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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. 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.

  7. 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.

  8. 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

  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. 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.

  5. 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.

  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. 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…

  9. 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.

  10. 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

  11. 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

  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

    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

  15. 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.

  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. 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

  15. 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.

  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

    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

  12. 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.

  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

    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)

  17. 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).

  18. 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.

  19. 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

  20. 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.

  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.

    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.

  6. 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.

  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

    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.

  9. 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.

  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

    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.

  19. 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

  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

    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

  1. 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

  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

    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

  5. 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.

  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. 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.

  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.

    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.

  5. 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

  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. 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

  16. 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)

  17. 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.

  18. 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.

  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.

  11. Spatiotemporal kinetics of γ-H2AX protein on charged particles induced DNA damage

    NASA Astrophysics Data System (ADS)

    Niu, H.; Chang, H. C.; Cho, I. C.; Chen, C. H.; Liu, C. S.; Chou, W. T.

    2014-08-01

    In several researches, it has been demonstrated that charged particles can induce more complex DNA damages. These complex damages have higher ability to cause the cell death or cell carcinogenesis. For this reason, clarifying the DNA repair mechanism after charged particle irradiation plays an important role in the development of charged particle therapy and space exploration. Unfortunately, the detail spatiotemporal kinetic of DNA damage repair is still unclear. In this study, we used γ-H2AX protein to investigate the spatiotemporal kinetics of DNA double strand breaks in alpha-particle irradiated HeLa cells. The result shows that the intensity of γ-H2AX foci increased gradually, and reached to its maximum at 30 min after irradiation. A good linear relationship can be observed between foci intensity and radiation dose. After 30 min, the γ-H2AX foci intensity was decreased with time passed, but remained a large portion (∼50%) at 48 h passed. The data show that the dissolution rate of γ-H2AX foci agreed with two components DNA repairing model. These results suggest that charged particles can induce more complex DNA damages and causing the retardation of DNA repair.

  12. Kinetic modeling of ion conduction in KcsA potassium channel.

    PubMed

    Mafé, Salvador; Pellicer, Julio; Cervera, Javier

    2005-05-22

    KcsA constitutes a potassium channel of known structure that shows both high conduction rates and selectivity among monovalent cations. A kinetic model for ion conduction through this channel that assumes rapid ion transport within the filter has recently been presented by Nelson. In a recent, brief communication, we used the model to provide preliminary explanations to the experimental current-voltage J-V and conductance-concentration g-S curves obtained for a series of monovalent ions (K(+),Tl(+), and Rb(+)). We did not assume rapid ion transport in the calculations, since ion transport within the selectivity filter could be rate limiting for ions other than native K(+). This previous work is now significantly extended to the following experimental problems. First, the outward rectification of the J-V curves in K(+) symmetrical solutions is analyzed using a generalized kinetic model. Second, the J-V and g-S curves for NH(4) (+) are obtained and compared with those of other ions (the NH(4) (+) J-V curve is qualitatively different from those of Rb(+) and Tl(+)). Third, the effects of Na(+) block on K(+) and Rb(+) currents through single KcsA channels are studied and the different blocking behavior is related to the values of the translocation rate constants characteristic of ion transport within the filter. Finally, the significantly decreased K(+) conductance caused by mutation of the wild-type channel is also explained in terms of this rate constant. In order to keep the number of model parameters to a minimum, we do not allow the electrical distance (an empirical parameter of kinetic models that controls the exponential voltage dependence of the dissociation rate) to vary with the ionic species. Without introducing the relatively high number of adjustable parameters of more comprehensive site-based models, we show that ion association to the filter is rate controlling at low concentrations, but ion dissociation from the filter and ion transport within the filter

  13. Dispersion characteristics of kinetic Alfven waves in a multi-ion plasma

    NASA Astrophysics Data System (ADS)

    Venugopal, Chandu; Jayapal, R.; Sreekala, G.; Jose, Blesson; Savithri Devi, E.; Antony, S.

    2014-06-01

    The stability of the kinetic Alfven wave (KAW) has been studied in a plasma composed of electrons, hydrogen and positively and negatively charged oxygen ions. Using the two potential theory of Hasegawa, we have derived an expression for the frequency and growth/damping rate of the KAW. The dispersion relation derived in this paper is a generalization of the dispersion relation of Hasegawa on two counts: (i) we use a more generalized distribution function and show that our relation reduces to the dispersion relation of Hasegawa in the limiting case, and (ii) it is applicable to a multi-ion plasma containing lighter ions and positively and negatively charged heavier ions. We find the growth rate of the wave increases with increasing drift velocities of the electrons. Negatively charged oxygen ions (O-) decrease the growth rate; however, the growth rate is very sensitively dependent on O- ion density, especially when its density is greater than that of the positively charged oxygen ions (O+). Interestingly, the dispersion characteristics of KAWs can be made insensitive to the presence of the heavier ions by an appropriate choice of their densities and temperatures.

  14. Kinetic theory of dust ion acoustic waves in a kappa-distributed plasma

    NASA Astrophysics Data System (ADS)

    Baluku, T. K.; Hellberg, M. A.

    2015-08-01

    Using a kinetic theory approach, dust ion acoustic (DIA) waves are investigated in an unmagnetized collisionless plasma with kappa-distributed electrons and ions, and Maxwellian dust grains of constant charge. Both analytical and numerical results, the latter following from the full solution of the associated dispersion relation, are presented, and a comparison is made. The effects of the ion and electron spectral indices, as well as the species' density ( ne/ni ) and temperature ( Te/Ti ) ratios, on the dispersion and damping of the waves are considered. In the long wavelength regime, increases in both the electron spectral index (κe) and the dust density fraction (reduced f =ne/ni ) lead to an increase in phase velocity. The range in wavelength over which modes are weakly damped increases with an increase in Te/Ti . However, the ion spectral index, κi, does not have a significant effect on the dispersion or damping of DIA waves.

  15. Kinetics Tuning of Li-Ion Diffusion in Layered Li(NixMnyCoz)O2.

    PubMed

    Wei, Yi; Zheng, Jiaxin; Cui, Suihan; Song, Xiaohe; Su, Yantao; Deng, Wenjun; Wu, Zhongzhen; Wang, Xinwei; Wang, Weidong; Rao, Mumin; Lin, Yuan; Wang, Chongmin; Amine, Khalil; Pan, Feng

    2015-07-01

    Using ab initio calculations combined with experiments, we clarified how the kinetics of Li-ion diffusion can be tuned in LiNixMnyCozO2 (NMC, x + y + z = 1) materials. It is found that Li-ions tend to choose oxygen dumbbell hopping (ODH) at the early stage of charging (delithiation), and tetrahedral site hopping (TSH) begins to dominate when more than 1/3 Li-ions are extracted. In both ODH and TSH, the Li-ions surrounded by nickel (especially with low valence state) are more likely to diffuse with low activation energy and form an advantageous path. The Li slab space, which also contributes to the effective diffusion barriers, is found to be closely associated with the delithiation process (Ni oxidation) and the contents of Ni, Co, and Mn. PMID:26098282

  16. Dispersion and absorption of longitudinal electro-kinetic wave in ion-implanted GaN semiconductor plasmas

    SciTech Connect

    Soni, Dilip; Sharma, Giriraj; Saxena, Ajay; Jadhav, Akhilesh

    2015-07-31

    An analytical study on propagation characteristics of longitudinal electro-kinetic (LEK) waves is presented. Based on multi-fluid model of plasma, we have derived a dispersion relation for LEK waves in colloid laden GaN semiconductor plasmas. It is assumed that ions are implanted to form colloids in the GaN sample. The colloids are continuously bombarded by the plasma particles and stick on them, but they acquire a net negative charge due to relatively higher mobility of electrons. It is found from the dispersion relation that the presence of charged colloids not only modifies the existing modes but also supports new novel modes of LEKWs. It is hoped that the study would enhance understanding on dispersion and absorption of LEKWs and help in singling out the appropriate configurations in which GaN crystal would be better suited for fabrication of microwave devices.

  17. The kinetics of the oxidation of pyrite by ferric ions and dissolved oxygen: An electrochemical study

    SciTech Connect

    Holmes, P.R.; Crundwell, F.K.

    2000-01-01

    The dissolution of pyrite is important in the geochemical cycling of iron and sulphur, in the formation of acid mine drainage, and in the extraction of metals by bacterial leaching. Many researchers have studied the kinetics of dissolution, and the rate of dissolution has often been found to be half-order in ferric ions or oxygen. Previous work has not adequately explained the kinetics of dissolution of pyrite. The dissolution of pyrite is an oxidation-reduction reaction. The kinetics of the oxidation and reduction half-reactions was studied independently using electrochemical techniques of voltammetry. The kinetics of the overall reaction was studied by the electrochemical technique of potentiometry, which consisted of measuring the mixed potential of a sample of corroding pyrite in solutions of different compositions. The kinetics of the half reactions are related to the kinetics of the overall dissolution reaction by the condition that there is no accumulation of charge. This principle is used to derive expressions for the mixed potential and the rate of dissolution, which successfully describe the mixed potential measurements and the kinetics of dissolution reported in the literature. It is shown that the observations of half-order kinetics and that the oxygen in the sulphate product arises from water are both a direct consequence of the electrochemical mechanism. Thus it is concluded that the electrochemical reaction steps occurring at the mineral-solution interface control the rate of dissolution. Raman spectroscopy was used to analyze reaction products formed on the pyrite surface. The results indicated that small amounts of polysulphides form on the surface of the pyrite. However, it was also found that the mixed (corrosion) potential does not change over a 14-day leaching period. This indicates that even though polysulphide material is present on the surface, it does not influence the rate of the reactions occurring at the surface. Measurement of the

  18. Modeling of a negative ion source. I. Gas kinetics and dynamics in the expansion region

    SciTech Connect

    Taccogna, F.; Schneider, R.; Longo, S.; Capitelli, M.

    2007-07-15

    The vibrational population distribution of the electronic ground state of H{sub 2} in the expansion region of a negative ion source is investigated using a kinetic Monte Carlo model. Operative conditions are referred to the inductively coupled plasma radio frequency negative ion source developed at IPP-Garching. The different excitation and relaxation processes are discussed, both bulk and surface contributions. In particular, due to the relatively high plasma density, the relevant role of direct low energy electron-impact excitation, surface Auger neutralization, and vibration-translation deactivation are recovered. Results of the present model will be used as input data for the neutral source model in the extraction region.

  19. Kinetics and thermodynamics of copper ions removal from wastewater by use of zeolite.

    PubMed

    Panayotova, M I

    2001-01-01

    Natural Bulgarian zeolite was tested for its ability to remove Cu2+ from model wastewater. Influence of process variables was investigated. It was found that the optimum wastewater to zeolite ratio is 100:1 and the optimum pH value of water to be treated is 5.5 to 7.5. Zeolite with finer particles shows a higher uptake capacity. The simultaneous presence of Ca2+ and Mg2+ in concentrations similar to their concentrations in Bulgarian natural water does not significantly influence the uptake of Cu2+. Zeolite modification by treating it with NaCl, CH3COONa and NaOH increases its uptake ability. Copper ions are strongly immobilized by modified zeolite and secondary pollution of water caused by its contact with preloaded zeolite is very low (1.5-2.5% of Cu2+ preliminary immobilized have been released back into acidified water). Contacting with 2 mol dm(-3) NaCl can easily regenerate loaded zeolite; best results were obtained for zeolite modified with NaCl. Requirements of Bulgarian standards for industrial wastewater can be met by a one-stage process for an initial Cu2+ concentration of 10 mg dm(-3), and by a two stage process for an initial Cu2+ concentration of 50 mg dm(-3). Uptake of Cu2+ by zeolite from neutral wastewater has proved to be as effective as Cu2+ removal by precipitation of copper hydroxide. The process of Cu2+ uptake by natural zeolite is best described by the kinetic equation for adsorption. This fact, together with the correlation found between the Cu2+ uptake and the amount of Na+, Ca2+ and K+ released into solution by zeolite shows that the ion exchange sorption plays the basic role in Cu2+ uptake by natural zeolite. The value obtained for the apparent activation energy (26.112 kJ mol(-1) implies that the process can be easily carried out with a satisfactory rate. The uptake equilibrium is best described by the Langmuir adsorption isotherm, with Langmuir constants KL= 6.4 x 10(-2) dm3 mg(-1) and M = 6.74 mg g(-1). The apparent equilibrium constant

  20. Entry Kinetics and Cell-Cell Transmission of Surface-Bound Retroviral Vector Particles

    PubMed Central

    O’Neill, Lee S.; Skinner, Amy M.; Woodward, Josha A.; Kurre, Peter

    2010-01-01

    Background Transduction with recombinant Human Immunodeficiency Virus (HIV) -1 derived lentivirus vectors is a multi-step process initiated by surface attachment and subsequent receptor-directed uptake into the target cell. We previously reported the retention of vesicular stomatitis virus G protein (VSV-G) pseudotyped particles on murine progenitor cells and their delayed cell-cell transfer. Methods To examine the underlying mechanism in more detail we used a combination of approaches focused on investigating the role of receptor-independent factors in modulating attachment. Results Studies of synchronized transduction herein reveal cell-type specific rates of vector particle clearance with substantial delays during particle entry into murine hematopoietic progenitor cells. The observed uptake kinetics from the surface of the 1° cell correlate inversely with the magnitude of transfer to 2° targets, corresponding with our initial observation of preferential cell-cell transfer in the context of brief vector exposures. We further demonstrate that vector particle entry into cells is associated with the cell–type specific abundance of extracellular matrix fibronectin. Residual particle – ECM binding and 2° transfer can be competitively disrupted by heparin exposure without affecting murine progenitor homing and repopulation. Conclusions While cellular attachment factors, including fibronectin, aid gene transfer by colocalizing particles to cells and disfavoring early dissociation from targets, they also appear to stabilize particles on the cell surface. Our study highlights the inadvertent consequences for cell entry and cell-cell transfer. PMID:20440757

  1. Theory and modelling of ion cusp particle signatures at Saturn

    NASA Astrophysics Data System (ADS)

    Jasinski, J. M.; Arridge, C. S.

    2013-12-01

    Cassini observations of Saturn's polar magnetosphere have revealed a variety of cusp-like particle signatures suggesting the presence of magnetopause reconnection. Some of these signatures display evidence of bursty unsteady reconnection. The presence of rapid planetary rotation and large Parker-spiral IMF conditions lead to unique effects on cusp signatures and we explore these aspects in this presentation. We present theoretical considerations of the cusp. We pay particular attention to the structure of energy-time ion dispersions and their generation by poleward and azimuthal convection of newly opened flux tubes, and the effect of periodicities in the Saturn system. This study is relevant to ongoing data exploitation from Cassini and to future observations from Juno. Comparisons will be made to Cassini observations of Saturn's cusp. We also present predicted signatures along Juno's trajectory.

  2. Hybrid simulations of magnetic reconnection with kinetic ions and fluid electron pressure anisotropy

    DOE PAGESBeta

    Le, A.; Daughton, W.; Karimabadi, H.; Egedal, J.

