dilute suspension of self-propelled slender particles confined between two infinite parallel plates and subject to a pressure-driven flow. We use a continuum kinetic model to describe the configuration of the particles in the system, in which the disturbance flows induced by the swimmers are taken into account, and use it to calculate estimates of the suspension viscosity for a range of channel widths and flow strengths typical of microfluidic experiments. Our results are in agreement with previous bulk models, and in particular, demonstrate that the effect of activity is strongest at low flow rates, where pushers tend to decrease the suspension viscosity whereas pullers enhance it. In stronger flows, dissipative stresses overcome the effects of activity leading to increased viscosities followed by shear-thinning. The effects of confinement and number density are also analyzed, and our results confirm the apparent transition to superfluidity reported in recent experiments on pusher suspensions at intermediate densities. We also derive an approximate analytical expression for the effective viscosity in the limit of weak flows and wide channels, and demonstrate good agreement between theory and numerical calculations. PMID:27375827

  4. Ion Density Fluctuations at the Kinetic Scale: Experimental Investigations

    NASA Astrophysics Data System (ADS)

    Nemecek, Z.; Safrankova, J.; Nemec, F.; Chen, C. H. K.

    2014-12-01

    It is well established that the solar wind undergoes a heating along its path through the solar system but the sources of this heating are still under debate. Among them, a gradual dissipation of large scale discontinuities toward smaller scales and, eventually, to the heat via turbulent cascades is frequently discussed.The contribution presents the analysis of ion density variations that are measured onboard the Spektr R spacecraft with a unique time resolution of 32 ms. The analysis reveals that (1) the mean frequency spectrum of density variations in the MHD range (up to about 0.05 Hz) is steeper than usually discussed -5/3, and (2) this part is followed by a plateau that is terminated near proton kinetic scales. We study the dependence of the slopes of different parts of the frequency spectra on background plasma parameters and discuss the results in view of present theories of Alfvenic turbulence in the solar wind.

  5. A hybrid model describing ion induced kinetic electron emission

    NASA Astrophysics Data System (ADS)

    Hanke, S.; Duvenbeck, A.; Heuser, C.; Weidtmann, B.; Wucher, A.

    2015-06-01

    We present a model to describe the kinetic internal and external electron emission from an ion bombarded metal target. The model is based upon a molecular dynamics treatment of the nuclear degree of freedom, the electronic system is assumed as a quasi-free electron gas characterized by its Fermi energy, electron temperature and a characteristic attenuation length. In a series of previous works we have employed this model, which includes the local kinetic excitation as well as the rapid spread of the generated excitation energy, in order to calculate internal and external electron emission yields within the framework of a Richardson-Dushman-like thermionic emission model. However, this kind of treatment turned out to fail in the realistic prediction of experimentally measured internal electron yields mainly due to the restriction of the treatment of electronic transport to a diffusive manner. Here, we propose a slightly modified approach additionally incorporating the contribution of hot electrons which are generated in the bulk material and undergo ballistic transport towards the emitting interface.

  6. Kinetic particle simulation of discharge and wall erosion of a Hall thruster

    SciTech Connect

    Cho, Shinatora; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2013-06-15

    The primary lifetime limiting factor of Hall thrusters is the wall erosion caused by the ion induced sputtering, which is predominated by dielectric wall sheath and pre-sheath. However, so far only fluid or hybrid simulation models were applied to wall erosion and lifetime studies in which this non-quasi-neutral and non-equilibrium area cannot be treated directly. Thus, in this study, a 2D fully kinetic particle-in-cell model was presented for Hall thruster discharge and lifetime simulation. Because the fully kinetic lifetime simulation was yet to be achieved so far due to the high computational cost, the semi-implicit field solver and the technique of mass ratio manipulation was employed to accelerate the computation. However, other artificial manipulations like permittivity or geometry scaling were not used in order to avoid unrecoverable change of physics. Additionally, a new physics recovering model for the mass ratio was presented for better preservation of electron mobility at the weakly magnetically confined plasma region. The validity of the presented model was examined by various parametric studies, and the thrust performance and wall erosion rate of a laboratory model magnetic layer type Hall thruster was modeled for different operation conditions. The simulation results successfully reproduced the measurement results with typically less than 10% discrepancy without tuning any numerical parameters. It is also shown that the computational cost was reduced to the level that the Hall thruster fully kinetic lifetime simulation is feasible.

  7. TOPICAL REVIEW: Kinetic phenomena in charged particle transport in gases, swarm parameters and cross section data

    NASA Astrophysics Data System (ADS)

    Petrovic, Z. Lj; Suvakov, M.; Nikitovic, Z.; Dujko, S.; Sasic, O.; Jovanovic, J.; Malovic, G.; Stojanovic, V.

    2007-02-01

    In this review we discuss the current status of the physics of charged particle swarms, mainly electrons. The whole field is analysed mainly through its relationship to plasma modelling and illustrated by some recent examples developed mainly by our group. The measurements of the swarm coefficients and the availability of the data are briefly discussed. More time is devoted to the development of complete electron molecule cross section sets along with recent examples such as NO, CF4 and HBr. We extend the discussion to the availability of ion and fast neutral data and how swarm experiments may serve to provide new data. As a point where new insight into the kinetics of charge particle transport is provided, the role of kinetic phenomena is discussed and recent examples are listed. We focus here on giving two examples on how non-conservative processes make dramatic effects in transport, the negative absolute mobility and the negative differential conductivity for positrons in argon. Finally we discuss the applicability of swarm data in plasma modelling and the relationship to other fields where swarm experiments and analysis make significant contributions. Based on the general invited lecture presented by the first author at ESCAMPIG 2006 at Lecce in Italy.

  8. Gyrokinetic particle simulations of kinetic ballooning mode in tokamak pedestal

    NASA Astrophysics Data System (ADS)

    Holod, Ihor

    2014-10-01

    The pedestal height and width in tokamak H-mode operation are widely believed to be constrained by mesoscale peeling-ballooning modes and microscopic kinetic ballooning modes (KBM). However, direct evidences of the KBM turbulence in pedestal are very limited. The role of the drift-Alfvenic microturbulence during the pedestal recovery period is not clear. Here we use gyrokinetic toroidal code (GTC) to study the edge instability of a DIII-D discharge #131997 using realistic geometry and plasma profiles and focusing on the pedestal region with steep pressure gradient. First, electrostatic simulations find a reactive trapped electron mode with an unusual eigenmode structure, which peaks at the poloidal angle θ = +/- π /2. The electron collisions decrease the growth rate by about one-half. Next, the plasma pressure is scanned in GTC electromagnetic simulations to identify the boundary for the KBM onset. At the finite electron beta an electromagnetic instability is found with KBM characteristics. The linear growth rate increases with βe and the mode propagation is in the ion diamagnetic direction. Nonlinear simulations of the KBM turbulence will also be presented. Work supported by DOE Grant DE-SC0010416, and in collaborations with GTC team.

  9. New forms of two-particle and one-particle kinetic equations

    NASA Astrophysics Data System (ADS)

    Saveliev, V. L.; Yonemura, S.

    2012-11-01

    Pair collisions are the main interaction process in the Boltzmann gas dynamics. By making use of exactly the same physical assumptions as was done by Ludwig Boltzmann we wrote the kinetic equation for two-particle distribution function of molecules in gas mixtures. Instead of the collision integral, there are the linear scattering operator and the chaos projector in the right part of this equation. We developed a new technique for factorization of the scattering operator on the bases of right inverses to the Casimir operator of the group of rotations. We exactly transformed the Boltzmann collision integral to the Landau-Fokker-Planck like form.

  10. Kinetics of ion-beam damage in lithium niobate

    SciTech Connect

    Garcia-Navarro, A.; Agullo-Lopez, F.; Bianconi, M.; Olivares, J.; Garcia, G.

    2007-04-15

    The damage kinetics induced by irradiation with a diversity of swift ions (O at 5 MeV; F at 5.1 MeV; Si at 5, 7.5, and 41 MeV; and Cl at 11 and 46 MeV) has been investigated in the range of 10{sup 12}-10{sup 15} at./cm{sup 2}. It covers from the initial stage where single damage tracks are isolated and well separated, up to the stage where a full amorphous layer is produced. The damage is characterized by the areal fraction of disorder derived from the Rutherford backscattering/channeling spectra. The data approximately fit an abrupt Avrami-type dependence with fluence. The fluence value at which 50% of the sample surface becomes disordered shows a clear increasing trend with the electronic stopping power of the ion. The trend is consistent with Monte Carlo simulations based on a recent model for defect creation. Moreover, the quantitative agreement for the defect generation rate appears also reasonable.

  11. Ion production rate in a boreal forest based on ion, particle and radiation measurements

    NASA Astrophysics Data System (ADS)

    Laakso, L.; Petäjä, T.; Lehtinen, K. E. J.; Kulmala, M.; Paatero, J.; Hõrrak, U.; Tammet, H.; Joutsensaari, J.

    2004-07-01

    In this study the ion production rates in a boreal forest are studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon concentration measurements. Both methods produce reasonable estimates for ion production rates. The average ion production rate calculated from aerosol particle size distribution and air ion mobility distribution measurements was 2.6 cm-3s-1 and based on external radiation and radon measurements 4.5 cm-3s-1. The first method based on ion and particle measurements gave lower values for the ion production rates especially during the day. A possible reason for this is that particle measurements started only from 3 nm, so the sink of small ions during the nucleation events was underestimated. Another reason is that the possible fogs, which caused an extra sink of small ions are not taken into account in the calculations. It may also be possible that the hygroscopic growth factors of aerosol particles were underestimated. A fourth possible reason for the discrepancy is the nucleation mechanism itself. If the ions were somehow present in the nucleation process, there could have been an additional ion sink during the nucleation days. On the other hand, not all the radiation energy is converted to ions and the possible effect of alpha recoil is also omitted.

  12. Ion production rate in a boreal forest based on ion, particle and radiation measurements

    NASA Astrophysics Data System (ADS)

    Laakso, L.; Petäjä, T.; Lehtinen, K. E. J.; Kulmala, M.; Paatero, J.; Hõrrak, U.; Tammet, H.; Joutsensaari, J.

    2004-09-01

    In this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon concentration measurements. Both methods produced reasonable estimates for ion production rates. The average ion production rate calculated from aerosol particle size distribution and air ion mobility distribution measurements was 2.6 ion pairs cm-3s-1, and based on external radiation and radon measurements, 4.5 ion pairs cm-3s-1. The first method based on ion and particle measurements gave lower values for the ion production rates especially during the day. A possible reason for this is that particle measurements started only from 3nm, so the sink of small ions during the nucleation events was underestimated. It may also be possible that the hygroscopic growth factors of aerosol particles were underestimated. Another reason for the discrepancy is the nucleation mechanism itself. If the ions are somehow present in the nucleation process, there could have been an additional ion sink during the nucleation days.

  13. Ion kinetic effects on the ignition and burn of inertial confinement fusion targets: A multi-scale approach

    SciTech Connect

    Peigney, B. E.; Larroche, O.

    2014-12-15

    In this article, we study the hydrodynamics and burn of the thermonuclear fuel in inertial confinement fusion pellets at the ion kinetic level. The analysis is based on a two-velocity-scale Vlasov-Fokker-Planck kinetic model that is specially tailored to treat fusion products (suprathermal α-particles) in a self-consistent manner with the thermal bulk. The model assumes spherical symmetry in configuration space and axial symmetry in velocity space around the mean flow velocity. A typical hot-spot ignition design is considered. Compared with fluid simulations where a multi-group diffusion scheme is applied to model α transport, the full ion-kinetic approach reveals significant non-local effects on the transport of energetic α-particles. This has a direct impact on hydrodynamic spatial profiles during combustion: the hot spot reactivity is reduced, while the inner dense fuel layers are pre-heated by the escaping α-suprathermal particles, which are transported farther out of the hot spot. We show how the kinetic transport enhancement of fusion products leads to a significant reduction of the fusion yield.

  14. Solar Particle Acceleration Radiation and Kinetics (SPARK). A mission to understand the nature of particle acceleration

    NASA Astrophysics Data System (ADS)

    Matthews, Sarah A.; Williams, David R.; Klein, Karl-Ludwig; Kontar, Eduard P.; Smith, David M.; Lagg, Andreas; Krucker, Sam; Hurford, Gordon J.; Vilmer, Nicole; MacKinnon, Alexander L.; Zharkova, Valentina V.; Fletcher, Lyndsay; Hannah, Iain G.; Browning, Philippa K.; Innes, Davina E.; Trottet, Gerard; Foullon, Clare; Nakariakov, Valery M.; Green, Lucie M.; Lamoureux, Herve; Forsyth, Colin; Walton, David M.; Mathioudakis, Mihalis; Gandorfer, Achim; Martinez-Pillet, Valentin; Limousin, Olivier; Verwichte, Erwin; Dalla, Silvia; Mann, Gottfried; Aurass, Henri; Neukirch, Thomas

    2012-04-01

    Energetic particles are critical components of plasma populations found throughout the universe. In many cases particles are accelerated to relativistic energies and represent a substantial fraction of the total energy of the system, thus requiring extremely efficient acceleration processes. The production of accelerated particles also appears coupled to magnetic field evolution in astrophysical plasmas through the turbulent magnetic fields produced by diffusive shock acceleration. Particle acceleration is thus a key component in helping to understand the origin and evolution of magnetic structures in, e.g. galaxies. The proximity of the Sun and the range of high-resolution diagnostics available within the solar atmosphere offers unique opportunities to study the processes involved in particle acceleration through the use of a combination of remote sensing observations of the radiative signatures of accelerated particles, and of their plasma and magnetic environment. The SPARK concept targets the broad range of energy, spatial and temporal scales over which particle acceleration occurs in the solar atmosphere, in order to determine how and where energetic particles are accelerated. SPARK combines highly complementary imaging and spectroscopic observations of radiation from energetic electrons, protons and ions set in their plasma and magnetic context. The payload comprises focusing-optics X-ray imaging covering the range from 1 to 60 keV; indirect HXR imaging and spectroscopy from 5 to 200 keV, γ-ray spectroscopic imaging with high-resolution LaBr3 scintillators, and photometry and source localisation at far-infrared wavelengths. The plasma environment of the regions of acceleration and interaction will be probed using soft X-ray imaging of the corona and vector magnetography of the photosphere and chromosphere. SPARK is designed for solar research. However, in addition it will be able to provide exciting new insights into the origin of particle acceleration in

  15. Cesium Ion Exchange Loading Kinetics Testing with SRF Resin

    SciTech Connect

    Russell, Renee L.; Rinehart, Donald E.; Brown, Garrett N.; Peterson, Reid A.

    2012-11-02

    Ion exchange using the Spherical Resorcinol-Formaldehyde (SRF) resin has been selected by the U.S. Department of Energy’s Office of River Protection for use in the Pretreatment Facility of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) and for potential application in an at-tank deployment for removing 137Cs. Recent proposed changes to the WTP ion exchange process baseline indicate that loading may include a broader range of sodium molarities (2 to 8 M) due to caustic leaching and higher temperatures (50°C) to alleviate post-filtration precipitation issues prior to reaching the ion exchange columns. Therefore, it is important to understand the behavior of SRF resin performance under the conditions expected with the new equipment and process changes. This research examined the impact of linear load velocity (4, 6, 8 cm/min), initial sodium concentration (2, 5, 8 M), initial sodium-to-cesium ratio (1.4E+05, 2.1E+05, 2.8E+05 mol/mol), initial sodium-to-hydroxide ratio (2.0, 3.0, 4.0 mol/mol), and resin degradation during extended solution flow using elevated temperature (45°, 50°, 55°, 60°, 65°, 75°C). Testing was performed using a~2mL column packed with SRF resin with feed flowing through it in an up-flow pattern. Samples were taken at set intervals and the data analyzed to help understand the impact of these conditions on the SRF resin performance. It was found that the loading kinetics were not significantly impacted by the sodium concentration over the range tested. However, the loading kinetics were impacted by the linear load velocity. These results indicated that at the test temperature, the adsorption of cesium is strongly dependent on mass transfer through the film and not significantly impacted by interparticle diffusion. Testing for extended times at elevated temperatures showed that the resin does degrade and loading capacity is reduced at and above 45°C. Above 60°C the resin appears to not load at all.

  16. Simulations of Magnetic Reconnection - Kinetic Mechanisms Underlying the Fluid Description of Ions

    NASA Technical Reports Server (NTRS)

    Aunai, icolas; Belmont, Gerard; Smets, Roch

    2012-01-01

    Because of its ability to transfer the energy stored in magnetic field together with the breaking of the flux freezing constraint, magnetic reconnection is considered as one of the most important phenomena in plasma physics. When it happens in a collision less environment such as the terrestrial magnetosphere, it should a priori be modelled with in the framework of kinetic physics. The evidence of kinetic features has incidentally for a long time, been shown by researchers with the help of both numerical simulations and satellite observations. However, most of our understanding of the process comes from the more intuitive fluid interpretation with simple closure hypothesis which do not include kinetic effects. To what extent are these two separate descriptions of the same phenomenon related? What is the role of kinetic effects in the averaged/fluid dynamics of reconnection? This thesis addresses these questions for the proton population in the particular case of anti parallel merging with the help of 2D Hybrid simulations. We show that one can not assume, as is usually done, that the acceleration of the proton flow is only due to the Laplace force. Our results show, for symmetric and asymmetric connection, the importance of the pressure force, opposed to the electric one on the separatrices, in the decoupling region. In the symmetric case, we emphasize the kinetic origin of this force by analyzing the proton distribution functions and explain their structure by studying the underlying particle dynamics. Protons, as individual particles, are shown to bounce in the electric potential well created by the Hall effect. The spatial divergence of this well results in a mixing in phase space responsible for the observed structure of the pressure tensor. A detailed energy budget analysis confirms the role of the pressure force for the acceleration; but, contrary to what is sometimes assumed, it also reveals that the major part of the incoming Poynting flux is transferred to

  17. Analyses of particles in beryllium by ion imaging

    SciTech Connect

    Price, C.W.; Norberg, J.C.; Evans and Associates, Redwood City, CA )

    1989-10-06

    Ion microanalysis using a {sup 133}Cs{sup +} primary ion beam and SIMS has sufficiently high sensitivity that it can be used to analyze Be for trace amounts of most elements. High sensitivity is important, because O, C, and other elements have low solubilities in Be, and reliable analyses of these elements becaome difficult as they approach their solid solubility limits (about 6 appm for O; C also is suspected to be within this range). Because of the low solubilities of these elements, major portions of their total concentrations can be contained in particles. Quantitative depth-profile analyses using ion-implanted standards are ideal to analyze the Be matrix, but if particles exist, supplementary techniques such as stereology are required to determine the amounts of the elements that are associated with the particles. This paper will demonstrate the use of ion imaging to identify various types of particles and determine their spatial distributions. 4 refs., 3 figs.

  18. Self-consistent ion-by-ion growth model for kinetic isotopic fractionation during calcite precipitation

    NASA Astrophysics Data System (ADS)

    Nielsen, Laura C.; DePaolo, Donald J.; De Yoreo, James J.

    2012-06-01

    Microscopic mechanisms operating at the mineral-aqueous interface control rates of growth and dissolution, isotope fractionation and trace element partitioning during crystal growth. Despite the importance of characterizing surface kinetic controls on isotopic partitioning, no self-consistent microscopic theory has yet been presented which can simultaneously model both mineral growth rate and isotopic composition. Using a kinetic theory for AB or di-ionic crystal growth, we derive a model to predict precipitation rate and isotope fractionation as a function of growth solution oversaturation and solution stoichiometry and apply the theory to calcium isotope fractionation during calcite precipitation. Our model assimilates the current understanding of surface controlled isotope fractionation with kinetic theories of ion-by-ion mineral growth to predict isotopic partitioning during the growth of ionic crystals. This approach accounts for the effect of solution composition on microscopic mineral surface structure and composition, providing numerous testable hypotheses for growth of sparingly soluble AB crystals such as calcite, namely: Both oversaturation and solution stoichiometry control growth rate and partitioning of isotopes during precipitation; for growth driven primarily by step propagation, distinct expressions describe dislocation- and 2D nucleation-driven growth rates, while the expression for isotope fractionation is the same for both mechanisms; mineral precipitation occurring via the formation of an amorphous precursor will generate isotope effects that are not compatible with ion-by-ion growth theory and may therefore be excluded from comparison; and, the absolute kinetic limit of isotope fractionation may not be accessible at high oversaturation due to the formation of amorphous precursors. Using calcite as a model system, we derive expressions for growth rate and isotopic fractionation as a function of oversaturation and Ca:CO32- in solution

  19. The Influence of Trapped Ions and Non-equilibrium EDF on Dust Particle Charging

    SciTech Connect

    Sukhinin, G. I.; Fedoseev, A. V.; Antipov, S. N.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    Dust particles charging in a low-pressure glow discharge was investigated theoretically with the help of model for trapped and free ions coupled with the self-consistent solution of Poisson equation for electric potential. Non-equilibrium (non-Maxwellian) character of electron energy distribution function depending on gas pressure and electric field was also taken into account on the basis of the solution of kinetic Boltzmann equation. The results were compared with the experimental measurements of dust particle charge depending on gas pressure. It was shown that the calculated effective charge, i.e. the difference of the dust particle charge and trapped ion charge, is in a fairly good agreement with the experimental data.

  20. Super-thermal particles in hot plasmas—Kinetic models, numerical solution strategies, and comparison to tokamak experiments

    NASA Astrophysics Data System (ADS)

    Lauber, Philipp

    2013-12-01

    The excitation of collective instabilities by super-thermal particles in hot plasmas and the related transport processes attract increasing interest due to their fundamental challenges for theoretical models and their practical importance for burning fusion plasmas. In fact, the physics of a self-heated thermonuclear plasma due to fusion-born 3.5 MeV α-particles is one of the most important outstanding fundamental research topics on the way to a fusion power plant with magnetic confinement. Within the last 10 years significant advances on both the theoretical and the experimental sides have been made leading to a more detailed and quantitative understanding of fast-particle-driven instabilities. On the theoretical side, the crucial step was to move from fluid models for the plasma background with a hybrid kinetic expression for the energetic particles to a fully kinetic model for all the plasma species, i.e. background ions, background electrons, and fast ions. This improvement allows one to describe consistently the resonant interaction between global plasma waves such as shear Alfvén and Alfvén-acoustic waves, and the particles via Landau damping, i.e. the dynamics parallel to the magnetic background field. Also, mode conversion mechanisms require the inclusion of background ion scales in a kinetic, non-perturbative way. This accurate treatment of the plasma background leads not only to changes in the linear mode properties such as frequency, growth/damping rate, and mode structure but also influences the non-linear dynamics. Due to major advances, innovations and installation of diagnostics in present day experiments, this comparison can be carried out in a more detailed and comprehensive way than a few years ago. For example, the measurement of damping rates via active external antennas, the imaging of 2D mode structures via electron-cyclotron-emission spectroscopy, and the direct detection of escaping fast ions allow to diagnose various kinetic features of

  1. Kinetic Particle-In Simulations of Transport in a Tokamak Scrape-Off Layer.

    NASA Astrophysics Data System (ADS)

    Procassini, Richard Joseph

    1990-01-01

    The focus of this thesis is the application of particle-in-cell (PIC) simulation techniques to the study of particle and energy transport in the scrape-off layer (SOL) of a tokamak fusion device. The PIC computer code that is used in this endeavor provides a fully-kinetic, self-consistent description of plasma transport in one spatial dimension (along the open magnetic field lines in the SOL) and two velocity components (v_ {|} and v_{ |}). The diverted-tokamak SOL system was modeled with various levels of physical complexity. The most rudimentary system studied, a collisionless bounded plasma-sheath region, was used to investigate the dependence of the potential structure on the source distribution function used to inject plasma into the SOL. The results from this study were in reasonable agreement with the predictions of previously developed analytic theories. The next level of complexity included the effects of Coulomb collisions. Plasma transport in the SOL was modeled over the wide range of collisionality encountered in current and near-term devices. The electron heat conduction flux in these simulations was limited to 11-21% of the free-streaming thermal flux. Finally, the atomic physics processes of charge exchange and ionization were included in the collisional model. These interactions between the charged-plasma and recycled-neutral particles can significantly affect energy transport through the SOL. This complete version of the kinetic PIC model was used to simulate SOL transport for various values of neutral particle density between the low-and high-recycling limits. The electron and ion kinetic energy fluxes to the divertor plate exhibit a marked decrease as the level of neutral particle recycling increases. The performance of the direct implicit PIC code has been determined with regard to the size of the time step Delta t and grid spacing Delta z. Each of the physics packages incorporated into the PIC code has been benchmarked against either available

  2. Activation energies of colloidal particle aggregation: towards a quantitative characterization of specific ion effects.

    PubMed

    Tian, Rui; Yang, Gang; Li, Hang; Gao, Xiaodan; Liu, Xinmin; Zhu, Hualing; Tang, Ying

    2014-05-21

    A quantitative description of specific ion effects is an essential and focused topic in colloidal and biological science. In this work, the dynamic light scattering technique was employed to study the aggregation kinetics of colloidal particles in the various alkali ion solutions with a wide range of concentrations. It indicated that the activation energies could be used to quantitatively characterize specific ion effects, which was supported by the results of effective hydrodynamic diameters, aggregation rates and critical coagulation concentrations. At a given concentration of 25 mmol L(-1), the activation energies for Li(+) are 1.2, 5.7, 28, and 126 times as much for Na(+), K(+), Rb(+), and Cs(+), respectively. Most importantly, the activation energy differences between two alkali cation species increase sharply with decrease of electrolyte concentrations, implying the more pronounced specific ion effects at lower concentrations. The dominant role of electrolyte cations during the aggregation of negatively charged colloidal particles was confirmed by alternative anions. Among the various theories, only the polarization effect can give a rational interpretation of the above specific ion effects, and this is substantially supported by the presence of strong electric fields from montmorillonite surfaces and its association mainly with electrolyte cations and montmorillonite particles. The classical induction theory, although with inclusion of electric field, requires significant corrections because it predicts an opposite trend to the experimentally observed specific ion effects. PMID:24603654

  3. Properties of ion-particle interaction and the ion drag force in complex (dusty) plasmas

    SciTech Connect

    Khrapak, Sergey A.

    2009-11-10

    In this paper a concise overview of recent results concerning the properties of ion-particle interaction and the ion drag force in complex (dusty) plasmas is presented. Two main theoretical approaches to calculate the ion drag force--binary collision and linear plasma response formalisms are discussed. When possible, theoretical results are compared with the results from experiments and numerical simulations.

  4. Neutral Particle Analyzer Measurements of Ion Behavior in NSTX

    SciTech Connect

    S.S. Medley; R.E. Bell; D.S. Darrow; A.L. Roquemore

    2002-02-06

    Initial results obtained with the Neutral Particle Analyzer (NPA) diagnostic on the National Spherical Torus Experiment (NSTX) are presented. Magnetohydrodynamic activity and reconnection events cause depletion of the deuterium energetic ion distribution created by neutral-beam injection. Adding High Harmonic Fast Wave Heating to neutral-beam-heated discharges results in the generation of an energetic ion tail above the beam injection energy. NPA measurements of the residual hydrogen ion temperature are in good agreement with those from recombination spectroscopy.

  5. Dominant particles and reactions in a two-temperature chemical kinetic model of a decaying SF6 arc

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohua; Gao, Qingqing; Fu, Yuwei; Yang, Aijun; Rong, Mingzhe; Wu, Yi; Niu, Chunping; Murphy, Anthony B.

    2016-03-01

    This paper is devoted to the computation of the non-equilibrium composition of an SF6 plasma, and determination of the dominant particles and reactions, at conditions relevant to high-voltage circuit breakers after current zero (temperatures from 12 000 K to 1000 K and a pressure of 4 atm). The non-equilibrium composition is characterized by departures from both thermal and chemical equilibrium. In thermal non-equilibrium process, the electron temperature (T e) is not equal to the heavy-particle temperature (T h), while for chemical non-equilibrium, a chemical kinetic model is adopted. In order to evaluate the reasonableness and reliability of the non-equilibrium composition, calculation methods for equilibrium composition based on Gibbs free energy minimization and kinetic composition in a one-temperature kinetic model are first considered. Based on the one-temperature kinetic model, a two-temperature kinetic model with the ratio T e/T h varying as a function of the logarithm of electron density ratio (n e/n\\text{e}\\max ) was established. In this model, T* is introduced to allow a smooth transition between T h and T e and to determine the temperatures for the rate constants. The initial composition in the kinetic models is obtained from the asymptotic composition as infinite time is approached at 12 000 K. The molar fractions of neutral particles and ions in the two-temperature kinetic model are consistent with the equilibrium composition and the composition obtained from the one-temperature kinetic model above 10 000 K, while significant differences appear below 10 000 K. Based on the dependence of the particle distributions on temperature in the two-temperature kinetic model, three temperature ranges, and the dominant particles and reactions in the respective ranges, are determined. The full model is then simplified into three models and the accuracy of the simplified models is assessed. The simplified models reduce the number of species and

  6. Determination of Dusty Particle Charge Taking into Account Ion Drag

    SciTech Connect

    Ramazanov, T. S.; Dosbolayev, M. K.; Jumabekov, A. N.; Amangaliyeva, R. Zh.; Orazbayev, S. A.; Petrov, O. F.; Antipov, S. N.

    2008-09-07

    This work is devoted to the experimental estimation of charge of dust particle that levitates in the stratum of dc glow discharge. Particle charge is determined on the basis of the balance between ion drag force, gravitational and electric forces. Electric force is obtained from the axial distribution of the light intensity of strata.

  7. Ion exchange kinetics of magnetic alginate ferrogel beads produced by external gelation.

    PubMed

    Teixeira, Vânea Ferreira Torres; Pereira, Nádia Rosa; Waldman, Walter Ruggeri; Ávila, Ana Luiza Cassiano Dias; Pérez, Victor Haber; Rodríguez, Rubén Jesus Sánchez

    2014-10-13

    This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Fick's second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network. PMID:25037343

  8. Interaction between chitosan and uranyl ions. Role of physical and physicochemical parameters on the kinetics of sorption

    SciTech Connect

    Piron, E. |; Accominotti, M.; Domard, A.

    1997-03-19

    This work corresponds to the first part of our studies on the interactions between chitosan particles dispersed in water and uranyl ions. The measurements were obtained by ICP, and we considered the role of various physical and physicochemical parameters related to chitosan. We showed that the crystallinity, the particle dimensions, and the swelling in water of chitosan are parameters which are connected together and govern the kinetic laws of metal diffusion and sorption. The molecular mobility of the polymer chains is then essential parameter. 31 refs., 5 figs., 3 tabs.

  9. Forward and reverse ion-exchange kinetics for some alkali and alkaline earth metal ions on amorphous zirconium(IV) aluminophosphate

    SciTech Connect

    Varshney, K.G.; Pandith, A.H.

    1999-10-26

    The Nernst-Planck equations are applied to study the ion-exchange kinetics on the surface of zirconium(IV) aluminophosphate for Li{sup +}/H{sup +}, Na{sup +}/H{sup +}, K{sup +}/H{sup +}, Mg{sup 2+}/H{sup +}, Ca{sup 2+}/H{sup +}, and Sr{sup 2+}/H{sup +} exchanges in the forward and reverse directions under the conditions favoring particle diffusion. On the basis of these studies, various physical parameters such as the self-diffusion coefficient (D{sub 0}), the energy of activation (E{sub a}), and the entropy of activation ({Delta}S*) have been determined and a correlation has been made of these parameters with the ion-exchange characteristics of the material. The study gives an insight into the ion-exchange processes going on in the exchanger phase and its potential use in metal ion separations.

  10. Scalings of energetic particle transport by ion temperature gradient microturbulence

    SciTech Connect

    Zhang Wenlu; Decyk, Viktor; Holod, Ihor; Xiao Yong; Lin Zhihong; Chen Liu

    2010-05-15

    Transport scaling of energetic particles by ion temperature gradient microturbulence in magnetized plasmas is studied in massively paralleled gyrokinetic particle-in-cell simulations. It is found that the diffusivity decreases drastically at high particles energy (E) to plasma temperature (T) ratio because of the averaging effects of the large gyroradius and drift-orbit width, and the fast wave-particle decorrelation. At high energy, the diffusivity follows a (E/T){sup -1} scaling for purely passing particles, a (E/T){sup -2} scaling for deeply trapped particles and a (E/T){sup -1} scaling for particles with an isotropic velocity distribution since the diffusivity therein is contributed mostly by the passing particles.

  11. Negative ion-driven associated particle neutron generator

    SciTech Connect

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2015-10-09

    We describe an associated particle neutron generator that employs a negative ion source to produce high neutron flux from a small source size. Furthermore, negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). Finally, the neutron generator can operate in either pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to similar to 108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.

  12. Negative ion-driven associated particle neutron generator

    DOE PAGESBeta

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2015-10-09

    We describe an associated particle neutron generator that employs a negative ion source to produce high neutron flux from a small source size. Furthermore, negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). Finally, the neutron generator can operate in eithermore » pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to similar to 108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.« less

  13. Negative ion-driven associated particle neutron generator

    NASA Astrophysics Data System (ADS)

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2016-01-01

    An associated particle neutron generator is described that employs a negative ion source to produce high neutron flux from a small source size. Negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). The neutron generator can operate in either pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to ~108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.

  14. Ion pre-acceleration in fully self-consistent particle-in-cell simulations of supercritical perpendicular reforming shocks in multiple ion species plasmas

    SciTech Connect

    Rekaa, V. L.; Chapman, S. C.; Dendy, R. O.