    2016-03-16

    We present the first hybrid simulations with kinetic ions and recently developed equations of state for the electron fluid appropriate for reconnection with a guide field. The equations of state account for the main anisotropy of the electron pressure tensor.Magnetic reconnection is studied in two systems, an initially force-free current sheet and a Harris sheet. The hybrid model with the equations of state is compared to two other models, hybrid simulations with isothermal electrons and fully kinetic simulations. Including the anisotropicequations of state in the hybrid model provides a better match to the fully kinetic model. In agreement with fullymore » kinetic results, the main feature captured is the formation of an electron current sheet that extends several ion inertial lengths. This electron current sheet modifies the Hall magnetic field structure near the X-line, and it is not observed in the standard hybrid model with isotropic electrons. The saturated reconnection rate in this regime nevertheless remains similar in all three models. Here, implications for global modeling are discussed.« less

  3. Simulated kinetic effects of the corona and solar cycle on high altitude ion transport at Mars

    NASA Astrophysics Data System (ADS)

    Curry, S. M.; Liemohn, M.; Fang, X.; Brain, D.; Ma, Y.

    2013-06-01

    We present results from the Mars Test Particle (MTP) simulation as part of a community‒wide model comparison in order to quantify the role of different neutral atmospheric conditions in planetary ion transport and escape. This study examines the effects of individual ion motion by simulating particle trajectories for three cases: solar minimum without the neutral corona, solar minimum with the inclusion of the neutral corona, and solar maximum with the inclusion of the neutral corona. The MTP simulates 1.5 billion test particles through background electric and magnetic fields computed by a global magnetohydrodynamic model. By implementing virtual detectors in the simulation, the MTP has generated velocity space distributions of pickup ions and quantifies the ion acceleration at different spatial locations. The study found that the inclusion of a hot neutral corona greatly affects the total O+ production and subsequent loss, roughly doubling the total escape for solar minimum conditions and directly contributing to high energy sources above 10 keV. The solar cycle influences the amount of O+ flux observed by the virtual detectors, increasing the O+ flux and total escape by an order of magnitude from solar minimum to maximum. Additionally, solar maximum case induces greater mass loading of the magnetic fields, which decreases the gyroradius of the ions and redirects a significant ion population downtail to subsequently escape.

  4. KINETIC MODELING OF PARTICLE ACCELERATION IN A SOLAR NULL-POINT RECONNECTION REGION

    SciTech Connect

    Baumann, G.; Haugbolle, T.; Nordlund, A.

    2013-07-10

    The primary focus of this paper is on the particle acceleration mechanism in solar coronal three-dimensional reconnection null-point regions. Starting from a potential field extrapolation of a Solar and Heliospheric Observatory (SOHO) magnetogram taken on 2002 November 16, we first performed magnetohydrodynamics (MHD) simulations with horizontal motions observed by SOHO applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan plane of the null point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms in the simulated pre-flare phase, featuring a power-law index of about -1.78. This work provides a first step toward bridging the gap between macroscopic scales on the order of hundreds of Mm and kinetic scales on the order of centimeter in the solar corona, and explains how to achieve such a cross-scale coupling by utilizing either physical modifications or (equivalent) modifications of the constants of nature. With their exceptionally high resolution-up to 135 billion particles and 3.5 billion grid cells of size 17.5 km-these simulations offer a new opportunity to study particle acceleration in solar-like settings.

  5. The dissolution kinetics of major elements in municipal solid waste incineration bottom ash particles

    NASA Astrophysics Data System (ADS)

    Bendz, David; Tüchsen, Peter L.; Christensen, Thomas H.

    2007-12-01

    Leaching and tracer experiments in batches at L/S 20 were performed with 3-month-old MSWI bottom ash separated into eight different particle sizes. The time-dependent leaching of major elements (Ca 2+, K +, Na +, Cl - and SO 4- 2 ) was monitored for up to 747 h. Physical properties of the particles, the specific surface (BET), pore volume and pore volume distribution over pore sizes (BJH) were determined for all particle classes by N 2 adsorption/desorption experiments. Some common features of physical pore structure for all particles were revealed. The specific surface and the particle pore volume were found to be negatively correlated with particle size, ranging from 3.2 m 2/g to 25.7 m 2/g for the surface area and from 0.0086 cm 3/g to 0.091 cm 3/g for the pore volume. Not surprisingly, the specific surface area was found to be the major material parameter that governed the leaching behavior for all elements (Ca 2+, K +, Na +, Cl - and SO 4- 2 ) and particle sizes. The diffusion resistance was determined independently by separate tracer (tritium) experiments. Diffusion gave a significant contribution to the apparent leaching kinetics for all elements during the first 10-40 h (depending on the particle size) of leaching and surface reaction was the overall rate controlling mechanism at late times for all particle sizes. For Ca 2+ and SO 4- 2 , the coupled effect of diffusion resistance and the degree of undersaturation in the intra particle pore volume was found to be a major rate limiting dissolution mechanism for both early and late times. The solubility control in the intra particulate porosity may undermine any attempt to treat bottom ash by washing out the sulfate. Even for high liquid/solid ratios, the solubility in the intra-particular porosity will limit the release rate.

  6. Ion-polycyclic aromatic hydrocarbon collisions: kinetic energy releases for specific fragmentation channels

    NASA Astrophysics Data System (ADS)

    Reitsma, G.; Zettergren, H.; Boschman, L.; Bodewits, E.; Hoekstra, R.; Schlathölter, T.

    2013-12-01

    We report on 30 keV He2 + collisions with naphthalene (C10H8) molecules, which leads to very extensive fragmentation. To unravel such complex fragmentation patterns, we designed and constructed an experimental setup, which allows for the determination of the full momentum vector by measuring charged collision products in coincidence in a recoil ion momentum spectrometer type of detection scheme. The determination of fragment kinetic energies is found to be considerably more accurate than for the case of mere coincidence time-of-flight spectrometers. In fission reactions involving two cationic fragments, typically kinetic energy releases of 2-3 eV are observed. The results are interpreted by means of density functional theory calculations of the reverse barriers. It is concluded that naphthalene fragmentation by collisions with keV ions clearly is much more violent than the corresponding photofragmentation with energetic photons. The ion-induced naphthalene fragmentation provides a feedstock of various small hydrocarbonic species of different charge states and kinetic energy, which could influence several molecule formation processes in the cold interstellar medium and facilitates growth of small hydrocarbon species on pre-existing polycyclic aromatic hydrocarbons.

  7. Independent-particle models for light negative atomic ions

    NASA Technical Reports Server (NTRS)

    Ganas, P. S.; Talman, J. D.; Green, A. E. S.

    1980-01-01

    For the purposes of astrophysical, aeronomical, and laboratory application, a precise independent-particle model for electrons in negative atomic ions of the second and third period is discussed. The optimum-potential model (OPM) of Talman et al. (1979) is first used to generate numerical potentials for eight of these ions. Results for total energies and electron affinities are found to be very close to Hartree-Fock solutions. However, the OPM and HF electron affinities both depart significantly from experimental affinities. For this reason, two analytic potentials are developed whose inner energy levels are very close to the OPM and HF levels but whose last electron eigenvalues are adjusted precisely with the magnitudes of experimental affinities. These models are: (1) a four-parameter analytic characterization of the OPM potential and (2) a two-parameter potential model of the Green, Sellin, Zachor type. The system O(-) or e-O, which is important in upper atmospheric physics is examined in some detail.

  8. Secondary particle tracks generated by ion beam irradiation

    NASA Astrophysics Data System (ADS)

    García, Gustavo

    2015-05-01

    The Low Energy Particle Track Simulation (LEPTS) procedure is a powerful complementary tool to include the effect of low energy electrons and positrons in medical applications of radiation. In particular, for ion-beam cancer treatments provides a detailed description of the role of the secondary electrons abundantly generated around the Bragg peak as well as the possibility of using transmuted positron emitters (C11, O15) as a complement for ion-beam dosimetry. In this study we present interaction probability data derived from IAM-SCAR corrective factors for liquid environments. Using these data, single electron and positron tracks in liquid water and pyrimidine have been simulated providing information about energy deposition as well as the number and type of interactions taking place in any selected ``nanovolume'' of the irradiated area. In collaboration with Francisco Blanco, Universidad Complutense de Madrid; Antonio Mu noz, Centro de Investigaciones Energéticas Medioambientales y Tecnológicas and Diogo Almeida, Filipe Ferreira da Silva, Paulo Lim ao-Vieira, Universidade Nova de Lisboa. Supported by the Spanish and Portuguese governments.

  9. Kinetics of chromium ion absorption by cross-linked polyacrylate films

    NASA Technical Reports Server (NTRS)

    May, C. E.

    1984-01-01

    Three cross-linked ion exchange membranes were studied as to their ability to absorb chromium ion from aqueous chromium III nitrate solutions. Attention was given to the mechanism of absorption, composition of the absorbed product, and the chemical bonding. The membranes were: calcium polyacrylate, polyacrylic acid, and a copolymer of acrylic acid and vinyl alcohol. For the calcium polyacrylate and the copolymer, parabolic kinetics were observed, indicating the formation of a chromium polyacrylate phase as a coating on the membrane. The rate of absorption is controlled by the diffusion of the chromium ion through this coating. The product formed in the copolymer involves the formation of a coordination complex of a chromium ion with 6 carboxylic acid groups from the same molecule. The absorption of the chromium ion by the polyacrylic acid membranes appears to be more complicated, involving cross-linking. This is due to the coordination of the chromium ion with carboxylic acid groups from more than one polymer molecule. The absorption rate of the chromium ion by the calcium salt membrane was found to be more rapid than that by the free polyacrylic acid membrane.

  10. Kinetic structure of slow shocks - Effects of the electromagnetic ion/ion cyclotron instability

    NASA Technical Reports Server (NTRS)

    Omidi, N.; Winske, D.

    1992-01-01

    The structure of slow magnetosonic shocks in the low beta regime is analyzed with attention given to ion heating and the effects of waves upstream of the electromagnetic ion/ion cyclotron (EMIIC) instability. Shock formation is assessed by means of three methods - a relaxation method and two based on dynamic flow interactions - to determine the effects of initialization and boundary conditions on the formation. Good solutions are found with the piston method and the similar flow-flow method in which the plasma is injected from two boundaries to form two slow shocks. Plasma parameters and shock normal angle are found to be the key variables dictating the structure of the magnetosonic shocks. Four unique classes of resultant shock structures are described in which classical, steady, or nonsteady behavior is found. The analysis also yields insight into the relationship between EMIIC instability and ion dissipation.

  11. On the dissolution kinetics of humic acid particles. Effect of monocarboxylic acids.

    PubMed

    Brigante, Maximiliano; Zanini, Graciela; Avena, Marcelo

    2008-05-01

    The dissolution kinetics of humic acid particles has been studied in batch experiments, and the effects of monocarboxylic (formic, acetic, and propionic) acids are reported. The dissolution rate of the particles is significantly affected by the presence of monocarboxylic acids in the pH range 4-10. At pH 7, for example, propionic acid increases 30 times this dissolution rate. The capacity of increasing the dissolution rate is in the order formic acidparticles. The results indicate that carboxylics and related compounds may affect markedly the mobility and transport of humic substances in the environment. PMID:18328533

  12. Nondiffusive mechanisms enhance protein uptake rates in ion exchange particles

    PubMed Central

    Dziennik, S. R.; Belcher, E. B.; Barker, G. A.; DeBergalis, M. J.; Fernandez, S. E.; Lenhoff, A. M.

    2003-01-01

    Scanning confocal fluorescence microscopy and multiphoton fluorescence microscopy were used to image the uptake of the protein lysozyme into individual ion exchange chromatography particles in a packed bed in real time. Self-sharpening concentration fronts penetrating into the particles were observed at low salt concentrations in all of the adsorbents studied, but persisted to 100 mM ionic strength only in some materials. In other adsorbents, diffuse profiles were seen at these higher salt concentrations, with the transition region exhibiting a pronounced fluorescence peak at the front at intermediate salt concentrations. These patterns in the uptake profiles are accompanied by significant increases in protein uptake rates that are also seen macroscopically in batch uptake experiments. The fluorescence peak appears to be a concentration overshoot that may develop, in part, from an electrokinetic contribution to transport that also enhances the uptake rate. Further evidence for an electrokinetic origin is that the effect is correlated with high adsorbent surface charge densities. Predictions of a mathematical model incorporating the electrokinetic effect are in qualitative agreement with the observations. These findings indicate that mechanisms other than diffusion contribute to protein transport in oppositely charged porous materials and may be exploited to achieve rapid uptake in process chromatography. PMID:12522150

  13. Overview of WARP: A particle code for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Friedman, Alex; Grote, David P.; Callahan, Debra A.; Langdon, A. Bruce; Haber, Irving

    1993-02-01

    The beams in a heavy ion beam driven inertial fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus, a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code's 3D package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL's planned ILSE experiments, to various 'recirculator' configurations, and to the study of equilibria and equilibration processes. Applications of the 3D package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.

  14. Overview of WARP, a particle code for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Friedman, Alex; Grote, David P.; Callahan, Debra A.; Langdon, A. Bruce; Haber, Irving

    1993-12-01

    The beams in a Heavy Ion beam driven inertial Fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code's 3d package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL's planned ILSE experiments, to various ``recirculator'' configurations, and to the study of equilibria and equilibration processes. Applications of the 3d package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.

  15. Overview of WARP, a particle code for Heavy Ion Fusion

    SciTech Connect

    Friedman, A.; Grote, D.P.; Callahan, D.A.; Langdon, A.B.; Haber, I.

    1993-02-22

    The beams in a Heavy Ion beam driven inertial Fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code`s 3d package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL`s planned ILSE experiments, to various ``recirculator`` configurations, and to the study of equilibria and equilibration processes. Applications of the 3d package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.

  16. Removal of lead and cadmium ions from aqueous solution by adsorption onto micro-particles of dry plants.

    PubMed

    Benhima, H; Chiban, M; Sinan, F; Seta, P; Persin, M

    2008-01-15

    In the present work, Pb(II) and Cd(II) ion adsorption onto inert organic matter (IOM) obtained from ground dried plants: Euphorbia echinus, Launea arborescens, Senecio anthophorbium growing in semi-arid zones of Morocco and Carpobrotus edulis as the Mediterranean plant has been studied. A suspension of plant deroed micro-particles adsorbs lead and cadmium present as ionic species, with a higher affinity for Pb(II). The kinetics and the maximum capacity adsorption depend on the type of plant as well as on the metal ions (atomic weight, ionic radius and electronegativity). The adsorption process is affected by various parameters such as contact time, solution volume to mass of plant particles ratio (m/V), particle size, solution pH and metal concentration. A dose of 25 g/l of adsorbent was optimal to obtain maximum adsorption of both metal ions. The maximum metal uptake was obtained with particles of organic matter of <50 microm. As to classical ionic adsorption phenomena, the adsorption of both metal ions increases with the increase of the initial concentration in the solution. For the two metal cations, the uptake efficiency of the studied plants ranged from: C. edulis>E. echinus>S. anthophorbium>L. arborescens, however, the differences are rather small. Two different waste water types (domestic and industrial) were tested and good results were obtained for removal of Pb(II) and Cd(II) at more than 90%. The removal of the metal and mineral ions waste water was observed for PO(4)(3-) at 88%, for NO(3)(-) at 96.5% and for metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using IOM as absorbent. PMID:17869071

  17. Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Melzani, Mickaël; Walder, Rolf; Folini, Doris; Winisdoerffer, Christophe; Favre, Jean M.