    2014-08-10

    Supernova remnant and heliopause termination shock plasmas may contain significant populations of minority heavy ions, with relative number densities n{sub α}/n{sub i} up to 50%. Preliminary kinetic simulations of collisionless shocks in these environments showed that the reformation cycle and acceleration mechanisms at quasi-perpendicular shocks can depend on the value of n{sub α}/n{sub i} . Shock reformation unfolds on ion spatio-temporal scales, requiring fully kinetic simulations of particle dynamics, together with the self-consistent electric and magnetic fields. This paper presents the first set of particle-in-cell simulations for two ion species, protons (n{sub p} ) and α-particles (n{sub α}), with differing mass and charge-to-mass ratios, that spans the entire range of n{sub α}/n{sub i} from 0% to 100%. The interplay between the differing gyro length scales and timescales of the ion species is crucial to the time-evolving phenomenology of the shocks, the downstream turbulence, and the particle acceleration at different n{sub α}/n{sub i} . We show how the overall energization changes with n{sub α}/n{sub i} , and relate this to the processes individual ions undergo in the shock region and in the downstream turbulence, and to the power spectra of magnetic field fluctuations. The crossover between shocks dominated by the respective ion species happens when n{sub α}/n{sub i} = 25%, and minority ion energization is strongest in this regime. Energization of the majority ion species scales with injection energy. The power spectrum of the downstream turbulence includes peaks at sequential ion cyclotron harmonics, suggestive of ion ring-beam collective instability.

  15. Dispensing targets for ion beam particle generators

    NASA Technical Reports Server (NTRS)

    Miller, C. G. (Inventor)

    1974-01-01

    A target for dispensing high energy protons or neutrons or ionized atoms or ionized molecules is provided which comprises a container for the target gas, which is at atmospheric or higher pressure. The container material can release the target gas in the spot where the container is heated above a predetermined temperature by the impact of an ion beam where protons or neutrons are desired, or by electrons where ionized atoms or molecules are desired. On the outside of the container, except for the region where the beam is to impact, there is deposited a layer of a metal which is imperious to gaseous diffusion. A further protective coating of a material is placed over the layer of metal, except at the region of the ion impact area in order to adsorb any unreacted gas in the vacuum in which the target is placed, to thereby prevent reduction of the high vacuum, as well as contamination of the interior of the vacuum chamber.

  16. Gyrokinetic and kinetic particle-in-cell simulations of guide-field reconnection. I. Macroscopic effects of the electron flows

    NASA Astrophysics Data System (ADS)

    Muñoz, P. A.; Told, D.; Kilian, P.; Büchner, J.; Jenko, F.

    2015-08-01

    In this work, we compare gyrokinetic (GK) with fully kinetic Particle-in-Cell (PIC) simulations of magnetic reconnection in the limit of strong guide field. In particular, we analyze the limits of applicability of the GK plasma model compared to a fully kinetic description of force free current sheets for finite guide fields (bg). Here, we report the first part of an extended comparison, focusing on the macroscopic effects of the electron flows. For a low beta plasma (βi = 0.01), it is shown that both plasma models develop magnetic reconnection with similar features in the secondary magnetic islands if a sufficiently high guide field (bg ≳ 30) is imposed in the kinetic PIC simulations. Outside of these regions, in the separatrices close to the X points, the convergence between both plasma descriptions is less restrictive (bg ≳ 5). Kinetic PIC simulations using guide fields bg ≲ 30 reveal secondary magnetic islands with a core magnetic field and less energetic flows inside of them in comparison to the GK or kinetic PIC runs with stronger guide fields. We find that these processes are mostly due to an initial shear flow absent in the GK initialization and negligible in the kinetic PIC high guide field regime, in addition to fast outflows on the order of the ion thermal speed that violate the GK ordering. Since secondary magnetic islands appear after the reconnection peak time, a kinetic PIC/GK comparison is more accurate in the linear phase of magnetic reconnection. For a high beta plasma (βi = 1.0) where reconnection rates and fluctuations levels are reduced, similar processes happen in the secondary magnetic islands in the fully kinetic description, but requiring much lower guide fields (bg ≲ 3).

  17. Gyrokinetic and kinetic particle-in-cell simulations of guide-field reconnection. I. Macroscopic effects of the electron flows

    SciTech Connect

    Muñoz, P. A. Kilian, P.; Büchner, J.; Told, D.; Jenko, F.

    2015-08-15

    In this work, we compare gyrokinetic (GK) with fully kinetic Particle-in-Cell (PIC) simulations of magnetic reconnection in the limit of strong guide field. In particular, we analyze the limits of applicability of the GK plasma model compared to a fully kinetic description of force free current sheets for finite guide fields (b{sub g}). Here, we report the first part of an extended comparison, focusing on the macroscopic effects of the electron flows. For a low beta plasma (β{sub i} = 0.01), it is shown that both plasma models develop magnetic reconnection with similar features in the secondary magnetic islands if a sufficiently high guide field (b{sub g} ≳ 30) is imposed in the kinetic PIC simulations. Outside of these regions, in the separatrices close to the X points, the convergence between both plasma descriptions is less restrictive (b{sub g} ≳ 5). Kinetic PIC simulations using guide fields b{sub g} ≲ 30 reveal secondary magnetic islands with a core magnetic field and less energetic flows inside of them in comparison to the GK or kinetic PIC runs with stronger guide fields. We find that these processes are mostly due to an initial shear flow absent in the GK initialization and negligible in the kinetic PIC high guide field regime, in addition to fast outflows on the order of the ion thermal speed that violate the GK ordering. Since secondary magnetic islands appear after the reconnection peak time, a kinetic PIC/GK comparison is more accurate in the linear phase of magnetic reconnection. For a high beta plasma (β{sub i} = 1.0) where reconnection rates and fluctuations levels are reduced, similar processes happen in the secondary magnetic islands in the fully kinetic description, but requiring much lower guide fields (b{sub g} ≲ 3)

  18. Dust particle diffusion in ion beam transport region.

    PubMed

    Miyamoto, N; Okajima, Y; Romero, C F; Kuwata, Y; Kasuya, T; Wada, M

    2016-02-01

    Dust particles of μm size produced by a monoplasmatron ion source are observed by a laser light scattering. The scattered light signal from an incident laser at 532 nm wavelength indicates when and where a particle passes through the ion beam transport region. As the result, dusts with the size more than 10 μm are found to be distributed in the center of the ion beam, while dusts with the size less than 10 μm size are distributed along the edge of the ion beam. Floating potential and electron temperature at beam transport region are measured by an electrostatic probe. This observation can be explained by a charge up model of the dust in the plasma boundary region. PMID:26932116

  19. Dust particle diffusion in ion beam transport region

    NASA Astrophysics Data System (ADS)

    Miyamoto, N.; Okajima, Y.; Romero, C. F.; Kuwata, Y.; Kasuya, T.; Wada, M.

    2016-02-01

    Dust particles of μm size produced by a monoplasmatron ion source are observed by a laser light scattering. The scattered light signal from an incident laser at 532 nm wavelength indicates when and where a particle passes through the ion beam transport region. As the result, dusts with the size more than 10 μm are found to be distributed in the center of the ion beam, while dusts with the size less than 10 μm size are distributed along the edge of the ion beam. Floating potential and electron temperature at beam transport region are measured by an electrostatic probe. This observation can be explained by a charge up model of the dust in the plasma boundary region.

  20. Light particle emissions in heavy ion reactions

    SciTech Connect

    Petitt, G.A.; Liu, Xin-Tao; Smathers, J.; Zhang, Ziang.

    1991-03-01

    We are completing another successful year of experimental work at the Holifield Heavy Ion Research Facility (HHIRF), the Los Alamos white neutron source facility, Brookhaven National Laboratory (BNL) and Georgia State University (GSU). A paper on energy division between the two heavy fragments in deep inelastic reactions between {sup 58}Ni + {sup 165}Ho was published in Physical Review C during the year. We have partially completed analysis of the data on the {sup 32}S + {sup 93}Nb system taken with the HILI detector system at the HHIRF. This paper discusses work on these topics and discusses the setup of a neutron detector for a neutron reaction experiment.

  1. Cluster kinetics model of particle separation in vibrated granular media

    NASA Astrophysics Data System (ADS)

    McCoy, Benjamin J.; Madras, Giridhar

    2006-01-01

    We model the Brazil-nut effect (BNE) by hypothesizing that granules form clusters that fragment and aggregate. This provides a heterogeneous medium in which the immersed intruder particle rises (BNE) or sinks (reverse BNE) according to relative convection currents and buoyant and drag forces. A simple relationship proposed for viscous drag in terms of the vibrational intensity and the particle to grain density ratio allows simulation of published experimental data for rise and sink times as functions of particle radius, initial depth of the particle, and particle-grain density ratio. The proposed model correctly describes the experimentally observed maximum in risetime.

  2. Cluster kinetics model of particle separation in vibrated granular media.

    PubMed

    McCoy, Benjamin J; Madras, Giridhar

    2006-01-01

    We model the Brazil-nut effect (BNE) by hypothesizing that granules form clusters that fragment and aggregate. This provides a heterogeneous medium in which the immersed intruder particle rises (BNE) or sinks (reverse BNE) according to relative convection currents and buoyant and drag forces. A simple relationship proposed for viscous drag in terms of the vibrational intensity and the particle to grain density ratio allows simulation of published experimental data for rise and sink times as functions of particle radius, initial depth of the particle, and particle-grain density ratio. The proposed model correctly describes the experimentally observed maximum in risetime. PMID:16486131

  3. Perturbed particle orbits and kinetic plasma response in non-axisymmetric tokamaks

    NASA Astrophysics Data System (ADS)

    Kim, Kimin; Park, J.-K.; Boozer, A. H.; Logan, N. C.; Wang, Z. R.; Menard, J. E.

    2014-10-01

    Non-axisymmetric magnetic fields interact with the drift trajectories of ions and electrons to create an anisotropic plasma pressure. The force produced by the gradient of this anisotropic pressure produces a torque, the Neoclassical Toroidal Viscosity (NTV), which tends to relax the plasma rotation to a specific offset rotation, and modifies the energy required to perturb the plasma. Complexities, such as resonances of the ExB drift with particle bounce frequencies, finite orbit width, and full collisional effects, require full numerical simulation to determine the NTV and the perturbation energy. The POCA delta-f drift kinetic particle code has been used to: (1) demonstrate the existence of the bounce resonances with the ExB drift and show that they often dominate the magnitude of the NTV, (2) show the NTV of perturbations with different toroidal mode numbers are generally decoupled, and (3) verify a quadratic NTV dependence on the asymmetric magnetic field. Such results imply the pressure anisotropy is linear in the magnetic perturbation and can produce a significant change in the applied non-axisymmetric field. Progress on integrating this pressure anisotropy into a perturbed equilibrium solver to obtain self-consistent solutions is presented. This work was supported by US DOE Contract DE-AC02-09CH11466.

  4. Hydrogen Reduction Kinetics of Magnetite Concentrate Particles Relevant to a Novel Flash Ironmaking Process

    NASA Astrophysics Data System (ADS)

    Wang, Haitao; Sohn, H. Y.

    2013-02-01

    A novel ironmaking technology is under development at the University of Utah. The purpose of this research was to determine comprehensive kinetics of the flash reduction reaction of magnetite concentrate particles by hydrogen. Experiments were carried out in the temperature range of 1423 K to 1673 K (1150 °C to 1400 °C) with the other experimental variables being hydrogen partial pressure and particle size. The nucleation and growth kinetics expression was found to describe the reduction rate of fine concentrate particles and the reduction kinetics had a 1/2-order dependence on hydrogen partial pressure and an activation energy of 463 kJ/mol. Unexpectedly, large concentrate particles reacted faster at 1423 K and 1473 K (1150 °C and 1200 °C), but the effect of particle size was negligible when the reduction temperature was above 1573 K (1300 °C). A complete reaction rate expression incorporating all these factors was formulated.

  5. Universal behavior of charged particle production in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Phobos Collaboration; Steinberg, Peter A.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Ballintijn, M.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; Garcia, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tang, J.-L.; Teng, R.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.

    2003-03-01

    The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at sqrt(s_NN) = 19.6, 130 and 200 GeV. Two kinds of universal behavior are observed in charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/pbar-p and e+e- data. N_tot/(N_part/2) in nuclear collisions at high energy scales with sqrt(s) in a similar way as N_tot in e+e- collisions and has a very weak centrality dependence. This feature may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.

  6. UNIVERSAL BEHAVIOR OF CHARGED PARTICLE PRODUCTION IN HEAVY ION COLLISIONS.

    SciTech Connect

    STEINBERG,P.A.FOR THE PHOBOS COLLABORATION

    2002-07-24

    The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at {radical}(s{sub NN}) = 19.6, 130 and 200 GeV. Two observations indicate universal behavior of charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/{bar p}p and e{sup +}e{sup -} data. / in nuclear collisions at high energy scales with {radical}s in a similar way as N{sub ch} in e{sup +}e{sup -} collisions and has a very weak centrality dependence. These features may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.

  7. Full-f Neoclassical Simulations toward a Predictive Model for H-mode Pedestal Ion Energy, Particle and Momentum Transport

    SciTech Connect

    Battaglia, D. J.; Boedo, J. A.; Burrell, K. H.; Chang, C. S.; Canik, J. M.; deGrassie, J. S.; Gerhardt, S. P.; Grierson, B. A.; Groebner, R. J.; Maingi, Rajesh; Smith, S. P.

    2014-09-01

    Energy and particle transport rates are decoupled in the H-mode edge since the ion thermal transport rate is primarily set by the neoclassical transport of the deuterium ions in the tail of the thermal energy distribution, while the net particle transport rate is set by anomalous transport of the colder bulk ions. Ion orbit loss drives the energy distributions away from Maxwellian, and describes the anisotropy, poloidal asymmetry and local minimum near the separatrix observed in the Ti profile. Non-Maxwellian distributions also drive large intrinsic edge flows, and the interaction of turbulence at the top of the pedestal with the intrinsic edge flow can generate an intrinsic core torque. The primary driver of the radial electric field (Er) in the pedestal and scrapeoff layer (SOL) are kinetic neoclassical effects, such as ion orbit loss of tail ions and parallel electron loss to the divertor. This paper describes the first multi-species kinetic neoclassical transport calculations for ELM-free H-mode pedestal and scrape-off layer on DIII-D using XGC0, a 5D full-f particle-in-cell drift-kinetic solver with self-consistent neutral recycling and sheath potentials. Quantitative agreement between the flux-driven simulation and the experimental electron density, impurity density and orthogonal measurements of impurity temperature and flow profiles is achieved by adding random-walk particle diffusion to the guiding-center drift motion. This interpretative technique quantifies the role of neoclassical, anomalous and neutral transport to the overall pedestal structure, and consequently illustrates the importance of including kinetic effects self-consistently in transport calculations around transport barriers.

  8. Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

    SciTech Connect

    Rosenberg, M. J. Zylstra, A. B.; Séguin, F. H.; Rinderknecht, H. G.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Waugh, C. J.; Sinenian, N.; Li, C. K.; Petrasso, R. D.; McKenty, P. W.; Hohenberger, M.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Betti, R.; Goncharov, V. N.; Knauer, J. P.; Sangster, T. C.; and others

    2014-12-15

    Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D{sub 2} and D{sup 3}He gas-filled “exploding-pusher” inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to the predictions of 2D DRACO hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.

  9. Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J.; Zylstra, A. B.; Séguin, F. H.; Rinderknecht, H. G.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Waugh, C. J.; Sinenian, N.; Li, C. K.; Petrasso, R. D.; McKenty, P. W.; Hohenberger, M.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Betti, R.; Goncharov, V. N.; Knauer, J. P.; Sangster, T. C.; LePape, S.; Mackinnon, A. J.; Pino, J.; McNaney, J. M.; Rygg, J. R.; Amendt, P. A.; Bellei, C.; Benedetti, L. R.; Berzak Hopkins, L.; Bionta, R. M.; Casey, D. T.; Divol, L.; Edwards, M. J.; Glenn, S.; Glenzer, S. H.; Hicks, D. G.; Kimbrough, J. R.; Landen, O. L.; Lindl, J. D.; Ma, T.; MacPhee, A.; Meezan, N. B.; Moody, J. D.; Moran, M. J.; Park, H.-S.; Remington, B. A.; Robey, H.; Rosen, M. D.; Wilks, S. C.; Zacharias, R. A.; Herrmann, H. W.; Hoffman, N. M.; Kyrala, G. A.; Leeper, R. J.; Olson, R. E.; Kilkenny, J. D.; Nikroo, A.

    2014-12-01

    Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D2 and D3He gas-filled "exploding-pusher" inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to the predictions of 2D draco hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.

  10. Particle based plasma simulation for an ion engine discharge chamber

    NASA Astrophysics Data System (ADS)

    Mahalingam, Sudhakar

    Design of the next generation of ion engines can benefit from detailed computer simulations of the plasma in the discharge chamber. In this work a complete particle based approach has been taken to model the discharge chamber plasma. This is the first time that simplifying continuum assumptions on the particle motion have not been made in a discharge chamber model. Because of the long mean free paths of the particles in the discharge chamber continuum models are questionable. The PIC-MCC model developed in this work tracks following particles: neutrals, singly charged ions, doubly charged ions, secondary electrons, and primary electrons. The trajectories of these particles are determined using the Newton-Lorentz's equation of motion including the effects of magnetic and electric fields. Particle collisions are determined using an MCC statistical technique. A large number of collision processes and particle wall interactions are included in the model. The magnetic fields produced by the permanent magnets are determined using Maxwell's equations. The electric fields are determined using an approximate input electric field coupled with a dynamic determination of the electric fields caused by the charged particles. In this work inclusion of the dynamic electric field calculation is made possible by using an inflated plasma permittivity value in the Poisson solver. This allows dynamic electric field calculation with minimal computational requirements in terms of both computer memory and run time. In addition, a number of other numerical procedures such as parallel processing have been implemented to shorten the computational time. The primary results are those modeling the discharge chamber of NASA's NSTAR ion engine at its full operating power. Convergence of numerical results such as total number of particles inside the discharge chamber, average energy of the plasma particles, discharge current, beam current and beam efficiency are obtained. Steady state results for

  11. Kinetic Stability of Non-IPR Fullerene Molecular Ions.

    PubMed

    Aihara, Jun-ichi; Nakagami, Yuto; Sekine, Rika

    2015-06-18

    Many fullerenes that violate the isolated pentagon rule (IPR) form stable metallofullerenes. In general, a fullerene cage is kinetically stabilized by acquiring a given number of electrons. Kinetic stability of negatively charged non-IPR fullerenes, including the recently isolated endohedral metallofullerene with a heptagonal face, was rationalized in terms of bond resonance energy (BRE). Interestingly, molecular anions of conventional fullerenes found in most isolated metallofullerenes are kinetically stable with large positive BREs for all CC bonds. As we pointed out in 1993, the IPR does not apply to charged fullerenes because π-bonds shared by two five-membered rings are aromatized to varying extents. PMID:26020361

  12. Studies of ion kinetic effects in OMEGA shock-driven implosions using fusion burn imaging

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J.; Seguin, F. H.; Rinderknecht, H. G.; Sio, H.; Zylstra, A. B.; Gatu Johnson, M.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.; Amendt, P. A.; Wilks, S. C.; Zimmerman, G.; Hoffman, N. M.; Kagan, G.; Molvig, K.; Glebov, V. Yu.; Stoeckl, C.; Marshall, F. J.; Seka, W.; Delettrez, J. A.; Sangster, T. C.; Betti, R.; Meyerhofer, D. D.; Atzeni, S.; Nikroo, A.

    2014-10-01

    Ion kinetic effects have been inferred in a series of shock-driven implosions at OMEGA from an increasing yield discrepancy between observations and hydrodynamic simulations as the ion-ion mean free path increases. To more precisely identify the nature and impact of ion kinetic effects, spatial burn profile measurements of DD and D3He reactions in these D3He-filled shock-driven implosions are presented and contrasted to both purely hydrodynamic models and models that include ion kinetic effects. It is shown that in implosions where the ion mean free path is equal to or greater than the size of the fuel region, purely hydrodynamic models fail to capture the observed burn profiles, while a model that includes ion diffusion is able to recover the observed burn profile shape. These results further elucidate the ion kinetic mechanisms that are present under long mean-free-path conditions after shock convergence in both shock-driven and ablatively-driven implosions. This work was supported in part by the U.S. DOE, NLUF, LLE, and LLNL.

  13. Comparison between kinetic-ballooning-mode-driven turbulence and ion-temperature-gradient-driven turbulence

    SciTech Connect

    Maeyama, S. Nakata, M.; Miyato, N.; Yagi, M.; Ishizawa, A.; Watanabe, T.-H.; Idomura, Y.

    2014-05-15

    Electromagnetic turbulence driven by kinetic ballooning modes (KBMs) in high-β plasma is investigated based on the local gyrokinetic model. Analysis of turbulent fluxes, norms, and phases of fluctuations shows that KBM turbulence gives narrower spectra and smaller phase factors than those in ion-temperature-gradient (ITG)-driven turbulence. This leads to the smaller transport fluxes in KBM turbulence than those in ITG turbulence even when they have similar linear growth rates. From the analysis of the entropy balance relation, it is found that the entropy transfer from ions to electrons through the field-particle interactions mainly drives electron perturbations, which creates radial twisted modes by rapid parallel motions of electrons in a sheared magnetic geometry. The nonlinear coupling between the dominant unstable mode and its twisted modes is important for the saturation of KBM turbulence, in contrast to the importance of zonal flow shearing in ITG turbulence. The coupling depends on the flux-tube domain with the one-poloidal-turn parallel length and on the torus periodicity constraint.

  14. Ion microprobe isotopic measurements of individual interplanetary dust particles

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.; Walker, R. M.; Zinner, E.

    1985-09-01

    The results of the first extended ion probe study of interplanetary dust particles (IDPs) are reported. The analytic procedures and the current limits on the precision and accurary of isotopic measurements of light elements are discussed in considerable detail. It is shown that isotopic measurements of several elements can be made on different individual fragments of a single IDP of 10-15 microns in size. The deuterium enrichments observed in several of the particles are shown to be intrinsic, providing independent proof that the particles are extraterrestrial. Carbon isotopic measurements on fragments of three IDPs give ratios similar to terrestrial values and show a largely uniform isotopic composition for a given particle. Small, but significant, differences in delta C-13 of about 40 percent between particles are seen.

  15. Electrostatic particle trap for ion beam sputter deposition

    DOEpatents

    Vernon, Stephen P.; Burkhart, Scott C.

    2002-01-01

    A method and apparatus for the interception and trapping of or reflection of charged particulate matter generated in ion beam sputter deposition. The apparatus involves an electrostatic particle trap which generates electrostatic fields in the vicinity of the substrate on which target material is being deposited. The electrostatic particle trap consists of an array of electrode surfaces, each maintained at an electrostatic potential, and with their surfaces parallel or perpendicular to the surface of the substrate. The method involves interception and trapping of or reflection of charged particles achieved by generating electrostatic fields in the vicinity of the substrate, and configuring the fields to force the charged particulate material away from the substrate. The electrostatic charged particle trap enables prevention of charged particles from being deposited on the substrate thereby enabling the deposition of extremely low defect density films, such as required for reflective masks of an extreme ultraviolet lithography (EUVL) system.

  16. Simulations of ion acceleration at non-relativistic shocks. III. Particle diffusion

    SciTech Connect

    Caprioli, D.; Spitkovsky, A.

    2014-10-10

    We use large hybrid (kinetic-protons-fluid-electrons) simulations to investigate the transport of energetic particles in self-consistent electromagnetic configurations of collisionless shocks. In previous papers of this series, we showed that ion acceleration may be very efficient (up to 10%-20% in energy), and outlined how the streaming of energetic particles amplifies the upstream magnetic field. Here, we measure particle diffusion around shocks with different strengths, finding that the mean free path for pitch-angle scattering of energetic ions is comparable with their gyroradii calculated in the self-generated turbulence. For moderately strong shocks, magnetic field amplification proceeds in the quasi-linear regime, and particles diffuse according to the self-generated diffusion coefficient, i.e., the scattering rate depends only on the amount of energy in modes with wavelengths comparable with the particle gyroradius. For very strong shocks, instead, the magnetic field is amplified up to non-linear levels, with most of the energy in modes with wavelengths comparable to the gyroradii of highest-energy ions, and energetic particles experience Bohm-like diffusion in the amplified field. We also show how enhanced diffusion facilitates the return of energetic particles to the shock, thereby determining the maximum energy that can be achieved in a given time via diffusive shock acceleration. The parameterization of the diffusion coefficient that we derive can be used to introduce self-consistent microphysics into large-scale models of cosmic ray acceleration in astrophysical sources, such as supernova remnants and clusters of galaxies.

  17. Generation of ion temperature anisotropy in kinetic hybrid-Vlasov simulations (Invited)

    NASA Astrophysics Data System (ADS)

    Perrone, D.; Valentini, F.; Servidio, S.; Dalena, S.; Veltri, P.

    2013-12-01

    The interplanetary medium is a multi-component and weakly collisional system generally observed to be in a fully turbulent regime [1,2]. The system dynamics at short spatial scales appears to be dominated by kinetic effects that drive the interstellar gas far from the configuration of thermodynamic equilibrium [3-5]. We present a numerical analysis of a turbulent plasma composed of kinetic ions (protons and alpha particles) and fluid electrons in the typical conditions of the solar-wind environment, developed by using a low-noise hybrid Vlasov-Maxwell code [6,7] in a five dimensional phase space configuration (two dimensions in physical space and three dimensions in velocity space) [8]. The ion dynamics at short spatial scales (shorter than the proton skin depth) display several interesting aspects, mainly consisting in the departure of the distribution functions from the typical Maxwellian configuration, which has been systematically quantified through the evalutation of the temperature anisotropy ratio (perpendicular to parallel temperature ratio) with respect to the local magnetic field. This temperature anisotropy appears to be a direct effect of the turbulent nature of the system dynamics. Moreover, the turbulent activity leads to the generation of coherent structures, such as vortices and current sheets. Conditioned ion temperature distributions suggest heating associated with coherent structures; the distribution of ion temperatures moves towards higher values with increasing PVI threshold for the upper inertial range in the turbulent spectra. This behavior is more evident for alpha particles than for protons. The physical phenomenology recovered in these numerical simulations reproduces very common features recovered in 'in situ' measurements in the turbulent solar wind [9-11], suggesting that the multi-ion Vlasov model represents a valid approach to the understanding of the nature of complex kinetic effects in astrophysical plasmas. [1] R. Bruno and V

  18. Ion-induced nucleation of pure biogenic particles.

    PubMed

    Kirkby, Jasper; Duplissy, Jonathan; Sengupta, Kamalika; Frege, Carla; Gordon, Hamish; Williamson, Christina; Heinritzi, Martin; Simon, Mario; Yan, Chao; Almeida, João; Tröstl, Jasmin; Nieminen, Tuomo; Ortega, Ismael K; Wagner, Robert; Adamov, Alexey; Amorim, Antonio; Bernhammer, Anne-Kathrin; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Chen, Xuemeng; Craven, Jill; Dias, Antonio; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Fuchs, Claudia; Guida, Roberto; Hakala, Jani; Hoyle, Christopher R; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Kim, Jaeseok; Krapf, Manuel; Kürten, Andreas; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Mathot, Serge; Molteni, Ugo; Onnela, Antti; Peräkylä, Otso; Piel, Felix; Petäjä, Tuukka; Praplan, Arnaud P; Pringle, Kirsty; Rap, Alexandru; Richards, Nigel A D; Riipinen, Ilona; Rissanen, Matti P; Rondo, Linda; Sarnela, Nina; Schobesberger, Siegfried; Scott, Catherine E; Seinfeld, John H; Sipilä, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Virtanen, Annele; Vogel, Alexander L; Wagner, Andrea C; Wagner, Paul E; Weingartner, Ernest; Wimmer, Daniela; Winkler, Paul M; Ye, Penglin; Zhang, Xuan; Hansel, Armin; Dommen, Josef; Donahue, Neil M; Worsnop, Douglas R; Baltensperger, Urs; Kulmala, Markku; Carslaw, Kenneth S; Curtius, Joachim

    2016-05-26

    Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution. PMID:27225125

  19. Ion-induced nucleation of pure biogenic particles

    NASA Astrophysics Data System (ADS)

    Kirkby, Jasper; Duplissy, Jonathan; Sengupta, Kamalika; Frege, Carla; Gordon, Hamish; Williamson, Christina; Heinritzi, Martin; Simon, Mario; Yan, Chao; Almeida, João; Tröstl, Jasmin; Nieminen, Tuomo; Ortega, Ismael K.; Wagner, Robert; Adamov, Alexey; Amorim, Antonio; Bernhammer, Anne-Kathrin; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Chen, Xuemeng; Craven, Jill; Dias, Antonio; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Fuchs, Claudia; Guida, Roberto; Hakala, Jani; Hoyle, Christopher R.; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Kim, Jaeseok; Krapf, Manuel; Kürten, Andreas; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Mathot, Serge; Molteni, Ugo; Onnela, Antti; Peräkylä, Otso; Piel, Felix; Petäjä, Tuukka; Praplan, Arnaud P.; Pringle, Kirsty; Rap, Alexandru; Richards, Nigel A. D.; Riipinen, Ilona; Rissanen, Matti P.; Rondo, Linda; Sarnela, Nina; Schobesberger, Siegfried; Scott, Catherine E.; Seinfeld, John H.; Sipilä, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Virtanen, Annele; Vogel, Alexander L.; Wagner, Andrea C.; Wagner, Paul E.; Weingartner, Ernest; Wimmer, Daniela; Winkler, Paul M.; Ye, Penglin; Zhang, Xuan; Hansel, Armin; Dommen, Josef; Donahue, Neil M.; Worsnop, Douglas R.; Baltensperger, Urs; Kulmala, Markku; Carslaw, Kenneth S.; Curtius, Joachim

    2016-05-01

    Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.

  20. On compositional variations of heavy ions during solar particle events

    NASA Technical Reports Server (NTRS)

    Klecker, B.; Scholer, M.; Hovestadt, D.; Fan, C. Y.; Fisk, L. A.; Gloeckler, G.; Ipavich, F. M.; Ogallagher, J. J.

    1981-01-01

    Intensity-time profiles of protons, alpha particles, and heavy ions (C, O, Fe) in the MeV/nucleon energy range have been analyzed for one solar particle event following the solar flare on September 23, 1978. The data have been obtained with the wide angle double dE/dx-E sensor of the Max-Planck-Institut/University of Maryland experiment onboard ISEE-3. Time variations in the iron to helium ratio of up to 2 orders of magnitude and a significant variation of the O/He ratio during this event have been found, whereas the C/O-ratio at the same energy/nucleon appears to be time independent. The influence of a rigidity dependent mean free path in interplanetary space and of rigidity dependent coronal propagation on heavy ion ratios during solar particle events was investigated.

  1. Kinetic shear Alfvén instability in the presence of impurity ions in tokamak plasmas

    SciTech Connect

    Lu, Gaimin; Shen, Y.; Xie, T.; He, Zhixiong; He, Hongda; Qi, Longyu; Cui, Shaoyan

    2013-10-15

    The effects of impurity ions on the kinetic shear Alfvén (KSA) instability in tokamak plasmas are investigated by numerically solving the integral equations for the KSA eigenmode in the toroidal geometry. The kinetic effects of hydrogen and impurity ions, including transit motion, finite ion Larmor radius, and finite-orbit-width, are taken into account. Toroidicity induced linear mode coupling is included through the ballooning-mode representation. Here, the effects of carbon, oxygen, and tungsten ions on the KSA instability in toroidal plasmas are investigated. It is found that, depending on the concentration and density profile of the impurity ions, the latter can be either stabilizing or destabilizing for the KSA modes. The results here confirm the importance of impurity ions in tokamak experiments and should be useful for analyzing experimental data as well as for understanding anomalous transport and control of tokamak plasmas.

  2. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    By examining the exact analytic solution of a kinetic model of collisional interaction of ionospheric ions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, we show that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a non-Maxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

  3. Kinetic energy of ions after Coulomb explosion of clusters induced by an intense laser pulse

    SciTech Connect

    Islam, Md. Ranaul; Saalmann, Ulf; Rost, Jan M.

    2006-04-15

    It is shown that the kinetic-energy distribution of ions emerging from a cluster target irradiated by an intense laser pulse arises from three main effects: (1) the spatial profile of the laser beam (2) the cluster size distribution in the experiment, and (3) possible saturation effects in the cluster ionization. Our model reveals that each of these effects leaves a characteristic fingerprint in the ion kinetic-energy spectrum. Moreover, it provides a quantitative link between observable ion spectra under experimental conditions and the ideal single-cluster result of a typical calculation.

  4. Sorption kinetics of Zn (II) ion by thermally treated rice husk

    NASA Astrophysics Data System (ADS)

    Ong, K. K.; Tarmizi, A. F. A.; Wan Yunus W. M., Z.; Safidin, K. M.; Fitrianto, A.; Hussin, A. G. A.; Azmi, F. M.

    2015-05-01

    Agricultural wastes such as orange peels, tea leave waste, rice husk and corn cobs have been widely studied as sorbents for heavy metal ion removal from various wastewaters. In order to understand their sorption mechanism, the adsorption kinetics is studied. This report describes the kinetics study of a thermally treated rice husk to adsorb Zn (II) ion from an aqueous solution. The adsorbent was obtained by heating the rice husk in a furnace at 500°C for two hours. Increase the contact period improved percentage of the removal of Zn (II) ion until an equilibrium was reached. The data obtained showed that the adsorption of Zn (II) ion by thermally treated rice husk obeyed pseudo-second order kinetics model, which is in agreement with chemisorption as the rate limiting mechanism.