    2014-10-01

    Magnetic reconnection is a leading mechanism for magnetic energy conversion and high-energy non-thermal particle production in a variety of high-energy astrophysical objects, including ones with relativistic ion-electron plasmas (e.g., microquasars or AGNs), a regime where first principle studies are scarce. We present 2D particle-in-cell (PIC) simulations of low β ion-electron plasmas under relativistic conditions, i.e., with inflow magnetic energy exceeding the plasma restmass energy. We identify outstanding properties: (i) For relativistic inflow magnetizations (here 10 ≤ σe ≤ 360), the reconnection outflows are dominated by thermal agitation instead of bulk kinetic energy. (ii) At high inflow electron magnetization (σe ≥ 80), the reconnection electric field is sustained more by bulk inertia than by thermal inertia. It challenges the thermal-inertia paradigm and its implications. (iii) The inflows feature sharp transitions at the entrance of the diffusion zones. These are not shocks but results from particle ballistic motions, all bouncing at the same location, provided that the thermal velocity in the inflow is far lower than the inflow E × B bulk velocity. (iv) Island centers are magnetically isolated from the rest of the flow and can present a density depletion at their center. (v) The reconnection rates are slightly higher than in non-relativistic studies. They are best normalized by the inflow relativistic Alfvén speed projected in the outflow direction, which then leads to rates in a close range (0.14-0.25), thus allowing for an easy estimation of the reconnection electric field.

  18. Hydrogen Reduction Kinetics of Hematite Concentrate Particles Relevant to a Novel Flash Ironmaking Process

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Mohassab, Yousef; Jiang, Tao; Sohn, Hong Yong

    2015-04-01

    As an integral part of developing a novel ironmaking process, the hydrogen reduction kinetics of hematite concentrate particles (average particle size 21 µm) were measured in the temperature range from 1423 K to 1623 K (1150 °C to 1350 °C). The novel ironmaking process aims at producing iron from iron oxide concentrates in a flash reactor using gaseous fuels and reductants, which will help reduce energy consumption and minimize greenhouse gas emissions. More than 90 pct reduction of hematite concentrate particles could be obtained by hydrogen at a temperature of 1573 K (1300 °C) and 3 seconds of residence time, indicating that hematite concentrate is suitable for the flash reduction process under development largely aimed at the use of magnetite concentrates. The nucleation and growth rate equation with the Avrami parameter, n, of 1.0 well described the kinetics of hematite reduction. The reduction rate has a 1st-order dependence on the partial pressure of hydrogen. The activation energy of the reaction was 214 kJ/mol, indicating strong temperature dependence. The following complete rate equation was developed that can satisfactorily predict the kinetics of hematite concentrate particles and is suitable for the design of a flash reactor: {{{d}}X}/{{{d}t}} = 4.41 × 107 × {{e}}^{{ - 214{,}000/RT}} × ( {p{{H}}2 - {p{{H}}2 {{O}}}/K} ) × (1 - X), where X is fractional reduction degree, R is 8.314 J/mol K, T is in K, p is in atm, and t is in seconds.

  19. Colloidal particle adsorption at liquid interfaces: capillary driven dynamics and thermally activated kinetics.

    PubMed

    Rahmani, Amir M; Wang, Anna; Manoharan, Vinothan N; Colosqui, Carlos E

    2016-08-14

    The adsorption of single colloidal microparticles (0.5-1 μm radius) at a water-oil interface has been recently studied experimentally using digital holographic microscopy [Kaz et al., Nat. Mater., 2012, 11, 138-142]. An initially fast adsorption dynamics driven by capillary forces is followed by an unexpectedly slow relaxation to equilibrium that is logarithmic in time and can span hours or days. The slow relaxation kinetics has been attributed to the presence of surface "defects" with nanoscale dimensions (1-5 nm) that induce multiple metastable configurations of the contact line perimeter. A kinetic model considering thermally activated transitions between such metastable configurations has been proposed [Colosqui et al., Phys. Rev. Lett., 2013, 111, 028302] to predict both the relaxation rate and the crossover point to the slow logarithmic regime. However, the adsorption dynamics observed experimentally before the crossover point has remained unstudied. In this work, we propose a Langevin model that is able to describe the entire adsorption process of single colloidal particles by considering metastable states produced by surface defects and thermal motion of the particle and liquid interface. Invoking the fluctuation dissipation theorem, we introduce a drag term that considers significant dissipative forces induced by thermal fluctuations of the liquid interface. Langevin dynamics simulations based on the proposed adsorption model yield close agreement with experimental observations for different microparticles, capturing the crossover from (fast) capillary driven dynamics to (slow) thermally activated kinetics. PMID:27373956

  20. Effect of the particle size of a heterogeneous catalyst on the kinetics of liquid-phase oxidation of tetralin

    SciTech Connect

    Artemov, A.V.; Vainshtein, E.F.

    1988-01-10

    The dependence of the initial rate of oxidation of tetralin on the particle size of the Co/sup 2 +//SiO/sub 2/ catalyst is shown. The method proposed permitted explanation of the dependence of the kinetics of liquid-phase processes in the absence of extra- and intradiffusion hindrances on the particle size of a heterogeneous catalyst and estimation of the values of the kinetic constants from this dependence.

  1. Angular momentum transport and particle acceleration during magnetorotational instability in a kinetic accretion disk.

    PubMed

    Hoshino, Masahiro

    2015-02-13

    Angular momentum transport and particle acceleration during the magnetorotational instability (MRI) in a collisionless accretion disk are investigated using three-dimensional particle-in-cell simulation. We show that the kinetic MRI can provide not only high-energy particle acceleration but also enhancement of angular momentum transport. We find that the plasma pressure anisotropy inside the channel flow with p(∥)>p(⊥) induced by active magnetic reconnection suppresses the onset of subsequent reconnection, which, in turn, leads to high-magnetic-field saturation and enhancement of the Maxwell stress tensor of angular momentum transport. Meanwhile, during the quiescent stage of reconnection, the plasma isotropization progresses in the channel flow and the anisotropic plasma with p(⊥)>p(∥) due to the dynamo action of MRI outside the channel flow contribute to rapid reconnection and strong particle acceleration. This efficient particle acceleration and enhanced angular momentum transport in a collisionless accretion disk may explain the origin of high-energy particles observed around massive black holes. PMID:25723200

  2. Efficient Production of High-energy Nonthermal Particles during Magnetic Reconnection in a Magnetically Dominated Ion-Electron Plasma

    NASA Astrophysics Data System (ADS)

    Guo, Fan; Li, Xiaocan; Li, Hui; Daughton, William; Zhang, Bing; Lloyd-Ronning, Nicole; Liu, Yi-Hsin; Zhang, Haocheng; Deng, Wei

    2016-02-01

    Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. In this Letter, we investigate nonthermal particle acceleration during magnetic reconnection in a magnetically dominated ion-electron plasma using fully kinetic simulations. For an ion-electron plasma with a total magnetization of {σ }0={B}2/(4π n({m}i+{m}e){c}2), the magnetization for each species is {σ }i˜ {σ }0 and {σ }e˜ ({m}i/{m}e){σ }0, respectively. We have studied the magnetically dominated regime by varying σe = 103-105 with initial ion and electron temperatures {T}i={T}e=5-20{m}e{c}2 and mass ratio {m}i/{m}e=1-1836. The results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2-3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is 1\\lt s\\lt 2 for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be {γ }{be}˜ {σ }e and {γ }{bi}˜ {σ }i, respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices sp are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. We discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds, especially the applications for explaining nonthermal high-energy emissions.

  3. Nonlinear Evolution of Ion Acoustic Solitary Waves in Earth's Magnetosphere: Fluid and Particle-In-Cell Simulations

    NASA Astrophysics Data System (ADS)

    Kakad, A.; Kakad, B. A.; Omura, Y.

    2014-12-01

    In recent spacecraft observations, coherent electrostatic solitary wave (ESWs) structures are observed in various regions of the Earth's magnetosphere. Over the years, many researchers have attempted to model these observations in terms of electron/ion acoustic solitary waves by using nonlinear fluid theory/simulations. The ESW structures predicted by fluid models can be inadequate due to its inability in handling kinetic effects. To provide clear view on the application of the fluid and kinetic treatments in modeling the ESWs, we perform both fluid and particle-in-cell (PIC) simulations of ion acoustic solitary waves (IASWs) and estimate the quantitative differences in their characteristics like speed, amplitude, and width. It is noted that a long time evolution of Gaussian type perturbations in the equilibrium electron and ion densities generated the nonlinear IASW structures in both fluid and PIC simulations. The IASW structures represent vortices of trapped electrons in PIC simulations. We find that the number of trapped electrons in the wave potential is higher for the large amplitude IASW, which are generated by large-amplitude initial density perturbation (IDP). The present fluid and PIC simulation results are in close agreement for small amplitude IDPs, whereas for large IDPs they show discrepancy in the amplitude, width, and speed of the IASW, which is attributed to negligence of kinetic effects in the former approach. The speed of IASW in the fluid simulations increases with the increase of IASW amplitude, while the reverse tendency is seen in the PIC simulation. The present study suggests that the fluid treatment is appropriate to model the IASW observations when the magnitude of phase velocity of IASW is less than the ion acoustic (IA) speed obtained from their linear dispersion relation, whereas when it exceeds IA speed, it is necessary to include the kinetic effects in the model.

  4. Electron and ion kinetics and anode plasma formation in two applied Br field ion diodes

    NASA Astrophysics Data System (ADS)

    Johnson, D. J.; Quintenz, J. P.; Sweeney, M. A.

    1985-02-01

    Two magnetically insulated ion diodes that utilize a radial applied-B field are described. Both diodes generate an annular beam that is extracted along the diode axis. The first diode operated at 1.2 MV and 600 kA for 25 ns and generated a 300-kA ion beam. The second operated at 300 kV, 100 kA and generated 15 kA of ion current. The first diode was used to study diode performance as a function of inner and outer anode-cathode gaps, the applied-B field, and transmission line current ratios. The second diode was used to study anode plasma formation. The diodes were operated below Bcrit, resulting in electron leakage to the anode, especially near the outer cathode. A definition of Bcrit applicable to extraction diodes is given and methods of improving ion production efficiency in these diodes are suggested. The strong correlation of ion production with visible light emission suggests, however, that the electron loss played an important role in anode turn-on. The breakdown of neutral gas desorbed by electron impact is thought to be the anode plasma production mechanism. The grazing incidence leakage electrons affect the breakdown by significantly enhancing space-charge-induced electric fields in the dielectric-filled anode grooves.

  5. Ion distribution effects of turbulence on a kinetic auroral arc model

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.; Chiu, Y. T.

    1982-01-01

    An inverted-V auroral arc structure plasma-kinetic model is extended to phenomenologically include the effects of electrostatic turbulence, with k-parallel/k-perpendicular being much less than unity. It is shown that, unless plasma sheet ions are very much more energetic than the electrons, anomalous resistivity is not a large contributor to parallel electrostatic potential drops, since the support of the observed potential drop requires a greater dissipation of energy than can be provided by the plasma sheet. Wave turbulence can, however, be present, with the ion cyclotron turbulence levels suggested by the ion resonance broadening saturation mechanism of Dum and Dupree (1970) being comparable to those observed on auroral field lines. The diffusion coefficient and net growth rate are much smaller than estimates based solely on local plasma properties.

  6. Ion distribution effects of turbulence on a kinetic auroral arc model

    NASA Astrophysics Data System (ADS)

    Cornwall, J. M.; Chiu, Y. T.

    1982-03-01

    An inverted-V auroral arc structure plasma-kinetic model is extended to phenomenologically include the effects of electrostatic turbulence, with k-parallel/k-perpendicular being much less than unity. It is shown that, unless plasma sheet ions are very much more energetic than the electrons, anomalous resistivity is not a large contributor to parallel electrostatic potential drops, since the support of the observed potential drop requires a greater dissipation of energy than can be provided by the plasma sheet. Wave turbulence can, however, be present, with the ion cyclotron turbulence levels suggested by the ion resonance broadening saturation mechanism of Dum and Dupree (1970) being comparable to those observed on auroral field lines. The diffusion coefficient and net growth rate are much smaller than estimates based solely on local plasma properties.

  7. Impedance Analysis of Ion Transport Through Supported Lipid Membranes Doped with Ionophores: A New Kinetic Approach

    PubMed Central

    Alvarez, P. E.; Vallejo, A. E.

    2008-01-01

    Kinetics of facilitated ion transport through planar bilayer membranes are normally analyzed by electrical conductance methods. The additional use of electrical relaxation techniques, such as voltage jump, is necessary to evaluate individual rate constants. Although electrochemical impedance spectroscopy is recognized as the most powerful of the available electric relaxation techniques, it has rarely been used in connection with these kinetic studies. According to the new approach presented in this work, three steps were followed. First, a kinetic model was proposed that has the distinct quality of being general, i.e., it properly describes both carrier and channel mechanisms of ion transport. Second, the state equations for steady-state and for impedance experiments were derived, exhibiting the input–output representation pertaining to the model’s structure. With the application of a method based on the similarity transformation approach, it was possible to check that the proposed mechanism is distinguishable, i.e., no other model with a different structure exhibits the same input–output behavior for any input as the original. Additionally, the method allowed us to check whether the proposed model is globally identifiable (i.e., whether there is a single set of fit parameters for the model) when analyzed in terms of its impedance response. Thus, our model does not represent a theoretical interpretation of the experimental impedance but rather constitutes the prerequisite to select this type of experiment in order to obtain optimal kinetic identification of the system. Finally, impedance measurements were performed and the results were fitted to the proposed theoretical model in order to obtain the kinetic parameters of the system. The successful application of this approach is exemplified with results obtained for valinomycin–K+ in lipid bilayers supported onto gold substrates, i.e., an arrangement capable of emulating biological membranes. PMID:19669528

  8. Dispersion characteristics of kinetic Alfven waves in a multi-ion cometary plasma

    NASA Astrophysics Data System (ADS)

    Jayapal, R.; Abraham, Noble P.; Blesson, Jose; Antony, S.; Anilkumar, C. P.; Venugopal, Chandu

    We have studied the stability of the kinetic Alfven wave in a plasma composed of hydrogen and positively and negatively charged oxygen ions and electrons which approximates very well the plasma environment around comet Halley. In the direction parallel to the magnetic field, the electrons have been modelled by a drifting Maxwellian distribution. In the perpendicular direction, another ring simulated by a loss cone type distribution, obtained by subtracting two Maxwellians with different temperatures, model all the constituents of the plasma. The dispersion relation derived for KAWs is a generalisation of the pioneering dispersion relation of Hasegawa on two counts: it has been extended to a plasma described by a generalised distribution function and to a multi - ion plasma containing positively and negatively charged ions. We find that the dispersion characteristics of the KAW can be made independent of the heavy ion parameters by an appropriate choice of densities and temperatures. The source of free energy for the instability is the drift velocity of the electrons; the growth rate increases with increasing drift velocity of the electrons. The positively charged heavier ions enhance the instability while the negatively charged heavier ions tend to damp the wave.

  9. Kinetic theory for the ion humps at the foot of the Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Jovanović, D.; Krasnoselskikh, V. V.

    2009-10-01

    The nonlinear kinetic theory is presented for the ion acoustic perturbations at the foot of the Earth's quasiperpendicular bow shock, that is characterized by weakly magnetized electrons and unmagnetized ions. The streaming ions, due to the reflection of the solar wind ions from the shock, provide the free energy source for the linear instability of the acoustic wave. In the fully nonlinear regime, a coherent localized solution is found in the form of a stationary ion hump, which is traveling with the velocity close to the phase velocity of the linear mode. The structure is supported by the nonlinearities coming from the increased population of the resonant beam ions, trapped in the self-consistent potential. As their size in the direction perpendicular to the local magnetic field is somewhat smaller that the electron Larmor radius and much larger that the Debye length, their spatial properties are determined by the effects of the magnetic field on weakly magnetized electrons. These coherent structures provide a theoretical explanation for the bipolar electric pulses, observed upstream of the shock by Polar and Cluster satellite missions.

  10. Active matter beyond mean-field: Ring-kinetic theory for self-propelled particles

    NASA Astrophysics Data System (ADS)

    Chou, Yen-Liang; Ihle, Thomas

    2015-02-01

    Recently, Hanke et al. [Phys. Rev. E 88, 052309 (2013), 10.1103/PhysRevE.88.052309] showed that mean-field kinetic theory fails to describe collective motion in soft active colloids and that correlations must not be neglected. Correlation effects are also expected to be essential in systems of biofilaments driven by molecular motors and in swarms of midges. To obtain correlations in an active matter system from first principles, we derive a ring-kinetic theory for Vicsek-style models of self-propelled agents from the exact N -particle evolution equation in phase space. The theory goes beyond mean-field and does not rely on Boltzmann's approximation of molecular chaos. It can handle precollisional correlations and cluster formation, which are both important to understand the phase transition to collective motion. We propose a diagrammatic technique to perform a small-density expansion of the collision operator and derive the first two equations of the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. An algorithm is presented that numerically solves the evolution equation for the two-particle correlations on a lattice. Agent-based simulations are performed and informative quantities such as orientational and density correlation functions are compared with those obtained by ring-kinetic theory. Excellent quantitative agreement between simulations and theory is found at not-too-small noises and mean free paths. This shows that there are parameter ranges in Vicsek-like models where the correlated closure of the BBGKY hierarchy gives correct and nontrivial results. We calculate the dependence of the orientational correlations on distance in the disordered phase and find that it seems to be consistent with a power law with an exponent around -1.8 , followed by an exponential decay. General limitations of the kinetic theory and its numerical solution are discussed.

  11. The kinetic features of ion dynamics in the closed magnetic configurations.

    NASA Astrophysics Data System (ADS)

    Malykhin, Andrey; Grigorenko, Elena; Malova, Helmi

    2016-04-01

    A lot of spacecraft observations showed that the closed magnetic configurations such as plasmoids and magnetic islands are often observed in the Earth magnetotail. The purpose of our study is to analyze the kinetic features of nonadiabatic ion dynamics in the current sheet (CS) inside a plasmoid and the efficiency of ion acceleration in such configurations. Trajectories of test ions of different masses (H+ i O+) were studied in the prescribed magnetic configuration similar to the one observed by Cluster spacecraft (s/c). The magnetic configuration consists of a single stationary plasmoid in the tail side of a near-Earth magnetic X-line. Everywhere in the system there is the constant and uniform dawn-dusk electric field Ey ~ 0.1 mV/m. Cold ion beams with the characteristics similar to the ones observed in the lobe were launched in the system. In the absence of electromagnetic fluctuations the plasmoid localization in the dawn-dusk direction imposes a limit on the ion energy gain in the course of ion nonadiabatic interaction with the plasmoid's CS (in the region of minimum |B| field). The ion dynamics and energy gain changed dramatically when we introduced the low-frequency electromagnetic fluctuations into the plasmoid. The spectra of the magnetic and electric field fluctuations were similar to the ones observed inside the plasmoids by Cluster spacecraft. Our analysis showed that in the presence of fluctuations the ion dynamics and energy gain are defined by the resonant interaction of ions with the wave harmonics. Ions can gain energy hundred times larger than their energy gain in the system without electromagnetic fluctuations. The inclusion of a guide magnetic field (By) significantly affects the ion dynamics inside the plasmoid. The presence of a guide field generates the "north-south" asymmetry in the ejection of nonadiabatic ions from the CS. The effects of the "north-south" asymmetry in the spatial distribution of the nonadiabatic ions inside the plasmoid on

  12. Kinetic Mie ellipsometry to determine the time-resolved particle growth in nanodusty plasmas

    NASA Astrophysics Data System (ADS)

    Groth, Sebastian; Greiner, Franko; Tadsen, Benjamin; Piel, Alexander

    2015-11-01

    The growth of nanometer-sized particles in a reactive argon-acetylene plasma is investigated by means of kinetic single-wavelength Mie ellipsometry from the change of the polarization state of scattered light. This requires advanced measurement techniques as well as complex methods for the analysis of the measured data. Today commercial devices reduce the metrological effort, but the data analysis is still a challenging topic. We present a scheme to gain time-resolved information about the size evolution of monodisperse spherical particles and to determine their optical properties, represented by the complex refractive index N, without limiting assumptions concerning the evolution of the particle size or the need for additional ex situ diagnostics. The method is applied on typical particle growth processes at varying optical depth and compared to ex situ SEM measurements. It is shown that more complex processes, including particle etching, can be analyzed. This demonstrates the applicability of the analysis on a strongly non-linear process.

  13. Kinetics of heterogeneous reactions of carbon and oxygen during combustion of porous carbon particles in oxygen

    SciTech Connect

    Gremyachkin, V.M.

    2006-05-15

    A model of combustion of a high-porosity carbon particle in oxygen is considered, which takes into account heterogeneous and homogeneous chemical reactions inside the particles and radiative heat transfer. The boundaries of the domain where the burning rate depends on the particle temperature are determined. The possibility of two combustion regimes is demonstrated: regime with a high burning rate, where the carbon-oxygen reaction proceeds in a layer adjacent to the particle surface, and regime with a low burning rate, where the reaction proceeds in the entire particle volume. In the regime with a high burning rate, the main product of the reaction between carbon and oxygen is carbon monoxide, whereas both carbon monoxide and carbon dioxide can be formed in the regime with a low burning rate. The kinetic equations of heterogeneous reactions C + O{sub 2} = CO{sub 2} and 2C + O{sub 2} = 2CO are determined, which reveal the retarding effect of carbon monoxide and dioxide on the rates of these reactions.

  14. The dynamics of particle disks. III - Dense and spinning particle disks. [development of kinetic theory for planetary rings

    NASA Technical Reports Server (NTRS)

    Araki, Suguru

    1991-01-01

    The kinetic theory of planetary rings developed by Araki and Tremaine (1986) and Araki (1988) is extended and refined, with a focus on the implications of finite particle size: (1) nonlocal collisions and (2) finite filling factors. Consideration is given to the derivation of the equations for the local steady state, the low-optical-depth limit, and the steady state at finite filling factors (including the effects of collision inelasticity, spin degrees of freedom, and self-gravity). Numerical results are presented in extensive graphs and characterized in detail. The importance of distinguishing effects (1) and (2) at low optical depths is stressed, and the existence of vertical density profiles with layered structures at high filling factors is demonstrated.

  15. Surface analysis of zeolites: An XPS, variable kinetic energy XPS, and low energy ion scattering study

    NASA Astrophysics Data System (ADS)

    Bare, Simon R.; Knop-Gericke, Axel; Teschner, Detre; Hävacker, Michael; Blume, Raoul; Rocha, Tulio; Schlögl, Robert; Chan, Ally S. Y.; Blackwell, N.; Charochak, M. E.; ter Veen, Rik; Brongersma, Hidde H.

    2016-06-01

    The surface Si/Al ratio in a series of zeolite Y samples has been obtained using laboratory XPS, synchrotron (variable kinetic energy) XPS, and low energy ion scattering (LEIS) spectroscopy. The non-destructive depth profile obtained using variable kinetic energy XPS is compared to that from the destructive argon ion bombardment depth profile from the lab XPS instrument. All of the data indicate that the near surface region of both the ammonium form and steamed Y zeolites is strongly enriched in aluminum. It is shown that when the inelastic mean free path of the photoelectrons is taken into account the laboratory XPS of aluminosilicates zeolites does not provide a true measurement of the surface stoichiometry, while variable kinetic energy XPS results in a more surface sensitive measurement. A comprehensive Si/Al concentration profile as a function of depth is developed by combining the data from the three surface characterization techniques. The LEIS spectroscopy reveals that the topmost atomic layer is further enriched in Al compared to subsequent layers.

  16. Adsorption of heavy metal ions using hierarchical CaCO3-maltose meso/macroporous hybrid materials: adsorption isotherms and kinetic studies.

    PubMed

    Ma, Xiaoming; Li, Liping; Yang, Lin; Su, Caiyun; Wang, Kui; Yuan, Shibao; Zhou, Jianguo

    2012-03-30

    Highly ordered hierarchical calcium carbonate is an important phase and has technological interest in the development of functional materials. The work describes hierarchical CaCO(3)-maltose meso/macroporous hybrid materials were synthesized using a simple gas-diffusion method. The uniform hexagonal-shaped CaCO(3)-maltose hybrid materials are formed by the hierarchical assembly of nanoparticles. The pore structure analysis indicates that the sample possesses the macroporous structure of mesoporous framework. The distinguishing features of the hierarchical CaCO(3)-maltose materials in water treatment involve not only high removal capacities, but also decontamination of trace metal ions. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum removal capacity of the CaCO(3)-maltose hybrid materials for Pb(2+), Cd(2+), Cu(2+), Co(2+), Mn(2+) and Ni(2+) ions was 3242.48, 487.80, 628.93, 393.70, 558.66 and 769.23 mg/g, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The adsorption and precipitation transformation mechanism can be considered due to hierarchical meso/macroporous structure, rich organic ligands of the CaCO(3)-maltose hybrid materials and the larger solubility product of CaCO(3). PMID:22326246

  17. Suppression in droplet growth kinetics by the addition of organics to sulfate particles

    NASA Astrophysics Data System (ADS)

    Wong, Jenny P. S.; Liggio, John; Li, Shao-Meng; Nenes, Athanasios; Abbatt, Jonathan P. D.

    2014-11-01

    Aerosol-cloud interactions are affected by the rate at which water vapor condenses onto particles during cloud droplet growth. Changes in droplet growth rates can impact cloud droplet number and size distribution. The current study investigated droplet growth kinetics of acidic and neutral sulfate particles which contained various amounts and types of organic compounds, from model compounds (carbonyls) to complex mixtures (α-pinene secondary organic aerosol and diesel engine exhaust). In most cases, the formed droplet size distributions were shifted to smaller sizes relative to control experiments (pure sulfate particles), due to suppression in droplet growth rates in the cloud condensation nuclei counter. The shift to smaller droplets correlated with increasing amounts of organic material, with the largest effect observed for acidic seed particles at low relative humidity. For all organics incorporated onto acidic particles, formation of high molecular weight compounds was observed, probably by acid-catalyzed Aldol condensation reactions in the case of carbonyls. To test the reversibility of this process, carbonyl experiments were conducted with acidic particles exposed to higher relative humidity. High molecular weight compounds were not measured in this case and no shift in droplet sizes was observed, suggesting that high molecular weight compounds are the species affecting the rate of water uptake. While these results provide laboratory evidence that organic compounds can slow droplet growth rates, the modeled mass accommodation coefficient of water on these particles (α > 0.1) indicates that this effect is unlikely to significantly affect cloud properties, consistent with infrequent field observations of slower droplet growth rates.

  18. A coarse-grained kinetic equation for neutral particles in turbulent fusion plasmas

    SciTech Connect

    Mekkaoui, A.; Marandet, Y.; Genesio, P.; Rosato, J.; Stamm, R.; Capes, H.; Koubiti, M.; Godbert-Mouret, L.; Catoire, F.

    2012-06-15

    A coarse-grained kinetic equation for neutral particles (atoms, molecules) in magnetized fusion plasmas, valid on time scales large compared to the turbulence correlation time, is presented. This equation includes the effects of plasma density fluctuations, described by gamma statistics, on the transport of neutral particles. These effects have so far been neglected in plasma edge modeling, in spite of the fact that the amplitude of fluctuations can be of order unity. Density fluctuations are shown to have a marked effect on the screening of neutrals and on the spatial localization of the ionization source, in particular at high density. The coarse-grained equations obtained in this work are readily implemented in edge code suites currently used for fusion plasma analysis and future divertor design (ITER, DEMO).

  19. The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets

    PubMed Central

    Wilson, R. J. H.; Kay, G.; Lilly, M. D.

    1968-01-01

    1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5·0–9·2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively. PMID:5673529

  20. Kinetics studies with fruit bromelain (Ananas comosus) in the presence of cysteine and divalent ions.

    PubMed

    Kaur, Tajwinder; Kaur, Amandeep; Grewal, Ravneet K

    2015-09-01

    The kinetics of cysteine and divalent ion modulation viz. Ca(2+), Cu(2+), Hg(2+) of fruit bromelain (EC 3.4.22.33) have been investigated in the present study. Kinetic studies revealed that at pH 4.5, cysteine induced V-type activation of bromelain catalyzed gelatin hydrolysis. At pH 3.5, Ca(2+) inhibited the enzyme noncompetitively, whereas, both K-and V-type activations of bromelain were observed in the presence of 0.5 mM Ca(2+) at pH 4.5 and 7.5. Bromelain was inhibited competitively at 0.6 mM Cu(2+) ions at pH 3.5, which changed to an uncompetitive inhibition at pH 4.5 and 7.5. An un-competitive inhibition of bromelain catalyzed gelatin hydrolysis was observed in the presence of 0.6 mM Hg(2+) at pH 3.5 and 4.5. These findings suggest that divalent ions modulation of fruit bromelain is pH dependent. PMID:26345013

  1. Impact of natural organic matter properties on the kinetics of suspended ion exchange process.

    PubMed

    Bazri, Mohammad Mahdi; Mohseni, Madjid

    2016-03-15

    Removal kinetics of four standard organic matter isolates under the application of strongly basic ion exchange resins (IEX) in suspended mode was studied under commercial application conditions. Suwannee River natural organic matter (SRNOM), SR fulvic acid (SRFA), and Pony Lake fulvic acid (PLFA) were greatly removed (>90%) and highly preferred by IEX resins (α > 5, over Cl(-), and HCO3(-)) while SR humic acid (SRHA) was the least preferred organic structure among the four isolates studied (α ≈ 1). Moreover, the efficacy of removal for fulvic acids (i.e., SRFA, PLFA) was consistent over consecutive reuse of IEX resins (i.e., loading cycles) whereas it decreased for SRNOM and SRHA over the course of operation. The stoichiometric correlation between the chloride released from the resins as a result of organic molecules uptake indicated that ion exchange was the dominant mechanism. Results obtained indicated that molecular weight and charge density of isolates played a major role in the performance of ion exchange process for organic matter removal. Furthermore, various empirical and physical models were evaluated using the experimental data and pore diffusion was found to be the rate-liming step during the uptake of organic matters; hence, it was used as the appropriate model to predict the kinetics of removal. Consequently, free liquid diffusivities and effective pore diffusion coefficients of organic molecules were estimated and findings were in agreement with the literature data that were obtained from spectrophotometric methods. PMID:26774263

  2. Three-Dimensional Perturbative Particle Simulation of Intense Ion Beams

    NASA Astrophysics Data System (ADS)

    Lee, W. Wei-Li; Stoltz, Peter H.; Davidson, Ronald C.; Qin, Hong

    1998-11-01

    A three-dimensional nonlinear perturbative (δ f) particle simulation scheme is under developement for studying the stability and transport properties of an intense ion beam propagating through background electrons and a periodic focusing lattice,(Q. Qian, W. Lee, and R. C. Davidson, Phys. Plasmas 4), 1915 (1997).^,(P. H. Stoltz, W. W. Lee, R. C. Davidson, this conference.) in which the distribution function is split into equilibrium and perturbed parts. To further facilitate the simulations, a mode expansion scheme (C. Z. Cheng and H. Okuda, J. Comp. Phys. 25), 133 (1977). for the perturbative scheme has been developed, in which only a few long wavelength modes along the direction of propagation are kept. The code will be useful for many applications in beam physics and is an intermediate step toward a fully three-dimensional multi-species code. The algorithm and its applications to the electron-proton instability (R. C. Davidson, P. H. Stoltz, W. W. Lee and T.-S. Wang, this conference.) in proton linacs and storage rings will be reported.