  5. The use of automated parameter searches to improve ion channel kinetics for neural modeling.

    PubMed

    Hendrickson, Eric B; Edgerton, Jeremy R; Jaeger, Dieter

    2011-10-01

    The voltage and time dependence of ion channels can be regulated, notably by phosphorylation, interaction with phospholipids, and binding to auxiliary subunits. Many parameter variation studies have set conductance densities free while leaving kinetic channel properties fixed as the experimental constraints on the latter are usually better than on the former. Because individual cells can tightly regulate their ion channel properties, we suggest that kinetic parameters may be profitably set free during model optimization in order to both improve matches to data and refine kinetic parameters. To this end, we analyzed the parameter optimization of reduced models of three electrophysiologically characterized and morphologically reconstructed globus pallidus neurons. We performed two automated searches with different types of free parameters. First, conductance density parameters were set free. Even the best resulting models exhibited unavoidable problems which were due to limitations in our channel kinetics. We next set channel kinetics free for the optimized density matches and obtained significantly improved model performance. Some kinetic parameters consistently shifted to similar new values in multiple runs across three models, suggesting the possibility for tailored improvements to channel models. These results suggest that optimized channel kinetics can improve model matches to experimental voltage traces, particularly for channels characterized under different experimental conditions than recorded data to be matched by a model. The resulting shifts in channel kinetics from the original template provide valuable guidance for future experimental efforts to determine the detailed kinetics of channel isoforms and possible modulated states in particular types of neurons. PMID:21243419

  6. Kinetic effects on streaming instabilities in electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Shan, S. Ali; Saleem, H.

    2009-02-01

    Streaming instabilities in electron-positron-ion plasmas are investigated using kinetic approach in several different limits. The effects of the variation of background temperatures of electrons Teo and positrons Tpo on the growth rates are also presented for the case of ion beam streaming into electron-positron plasmas and positrons beam streaming into electron-ion plasmas. It is noticed that the increase of number density of positrons gives a destabilizing trend to the electrostatic perturbations in the system.

  7. Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM

    SciTech Connect

    Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, Ditte; Rusanen, A.; Boy, Michael; Swietlicki, E.; Svenningsson, Birgitta; Zelenyuk, Alla; Pagels, J.

    2014-08-11

    We have developed the novel Aerosol Dynamics, gas- and particle- phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: 1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), 2) the slow and almost particle size independent evaporation of α-pinene secondary organic aerosol (SOA) particles, and 3) the influence of chamber wall effects on the observed SOA formation in smog chambers.

  8. A computer model of particle balance in ECR ion sources

    NASA Astrophysics Data System (ADS)

    Shirkov, G. D.; Philippov, A. V.

    2008-12-01

    The investigation of the widespread model of particle balance and energy transport [1-5] for calculating the ion charge state distribution (CSD) in an electron cyclotron resonance (ECR) ion source [6] is given. The modification of this model that makes it possible to describe the confinement and accumulation processes of highly charged ions in ECR plasma for the case of gas mixing is more precisely discussed. The discussion of the new technique for calculating the time confinement of ions and electrons, which is based on the Pastukhov theory [7, 8], is given: calculation of confinement times during two step minimization of special type functionals. The preliminary results obtained with this approach have been compared with available experimental data.

  9. Measurement of secondary particle production induced by particle therapy ion beams impinging on a PMMA target

    NASA Astrophysics Data System (ADS)

    Toppi, M.; Battistoni, G.; Bellini, F.; Collamati, F.; De Lucia, E.; Durante, M.; Faccini, R.; Frallicciardi, P. M.; Marafini, M.; Mattei, I.; Morganti, S.; Muraro, S.; Paramatti, R.; Patera, V.; Pinci, D.; Piersanti, L.; Rucinski, A.; Russomando, A.; Sarti, A.; Sciubba, A.; Senzacqua, M.; Solfaroli Camillocci, E.; Traini, G.; Voena, C.

    2016-05-01

    Particle therapy is a technique that uses accelerated charged ions for cancer treatment and combines a high irradiation precision with a high biological effectiveness in killing tumor cells [1]. Informations about the secondary particles emitted in the interaction of an ion beam with the patient during a treatment can be of great interest in order to monitor the dose deposition. For this purpose an experiment at the HIT (Heidelberg Ion-Beam Therapy Center) beam facility has been performed in order to measure fluxes and emission profiles of secondary particles produced in the interaction of therapeutic beams with a PMMA target. In this contribution some preliminary results about the emission profiles and the energy spectra of the detected secondaries will be presented.

  10. Kinetics of ion and prompt electron emission from laser-produced plasma

    SciTech Connect

    Farid, N.; Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics and Optical Engineering, Dalian University of Technology, Dalian ; Harilal, S. S.; Hassanein, A.; Ding, H.

    2013-07-15

    We investigated ion emission dynamics of laser-produced plasma from several elements, comprised of metals and non-metals (C, Al, Si, Cu, Mo, Ta, W), under vacuum conditions using a Faraday cup. The estimated ion flux for various targets studied showed a decreasing tendency with increasing atomic mass. For metals, the ion flux is found to be a function of sublimation energy. A comparison of temporal ion profiles of various materials showed only high-Z elements exhibited multiple structures in the ion time of flight profile indicated by the observation of higher peak kinetic energies, which were absent for low-Z element targets. The slower ions were seen regardless of the atomic number of target material propagated with a kinetic energy of 1–5 keV, while the fast ions observed in high-Z materials possessed significantly higher energies. A systematic study of plasma properties employing fast photography, time, and space resolved optical emission spectroscopy, and electron analysis showed that there existed different mechanisms for generating ions in laser ablation plumes. The origin of high kinetic energy ions is related to prompt electron emission from high-Z targets.

  11. Kinetic Simulation and Visualization of Ion Ring Instability in Interstellar Plasma

    NASA Astrophysics Data System (ADS)

    Ernst, A. E.; Florinski, V. A.; Heerikhuisen, J.

    2015-12-01

    First observed by the Interstellar Boundary Explorer (IBEX) in 2009, the mysterious band of neutral atom flux known as the IBEX ribbon is commonly attributed to the effect of a charge exchange between energetic neutral atoms originating in the inner heliosheath and secondary pickup ions (PUIs) gyrating in rings about local galactic magnetic field lines in the outer heliosheath and interstellar space. Underpinning this theory is the assumption that the newly formed PUI ring is fairly stable relative to wave generation, an assumption that has been challenged by previous simulations of ions in the local interstellar medium (LISM). However, recent data received from Voyager 1 as it entered interstellar space indicates that the LISM is much quieter than previously thought. Using linear kinetic theory and newly developed hybrid simulation software, equipped with a binning algorithm and Python interface to VisIt for 3D visualization, we reexamine the 2010 simulation of Florinski et al., investigate other possible PUI ring distributions such as the Gauss torus, and run new large scale simulations with over a billion particles for an unprecedented reduction in numerical noise. We also simulate PUI ring stability away from the ribbon, including the direction of Voyager 1's trajectory, allowing us to compare our results with actual measurements of magnetic fluctuations in the LISM. Using these improved methods, we hope to gain new insight into the previously observed instability of PUI rings in the LISM. Preliminary results suggest that while broadened rings show very low levels of turbulence (in contrast with narrow rings of PUIs, which demonstrate abundant magnetic fluctuations at resonant frequency), some particle scattering occurred for every type of ring studied. The results of these simulations will be of critical importance to existing theories about the origins of the IBEX ribbon.

  12. The Modeling of Pickup Ion or Energetic Particle Mediated Plasmas

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; Mostafavi, P.; Hunana, P.

    2016-05-01

    Suprathermal energetic particles, such as solar energetic particles (SEPs) in the inner heliosphere and pickup ions (PUIs) in the outer heliosphere and the very local interstellar medium, often form a thermodynamically dominant component in their various environments. In the supersonic solar wind beyond > 10 AU, in the inner heliosheath (IHS), and in the very local interstellar medium (VLISM), PUIs do not equilibrate collisionally with the background plasma. Similarly, SEPs do not equilibrate collisionally with the background solar wind in the inner heliosphere. In the absence of equilibration between plasma components, a separate coupled plasma description for the energetic particles is necessary. Using a collisionless Chapman-Enskog expansion, we derive a closed system of multi-component equations for a plasma comprised of thermal protons and electrons, and suprathermal particles (SEPs, PUIs). The energetic particles contribute an isotropic scalar pressure to leading order, a collisionless heat flux at the next order, and a collisionless stress tensor at the second-order. The collisionless heat conduction and viscosity in the multi-fluid description results from a nonisotropic energetic particle distribution. A simpler single-fluid MHD-like system of equations with distinct equations of state for both the background plasma and the suprathermal particles is derived. We note briefly potential pitfalls that can emerge in the numerical modeling of collisionless plasma flows that contain a dynamically important energetic particle component.

  13. Particle Size Effect on Wetting Kinetics of a Nanosuspension Drop: MD Simulations

    NASA Astrophysics Data System (ADS)

    Shi, Baiou; Webb, Edmund

    The behavior of nano-fluids, or fluid suspensions containing nanoparticles, has garnered tremendous attention recently for applications in advanced manufacturing. In our previous results from MD simulations, for a wetting system with different advancing contact angles, cases where self-pinning was observed were compared to cases where it was not and relevant forces on particles at the contact line were computed. To advance this work, the roles of particle size and particle loading are examined. Results presented illustrate how particle size affects spreading kinetics and how this connects to dynamic droplet morphology and relevant forces that exist nearby the contact line region. Furthermore, increased particle size in simulations permits a more detailed investigation of particle/substrate interfacial contributions to behavior observed at the advancing contact line. Based on changes in spreading kinetics with particle size, forces between the particle and liquid front are predicted and compared to those computed from simulations. At high loading, particle/particle interactions become relevant and forces computed between particles entrained to an advancing contact line will be presented.

  14. The possible role of anisotropy in kinetic electronic excitation of solids by particle bombardment

    NASA Astrophysics Data System (ADS)

    Heuser, C.; Marpe, M.; Diesing, D.; Wucher, A.

    2011-06-01

    The kinetic excitation of a solid surface by impact of energetic particles is investigated by means of internal electron emission across a buried metal-insulator-metal (MIM) tunnel junction. By bombarding the top metal surface of such a device with keV noble gas ions, internal emission yields were determined as a function of projectile impact energy and angle of incidence with respect to the surface normal. In order to understand the observed impact angle dependence, we apply a modified formalism originally published to describe external electron emission. As a result, we find that the measured data can be explained by assuming the spatial distribution of excited electrons propagating towards the buried oxide interface to be strongly influenced by the projectile impact angle. A simple ballistic model assuming excited electrons generated by direct collisions with the projectile to preferably propagate along the direction of the original projectile motion, while electrons excited by scattering from moving recoils propagate isotropically, appears to describe the observed experimental data quite well.

  15. Fragmentation of water by ion impact: Kinetic energy release spectra

    SciTech Connect

    Rajput, Jyoti; Safvan, C. P.

    2011-11-15

    The fragmentation of isolated water molecules on collision with 450-keV Ar{sup 9+} has been studied using time-of-flight mass spectrometry employing multihit detection. The kinetic energy release spectrum for the dissociation of [H{sub 2}O]{sup 2+ White-Star} into (H{sup White-Star },H{sup +},O{sup +}) fragments has been measured where H{sup White-Star} is a neutral Rydberg hydrogen atom. Ab initio calculations are carried out for the lowest states of [H{sub 2}O]{sup q+} with q=2 and 3 to help interpret the kinetic energy release spectra.

  16. Particle-In-Cell/Monte Carlo Simulation of Ion Back BomBardment in a High Average Current RF Photo-Gun

    SciTech Connect

    Qiang, J.

    2009-10-17

    In this paper, we report on study of ion back bombardment in a high average current radio-frequency (RF) photo-gun using a particle-in-cell/Monte Carlo simulation method. Using this method, we systematically studied effects of gas pressure, RF frequency, RF initial phase, electric field profile, magnetic field, laser repetition rate, different ion species on ion particle line density distribution, kinetic energy spectrum, and ion power line density distribution back bombardment onto the photocathode. Those simulation results suggested that effects of ion back bombardment could increase linearly with the background gas pressure and laser repetition rate. The RF frequency has significantly affected the ion motion inside the gun so that the ion power deposition on the photocathode in an RF gun can be several orders of magnitude lower than that in a DC gun. The ion back bombardment can be minimized by appropriately choosing the electric field profile and the initial phase.

  17. Effect of wave-particle interaction on the outflow of ions at high latitudes

    NASA Technical Reports Server (NTRS)

    Barakat, Abdallah R.

    1991-01-01

    The objective of the research is to use the low-frequency wave spectrum measured by the Plasma Wave Instrument on the DE-1 spacecraft to include the wave-particle interaction (WPI) in the different polar wind models that are available at Utah State University. A Monte Carlo technique was used to simulate the ion diffusion in the velocity space due to scattering by the waves. This enabled us to study the effect of WPI on the magnitude as well as the composition of the outflow of the ionospheric ions. In particular, in the first year the 1-D semi-kinetic code developed by Barakat and Schunk (1983) was modified in order to include the effect of the WPI.

  18. Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells.

    PubMed

    Amuda, O S; Adelowo, F E; Ologunde, M O

    2009-02-01

    A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63mgCr(VI)/g at initial pH of 3.0 at 30 degrees C for the particle size of 1.00-1.25mm with the use of 12.5, 16.5 and 2.1g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater. PMID:19022632

  19. Kinetic studies of wave-particle interactions in cosmic-ray acceleration

    NASA Astrophysics Data System (ADS)

    Pohl, Martin; Niemiec, Jacek; Stroman, Thomas; Bret, Antoine; Roeken, Christian

    Shock acceleration relies on the presence of magnetic-field fluctuations that can scatter rela-tivistic charged particles in both the upstream and downstream regions of the shock. We report on kinetic particle-in-cell simulations of the non-linear evolution of magnetic turbulence that arises upstream of the shock as well as at the shock itself. We will in particular address the relation between modes seen in the simulations and waves expected on the grounds of a linear instability analysis, the efficiency of small-scale turbulence in scattering relativistic particles, and the influence of accelerated particles on the formation of the shock itself.

  20. Approximate models for the ion-kinetic regime in inertial-confinement-fusion capsule implosions

    DOE PAGESBeta

    Hoffman, Nelson M.; Zimmerman, George B.; Molvig, Kim; Rinderknecht, Hans G.; Rosenberg, Michael J.; Albright, B. J.; Simakov, Andrei N.; Sio, Hong; Zylstra, Alex B.; Johnson, Maria Gatu; et al

    2015-05-19

    “Reduced” (i.e., simplified or approximate) ion-kinetic (RIK) models in radiation-hydrodynamic simulations permit a useful description of inertial-confinement-fusion (ICF) implosions where kinetic deviations from hydrodynamic behavior are important. For implosions in or near the kinetic regime (i.e., when ion mean free paths are comparable to the capsule size), simulations using a RIK model give a detailed picture of the time- and space-dependent structure of imploding capsules, allow an assessment of the relative importance of various kinetic processes during the implosion, enable explanations of past and current observations, and permit predictions of the results of future experiments. The RIK simulation method describedmore » here uses moment-based reduced kinetic models for transport of mass, momentum, and energy by long-mean-free-path ions, a model for the decrease of fusion reactivity owing to the associated modification of the ion distribution function, and a model of hydrodynamic turbulent mixing. The transport models are based on local gradient-diffusion approximations for the transport of moments of the ion distribution functions, with coefficients to impose flux limiting or account for transport modification. After calibration against a reference set of ICF implosions spanning the hydrodynamic-to-kinetic transition, the method has useful, quantifiable predictive ability over a broad range of capsule parameter space. Calibrated RIK simulations show that an important contributor to ion species separation in ICF capsule implosions is the preferential flux of longer-mean-free-path species out of the fuel and into the shell, leaving the fuel relatively enriched in species with shorter mean free paths. Also, the transport of ion thermal energy is enhanced in the kinetic regime, causing the fuel region to have a more uniform, lower ion temperature, extending over a larger volume, than implied by clean simulations. We expect that the success of our simple

  1. Approximate models for the ion-kinetic regime in inertial-confinement-fusion capsule implosions

    SciTech Connect

    Hoffman, Nelson M.; Zimmerman, George B.; Molvig, Kim; Rinderknecht, Hans G.; Rosenberg, Michael J.; Albright, B. J.; Simakov, Andrei N.; Sio, Hong; Zylstra, Alex B.; Johnson, Maria Gatu; Séguin, Fredrick H.; Frenje, Johan A.; Li, C. K.; Petrasso, Richard D.; Higdon, David M.; Srinivasan, Gowri; Glebov, Vladimir Yu.; Stoeckl, Christian; Seka, Wolf; Sangster, T. Craig

    2015-05-19

    “Reduced” (i.e., simplified or approximate) ion-kinetic (RIK) models in radiation-hydrodynamic simulations permit a useful description of inertial-confinement-fusion (ICF) implosions where kinetic deviations from hydrodynamic behavior are important. For implosions in or near the kinetic regime (i.e., when ion mean free paths are comparable to the capsule size), simulations using a RIK model give a detailed picture of the time- and space-dependent structure of imploding capsules, allow an assessment of the relative importance of various kinetic processes during the implosion, enable explanations of past and current observations, and permit predictions of the results of future experiments. The RIK simulation method described here uses moment-based reduced kinetic models for transport of mass, momentum, and energy by long-mean-free-path ions, a model for the decrease of fusion reactivity owing to the associated modification of the ion distribution function, and a model of hydrodynamic turbulent mixing. The transport models are based on local gradient-diffusion approximations for the transport of moments of the ion distribution functions, with coefficients to impose flux limiting or account for transport modification. After calibration against a reference set of ICF implosions spanning the hydrodynamic-to-kinetic transition, the method has useful, quantifiable predictive ability over a broad range of capsule parameter space. Calibrated RIK simulations show that an important contributor to ion species separation in ICF capsule implosions is the preferential flux of longer-mean-free-path species out of the fuel and into the shell, leaving the fuel relatively enriched in species with shorter mean free paths. Also, the transport of ion thermal energy is enhanced in the kinetic regime, causing the fuel region to have a more uniform, lower ion temperature, extending over a larger volume, than implied by clean simulations. We expect that the success of our simple approach