  3. Reaction kinetic parameters for ion transport from steady-state current-voltage curves.

    PubMed Central

    Gradmann, D; Klieber, H G; Hansen, U P

    1987-01-01

    This study demonstrates possible ways to estimate the rate constants of reaction kinetic models for ion transport from steady-state current-voltage data as measured at various substrate concentrations. This issue is treated theoretically by algebraic reduction and extension of a reaction kinetic four-state model for uniport. Furthermore, an example for application is given; current-voltage data from an open K+ selective channel (Schroeder, J.I., R. Hedrich, and J.M. Fernandez, 1984, Nature (Lond.), 312:361-362) supplemented by some new data have been evaluated. The analysis yields absolute numerical estimates of the 14 rate constants of a six-state model, which is discussed in a wider context. PMID:2437973

  4. Kinetic evidence for five-coordination in AlOH(aq)2+ ion.

    PubMed

    Swaddle, Thomas W; Rosenqvist, Jörgen; Yu, Ping; Bylaska, Eric; Phillips, Brian L; Casey, William H

    2005-06-01

    Trivalent aluminum ions are important in natural bodies of water, but the structure of their coordination shell is a complex unsolved problem. In strong acid (pH < 3.0), Al(III) exists almost entirely as the octahedral Al(H2O)6(3+) ion, whereas in basic conditions (pH > 7), a tetrahedral Al(OH)(4- structure prevails. In the biochemically and geochemically critical pH range of 4.3 to 7.0, the ion structures are less clear. Other hydrolytic species, such as AlOH(aq)2+, exist and are traditionally assumed to be hexacoordinate. We show, however, that the kinetics of proton and water exchange on aqueous Al(III), coupled with Car-Parrinello simulations, support a five-coordinate Al(H2O)4OH2+ ion as the predominant form of AlOH(aq)2+ under ambient conditions. This result contrasts Al(III) with other trivalent metal aqua ions, for which there is no evidence for stable pentacoordinate hydrolysis products. PMID:15860592

  5. Factors affecting ion kinetic temperature, number density, and containment time in the NASA Lewis bumpy-torus plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1977-01-01

    The degree of toroidal symmetry of the plasma, the number of midplane electrode rings, the configuration of electrode rings, and the location of the diagnostic instruments with respect to the electrode rings used to generate the plasma are discussed. Impurities were deliberately introduced into the plasma, and the effects of the impurity fraction on ion kinetic temperature and electron number density were observed. It is concluded that, if necessary precautions are taken, the plasma communicates extremely well along the magnetic field lines and displays a high degree of symmetry from sector to sector for a wide range of electrode ring configurations and operating conditions. Finally, some characteristic data taken under nonoptimized conditions are presented, which include the highest electron number density and the longest particle containment time (1.9 msec) observed. Also, evidence from a paired comparison test is presented which shows that the electric field acting along the minor radius of the toroidal plasma improves the plasma density and the calculated containment time more than an order of magnitude if the electric field points inward, relative to the values observed when it points (and pushes ions) radially outward.

  6. Gyrokinetic and kinetic particle-in-cell simulations of guide-field reconnection

    NASA Astrophysics Data System (ADS)

    Munoz Sepulveda, Patricio Alejandro; Büchner, Jörg; Kilian, Patrick; Told, Daniel; Jenko, Frank

    2016-07-01

    Fully kinetic Particle-in-Cell (PIC) simulations of (strong) guide-field reconnection can be computationally very demanding, due to the intrinsic stability and accuracy conditions required by this numerical method. One convenient approach to circumvent this issue is using gyrokinetic theory, an approximation of the Vlasov-Maxwell equations for strongly magnetized plasmas that eliminates the fast gyromotion, and thus reduces the computational cost. Although previous works have started to compare the features of reconnection between both approaches, a complete understanding of the differences is far from being complete. This knowledge is essential to discern the limitations of the gyrokinetic simulations of magnetic reconnection when applied to scenarios with moderate guide fields, such as the Solar corona, in contrast to most of the fusion/laboratory plasmas. We extend a previous work by our group, focused in the differences in the macroscopic flows, by analyzing the heating processes and non-thermal features developed by reconnection between both plasma approximations. We relate these processes by identifying some high-frequency cross-streaming instabilities appearing only in the fully kinetic approach. We characterize the effects of these phenonema such as anisotropic electron heating, beam formation and turbulence under different parameter regimes. And finally, we identify the conditions under which these instabilities tends to become negligible in the fully kinetic model, and thus a comparison with gyrokinetic theory becomes more reliable.

  7. A Kinetic 13-Moment Boundary Conditions Method for Particle Simulations of Viscous Rarefied Flows

    NASA Astrophysics Data System (ADS)

    Averkin, Sergey; Gatsonis, Nikolaos

    2015-11-01

    The kinetic 13-moment (Navier-Stokes-Fourrier) boundary condition method is developed for direct simulation Monte Carlo (DSMC) simulations of rarefied gas flows. The particles are injected into the computational domain from the inlet and outlet following the first-order Chapman-Enskog distribution function. The unknown parameters of the Chapman-Enskog distribution function are reconstructed from the full 13-moment (Navier-Stokes-Fourier) equations discretized on the boundaries with the wave amplitudes calculated by the local one dimensional inviscid (LODI) formulation used in compressible (continuous) flow computations. The kinetic-moment boundary conditions are implemented in an unstructured 3D DSMC (U3DSMC) code and are supplemented with a neighboring-cell sampling approach and a time-average smoothing techniques to speed up convergence and reduce fluctuations. Simulations of a pressure-driven viscous subsonic flow in a circular tube are used for verification and validation of the boundary conditions. In addition, the present method is compared to the previously developed kinetic-moment boundary conditions derived from the five-moment (Euler) equations. AFOSR-FA9550-14-1-0366 Computational Mathematics Program.

  8. Rate theory of solvent exchange and kinetics of Li(+) - BF4 (-)/PF6 (-) ion pairs in acetonitrile.

    PubMed

    Dang, Liem X; Chang, Tsun-Mei

    2016-09-01

    In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li(+) and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li(+) in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li(+)-[BF4] and Li(+)-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li(+). We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li(+)-[BF4] and Li(+)-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems. PMID:27608999

  9. Physico-chemical requirements and kinetics of membrane fusion of flavivirus-like particles.

    PubMed

    Espósito, Danillo L A; Nguyen, Jennifer B; DeWitt, David C; Rhoades, Elizabeth; Modis, Yorgo

    2015-07-01

    Flaviviruses deliver their RNA genome into the host-cell cytoplasm by fusing their lipid envelope with a cellular membrane. Expression of the flavivirus pre-membrane and envelope glycoprotein genes in the absence of other viral genes results in the spontaneous assembly and secretion of virus-like particles (VLPs) with membrane fusion activity. Here, we examined the physico-chemical requirements for membrane fusion of VLPs from West Nile and Japanese encephalitis viruses. In a bulk fusion assay, optimal hemifusion (or lipid mixing) efficiencies were observed at 37 °C. Fusion efficiency increased with decreasing pH; half-maximal hemifusion was attained at pH 5.6. The anionic lipids bis(monoacylglycero)phosphate and phosphatidylinositol-3-phosphate, when present in the target membrane, significantly enhanced fusion efficiency, consistent with the emerging model that flaviviruses fuse with intermediate-to-late endosomal compartments, where these lipids are most abundant. In a single-particle fusion assay, VLPs catalysed membrane hemifusion, tracked as lipid mixing with the cellular membrane, on a timescale of 7-20 s after acidification. Lipid mixing kinetics suggest that hemifusion is a kinetically complex, multistep process. PMID:25740960

  10. Effects of Prepolymerized Particle Size and Polymerization Kinetics on Volumetric Shrinkage of Dental Modeling Resins

    PubMed Central

    Ha, Jung-Yun; Chun, Ju-Na; Son, Jun Sik; Kim, Kyo-Han

    2014-01-01

    Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA) resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control). The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes) were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P > 0.05) or significantly larger (P < 0.05) than that of the control resin and were related to the polymerization kinetics (P < 0.05) rather than the PMMA bead size (P = 0.335). Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins. PMID:24779020

  11. Target search kinetics of self-propelled particles in a confining domain

    NASA Astrophysics Data System (ADS)

    Wang, Jiajun; Chen, Yuhao; Yu, Wancheng; Luo, Kaifu

    2016-05-01

    We present a numerical investigation of the search kinetics of self-propelled particles (SPPs) to a target located at the center or at the boundary of a confining domain. When searching a target located at the center of a circular confining domain, the search efficiency of SPPs is improved compared to that of Brownian particles if the rotational diffusion is not too slow. In this case, the mean search time τ could be minimized with proper combinations of the characteristic rotation time τθ and the self-propulsion velocity v0. It is further shown to be a consequence of the interplay between the enhanced diffusion and the thigmotactism (boundary-following behavior) of SPPs due to the self-propulsion. However, for a target located at the boundary of the circular confining domain, we find that the search process is continuing to be accelerated with increasing τθ or v0. Our results highlight the role of the target position in the search kinetics, and open up new opportunities to optimize the search process of SPPs by taking accurate controls over their motions.

  12. DRIFT-KINETIC MODELING OF PARTICLE ACCELERATION AND TRANSPORT IN SOLAR FLARES

    SciTech Connect

    Minoshima, T.; Masuda, S.; Miyoshi, Y.

    2010-05-01

    Based on the drift-kinetic theory, we develop a model for particle acceleration and transport in solar flares. The model describes the evolution of the particle distribution function by means of a numerical simulation of the drift-kinetic Vlasov equation, which allows us to directly compare simulation results with observations within an actual parameter range of the solar corona. Using this model, we investigate the time evolution of the electron distribution in a flaring region. The simulation identifies two dominant mechanisms of electron acceleration. One is the betatron acceleration at the top of closed loops, which enhances the electron velocity perpendicular to the magnetic field line. The other is the inertia drift acceleration in open magnetic field lines, which produces antisunward electrons. The resulting velocity space distribution significantly deviates from an isotropic distribution. The former acceleration can be a generation mechanism of electrons that radiate loop-top nonthermal emissions, and the latter of escaping electrons from the Sun that should be observed by in situ measurements in interplanetary space and resulting radio bursts through plasma instabilities.

  13. Physico-chemical requirements and kinetics of membrane fusion of flavivirus-like particles

    PubMed Central

    Espósito, Danillo L. A.; Nguyen, Jennifer B.; DeWitt, David C.; Rhoades, Elizabeth

    2015-01-01

    Flaviviruses deliver their RNA genome into the host-cell cytoplasm by fusing their lipid envelope with a cellular membrane. Expression of the flavivirus pre-membrane and envelope glycoprotein genes in the absence of other viral genes results in the spontaneous assembly and secretion of virus-like particles (VLPs) with membrane fusion activity. Here, we examined the physico-chemical requirements for membrane fusion of VLPs from West Nile and Japanese encephalitis viruses. In a bulk fusion assay, optimal hemifusion (or lipid mixing) efficiencies were observed at 37 °C. Fusion efficiency increased with decreasing pH; half-maximal hemifusion was attained at pH 5.6. The anionic lipids bis(monoacylglycero)phosphate and phosphatidylinositol-3-phosphate, when present in the target membrane, significantly enhanced fusion efficiency, consistent with the emerging model that flaviviruses fuse with intermediate-to-late endosomal compartments, where these lipids are most abundant. In a single-particle fusion assay, VLPs catalysed membrane hemifusion, tracked as lipid mixing with the cellular membrane, on a timescale of 7–20 s after acidification. Lipid mixing kinetics suggest that hemifusion is a kinetically complex, multistep process. PMID:25740960

  14. Size Resolved High Temperature Oxidation Kinetics of Nano-Sized Titanium and Zirconium Particles.

    PubMed

    Zong, Yichen; Jacob, Rohit J; Li, Shuiqing; Zachariah, Michael R

    2015-06-18

    While ultrafine metal particles offer the possibility of very high energy density fuels, there is considerable uncertainty in the mechanism by which metal nanoparticles burn, and few studies that have examined the size dependence to their kinetics at the nanoscale. In this work we quantify the size dependence to the burning rate of titanium and zirconium nanoparticles. Nanoparticles in the range of 20-150 nm were produced via pulsed laser ablation, and then in-flight size-selected using differential electrical mobility. The size-selected oxide free metal particles were directly injected into the post flame region of a laminar flame to create a high temperature (1700-2500 K) oxidizing environment. The reaction was monitored using high-speed videography by tracking the emission from individual nanoparticles. We find that sintering occurs prior to significant reaction, and that once sintering is accounted for, the rate of combustion follows a near nearly (diameter)(1) power-law dependence. Additionally, Arrhenius parameters for the combustion of these nanoparticles were evaluated by measuring the burn times at different ambient temperatures. The optical emission from combustion was also used to model the oxidation process, which we find can be reasonably described with a kinetically controlled shrinking core model. PMID:25914926

  15. Target search kinetics of self-propelled particles in a confining domain.

    PubMed

    Wang, Jiajun; Chen, Yuhao; Yu, Wancheng; Luo, Kaifu

    2016-05-28

    We present a numerical investigation of the search kinetics of self-propelled particles (SPPs) to a target located at the center or at the boundary of a confining domain. When searching a target located at the center of a circular confining domain, the search efficiency of SPPs is improved compared to that of Brownian particles if the rotational diffusion is not too slow. In this case, the mean search time τ could be minimized with proper combinations of the characteristic rotation time τθ and the self-propulsion velocity v0. It is further shown to be a consequence of the interplay between the enhanced diffusion and the thigmotactism (boundary-following behavior) of SPPs due to the self-propulsion. However, for a target located at the boundary of the circular confining domain, we find that the search process is continuing to be accelerated with increasing τθ or v0. Our results highlight the role of the target position in the search kinetics, and open up new opportunities to optimize the search process of SPPs by taking accurate controls over their motions. PMID:27250320

  16. Calculated half-lives and kinetic energies for spontaneous emission of heavy ions from nuclei

    SciTech Connect

    Poenaru, D.N.; Greiner, W.; Depta, K.; Ivascu, M.; Mazilu, D.; Sandulescu, A.

    1986-05-01

    The most probable decays by spontaneous emission of heavy ions are listed for nuclides with Z = 47--106 and total half-lives>1 ..mu..sec. Partial half-lives, branching ratios relative to ..cap alpha.. decay, kinetic energies, and Q values are estimated by using the analytical superasymmetric fission model, a semiempirical formula for those ..cap alpha..-decay lifetimes which have not been measured, and the new Wapstra--Audi mass tables. Numerous ''stable'' nuclides with Z>40 are found to be metastable with respect to the new decay modes. The current experimental status is briefly reviewed.

  17. Final Report: Mechanisms of sputter ripple formation: coupling among energetic ions, surface kinetics, stress and composition

    SciTech Connect

    Chason, Eric; Shenoy, Vivek

    2013-01-22

    Self-organized pattern formation enables the creation of nanoscale surface structures over large areas based on fundamental physical processes rather than an applied template. Low energy ion bombardment is one such method that induces the spontaneous formation of a wide variety of interesting morphological features (e.g., sputter ripples and/or quantum dots). This program focused on the processes controlling sputter ripple formation and the kinetics controlling the evolution of surfaces and nanostructures in high flux environments. This was done by using systematic, quantitative experiments to measure ripple formation under a variety of processing conditions coupled with modeling to interpret the results.

  18. Kinetic approach to evaluate the energy and entropy of activation for the exchange of alkaline earth metal ions on tin(IV) tungstate cation exchanger

    SciTech Connect

    Varshney, K.G.; Khan, A.A.; Varshney, K.; Agrawal, S.

    1984-01-01

    A new approach based on the Nernst-Planck equations has been applied to study the reaction kinetics on the surface of tin(IV) tungstate for the Mg(II)-H(I), Ca(II)-H(I), Sr(II)-H(I) and Ba(II)-H(I) exchanges under the conditions favouring a particle diffusion phenomenon. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated which give some informations regarding the mechanism of ion-exchange on the surface of inorganic materials. 25 references, 3 figures, 3 tables.

  19. Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

    DOE PAGESBeta

    Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.; Atzeni, S.; Rinderknecht, H. G.; Hoffman, N. M.; Zylstra, A. B.; Li, C. K.; Sio, H.; Gatu Johnson, M.; et al

    2015-06-02

    The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurementsmore » of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

  20. Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK ˜ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.

  1. Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

    SciTech Connect

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

    2015-06-02

    The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.

  2. Adaptation of an Ambient Ion Monitor for Detection of Amines in Airborne Particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural facilities are the source of particles and gases that can exhibit an influence on air quality. Particle mass concentration influences from agricultural sources can include both primary emissions and secondary particle formation through emission of gaseous precursors. An ambient ion moni...

  3. Kinetics of gas-to-liquid and liquid-to-solid transfer of particles in metal-matrix composites

    NASA Technical Reports Server (NTRS)

    Stefanescu, D. M.; Rana, F.; Moitra, A.; Kacar, S.

    1990-01-01

    Analytical models for transfer of particles from gas to liquid and from liquid to solid are introduced. The model for calculation of the pushing/engulfment transition in directionally solidified particulate metal matrix composites, considers process thermodynamics, process kinetics, thermophysical properties and buoyant forces. Based on processing variables (solidification velocity and direction) and on material variables (interface energies, particle size, particle and liquid density, volume fraction of particles and particle/liquid thermal conductivity ratio) four types of behavior were predicted. Also, two numerical models for liquid-to-solid transfer are discussed, as well as the limitations of presently available models.

  4. Kinetic Release of Alkalinity from Particle-Containing Oil-in-Water Emulsions

    NASA Astrophysics Data System (ADS)

    Muller, K.; Chapra, S. C.; Ramsburg, A.

    2014-12-01

    Oil-in-water emulsions are typically employed during remediation to promote biotic reduction of contaminants. Emulsions, however, hold promise for encapsulated delivery of many types of active ingredients required for successful site remediation or long-term site stewardship. Our research is currently focused on using alkalinity-containing particles held within oil-in-water emulsions to sustain control of subsurface pH. Here we describe results from laboratory experiments and mathematical modeling conducted to quantify the kinetics associated with the emulsion delivery and alkalinity release process. Kinetically stable oil-in-water emulsions containing (~60 nmCaCO3 or ~100 nm MgO particles) were previously developed using soybean oil and Gum Arabic as a stabilizing agent. Batch and column experiments were employed to assess the accessibility and release of the alkalinity from the emulsion. Successive additions of HCl were used in batch systems to produce several pH responses (pH rebounds) that were subsequently modeled to elucidate release mechanisms and rates for varying emulsion compositions and particle types. Initial results suggest that a linear-driving-force model is generally able to capture the release behavior in the batch system when the temporally-constant, lumped mass-transfer coefficient is scaled by the fraction of particle mass remaining within the droplets. This result suggests that the rate limiting step in the release process may be the interphase transfer of reactive species at the oil-water interface. 1-d column experiments were also completed in order to quantify the extent and rate of alkalinity release from emulsion droplets retained in a sandy medium. Alkalinity release from the retained droplets treated a pH 4 influent water for 25-60 pore volumes (the duration depended on particle type and mass loading), and the cessation in treatment corresponded to exhaustion of the particle mass held within the oil. Column experiments were simulated

  5. Quantifying the kinetic limitations of atmospheric gas-to-particle conversion

    NASA Astrophysics Data System (ADS)

    Booth, A.; Murphy, B.; Riipinen, I.; Percival, C.; Topping, D. O.

    2013-12-01

    Atmospheric aerosol particles, from anthropogenic and biogenic sources, remain a major uncertainty in the Earth system: they impact the climate by directly scattering and absorbing solar radiation, as well as regulating the properties of clouds. On regional scales, aerosols are among the main pollutants deteriorating air quality, their impacts on both poorly quantified. Reducing these uncertainties requires accurate knowledge on the composition, concentrations and size distributions of these particles as they reside in the atmosphere. Unfortunately, there are currently huge uncertainties in many fundamental parameters that are required to predict their environmental impacts. This is largely down to the fact that a significant fraction of atmospheric aerosol particles are comprised of organic material (20-90% of particle mass), containing potentially thousands of compounds with largely uncertain properties It is becoming increasingly evident that aerosols exist as metastable amorphous states, rather than simple liquid/solid mixtures. Empirical evidence suggests that particles can form glass like substances. As the glass transition temperature is approached, an increase in viscosity leads to a reduced rate of molecular diffusion and an arrested non-equilibrium structure. Partitioning between the gas and condensed phase is kinetically limited in such amorphous states. Traditional organic aerosol models do not account for this, they assume that 1) the aerosol phase is a well-mixed non-viscous liquid; 2) the aerosol phase instantaneously equilibrates with the gas phase constituents. This adds significant uncertainty to predictions of gas/particle mass transfer as mixing timescales are ultimately governed by the diffusion coefficients of the aerosol constituents in the aerosol, which, on the other hand, are connected to the viscosity of the particulate matter. For typical aerosol sizes, the characteristic time for mixing could increase from a few milliseconds to hours or

  6. Particle-In-Cell/Monte Carlo Simulation of Ion Back Bombardment in Photoinjectors

    SciTech Connect

    Qiang, Ji; Corlett, John; Staples, John

    2009-03-02

    In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H{sub 2} ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns.

  7. LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS

    SciTech Connect

    Bourouaine, Sofiane; Verscharen, Daniel; Chandran, Benjamin D. G.; Maruca, Bennett A.; Kasper, Justin C.

    2013-11-01

    Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure and anisotropy driven instabilities such as the Alfvén/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W) instabilities. In this Letter, we use a long period of in situ measurements provided by the Wind spacecraft's Faraday cups to investigate the combined constraint on the alpha proton differential flow velocity and the alpha particle temperature anisotropy due to A/IC and FM/W instabilities. We show that the majority of the data are constrained to lie within the region of parameter space in which A/IC and FM/W waves are either stable or have extremely low growth rates. In the minority of observed cases in which the growth rate of the A/IC (FM/W) instability is comparatively large, we find relatively higher values of T {sub α}/T {sub p} (T {sub ∥α}/T {sub ∥p}) when the alpha proton differential flow velocity is small, where T {sub α} and T {sub p} (T {sub ∥α} and T {sub ∥p}) are the perpendicular (parallel) temperatures of alpha particles and protons. We conjecture that this observed feature might arise from preferential alpha particle heating which can drive the alpha particles beyond the instability thresholds.

  8. Full particle-in-cell simulations of kinetic equilibria and the role of the initial current sheet on steady asymmetric magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Dargent, J.; Aunai, N.; Belmont, G.; Dorville, N.; Lavraud, B.; Hesse, M.

    2016-06-01

    Tangential current sheets are ubiquitous in space plasmas and yet hard to describe with a kinetic equilibrium. In this paper, we use a semi-analytical model, the BAS model, which provides a steady ion distribution function for a tangential asymmetric current sheet and we prove that an ion kinetic equilibrium produced by this model remains steady in a fully kinetic particle-in-cell simulation even if the electron distribution function does not satisfy the time independent Vlasov equation. We then apply this equilibrium to look at the dependence of magnetic reconnection simulations on their initial conditions. We show that, as the current sheet evolves from a symmetric to an asymmetric upstream plasma, the reconnection rate is impacted and the X line and the electron flow stagnation point separate from one another and start to drift. For the simulated systems, we investigate the overall evolution of the reconnection process via the classical signatures discussed in the literature and searched in the Magnetospheric MultiScale data. We show that they seem robust and do not depend on the specific details of the internal structure of the initial current sheet.

  9. Ion acoustic and dust acoustic waves at finite size of plasma particles

    SciTech Connect

    Andreev, Pavel A. Kuz'menkov, L. S.

    2015-03-15

    We consider the influence of the finite size of ions on the properties of classic plasmas. We focus our attention at the ion acoustic waves for electron-ion plasmas. We also consider the dusty plasmas where we account the finite size of ions and particles of dust and consider the dispersion of dust acoustic waves. The finite size of particles is a classical effect as well as the Coulomb interaction. The finite size of particles considerably contributes to the properties of the dense plasmas in the small wavelength limit. Low temperature dense plasmas, revealing the quantum effects, are also affected by the finite size of plasma particles. Consequently, it is important to consider the finite size of ions in the quantum plasmas as well.

  10. Kinetic modeling of Europa's neutral atmosphere and pick-up ions

    NASA Astrophysics Data System (ADS)

    Tenishev, V.; Rubin, M.; Borovikov, D.; Jia, X.; Combi, M. R.; Gombosi, T. I.

    2013-12-01

    Europa was the highest priority outer planet exploration target in the 2007 NASA Science Plan, the 2006 Solar System Exploration Roadmap, and the 2003 planetary sciences Decadal Survey. The in-depth exploration of the plasma environment of Jupiter's moon Europa and investigation of its interaction with moon's surface and atmosphere remains a central objective of any proposed Europa Jupiter System Mission. The neutral species in Europa's atmosphere are mostly provided by ion sputtering of the water ice surface. Energetic ions and electrons from the Jovian magnetosphere produce molecular oxygen O2, the dominant species in Europa's atmosphere. Very close to the moon's surface the probability for collisional interaction between the species is close to the limit for a surface bound exosphere. The main loss mechanisms for neutrals are electron impact ionization, photoionization, as well as escape when neutral particles leave Europa's Hill sphere at roughly 8.7 Europa radii. The neutral and plasma environment of Europa are a tightly coupled system. A detailed study of this system requires coupled models of both the plasma and neutral environment. In this study we use coupled state-of-the-art computer models developed at the University of Michigan. In particular we include the BATSRUS MHD code of the Space Weather Modeling Framework (SWMF) and the Adaptive Mesh Particle Simulator (AMPS) model based on the DSMC method that both have well proven heritage in numerous space applications. In this investigation we calculate the plasma distribution in the vicinity of Europa at different locations along its orbit. The energetic ion flux derived from these calculations is used for simulation of the neutral particle sputtering that form Europa's atmosphere. The subsequent ionization of these neutral particles is the source of the pick-up ions. Populations of the neutrals and ions are calculated by tracing trajectories of the individual particles with accounting for both Europa

  11. Kinetic properties of the particle-in-cell simulation of a Lorentz plasma

    NASA Astrophysics Data System (ADS)

    Lin-Liu, Y. R.; Lin, T. Y.; Chen, S. H.

    2010-11-01

    The phenomenon of numerical thermalization in the standard particle-in-cell (PIC) simulation of Vlasov plasmas has been extensively studied at the early stage of its development [1] and was considered well understood. However, it was recently reported [2] that the well-established scaling law for the thermalization time could be compromised by the presence of an additional stochastic force acting on the particles, which is used to simulate collisional processes in a weakly ionized gas. In the present work, we are interested in the problem of electron-ion collisions in a fully ionized plasma. We investigate the thermal relaxation phenomenon in the PIC simulation of a Lorentz plasma in one dimension [3]. The pitch-angle scattering of the electrons by the stationary ion background is modeled by a Monte-Carlo algorithm. The numerical results obtained indicate that the thermal relaxation time is proportional to ND (the number of particles per Debye length), and not ND^2 as in the standard PIC simulations. Our results appear to complement those found by the previous study [2]. [4pt] [1] C. K. Birdsall and A. B. Langdon, Plasma Physics via Computer Simulation (McGraw-Hill, New York, 1985). [0pt] [2] M. M. Turner, Phys. of Plasmas 13, 033506 (2006). [0pt] [3] R. Shanny, J. M. Dawson, and J. M. Greene, Phys. of Fluids 10, 1281 (1967).

  12. Retention of phosphorous ions on natural and engineered waste pumice: Characterization, equilibrium, competing ions, regeneration, kinetic, equilibrium and thermodynamic study

    NASA Astrophysics Data System (ADS)

    Karimaian, Kamal Aldin; Amrane, Abdeltif; Kazemian, Hossein; Panahi, Reza; Zarrabi, Mansur

    2013-11-01

    Natural and Mg2+ modified pumice were used for the removal of phosphorous. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. In the optimal conditions, namely at equilibrium time (30 min), for a phosphorus concentration of 15 mg/L and pH 6, 69 and 97% phosphorus removals were achieved using 10 g/L of natural and modified pumice adsorbents, respectively. Maximum adsorption capacities were 11.88 and 17.71 mg/g by natural and modified pumice, respectively. Pseudo-second order kinetic model was the most relevant to describe the kinetic of phosphorus adsorption. External mass transfer coefficient decreased for increasing phosphorous concentration and film diffusion was found to be the rate-controlling step. Only a very low dissolution of the adsorbent was observed, leading to a low increase in conductivity and turbidity. Removal efficiency decreased for increasing ionic strength. It also decreased in the presence of competing ions; however modified pumice remained effective, since 67% of phosphorus was removed, versus only 17% for the natural pumice. The efficiency of the modified pumice was confirmed during the regeneration tests, since 96% regeneration yield was obtained after 510 min experiment, while only 22% was observed for the raw pumice.

  13. Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

    PubMed Central

    Pflieger, Rachel; Chave, Tony; Virot, Matthieu; Nikitenko, Sergey I.

    2014-01-01

    The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects. PMID:24747272

  14. Time-resolved electron kinetics in swift heavy ion irradiated solids

    NASA Astrophysics Data System (ADS)

    Medvedev, N. A.; Rymzhanov, R. A.; Volkov, A. E.