  2. Approximate models for the ion-kinetic regime in inertial-confinement-fusion capsule implosions

    NASA Astrophysics Data System (ADS)

    Hoffman, Nelson M.; Zimmerman, George B.; Molvig, Kim; Rinderknecht, Hans G.; Rosenberg, Michael J.; Albright, B. J.; Simakov, Andrei N.; Sio, Hong; Zylstra, Alex B.; Gatu Johnson, Maria; Séguin, Fredrick H.; Frenje, Johan A.; Li, C. K.; Petrasso, Richard D.; Higdon, David M.; Srinivasan, Gowri; Glebov, Vladimir Yu.; Stoeckl, Christian; Seka, Wolf; Sangster, T. Craig

    2015-05-01

    "Reduced" (i.e., simplified or approximate) ion-kinetic (RIK) models in radiation-hydrodynamic simulations permit a useful description of inertial-confinement-fusion (ICF) implosions where kinetic deviations from hydrodynamic behavior are important. For implosions in or near the kinetic regime (i.e., when ion mean free paths are comparable to the capsule size), simulations using a RIK model give a detailed picture of the time- and space-dependent structure of imploding capsules, allow an assessment of the relative importance of various kinetic processes during the implosion, enable explanations of past and current observations, and permit predictions of the results of future experiments. The RIK simulation method described here uses moment-based reduced kinetic models for transport of mass, momentum, and energy by long-mean-free-path ions, a model for the decrease of fusion reactivity owing to the associated modification of the ion distribution function, and a model of hydrodynamic turbulent mixing. The transport models are based on local gradient-diffusion approximations for the transport of moments of the ion distribution functions, with coefficients to impose flux limiting or account for transport modification. After calibration against a reference set of ICF implosions spanning the hydrodynamic-to-kinetic transition, the method has useful, quantifiable predictive ability over a broad range of capsule parameter space. Calibrated RIK simulations show that an important contributor to ion species separation in ICF capsule implosions is the preferential flux of longer-mean-free-path species out of the fuel and into the shell, leaving the fuel relatively enriched in species with shorter mean free paths. Also, the transport of ion thermal energy is enhanced in the kinetic regime, causing the fuel region to have a more uniform, lower ion temperature, extending over a larger volume, than implied by clean simulations. We expect that the success of our simple approach

  3. Measurement Of Kinetic Energy Distribution Of Positive Ions From Electron Induced Dissociation Of Pyrimidine Molecule

    NASA Astrophysics Data System (ADS)

    Milosavljevic, A. R.; Maljkovic, J. B.; Sevic, D.; Cadez, I.; Marinkovic, B. P.

    2010-07-01

    We report preliminary results on measurements of kinetic energy distribution of positive ions formed upon electron induced dissociative ionization of gaseous pyrimidine molecule (C4H4N2). The kinetic energy spectra were recorded without precedent mass/charge analysis, for different incident electron energies (50-250 eV) and different detection angles (40-90) with respect to the incident beam direction. An influence of the residual gas background to the recorded distributions has been investigated.

  4. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    NASA Astrophysics Data System (ADS)

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2016-07-01

    The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me . The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where k →.B → =0 , consistent with previous analytical and simulation studies. Here, B → is the equilibrium magnetic field and k → is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at k →.B → ≠0 . In addition, the simulation results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.

  5. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    DOE PAGESBeta

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2016-07-07

    The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and simulation studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the simulation results indicate that varying mi/me, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.« less

  6. Sheath and presheath in ion-ion plasmas via particle-in-cell simulation

    SciTech Connect

    Meige, A.; Leray, G.; Raimbault, J.-L.; Chabert, P.

    2008-02-11

    A full particle-in-cell simulation is developed to investigate electron-free plasmas constituted of positive and negative ions under the influence of a dc bias voltage. It is shown that high-voltage sheaths following the classical Child-law sheaths form within a few microseconds (which corresponds to the ion transit time) after the dc voltage is applied. It is also shown that there exists the equivalent of a Bohm criterion where a presheath accelerates the ions collected at one of the electrodes up to the sound speed before they enter the sheath. From an applied perspective, this leads to smaller sheaths than one would expect.

  7. Ion-counting nanodosemeter with particle tracking capabilities.

    PubMed

    Bashkirov, V; Schulte, R; Breskin, A; Chechik, R; Schemelinin, S; Garty, G; Wroe, A; Sadrozinski, H; Grosswendt, B

    2006-01-01

    An ion-counting nanodosemeter (ND) yielding the distribution of radiation-induced ions in a low-pressure gas within a millimetric, wall-less sensitive volume (SV) was equipped with a silicon microstrip telescope that tracks the primary particles, allowing correlation of nanodosimetric data with particle position relative to the SV. The performance of this tracking ND was tested with a broad 250 MeV proton beam at Loma Linda University Medical Center. The high-resolution tracking capability made it possible to map the ion registration efficiency distribution within the SV, for which only calculated data were available before. It was shown that tracking information combined with nanodosimetric data can map the ionisation pattern of track segments within 150 nm-equivalent long SVs with a longitudinal resolution of approximately 5 tissue-equivalent nanometers. Data acquired in this work were compared with results of Monte Carlo track structure simulations. The good agreement between 'tracking nanodosimetry' data acquired with the new system and simulated data supports the application of ion-counting nanodosimetry in experimental track-structure studies. PMID:17283009

  8. Absorption of calcium ions on oxidized graphene sheets and study its dynamic behavior by kinetic and isothermal models

    NASA Astrophysics Data System (ADS)

    Fathy, Mahmoud; Abdel Moghny, Th.; Mousa, Mahmoud Ahmed; El-Bellihi, Abdel-Hameed A.-A.; Awadallah, Ahmed E.

    2016-07-01

    Sorption of calcium ion from the hard underground water using novel oxidized graphene (GO) sheets was studied in this paper. Physicochemical properties and microstructure of graphene sheets were investigated using Raman spectrometer, thermogravimetry analyzer, transmission electron microscope, scanning electron microscope. The kinetics adsorption of calcium on graphene oxide sheets was examined using Lagergren first and second orders. The results show that the Lagergren second-order was the best-fit model that suggests the conception process of calcium ion adsorption on the Go sheets. For isothermal studies, the Langmuir and Freundlich isotherm models were used at temperatures ranging between 283 and 313 K. Thermodynamic parameters resolved at 283, 298 and 313 K indicating that the GO adsorption was exothermic spontaneous process. Finally, the graphene sheets show high partiality toward calcium particles and it will be useful in softening and treatment of hard water.

  9. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    Examination of the exact analytic solution of a kinetic model of collisional interaction of ionospheric fions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, shows that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a nonMaxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

  10. Kinetic pathways of ion pair dissociation in water

    SciTech Connect

    Geissler, P.L.; Dellago, C.; Chandler, D.

    1999-05-06

    The authors have successfully applied the transition path sampling method to the deterministic dynamics of a many-body system with long-ranged interactions. The process they investigate, dissociation of a model Na{sup +}Cl{sup {minus}} ion pair in water, involves a wide range of transition pathways in which collective solvent motions play an important role. Transition states along these pathways encompass a broad distribution of ionic separations. Ion pairs in contact remain associated for {approximately}20 ps on average, a time scale considerably longer than the {approximately}3ps predicted by transition state theory with ionic separation as the order parameter. In contrast to theories of barrier crossing based upon frictional effects (with or without memory), the authors find that the discrepancy between these time scales arises from neglected solvent free energy barriers rather than stochastic buffeting of the ion pair.

  11. A new setup for the investigation of swift heavy ion induced particle emission and surface modifications.

    PubMed

    Meinerzhagen, F; Breuer, L; Bukowska, H; Bender, M; Severin, D; Herder, M; Lebius, H; Schleberger, M; Wucher, A

    2016-01-01

    The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator. PMID:26827329

  12. A new setup for the investigation of swift heavy ion induced particle emission and surface modifications

    NASA Astrophysics Data System (ADS)

    Meinerzhagen, F.; Breuer, L.; Bukowska, H.; Bender, M.; Severin, D.; Herder, M.; Lebius, H.; Schleberger, M.; Wucher, A.

    2016-01-01

    The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator.

  13. Influence of radioactivity on surface charging and aggregation kinetics of particles in the atmosphere.

    PubMed

    Kim, Yong-Ha; Yiacoumi, Sotira; Lee, Ida; McFarlane, Joanna; Tsouris, Costas

    2014-01-01

    Radioactivity can influence surface interactions, but its effects on particle aggregation kinetics have not been included in transport modeling of radioactive particles. In this research, experimental and theoretical studies have been performed to investigate the influence of radioactivity on surface charging and aggregation kinetics of radioactive particles in the atmosphere. Radioactivity-induced charging mechanisms have been investigated at the microscopic level, and heterogeneous surface potential caused by radioactivity is reported. The radioactivity-induced surface charging is highly influenced by several parameters, such as rate and type of radioactive decay. A population balance model, including interparticle forces, has been employed to study the effects of radioactivity on particle aggregation kinetics in air. It has been found that radioactivity can hinder aggregation of particles because of similar surface charging caused by the decay process. Experimental and theoretical studies provide useful insights into the understanding of transport characteristics of radioactive particles emitted from severe nuclear events, such as the recent accident of Fukushima or deliberate explosions of radiological devices. PMID:24308778

  14. A Kinetic Model of Acceleration and Heating of Coronal Hole Minor Ions

    SciTech Connect

    Isenberg, Philip A.; Vasquez, Bernard J.

    2008-08-25

    The specific microphysical mechanism which generates the fast solar wind in collisionless coronal holes is still not known. Observations show that the wind results from strong ion heating perpendicular to the magnetic field which starts at the very bottom of the corona. A major clue toward identifying the responsible mechanism is that it preferentially heats the heavy ions relative to the protons. Since this preferential heating occurs at heights where ion collisions are no longer effective, a kinetic treatment is necessary to understand and test any candidate mechanisms. We describe the current state of a kinetic model we are constructing which will test the preferential heating due to the resonant cyclotron interaction with parallel-propagating ion cyclotron waves.

  15. Particle kinetic simulation of high altitude hypervelocity flight

    NASA Technical Reports Server (NTRS)

    Heinemann, Klaus; Boyd, Iain D.; Haas, Brian L.

    1993-01-01

    In this grant period, the focus has been on the effects of thermo-chemical nonequilibrium in low-density gases, and on interactions between such gases and solid surfaces. Such conditions apply to hypersonic flows of re-entry vehicles, and to the expansion plumes of small rockets. Due to the nonequilibrium nature of these flows, a particle approach has been adopted. The method continues to undergo refinement and application to typical flows of interest. A number of studies have been performed for flows in thermo-chemical nonequilibrium. The effects of vibrational nonequilibrium on the rate of dissociation were studied for diatomic nitrogen. It was found that a new model reproduced the nonequilibrium behavior observed experimentally.

  16. GREEN'S Function and Super-Particle Methods for Kinetic Simulation of Heteroepitaxy

    NASA Astrophysics Data System (ADS)

    Lam, Chi-Hang; Lung, M. T.

    Arrays of nanosized three dimensional islands are known to self-assemble spontaneously on strained heteroepitaxial thin films. We simulate the dynamics using kinetic Monte Carlo method based on a ball and spring lattice model. Green's function and super-particle methods which greatly enhance the computational efficiency are explained.

  17. Fundamental equations of a mixture of gas and small spherical solid particles from simple kinetic theory.

    NASA Technical Reports Server (NTRS)

    Pai, S. I.

    1973-01-01

    The fundamental equations of a mixture of a gas and pseudofluid of small spherical solid particles are derived from the Boltzmann equation of two-fluid theory. The distribution function of the gas molecules is defined in the same manner as in the ordinary kinetic theory of gases, but the distribution function for the solid particles is different from that of the gas molecules, because it is necessary to take into account the different size and physical properties of solid particles. In the proposed simple kinetic theory, two additional parameters are introduced: one is the radius of the spheres and the other is the instantaneous temperature of the solid particles in the distribution of the solid particles. The Boltzmann equation for each species of the mixture is formally written, and the transfer equations of these Boltzmann equations are derived and compared to the well-known fundamental equations of the mixture of a gas and small solid particles from continuum theory. The equations obtained reveal some insight into various terms in the fundamental equations. For instance, the partial pressure of the pseudofluid of solid particles is not negligible if the volume fraction of solid particles is not negligible as in the case of lunar ash flow.

  18. Micromechanical Modeling of Storage Particles in Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Purkayastha, Rajlakshmi Tarun

    The effect of stress on storage particles within a lithium ion battery, while acknowledged, is not understood very well. In this work three non-dimensional parameters were identified which govern the stress response within a spherical storage particle. These parameters are developed using material properties such as the diffusion coefficient, particle radius, partial molar volume and Young's modulus. Stress maps are then generated for various values of these parameters for fixed rates of insertion, applying boundary conditions similar to those found in a battery. Stress and concentration profiles for various values of these parameters show the coupling between stress and concentration is magnified depending on the values of the parameters. These maps can be used for different materials, depending on the value of the dimensionless parameters. The value of maximum stress generated is calculated for extraction as well as insertion of lithium into the particle. The model was then used to study to ellipsoidal particles in order to ascertain the effect of geometry on the maximum stress within the particle. By performing a parameter study, we can identify those materials for which particular aspect ratios of ellipsoids are more beneficial, in terms of reducing stress. We find that the stress peaks at certain aspect ratios, mostly at 2 and 1/ 2 . A parameter study was also performed on cubic particle. The values of maximum stresses for both insertion and extraction of lithium were plotted as contour plots. It was seen that the material parameters influenced the location of the maximum stress, with the maximum stress occurring either at the center of the edge between two faces or the point at the center of a face. Newer materials such as silicon are being touted as new lithium storage materials for batteries due to their higher capacity. Their tendency to rapidly loose capacity in a short period of time has led to a variety designs such are the use of carbon nanotubes or

  19. Kinetic study of ion acoustic twisted waves with kappa distributed electrons

    NASA Astrophysics Data System (ADS)

    Arshad, Kashif; Aman-ur-Rehman, Mahmood, Shahzad

    2016-05-01

    The kinetic theory of Landau damping of ion acoustic twisted modes is developed in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons and Maxwellian ions. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the ion acoustic twisted waves in a non-thermal plasma. The strong damping effects of ion acoustic twisted waves at low values of temperature ratio of electrons and ions are also obtained by using exact numerical method and illustrated graphically, where the weak damping wave theory fails to explain the phenomenon properly. The obtained results of Landau damping rates of the twisted ion acoustic wave are discussed at different values of azimuthal wave number and non-thermal parameter kappa for electrons.

  20. Acute toxicity and accumulation of ZnO NPs in Ceriodaphnia dubia: Relative contributions of dissolved ions and particles.

    PubMed

    Bhuvaneshwari, M; Iswarya, V; Nagarajan, R; Chandrasekaran, N; Mukherjee, Amitava

    2016-08-01

    Although the ecotoxicological effects of various metal oxide nanoparticles on aquatic organisms are being actively studied, the contributions of particles and dissolved ions towards toxicity are still not well understood. The current study aims to assess the contribution of ZnO NP(particle) and ZnO NP(ion) to the overall toxicity and accumulation of ZnO NP(total) in Ceriodaphnia dubia. The aggregation and dissolution kinetics were studied for three different sizes (50nm, 100nm and bulk) of ZnO particles at 0.05, 0.12, 0.25 and 0.5mg/L concentrations in the sterile lake water medium at 6, 12, 24, and 48h intervals. The 48h LC50 of ZnO NP(total) was found to be 0.431, 0.605 and 0.701mg/L for 50, 100nm and bulk particles exposure. However, LC50 of Zn(ion) was found to be 1.048, 1.343 and 2.046mg/L for dissolved ions from different sizes (50nm, 100nm, and bulk) of ZnO particles. At LC50 concentration, the accumulation of 90-95% was noted for the NP(particles) across the sizes employed, while only about 4-5% contribution was from the NP(ion) to the overall accumulation NP(total). The relative contribution of ZnO NP(ion) to overall toxicity and accumulation was found to be lesser than that of ZnO NP(particles) across the sizes used in the study. PMID:27424101

  1. Kinetics of aggregation in non-Brownian magnetic particle dispersions in the presence of perturbations

    NASA Astrophysics Data System (ADS)

    Donado, F.; Sandoval, U.; Carrillo, J. L.

    2009-01-01

    An experimental and theoretical study on the kinetics of the aggregation process of magnetic particles dispersed in mineral oils is presented. A static magnetic field and an oscillating magnetic perturbation are applied on the dispersion. In the low-particle concentrations, the effects on the aggregation of the frequency, the concentration of particles and the viscosity of the liquid are analyzed. It was found that the behavior of the cluster length as a function of the main control parameters can be accurately characterized by scaling relations. The physical characteristics of the aggregates are discussed in relation to measurements of viscosity as a function of time.