    2015-09-01

    The event-by-event Monte Carlo model, TREKIS, was developed to describe the excitation of the electron subsystems of various solids by a penetrating swift heavy ion (SHI), the spatial spreading of generated fast electrons, and secondary electron and hole cascades. Complex dielectric function formalism is used to obtain relevant cross sections. This allows the recognition of fundamental effects resulting from the collective response of the electron subsystem of a target for excitation that is not possible within the binary collision approximation of these cross sections, e.g. the differences in the electronic stopping of an ion and in the electron mean free paths for different structures (phases) of a material. A systematic study performed with this model for different materials (insulators, semiconductors and metals) revealed effects which may be important for an ion track: e.g. the appearance of a second front of excess electronic energy propagation outwards from the track core following the primary front of spreading of generated electrons. We also analyze how the initial ballistic spatial spreading of fast electrons generated in a track turns to the diffusion ~10 fs after ion passage. Detailed time-resolved simulations of electronic subsystem kinetics helped in understanding the reasons behind enhanced silicon resistance to SHI irradiation in contrast to easily produced damage in this material by femtosecond laser pulses. We demonstrate that the fast spreading of excited electrons from the track core on a sub-100 fs timescale prevents the Si lattice from nonthermal melting in a relaxing SHI track.

  15. A study of line widths and kinetic parameters of ions in the solar corona

    NASA Astrophysics Data System (ADS)

    Zhao, G. Q.; Wu, D. J.; Wang, C. B.

    2014-10-01

    Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables ( σ/ λ)2 and M -1, where σ, λ and M are the half-width of the observed line profile at , the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around 2.8 MK at heights of 57″ and 102″. The non-thermal velocity is typical 21.6 km s-1 at height of 57″ and 25.2 km s-1 at height of 102″.

  16. Kinetic temperatures of iron ions in the solar wind observed with STEREO/PLASTIC

    NASA Astrophysics Data System (ADS)

    Bochsler, Peter; Lee, Martin A.; Karrer, Reto; Popecki, Mark A.; Galvin, Antoinette B.; Kistler, Lynn M.; Möbius, Eberhard; Farrugia, Charles J.; Kucharek, Harald; Simunac, Kristin D. C.; Blush, Lisa M.; Daoudi, Hagar; Wurz, Peter; Klecker, Berndt; Wimmer-Schweingruber, Robert F.; Thompson, Barbara; Luhmann, Janet G.; Jian, Lan K.; Russell, Christopher T.; Opitz, Andrea

    2010-03-01

    STEREO/PLASTIC provides detailed information on the three-dimensional velocity distributions of solar wind iron ions with a time resolution of 5 minutes. In general the distributions at 1 AU contain complicated structures showing persistence over several records, i.e., over intervals of up to 30 minutes, but no clear correlation of the properties of these distributions with the direction of the ambient magnetic field is evident. We have performed a statistical analysis using nearly 9000 observations. Iron ions follow the same trends as protons, alpha particles, and electrons: The ratio T⊥/T|| seems to be limited by the ion cyclotron instability, whereas T||/T⊥ is bounded by the firehose instability.

  17. Kinetic freeze-out temperature and flow velocity extracted from transverse momentum spectra of final-state light flavor particles produced in collisions at RHIC and LHC

    NASA Astrophysics Data System (ADS)

    Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

    2016-04-01

    The transverse momentum spectra of final-state light flavor particles produced in proton-proton ( p - p , copper-copper (Cu-Cu), gold-gold (Au-Au), lead-lead (Pb-Pb), and proton-lead ( p -Pb) collisions for different centralities at relativistic heavy ion collider (RHIC) and large hadron collider (LHC) energies are studied in the framework of a multisource thermal model. The experimental data measured by the STAR, CMS, and ALICE Collaborations are consistent with the results calculated by the multi-component Erlang distribution and Tsallis Statistics. The effective temperature and real temperature (kinetic freeze-out temperature) of the interacting system at the stage of kinetic freeze-out, the mean transverse flow velocity and mean flow velocity of particles, and the relationships between them are extracted. The dependences of effective temperature and mean (transverse) momentum on rest mass, moving mass, centrality, and center-of-mass energy, and the dependences of kinetic freeze-out temperature and mean (transverse) flow velocity on centrality, center-of-mass energy, and system size are obtained.

  18. Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities

    SciTech Connect

    Tarvainen, O. Laulainen, J.; Komppula, J.; Kronholm, R.; Kalvas, T.; Koivisto, H.; Izotov, I.; Mansfeld, D.; Skalyga, V.

    2015-02-15

    Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space available for the optimization of high charge state ion currents. The most critical parameter in terms of plasma stability is the strength of the solenoid magnetic field. It is demonstrated that due to the instabilities the optimum B{sub min}-field in single frequency heating mode is often ≤0.8B{sub ECR}, which is the value suggested by the semiempirical scaling laws guiding the design of modern ECRISs. It is argued that the effect can be attributed not only to the absolute magnitude of the magnetic field but also to the variation of the average magnetic field gradient on the resonance surface.

  19. Ion kinetics and self pulsing in DC microplasma discharges at atmospheric and higher pressure

    NASA Astrophysics Data System (ADS)

    Mahamud, Rajib; Farouk, Tanvir I.

    2016-04-01

    Atmospheric pressure microplasma devices have been the subject of considerable interest and research during the last decade. Most of the operation regime of the plasma discharges studied fall in the ‘abnormal’, ‘normal’ and ‘corona’ modes—increasing and a ‘flat’ voltage current characteristics. However, the negative differential resistance regime at atmospheric and high pressures has been less studied and possesses unique characteristics that can be employed for novel applications. In this work, the role of ion kinetics especially associated with trace impurities; on the self pulsing behavior has been investigated. Detailed numerical simulations have been conducted with a validated model for a helium-nitrogen feed gas mixture. Different oscillatory modes were observed where the discharge was found to undergo complete or partial relaxation. Trace amount of nitrogen was found to significantly alter the pulsing characteristics. External parameters influencing these self oscillations are also studied and aspects of the ion kinetics on the oscillatory behavior are discussed.

  20. Plasma Turbulence and Kinetic Instabilities at Ion Scales in the Expanding Solar Wind

    NASA Astrophysics Data System (ADS)

    Hellinger, Petr; Matteini, Lorenzo; Landi, Simone; Verdini, Andrea; Franci, Luca; Trávníček, Pavel M.

    2015-10-01

    The relationship between a decaying strong turbulence and kinetic instabilities in a slowly expanding plasma is investigated using two-dimensional (2D) hybrid expanding box simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we start with a spectrum of large-scale, linearly polarized, random-phase Alfvénic fluctuations that have energy equipartition between kinetic and magnetic fluctuations and vanishing correlation between the two fields. A turbulent cascade rapidly develops; magnetic field fluctuations exhibit a power-law spectrum at large scales and a steeper spectrum at ion scales. The turbulent cascade leads to an overall anisotropic proton heating, protons are heated in the perpendicular direction, and, initially, also in the parallel direction. The imposed expansion leads to generation of a large parallel proton temperature anisotropy which is at later stages partly reduced by turbulence. The turbulent heating is not sufficient to overcome the expansion-driven perpendicular cooling and the system eventually drives the oblique firehose instability in a form of localized nonlinear wave packets which efficiently reduce the parallel temperature anisotropy. This work demonstrates that kinetic instabilities may coexist with strong plasma turbulence even in a constrained 2D regime.

  1. (S)-5-(p-Nitrobenzyl)-PCTA, a Promising Bifunctional Ligand with Advantageous Metal Ion Complexation Kinetics

    PubMed Central

    Tircsó, Gyula; Benyó, Enikő Tircsóné; Suh, Eul Hyun; Jurek, Paul; Kiefer, Garry E.; Sherry, A. Dean; Kovács, Zoltán

    2009-01-01

    A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N, N′, N″-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine. pH-potentiometric studies showed that the basicities of p-nitrobenzyl-PCTA and the parent ligand PCTA were similar. The stability of M(NO2-Bn-PCTA) (M = Mg2+, Ca2+, Cu2+, Zn2+) complexes was similar to that of the corresponding PCTA complexes while the stability of Ln3+ complexes of the bifunctional ligand is somewhat lower than that of PCTA chelates. The rate of complex formation of Ln(NO2-Bn-PCTA) complexes was found to be quite similar to that of PCTA, a ligand known to exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid catalyzed decomplexation kinetic studies of the selected Ln(NO2-Bn-PCTA) complexes showed that the kinetic inertness of the complexes was comparable to that of Ln(DOTA) chelates making the bifunctional ligand NO2-Bn-PCTA suitable for labeling biological vectors with radioisotopes for nuclear medicine applications. PMID:19220012

  2. Pb(II) ion-imprinted micro-porous particles for the selective separation of Pb(II) ions.

    PubMed

    Jiang, Yang; Kim, Dukjoon

    2014-11-01

    Pb(II) ion-imprinted micro-porous particles were prepared from the ionic complexes formed between vinyl pyridine functional monomers and template Pb(II) ions. The self-assembled Pb(II)/monomer complex was suspension polymerized in the presence of divinylbenzene cross-linker. The prepared micro-particles were 400-600 μm in size. Their chemical and physical structures, morphologies, and adsorption capacity were analyzed by energy dispersive X-ray spectrometry (EDX) Brunauer-Emmett-Teller (BET) analysis, scanningelectron microscopy (SEM), and atomic adsorption spectroscopy (AAS). The adsorption capacity of the imprinted polymer for the Pb(II) template ions was significantly affected by the initial concentration and the pH of the feed solution. Adsorptionis rapid in the first 1 h, after which it slowly increases to equilibrium. The imprinted particles showed high selectivity for lead ions; the adsorption capacity for the Pb(II) ions, 28 mg g(-1) polymer, was much higher than those for other metal ions such as Ni(II)Zn(II), Fe(II), or Cd(II). The imprinted particles maintain high standards of their adsorption ability after 10 repeated uses. PMID:25958566

  3. Effect of the specific surface area on thermodynamic and kinetic properties of nanoparticle anatase TiO2 in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Madej, Edyta; Klink, Stefan; Schuhmann, Wolfgang; Ventosa, Edgar; La Mantia, Fabio

    2015-11-01

    Anatase TiO2 nanoparticles with a specific surface area of 100 m2 g-1 and 300 m2 g-1 have been investigated as negative insertion electrode material for lithium-ion batteries. Galvanostatic intermittent titration (GITT) and electrochemical impedance spectroscopy (EIS) were used to investigate the effect of the specific surface area on the performance of the material. GITT was performed at C/10 rate, followed by an EIS measurement after each relaxation step. Separation of kinetic and thermodynamic contributions to the overpotential of the phase transformation on Li+ (de-)insertion allowed revealing a dependency of both terms on the specific surface area. The material with higher surface area undergoes intrinsic transformation during the initial cycles affecting the thermodynamics of (de-)insertion while the sample with lower surface area shows large and asymmetric kinetic hindrances. For the material with 15 nm particles, Li+ de-insertion appears to have a higher resistance than lithium insertion.

  4. A comparison between determination of trace amounts of sulfide in the presence and absence of micelle particles in natural waters (Qazvin, Iran): a kinetic spectrophotometric approach.

    PubMed

    Alizadeh, Nina; Mahjoub, Mohammad

    2015-05-01

    A new sensitive kinetic spectrophotometric method described for the determination of trace amounts of sulfides based on the addition reaction of sulfide ions with malachite green has been investigated in aqueous and micellar media at 25 °C. The variables affecting the rate of the reaction were investigated, and the optimum conditions were established. Under the optimum experimental conditions, decreases in the absorbance of malachite green at 615 nm in the absence and 630 nm in the presence of micelle particles, their λ max, were proportional to the concentrations of sulfide ions at the first 15 and 25 s from initiation of the reaction. The working curve was linear over the concentration range 50-1200 ng mL(-1) of sulfide ions with a fixed time method at the first 15 and 25 s from initiation of the reaction in aqueous medium and 25-1750 ng mL(-1) with a fixed time method at the first 15 s and 25-1500 ng mL(-1) for primitive 25 s in micellar medium. For the proposed kinetic method, the experimental and theoretical limit of detection (LOD) and limit of quantification (LOQ) in the presence and absence of micelle particles were obtained and tabulated at Δt = 15 and 25 s. The effective range concentration was achieved from the plot of Ringbom in both media and reported. Different surfactants, such as nonionic surfactant (Triton-X100), anionic surfactant sodium dodecyl sulfate (SDS), and cationic surfactant cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), were investigated and Triton X-100 selected as a suitable surfactant. To valuable vision into the reaction pathways, pseudo-first-order condition was applied and different kinetic parameters like ΔG (≠), ΔE (≠), ΔS (≠), and ΔH (≠) computed. The 2:1 stoichiometry of malachite green to sulfide ions was indicated by the results of mole ratio and Job's method of continuous variation. The effect of different environments on the interfering of various ions on sulfide

  5. Kinetic Modeling of the Neutral Gas, Ions, and Charged Dust in Europa's Exosphere

    NASA Astrophysics Data System (ADS)

    Tenishev, V.; Borovikov, D.; Rubin, M.; Jia, X.; Combi, M. R.

    2015-12-01

    The interaction of the Jovian magnetosphere with Europa has been a subject of active research during the last few decades both through in-situ and remote sensing observations as well as theoretical considerations. Linking the magnetosphere and the moon's surface and interior, Europa's exosphere has become one of the primary objects of study in the field. Understanding the physical processes occurring in the exosphere and its chemical composition is required for the understanding of the interaction between Europa and Jupiter. Europa's surface-bound exosphere originates mostly from ion sputtering of the water ice surface. Minor neutral species and ions of exospheric origin are produced via photolytic and electron impact reactions. The interaction of the Jovian magnetosphere and Europa affects the exospheric population of both neutrals and ions via source and loss processes. Moreover, the Lorentz force causes the newly created exospheric ions to move preferably aligned with the magnetic field lines. Contrary to the ions, heavier and slow-moving charged dust grains are mostly affected by gravity and the electric field component of the Lorentz force. As a result, escaping dust forms a narrow tail aligned in the direction of the convection electric field. Here we present results of a kinetic model of the neutral species (H2O, OH, O2, O, and H), ions (O+, O2+, H+, H2+, H2O+, and OH+), and neutral and charged dust in Europa's exosphere. In our model H2O and O2 are produced via sputtering and other exospheric neutral and ions species are produced via photolytic and electron impact reactions. For the charged dust we compute the equilibrium grain charge by balancing the electron and ion collecting currents according to the local plasma flow conditions at the grain's location. For the tracking of the ions, charged dust, and the calculation of the grains' charge we use plasma density and velocity, and the magnetic field derived from our multi-fluid MHD model of Europa

  6. Protein adsorption onto nanoparticles induces conformational changes: Particle size dependency, kinetics, and mechanisms

    PubMed Central

    Satzer, Peter; Svec, Frantisek; Sekot, Gerhard

    2015-01-01

    The use of nanomaterials in bioapplications demands a detailed understanding of protein–nanoparticle interactions. Proteins can undergo conformational changes while adsorbing onto nanoparticles, but studies on the impact of particle size on conformational changes are scarce. We have shown that conformational changes happening upon adsorption of myoglobin and BSA are dependent on the size of the nanoparticle they are adsorbing to. Out of eight initially investigated model proteins, two (BSA and myoglobin) showed conformational changes, and in both cases this conformational change was dependent on the size of the nanoparticle. Nanoparticle sizes ranged from 30 to 1000 nm and, in contrast to previous studies, we attempted to use a continuous progression of sizes in the range found in live viruses, which is an interesting size of nanoparticles for the potential use as drug delivery vehicles. Conformational changes were only visible for particles of 200 nm and bigger. Using an optimized circular dichroism protocol allowed us to follow this conformational change with regard to the nanoparticle size and, thanks to the excellent temporal resolution also in time. We uncovered significant differences between the unfolding kinetics of myoglobin and BSA. In this study, we also evaluated the plausibility of commonly used explanations for the phenomenon of nanoparticle size‐dependent conformational change. Currently proposed mechanisms are mostly based on studies done with relatively small particles, and fall short in explaining the behavior seen in our studies.