  2. Measurement of ion cascade energies through resolution degradation of alpha particle microcalorimeters

    SciTech Connect

    Horansky, Robert D.; Stiehl, Gregory M.; Beall, James A.; Irwin, Kent D.; Ullom, Joel N.; Plionis, Alexander A.; Rabin, Michael W.

    2010-02-15

    Atomic cascades caused by ions impinging on bulk materials have remained of interest to the scientific community since their discovery by Goldstein in 1902. While considerable effort has been spent describing and, more recently, simulating these cascades, tools that can study individual events are lacking and several aspects of cascade behavior remain poorly known. These aspects include the material energies that determine cascade magnitude and the variation between cascades produced by monoenergetic ions. We have recently developed an alpha particle detector with a thermodynamic resolution near 100 eV full-width-at-half-maximum (FWHM) and an achieved resolution of 1.06 keV FWHM for 5.3 MeV particles. The detector relies on the absorption of particles by a bulk material and a thermal change in a superconducting thermometer. The achieved resolution of this detector provides the highest resolving power of any energy dispersive technique and a factor of 8 improvement over semiconductor detectors. The exquisite resolution can be directly applied to improved measurements of fundamental nuclear decays and nuclear forensics. In addition, we propose that the discrepancy between the thermodynamic and achieved resolution is due to fluctuations in lattice damage caused by ion-induced cascades in the absorber. Hence, this new detector is capable of measuring the kinetic energy converted to lattice damage in individual atomic cascades. This capability allows new measurements of cascade dynamics; for example, we find that the ubiquitous modeling program, SRIM, significantly underestimates the lattice damage caused in bulk tin by 5.3 MeV alpha particles.

  3. Kinetics of the Reduction of Metalloproteins by Chromous Ion

    PubMed Central

    Dawson, J. W.; Gray, H. B.; Holwerda, R. A.; Westhead, E. W.

    1972-01-01

    The reduction of Cu(330) in Rhus vernicifera laccase by chromous ion is 30% faster than reduction of Cu(614) at room temperature [pH 4.8, μ = 0.1 (NaCl)], and two parallel first-order paths, attributed to heterogeneity of the protein, are observed at both wavelengths. The reactions of stellacyanin, spinach and French-bean plastocyanins, and cytochrome c with chromous ion under similar conditions are faster than that with laccase by factors of 102 to 104, and are first order in protein concentration. Comparison of rates and activation parameters for the reduction of “blue” copper in laccase, stellacyanin, and the two plastocyanins indicates that reduction of the Cu(614) site in laccase may occur by intramolecular electron transfer from one of the Cu(330) sites. Our value of ΔH‡ (17.4 kcal/mol) for the chromous ion reduction of cytochrome c is consistent with a mechanism in which major conformational changes in the protein must accompany electron transfer. PMID:4500552

  4. Crystal-amorphous-silicon interface kinetics under ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Priolo, F.; La Ferla, A.; Spinella, C.; Rimini, E.; Campisano, S. U.; Ferla, G.

    1990-01-01

    Our recent work on ion-beam-assisted epitaxial growth of amorphous Si layers on single crystal substrates is reviewed. The crystallization was induced by a 600 keV Kr2+ beam at a dose rate of 1×1012/cm2 · s. During irradiations the samples were mounted on a resistively heated copper block whose temperature was maintained constant in the range 250-450°C. The planar motion of the crystal-amorphous interface was monitored in situ by dynamic reflectivity measurements. This technique allows the ion-induced growth rate to be measured with a very high precision. We have observed that this growth rate scales linearly with the energy deposited into elastic collisions at the crystal-amorphous interface by the impinging ions. Moreover, the rate shows an Arrhenius temperature dependence with a well defined activation energy of 0.32±0.05 eV. The dependence of this process on substrate orientation and on impurities either dissolved in the amorphous layer or present at very high concentration at the crystal-amorphous interface is also discussed.

  5. Crystal-amorphous-silicon interface kinetics under ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Priolo, F.; La Ferla, A.; Spinella, C.; Rimini, E.; Campisano, S. U.; Ferla, G.

    1989-11-01

    Our recent work on ion-beam-assisted epitaxial growth of amorphous Si layers on single crystal substrates is reviewed. The crystallization was induced by a 600 keV Kr 2+ beam at a dose rate of 1×10 12/cm 2 · s. During irradiations the samples were mounted on a resistively heated copper block whose temperature was maintained constant in the range 250-450°C. The planar motion of the crystal-amorphous interface was monitored in situ by dynamic reflectivity measurements. This technique allows the ion-induced growth rate to be measured with a very high precision. We have observed that this growth rate scales linearly with the energy deposited into elastic collisions at the crystal-amorphous interface by the impinging ions. Moreover, the rate shows an Arrhenius temperature dependence with a well defined activation energy of 0.32±0.05 eV. The dependence of this process on substrate orientation and on impurities either dissolved in the amorphous layer or present at very high concentration at the crystal-amorphous interface is also discussed.

  6. Particle-production mechanism in relativistic heavy-ion collisions

    SciTech Connect

    Bush, B.W.; Nix, J.R.

    1994-07-01

    We discuss the production of particles in relativistic heavy-ion collisions through the mechanism of massive bremsstrahlung, in which massive mesons are emitted during rapid nucleon acceleration. This mechanism is described within the framework of classical hadrodynamics for extended nucleons, corresponding to nucleons of finite size interacting with massive meson fields. This new theory provides a natural covariant microscopic approach to relativistic heavy-ion collisions that includes automatically spacetime nonlocality and retardation, nonequilibrium phenomena, interactions among all nucleons, and particle production. Inclusion of the finite nucleon size cures the difficulties with preacceleration and runaway solutions that have plagued the classical theory of self-interacting point particles. For the soft reactions that dominate nucleon-nucleon collisions, a significant fraction of the incident center-of-mass energy is radiated through massive bremsstrahlung. In the present version of the theory, this radiated energy is in the form of neutral scalar ({sigma}) and neutral vector ({omega}) mesons, which subsequently decay primarily into pions with some photons also. Additional meson fields that are known to be important from nucleon-nucleon scattering experiments should be incorporated in the future, in which case the radiated energy would also contain isovector pseudoscalar ({pi}{sup +}, {pi}{sup {minus}}, {pi}{sup 0}), isovector scalar ({delta}{sup +}, {delta}{sup {minus}}, {delta}{sup 0}), isovector vector ({rho}{sup +}, {rho}{sup {minus}}, {rho}{sup 0}), and neutral pseudoscalar ({eta}) mesons.

  7. Deposition characteristics of copper particles on roughened substrates through kinetic spraying

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Bae, Gyuyeol; Lee, Changhee

    2009-01-01

    In this paper, a systematic study of copper particle deposition behavior on polished and roughened surfaces (aluminum and copper) in kinetic spray process has been performed. The particle deformation behavior was simulated through finite element analysis (FEA) software ABAQUS explicit 6.7-2. The particle-substrate contact time, contact temperature and contact area upon impact have been estimated for smooth and three different roughened substrate cases. Copper powders were deposited on smooth and grit-blasted copper and aluminium substrates and characterized through scanning electron microscopy and Romulus bond strength analyzer. The results indicate that the deformation and the resultant bonding were higher for the roughened substrates than that of smooth. The characteristic factors for bonding are reported and discussed. Thus the substrate roughness appears to be beneficial for the initial deposition efficiency of the kinetic spray process.

  8. Nucleation pathway and kinetics of phase-separating active Brownian particles.

    PubMed

    Richard, David; Löwen, Hartmut; Speck, Thomas

    2016-06-28

    Suspensions of purely repulsive but self-propelled Brownian particles might undergo phase separation, a phenomenon that strongly resembles the phase separation of passive particles with attractions. Here we employ computer simulations to study the nucleation kinetics and the microscopic pathway active Brownian disks take in two dimensions when quenched from the homogeneous suspension to propulsion speeds beyond the binodal. We find the same qualitative behavior for the nucleation rate as a function of density as for a passive suspension undergoing liquid-vapor separation, suggesting that the scenario of an effective free energy also extends to the kinetics of phase separation. We study the transition in more detail through a committor analysis and find that transition states are best described by a combination of cluster size and the radial polarization of particles in the cluster. PMID:27126952

  9. Enantioselective Selenocyclization via Dynamic Kinetic Resolution of Seleniranium Ions by Hydrogen-Bond Donor Catalysts

    PubMed Central

    2015-01-01

    Highly enantioselective selenocyclization reactions are promoted by the combination of a new chiral squaramide catalyst, a mineral acid, and an achiral Lewis base. Mechanistic studies reveal that the enantioselectivity originates from the dynamic kinetic resolution of seleniranium ions through anion-binding catalysis. PMID:25380129

  10. 3-D Full-kinetic Simulations of the Solar Wind Interaction with Lunar Magnetic Anomalies: Particle Behaviour

    NASA Astrophysics Data System (ADS)

    Deca, J.; Divin, A. V.; Wang, X.; Lembege, B.; Markidis, S.; Lapenta, G.; Horanyi, M.

    2015-12-01

    We present three-dimensional full-kinetic electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier MHD and hybrid simulations, the full-kinetic nature of iPic3D allows to self-consistently investigate space charge effects, and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe the general mechanism of the interaction of both a horizontal and vertical dipole model embedded just below the lunar surface focussing on the ion and electron kinetic behaviour of the system. It is shown that the configurations are largely dominated by electron motion, because the LMA scale size is small with respect to the gyro-radius of the solar wind ions. The formation of mini-magnetospheres is an electrostatic effect. Additionally, we discuss typical particle trajectories as well as complete particle distribution functions covering thermal and suprathermal energies, within the interaction region and on viable spacecraft altitudes. Our work opens new frontiers of research toward a deeper understanding of LMAs and is ideally suited to be compared with field or particle observations from spacecraft such as Kaguya (SELENE), Lunar Prospector or ARTEMIS. The ability to evaluate the implications for future lunar exploration as well as lunar science in general hinges on a better understanding of LMAs.This research has received funding from the European Commission's FP7 Program with the grant agreement EHEROES (project 284461, www.eheroes.eu). The simulations were conducted on the computational resources provided by the PRACE Tier-0 project 2013091928 (SuperMUC). This research was supported by the Swedish National Space Board

  11. Particle kinetic simulation of high altitude hypervelocity flight

    NASA Technical Reports Server (NTRS)

    Haas, Brian L.

    1993-01-01

    In this grant period, the focus has been on enhancement and application of the direct simulation Monte Carlo (DSMC) particle method for computing hypersonic flows of re-entry vehicles. Enhancement efforts dealt with modeling gas-gas interactions for thermal non-equilibrium relaxation processes and gas-surface interactions for prediction of vehicle surface temperatures. Both are important for application to problems of engineering interest. The code was employed in a parametric study to improve future applications, and in simulations of aeropass maneuvers in support of the Magellan mission. Detailed comparisons between continuum models for internal energy relaxation and DSMC models reveals that several discrepancies exist. These include definitions of relaxation parameters and the methodologies for implementing them in DSMC codes. These issues were clarified and all differences were rectified in a paper (Appendix A) submitted to Physics of Fluids A, featuring several key figures in the DSMC community as co-authors and B. Haas as first author. This material will be presented at the Fluid Dynamics meeting of the American Physical Society on November 21, 1993. The aerodynamics of space vehicles in highly rarefied flows are very sensitive to the vehicle surface temperatures. Rather than require prescribed temperature estimates for spacecraft as is typically done in DSMC methods, a new technique was developed which couples the dynamic surface heat transfer characteristics into the DSMC flow simulation code to compute surface temperatures directly. This model, when applied to thin planar bodies such as solar panels, was described in AIAA Paper No. 93-2765 (Appendix B) and was presented at the Thermophysics Conference in July 1993. The paper has been submitted to the Journal of Thermophysics and Heat Transfer. Application of the DSMC method to problems of practical interest requires a trade off between solution accuracy and computational expense and limitations. A

  12. The composition of heavy ions in solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Fan, C. Y.; Gloeckler, G.; Hovestadt, D.

    1983-01-01

    Recent advances in determining the elemental, charge state, and isotopic composition of or approximate to 1 to or approximate to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations. Average values of relative abundances measured in a large number of SEP events were found to be roughly energy independent in the approx. 1 to approx. 20 MeV per nucleon range, and showed a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs revealed the surprisingly common presence of energetic He(+) along with heavy ion with typically coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events showed these to be consistent with the universal composition except for the puzzling overabundance of the SEP(22)Ne/(20)Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of (3)He rich, heavy ion rich and carbon poor SEP events, along with direct measurements of the ionization states of SEPs provided essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production.

  13. The composition of heavy ions in solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Fan, C. Y.; Gloeckler, G.; Hovestadt, D.

    1984-01-01

    Recent advances in determining the elemental, charge state, and isotopic composition of or approximate to 1 to or approximate to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations. Average values of relative abundances measured in a large number of SEP events were found to be roughly energy independent in the approx. 1 to approx. 20 MeV per nucleon range, and showed a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs revealed the surprisingly common presence of energetic He(+) along with heavy ion with typically coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events showed these to be consistent with the universal composition except for the puzzling overabundance of the SEP(22)Ne/(20)Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of (3)He rich, heavy ion rich and carbon poor SEP events, along with direct measurements of the ionization states of SEPs provided essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production. Previously announced in STAR as N83-20886

  14. The Effects of Ion heating in Martian Magnetic Crustal Fields: Particle Tracing and Ion Distributions

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.

    2014-12-01

    Ion heating is a process that may allow low energy ions within the Martian ionosphere to be accelerated and escape. Ion heating can be especially efficient if the ions stay in the heating region for long time durations. With this in mind, the magnetic crustal field regions on Mars are particularly interesting. We focus on ions present within these regions, where changes in magnetic field strength and direction can heat these ions. Since crustal magnetic fields can maintain a trapped particle population it is unclear how efficiently plasma can be built up that can later escape to space. We investigate here two drivers: rotation of the planet and the solar wind pressure. As crustal fields rotate from the wake of the planet to the sub solar point and back, they experience compression and expansion over time scales of ~24 hours. The solar wind pressure on the other hand can cause variations over much shorter time scales (minutes). The effect of these two drivers using a particle tracing simulation that solves the Lorentz force is presented. O+ ions are seeded within the simulation box. The magnetic environment is a linear sum of a dipole field and a solar wind magnetic field. The dipole field represents the magnetic crustal field and the dipole strength is chosen to be consistent with MGS magnetometer observations of Martian crustal field regions. By increasing the solar wind strength the magnetic dipole is compressed. Decreasing solar wind strength allows the dipole to expand. Small magnitude, short time scale variations can be imposed over the top of this larger variation to represent short time scale solar wind variations. Since the purpose of this analysis is to understand the changes of the ion distribution inside the crustal field, simplistic assumptions of the field outside the crustal field can be made. Initial results are presented, with the focus on two main questions: (a) can low energy ions be heated and escape the closed dipole field lines as a result of

  15. Kinetic and Potential Sputtering of Lunar Regolith: Contribution of Solar-Wind Heavy Ions

    NASA Technical Reports Server (NTRS)

    Meyer, F. W.; Harris, P. R.; Meyer, H. M., III; Hijiazi, H.; Barghouty, A. F.

    2013-01-01

    Sputtering of lunar regolith by protons as well as solar-wind heavy ions is considered. From preliminary measurements of H+, Ar+1, Ar+6 and Ar+9 ion sputtering of JSC-1A AGGL lunar regolith simulant at solar wind velocities, and TRIM simulations of kinetic sputtering yields, the relative contributions of kinetic and potential sputtering contributions are estimated. An 80-fold enhancement of oxygen sputtering by Ar+ over same-velocity H+, and an additional x2 increase for Ar+9 over same-velocity Ar+ was measured. This enhancement persisted to the maximum fluences investigated is approximately 1016/cm (exp2). Modeling studies including the enhanced oxygen ejection by potential sputtering due to the minority heavy ion multicharged ion solar wind component, and the kinetic sputtering contribution of all solar wind constituents, as determined from TRIM sputtering simulations, indicate an overall 35% reduction of near-surface oxygen abundance. XPS analyses of simulant samples exposed to singly and multicharged Ar ions show the characteristic signature of reduced (metallic) Fe, consistent with the preferential ejection of oxygen atoms that can occur in potential sputtering of some metal oxides.

  16. Kinetic and potential sputtering of lunar regolith: The contribution of the heavy (minority) solar wind ions

    NASA Astrophysics Data System (ADS)

    Meyer, F. W.; Harris, P. R.; Meyer, H. M., III; Hijazi, H.; Barghouty, A. F.

    2013-06-01

    In this paper the sputtering of lunar regolith by protons and solar wind heavy ions is considered. From preliminary measurements of H+, Ar+1, Ar+6 and Ar+9 ion sputtering of JSC-1A AGGL lunar regolith simulant at solar wind velocities, and TRIM simulations of kinetic sputtering yields, the relative contributions of kinetic and potential sputtering contributions are estimated. An 80-fold enhancement of oxygen sputtering by Ar+ over same-velocity H+, and an additional x2 increase for Ar+9 over same-velocity Ar+ was measured. This enhancement persisted to the maximum fluences investigated (~1016/cm2). Modeling studies including the enhanced oxygen ejection by potential sputtering due to the minority heavy ion multicharged ion solar wind component, and the kinetic sputtering contribution of all solar wind constituents, as determined from TRIM sputtering simulations, indicate an overall 35% reduction of near-surface oxygen abundance. XPS analyses of simulant samples exposed to singly and multicharged Ar ions show the characteristic signature of reduced (metallic) Fe, consistent with the preferential ejection of oxygen atoms that can occur in potential sputtering of some metal oxides.

  17. Analogue of cosmological particle creation in an ion trap.

    PubMed

    Schützhold, Ralf; Uhlmann, Michael; Petersen, Lutz; Schmitz, Hector; Friedenauer, Axel; Schätz, Tobias

    2007-11-16

    We study phonons in a dynamical chain of ions confined by a trap with a time-dependent (axial) potential strength and demonstrate that they behave in the same way as quantum fields in an expanding or contracting Universe. Based on this analogy, we present a scheme for the detection of the analogue of cosmological particle creation which should be feasible with present day technology. In order to test the quantum nature of the particle creation mechanism and to distinguish it from classical effects such as heating, we propose to measure the two-phonon amplitude via the 2nd red sideband transition and to compare it with the one-phonon amplitude (1st red sideband). PMID:18233131

  18. Analogue of Cosmological Particle Creation in an Ion Trap

    SciTech Connect

    Schuetzhold, Ralf; Uhlmann, Michael; Petersen, Lutz; Schmitz, Hector; Friedenauer, Axel; Schaetz, Tobias

    2007-11-16

    We study phonons in a dynamical chain of ions confined by a trap with a time-dependent (axial) potential strength and demonstrate that they behave in the same way as quantum fields in an expanding or contracting Universe. Based on this analogy, we present a scheme for the detection of the analogue of cosmological particle creation which should be feasible with present day technology. In order to test the quantum nature of the particle creation mechanism and to distinguish it from classical effects such as heating, we propose to measure the two-phonon amplitude via the 2nd red sideband transition and to compare it with the one-phonon amplitude (1st red sideband)

  19. Charge-state dependence of kinetic electron emission induced by slow ions in metals

    SciTech Connect

    Juaristi, J.I.; Dubus, A.; Roesler, M.

    2003-07-01

    A calculation is performed in order to analyze the charge-state dependence of the kinetic electron emission induced by slow ions in metals. All stages of the emission process are included: the excitation of the electrons, the neutralization of the projectile during its passage through the solid, and the transport of the excited electrons from where they are created to the surface. It is shown that the number of excited electrons depends strongly on the ion charge state. Nevertheless, due to the fast neutralization of the ions within the escape depth of the excited electrons, no significant initial charge-state dependence is expected in the kinetic electron yield. This result is consistent with available experimental data.

  20. Automated System for Kinetic Analysis of Particle Size Distributions for Pharmaceutically Relevant Systems

    PubMed Central

    Green, John-Bruce D.; Carter, Phillip W.; Zhang, Yingqing; Patel, Dipa; Kotha, Priyanka

    2014-01-01

    Detailing the kinetics of particle formation for pharmaceutically relevant solutions is challenging, especially when considering the combination of formulations, containers, and timescales of clinical importance. This paper describes a method for using commercial software Automate with a stream-selector valve capable of sampling container solutions from within an environmental chamber. The tool was built to monitor changes in particle size distributions via instrumental particle counters but can be adapted to other solution-based sensors. The tool and methodology were demonstrated to be highly effective for measuring dynamic changes in emulsion globule distributions as a function of storage and mixing conditions important for parenteral nutrition. Higher levels of agitation induced the fastest growth of large globules (≥5 μm) while the gentler conditions actually showed a decrease in the number of these large globules. The same methodology recorded calcium phosphate precipitation kinetics as a function of [Ca2+] and pH. This automated system is readily adaptable to a wide range of pharmaceutically relevant systems where the particle size is expected to vary with time. This instrumentation can dramatically reduce the time and resources needed to probe complex formulation issues while providing new insights for monitoring the kinetics as a function of key variables. PMID:25140276

  1. Modeling of hydrogen production methods: Single particle model and kinetics assessment

    SciTech Connect

    Miller, R.S.; Bellan, J.

    1996-10-01

    The investigation carried out by the Jet Propulsion Laboratory (JPL) is devoted to the modeling of biomass pyrolysis reactors producing an oil vapor (tar) which is a precursor to hydrogen. This is an informal collaboration with NREL whereby JPL uses the experimentally-generated NREL data both as initial and boundary conditions for the calculations, and as a benchmark for model validation. The goal of this investigation is to find drivers of biomass fast-pyrolysis in the low temperature regime. The rationale is that experimental observations produce sparse discrete conditions for model validation, and that numerical simulations produced with a validated model are an economic way to find control parameters and an optimal operation regime, thereby circumventing costly changes in hardware and tests. During this first year of the investigation, a detailed mathematical model has been formulated for the temporal and spatial accurate modeling of solid-fluid reactions in biomass particles. These are porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas phase flow. The methodology has been applied to the pyrolysis of spherically symmetric biomass particles by considering previously published kinetics schemes for both cellulose and wood. The results show that models which neglect the thermal and species boundary layers exterior to the particle will generally over predict both the pyrolysis rates and experimentally obtainable tar yields. An evaluation of the simulation results through comparisons with experimental data indicates that while the cellulose kinetics is reasonably accurate, the wood pyrolysis kinetics is not accurate; particularly at high reactor temperatures. Current effort in collaboration with NREL is aimed at finding accurate wood kinetics.

  2. Overview of Particle and Heavy Ion Transport Code System PHITS

    NASA Astrophysics Data System (ADS)

    Sato, Tatsuhiko; Niita, Koji; Matsuda, Norihiro; Hashimoto, Shintaro; Iwamoto, Yosuke; Furuta, Takuya; Noda, Shusaku; Ogawa, Tatsuhiko; Iwase, Hiroshi; Nakashima, Hiroshi; Fukahori, Tokio; Okumura, Keisuke; Kai, Tetsuya; Chiba, Satoshi; Sihver, Lembit

    2014-06-01

    A general purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS, is being developed through the collaboration of several institutes in Japan and Europe. The Japan Atomic Energy Agency is responsible for managing the entire project. PHITS can deal with the transport of nearly all particles, including neutrons, protons, heavy ions, photons, and electrons, over wide energy ranges using various nuclear reaction models and data libraries. It is written in Fortran language and can be executed on almost all computers. All components of PHITS such as its source, executable and data-library files are assembled in one package and then distributed to many countries via the Research organization for Information Science and Technology, the Data Bank of the Organization for Economic Co-operation and Development's Nuclear Energy Agency, and the Radiation Safety Information Computational Center. More than 1,000 researchers have been registered as PHITS users, and they apply the code to various research and development fields such as nuclear technology, accelerator design, medical physics, and cosmic-ray research. This paper briefly summarizes the physics models implemented in PHITS, and introduces some important functions useful for specific applications, such as an event generator mode and beam transport functions.

  3. Ion beam sputtering of Ag - Angular and energetic distributions of sputtered and scattered particles

    NASA Astrophysics Data System (ADS)

    Feder, René; Bundesmann, Carsten; Neumann, Horst; Rauschenbach, Bernd

    2013-12-01

    Ion beam sputter deposition (IBD) provides intrinsic features which influence the properties of the growing film, because ion properties and geometrical process conditions generate different energy and spatial distribution of the sputtered and scattered particles. A vacuum deposition chamber is set up to measure the energy and spatial distribution of secondary particles produced by ion beam sputtering of different target materials under variation of geometrical parameters (incidence angle of primary ions and emission angle of secondary particles) and of primary ion beam parameters (ion species and energies).

  4. Hybrid (Kinetic Ion/Fluid Electron) Simulations of Reconnection Including Electron Pressure Anisotropy

    NASA Astrophysics Data System (ADS)

    Le, A.; Daughton, W. S.

    2015-12-01

    Fully kinetic simulations have shown that the structure of the thin current sheets that form during collisionless reconnection can fall into a variety of regimes depending on the electron pressure anisotropy [1]. Furthermore, recent two-fluid simulations with anisotropic electron equations of state appropriate for reconnection confirm that the electron pressure anisotropy may drive highly elongated current sheets in the reconnection exhaust [2]. While fully kinetic simulations are useful to model small regions of the Earth's magnetosphere, they are still far too expensive for global modeling. Thus, we have implemented the electron equations of state in the hybrid (kinetic ions and fluid electrons) code H3D [3], and initial 2D hybrid simulations of reconnection agree well with fully kinetic simulations. The updated hybrid code is a first step towards including electron anisotropy and full ion kinetics in global simulations of Earth's magnetosphere and laboratory experiments. [1] Le et al., Phys. Rev. Lett. 110, 135004 (2013)[2] Ohia et al., Phys. Rev. Lett. 109, 115004 (2012) [3] Karimabadi et al., Phys. Plasmas 21, 062308 (2014)

  5. Dynamics of pickup ion velocity distribution function in Titan's plasma environment (TA encounter): 3D hybrid kinetic modeling and comparison with CAPS observations

    NASA Astrophysics Data System (ADS)

    Simpson, D. G.; Lipatov, A. S.; Sittler, E. C.; Hartle, R. E.; Cooper, J. F.

    2013-12-01

    Wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of the low-frequency waves and the formation of the particle velocity distribution function, e.g. ring/shell-like distributions, etc. The kinetic approach is important for estimation of the collision processes e.g. a charge exchange. The particle velocity distribution function also plays a key role for understanding the observed particle fluxes. In this report we discuss the ion velocity distribution function dynamics from 3D hybrid modeling. The modeling is based on recent analysis of the Cassini Plasma Spectrometer (CAPS) ion measurements during the TA flyby. In our model the background ions, all pickup ions, and ionospheric ions are considered as particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. The temperatures of the background electrons and pickup electrons were also included into the generalized Ohm's law. We also take into account the collisions between the ions and neutrals. We use Chamberlain profiles for the exosphere's components and include a simple ionosphere model with M=28 ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Our modeling shows that interaction between background plasma and pickup ions H+, H2+, CH4+ and N2+ has a more complicated structure than was observed in the T9 flyby and modeling due to the large gyroradius of the background O+ ions [1,2,3,4]. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS TA observations. We also compare our kinetic modeling with other hybrid and MHD modeling of Titan's environment. References [1] Sittler, E.C., et al., Energy Deposition Processes in Titan's Upper Atmosphere and Its Induced Magnetosphere. In: Titan from Cassini-Huygens, Brown, R.H., Lebreton J.P., Waite, J.H., Eds

  6. Kinetics of the oxidative degradation of formaldehyde with electrogenerated hypochlorite ion

    SciTech Connect

    Do, J.S.; Yeh, W.C.; Chao, I.Y.

    1997-02-01

    Aldehydes pose a potential problem in waste waters coming from a variety of process industry sources and must be treated before industrial waste waters can be discharged. The mechanisms and kinetics of the anodic oxidation of chloride ion on SnO{sub 2}-PdO-RuO{sub 2}-TiO{sub 2}/Ti (SPR) anode and the oxidation of formaldehyde with hypochlorite ion were studied, and the new kinetic data based on theoretical analysis were evaluated in this investigation. The reaction order of the anodic oxidation of chloride ion on SPR was unity. Also, the oxidation of formaldehyde with hypochlorite ion was second order in formaldehyde and first order in hypochlorite ion. Furthermore, the activation energy was evaluated as 37.9 kJ/mol. Formaldehyde was degraded from 3,000 to 279 ppm, and the degradation fraction was 90.7% when the electrolysis time was 111 min. A model calculation of the in situ oxidative degradation of formaldehyde with electrogenerated hypochlorite ion correlated well with experimental results.

  7. Ion kinetics in Ar/H2 cold plasmas: the relevance of ArH+

    PubMed Central

    Jiménez-Redondo, Miguel; Cueto, Maite; Doménech, José Luis; Tanarro, Isabel; Herrero, Víctor J.

    2015-01-01

    The recent discovery of ArH+ in the interstellar medium has awakened the interest in the chemistry of this ion. In this work, the ion-molecule kinetics of cold plasmas of Ar/H2 is investigated in glow discharges spanning the whole range of [H2]/([H2]+[Ar]) proportions for two pressures, 1.5 and 8 Pa. Ion concentrations are determined by mass spectrometry, and electron temperatures and densities, with Langmuir probes. A kinetic model is used for the interpretation of the results. The selection of experimental conditions evinces relevant changes with plasma pressure in the ion distributions dependence with the H2 fraction, particularly for the major ions: Ar+, ArH+ and H3+. At 1.5 Pa, ArH+ prevails for a wide interval of H2 fractions: 0.3<[H2]/([H2]+[Ar])<0.7. Nevertheless, a pronounced displacement of the ArH+ maximum towards the lowest H2 fractions is observed at 8 Pa, in detriment of Ar+, which becomes restricted to very small [H2]/([H2]+[Ar]) ratios, whereas H3+ becomes dominant for all [H2]/([H2]+[Ar]) > 0.1. The analysis of the data with the kinetic model allows the identification of the sources and sinks of the major ions over the whole range of experimental conditions sampled. Two key factors turn out to be responsible for the different ion distributions observed: the electron temperature, which determines the rate of Ar+ formation and thus of ArH+, and the equilibrium ArH+ + H2 ⇄ H3+ + Ar, which can be strongly dependent of the degree of vibrational excitation of H3+. The results are discussed and compared with previously published data on other Ar/H2 plasmas. PMID:26702354

  8. Kinetics of reactive ion etching upon single-walled carbon nanotubes

    SciTech Connect

    Kato, Toshiaki; Hatakeyama, Rikizo

    2008-01-21

    The remarkable etching reaction of single-walled carbon nanotubes (SWNTs) has been observed in their growth of the parameter-controlled plasma chemical vapor deposition (CVD). The time evolution study of the SWNTs growth leads to establishing a growth equation which can completely express the growth kinetics of SWNTs in the plasma CVD. The growth equation is found to reveal that there are several key parameters which directly affect the etching reaction of SWNTs. Furthermore, such kinetics of the SWNT etching in plasmas can perfectly be explained with a reactive ion etching model.

  9. The effect of mechanical vibration on the dust particle kinetic temperature measurement

    NASA Astrophysics Data System (ADS)

    Kong, Jie; Qiao, Ke; Matthews, Lorin; Hyde, Truell

    2015-11-01

    An important parameter in governing the self-assembly of structures in a complex (dusty) plasma is the coupling parameter Γ, the ratio of the electrostatic energy of the charged dust to the dust thermal energy. In a GEC rf reference cell, the dust thermal energy can come from collisions with the neutral gas, fluctuations of the confining electric field or changes in the charge on the dust particle itself. Experimentally, the kinetic energy of the dust can be determined using the Gaussian thermal velocity probability distribution. However, recent measurements of the dust particle velocity probability distribution function have shown that external mechanical vibrations of the plasma chamber can have a significant effect on the result. This investigation compares measurements of the dust kinetic temperature with and without external vibrations to the GEC cell. Support from the NSF and the DOE (award numbers PHY-1262031 and PHY-1414523) is gratefully acknowledged.

  10. Kinetics of the reduction of pyridinium ions by 2-hydroxy-2-propyl radicals in aqueous solution

    SciTech Connect

    Shimura, M.; Espenson, J.H.

    1983-01-19

    Kinetic measurements were made for the reductions of the pyridinium ions derived from pyridine, 4-methylpyridine, 3-hydroxypyridine, nicotinamide, and isonicotinamide as well as 1-methylpyridinium and 1,4-dimethylpyridinium ions by 2-hydroxy-2-propyl radicals, which were generated by the homolytic cleavage of the chromium-carbon bond in (H/sub 2/O)/sub 5/CrC(CH/sub 3/)/sub 2/OH/sup 2 +/. The rate constants (dm/sup 3/ mol/sup -1/ s/sup -1/) at 25.0/sup 0/C and an ionic strength of 1.0M (LiClO/sub 4/) are as follows: pyridinium ion, 9.6 x 10/sup 5/; 1-methylpyridinium ion, 3.7 x 10/sup 5/; 4-methylpyridinium ion, 7.3 x 10/sup 4/; 1,4-dimethylpyridinium ion, less than or equal to1 x 10/sup 4/; 3-hydroxypyridinium ion, 1.4 x 10/sup 8/; 3-(aminocarbonyl)pyridinium ion, 7.9 x 10/sup 8/; 4-(aminocarbonyl)pyridinium ion, 1.2 x 10/sup 9/. The rate constants are reasonably well correlated by the Hammett p-sigma equation with p = +8.5. The first two compounds show a second kinetic term corresponding to the rate law k'(Cr/sup 2 +/)(pyH/sup +/)(.C-(CH/sub 3/)/sub 2/OH)(H/sup +/)/sup -1/, consistent with reduction of a Cr(II)-pyridine complex by the free radical.