  7. Variational Formulation of Particle Algorithms for Kinetic E&M Plasma Simulations

    NASA Astrophysics Data System (ADS)

    Stamm, Alexander; Shadwick, Bradley; Evstatiev, Evstati

    2013-10-01

    A rigorous variational method was used to derive a self-consistent set of equations of motion from a discretized Lagrangian to study kinetic plasmas. Discretization of the Lagrangian was performed by reduction of the phase-space distribution function to a collection of finite-sized macro-particles of arbitrary shape and discretization of field quantities onto a spatial grid. The equations of motion were then obtained by demanding the action be stationary. This approach may be used in both lab frame and moving window coordinates, which improve computational efficiency when modeling laser-plasma interactions. The primary advantage of the variational approach is preservation of Lagrangian symmetries, which in our case leads to energy conservation and avoids difficulties with grid heating. Additionally, this approach decouples particle size from grid spacing and relaxes restrictions on particle shape, leading to a decrease in numerical noise. The variational approach also guarantees consistent ordering and is amiable to higher order methods in both space and time. Simulations conducted with the new equations of motion demonstrate the desired energy conservation and a decrease in numerical noise. This work was supported by the U.S. Department of Education grant P200A090156 and by the U.S. Department of Energy under Contract No. DE-FG02-08ER55000.

  8. Kinetics and proposed mechanism of the reaction of an immunoinhibition, particle-enhanced immunoassay.

    PubMed

    Thompson, J C; Craig, A R; Davey, C L; Newman, D J; Lonsdale, M L; Bucher, W J; Nagle, P D; Price, C P

    1997-12-01

    We report kinetic studies on the reaction of a latex agglutination immunoassay used to quantify phenytoin in serum. In this assay, polystyrene particles with a covalently attached analog of phenytoin react with an antiphenytoin monoclonal antibody to form light-scattering aggregates, with the rate of this reaction being decreased by addition of phenytoin from sample. In the absence of free (sample) phenytoin, this reaction did not exhibit a maximum rate of agglutination in the presence of excess antibody, i.e., an equivalence point. Furthermore, agglutination was inhibitable by free phenytoin even when the latter was added after agglutination of particles with antibody had begun. Most significantly, the immunoagglutination proceeded in an identical fashion with monovalent F(ab) fragment. These data are consistent with low-affinity immunospecific particle-antibody complexation, which then induces colloidal aggregation, without requiring immunospecific bridging by antibody molecules. The described mechanism is not generalizable to all latex agglutination immunoassays, although disturbance of colloidal stability may be a component in most assays. PMID:9439458

  9. Particle-Size-Grouping Model of Precipitation Kinetics in Microalloyed Steels

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Thomas, Brian G.

    2012-03-01

    The formation, growth, and size distribution of precipitates greatly affects the microstructure and properties of microalloyed steels. Computational particle-size-grouping (PSG) kinetic models based on population balances are developed to simulate precipitate particle growth resulting from collision and diffusion mechanisms. First, the generalized PSG method for collision is explained clearly and verified. Then, a new PSG method is proposed to model diffusion-controlled precipitate nucleation, growth, and coarsening with complete mass conservation and no fitting parameters. Compared with the original population-balance models, this PSG method saves significant computation and preserves enough accuracy to model a realistic range of particle sizes. Finally, the new PSG method is combined with an equilibrium phase fraction model for plain carbon steels and is applied to simulate the precipitated fraction of aluminum nitride and the size distribution of niobium carbide during isothermal aging processes. Good matches are found with experimental measurements, suggesting that the new PSG method offers a promising framework for the future development of realistic models of precipitation.

  10. Kinetic theory of phase space plateaux in a non-thermal energetic particle distribution

    SciTech Connect

    Eriksson, F. Nyqvist, R. M.; Lilley, M. K.

    2015-09-15

    The transformation of kinetically unstable plasma eigenmodes into hole-clump pairs with temporally evolving carrier frequencies was recently attributed to the emergence of an intermediate stage in the mode evolution cycle, that of an unmodulated plateau in the phase space distribution of fast particles. The role of the plateau as the hole-clump breeding ground is further substantiated in this article via consideration of its linear and nonlinear stability in the presence of fast particle collisions and sources, which are known to affect the production rates and subsequent frequency sweeping of holes and clumps. In particular, collisional relaxation, as mediated by e.g. velocity space diffusion or even simple Krook-type collisions, is found to inhibit hole-clump generation and detachment from the plateau, as it should. On the other hand, slowing down of the fast particles turns out to have an asymmetrically destabilizing/stabilizing effect, which explains the well-known result that collisional drag enhances holes and their sweeping rates but suppresses clumps. It is further demonstrated that relaxation of the plateau edge gradients has only a minor quantitative effect and does not change the plateau stability qualitatively, unless the edge region extends far into the plateau shelf and the corresponding Landau pole needs to be taken into account.

  11. Ion kinetic simulations of the formation and propagation of a planar collisional shock wave in a plasma

    SciTech Connect

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

    1993-09-01

    Ion kinetic simulations of the formation and propagation of planar shock waves in a hydrogen plasma have been performed at Mach numbers 2 and 5, and compared to fluid simulations. At Mach 5, the shock transition is far wider than expected on the basis of comparative fluid calculations. This enlargement is due to hot ions streaming from the hot plasma into the cold plasma and is found to be limited by the electron preheating layer, essentially because electron--ion collisions slow down these energetic ions very effectively in the cold upstream region. Double-humped ion velocity distributions formed in the transition region, which are particularly prominent during the shock formation, are found not to be unstable to any electrostatic mode, due to electron Landau damping. At Mach numbers of 2 and below, no such features are seen in velocity space, and there is very little difference between the profiles from the kinetic and fluid simulations.

  12. Production of low-Z ions in the Dresden superconducting electron ion beam source for medical particle therapy

    SciTech Connect

    Zschornack, G.; Ritter, E.; Schwan, A.; Ullmann, F.; Grossmann, F.; Ovsyannikov, V. P.

    2012-02-15

    We report on experiments with a new superconducting electron beam ion source (EBIS-SC), the Dresden EBIS-SC, with the objective to meet the main requirements for their application in particle-therapy facilities. Synchrotrons as well as innovative accelerator concepts, such as high-gradient linacs which are driven by a large-current cyclotron (CYCLINACS) and direct drive RF linear accelerators may benefit from the advantages of EBISs in regard to their functional principle. First experimental studies of the production of low-Z ions such as H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, C{sup 4+}, and C{sup 6+} are presented. Particular attention is paid to the ion output, i.e., the number of ions per pulse and per second, respectively. Important beam parameters in this context are, among others, ion pulse shaping, pulse repetition rates, beam emittance, and ion energy spread.

  13. Kinetics of the Reduction of Hematite Concentrate Particles by Carbon Monoxide Relevant to a Novel Flash Ironmaking Process

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Mohassab, Yousef; Zhang, Shengqin; Sohn, Hong Yong

    2015-08-01

    A novel ironmaking process is under development at the University of Utah to produce iron directly from iron oxides concentrates by the gas-solid flash reaction using gaseous fuels and reductants. This process will reduce energy consumption and minimize carbon dioxide emissions. Having investigated the hydrogen reduction kinetics of magnetite and hematite concentrate particles relevant to the novel flash ironmaking process, the carbon monoxide reduction kinetics of hematite concentrate particles (average particle size 21 µm) was determined in the temperature range 1473 K to 1623 K (1200 °C to 1350 °C) under various carbon monoxide partial pressures. At 1623 K (1350 °C) and residence time 5 seconds, the reduction degree of hematite concentrate particles was more than 90 pct under a pure carbon monoxide. This is slower than reduction by hydrogen but still significant, indicating that CO will contribute to the reduction of hematite concentrate in the flash process. The kinetics of CO reduction separately from hydrogen is important for understanding and analyzing the complex kinetics of hematite reduction by the H2 + CO mixtures. The nucleation and growth rate equation with the Avrami parameter n = 1.0 adequately described the carbon monoxide reduction kinetics of hematite concentrate particles. The reduction rate is of 1st order with respect to the partial pressure of carbon monoxide and the activation energy of the reaction was 231 kJ/mol, indicating strong temperature dependence. The following complete rate equation was developed that can satisfactorily predict the carbon monoxide reduction kinetics of hematite concentrate particles and is suitable for the design of a flash reactor where X is the fraction of oxygen removed from iron oxide, R is 8.314 J/mol K, T is in K, p is in atm, and t is in seconds.

  14. Self-Assembly of Measles Virus Nucleocapsid-like Particles: Kinetics and RNA Sequence Dependence.

    PubMed

    Milles, Sigrid; Jensen, Malene Ringkjøbing; Communie, Guillaume; Maurin, Damien; Schoehn, Guy; Ruigrok, Rob W H; Blackledge, Martin

    2016-08-01

    Measles virus RNA genomes are packaged into helical nucleocapsids (NCs), comprising thousands of nucleo-proteins (N) that bind the entire genome. N-RNA provides the template for replication and transcription by the viral polymerase and is a promising target for viral inhibition. Elucidation of mechanisms regulating this process has been severely hampered by the inability to controllably assemble NCs. Here, we demonstrate self-organization of N into NC-like particles in vitro upon addition of RNA, providing a simple and versatile tool for investigating assembly. Real-time NMR and fluorescence spectroscopy reveals biphasic assembly kinetics. Remarkably, assembly depends strongly on the RNA-sequence, with the genomic 5' end and poly-Adenine sequences assembling efficiently, while sequences such as poly-Uracil are incompetent for NC formation. This observation has important consequences for understanding the assembly process. PMID:27270664

  15. Varying the counter ion changes the kinetics, but not the final structure of colloidal gels.

    PubMed

    Zhang, Li; Mikhailovskaya, Alesya; Constantin, Doru; Foffi, Giuseppe; Tavacoli, Joseph; Schmitt, Julien; Muller, François; Rochas, Cyrille; Wang, Nan; Langevin, Dominique; Salonen, Anniina

    2016-02-01

    We show that, while the gelation of colloidal silica proceeds much faster in the presence of added KCl than NaCl, the final gels are very similar in structure and properties. We have studied the gelation process by visual inspection and by small angle X-ray scattering for a range of salt and silica particle concentrations. The characteristic times of the early aggregation process and the formation of a stress-bearing structure with both salts are shown to collapse onto master curves with single multiplicative constants, linked to the stability ratio of the colloidal suspensions. The influence of the salt type and concentration is confirmed to be mainly kinetic, as the static structure factors and viscoelastic moduli of the gels are shown to be equivalent at normalized times. While there is strong variation in the kinetics, the structure and properties of the gel at long-times are shown to be mainly controlled by the concentration of particles, and hardly influenced by the type or the concentration of salt. This suggests that the differences between gels generated by different salts are only transient in time. PMID:26520820

  16. Particle Production in Strong Electromagnetic Fields in Relativistic Heavy-Ion Collisions

    DOE PAGESBeta

    Tuchin, Kirill

    2013-01-01

    I reviewmore » the origin and properties of electromagnetic fields produced in heavy-ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches ~ m π 2 at RHIC and ~ 10 m π 2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane, and therefore all kinetic coefficients are anisotropic. I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry. Very strong electromagnetic field has an important impact on particle production. I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate J / ψ dissociation via Lorentz ionization mechanism, and examine electromagnetic radiation by plasma. I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation.« less

  17. Interaction of Virus-Like Particles with Vesicles Containing Glycolipids: Kinetics of Detachment.

    PubMed

    Nasir, Waqas; Bally, Marta; Zhdanov, Vladimir P; Larson, Göran; Höök, Fredrik

    2015-09-01

    Many viruses interact with their host cells via glycosphingolipids (GSLs) and/or glycoproteins present on the outer cell membrane. This highly specific interaction includes virion attachment and detachment. The residence time determined by the detachment is particularly interesting, since it is directly related to internalization and infection as well as to virion egress and spreading. In an attempt to deepen the understanding of virion detachment kinetics, we have used total internal reflection fluorescence (TIRF) microscopy to probe the interaction between individual fluorescently labeled GSL-containing lipid vesicles and surface-bound virus-like particles (VLPs) of a norovirus genotype II.4 strain. The distribution of the VLP-vesicle residence time was investigated for seven naturally occurring GSLs, all of which are candidates for the not yet identified receptor(s) mediating norovirus entry into host cells. As expected for interactions involving multiple GSL binding sites at a viral capsid, the detachment kinetics displayed features typical for a broad activation-energy distribution for all GSLs. Detailed inspection of these distributions revealed significant differences among the different GSLs. The results are discussed in terms of strength of the interaction, vesicle size, as well as spatial distribution and clustering of GSLs in the vesicle membrane. PMID:26260011

  18. Kinetics of O{sub 3} decomposition and heterogeneous chemistry on aluminum oxide particles

    SciTech Connect

    Hanning-Lee, M.A.; Brady, B.B.; Syage, J.A.

    1996-10-01

    Measurements of chemistry on aluminum oxide particles pertinent to solid rocket motor plume/stratosphere interactions are reported. A new method for measuring heterogeneous chemistry is described based on real-time studies of the kinetics by absorption spectroscopy and mass spectrometry. These measurements complement similar measurements in a flow tube reactor, but have certain advantages in disentangling adsorption/desorption kinetics from equilibrium properties. Catalytic decay of ozone has been expressed as a reaction probability {eta} on different grades of alumina. {eta} ranges from 10{sup -5} to 10{sup -3} over the temperature range 20 to 200{degrees}C, respectively. At stratospheric temperatures (-60{degrees}C), the reaction probability increases to about 10{sup -4} possibly reflecting an increased surface residence time for ozone with decreasing temperature. Adsorption and desorption rate coefficients are presented for plume species of high activity such as ozone, water, and HCl. These measurements enable an assessment of the impact of SRM plumes on stratospheric ozone depletion.

  19. Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis Bumpy Torus plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1976-01-01

    Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

  20. Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1976-01-01

    Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

  1. The impact of the initial state on the kinetics of oxidation ion- modified fuel cladding alloy E110

    NASA Astrophysics Data System (ADS)

    Kalin, B. A.; Volkov, N. V.; Valikov, R. A.; Yashin, A. S.; Yakutkina, T. V.

    2016-04-01

    The paper examines the impact of the initial state (the presence of impurities, surface preparation), and surface alloying on the kinetics of the oxidation of fuel cladding alloy E110. The studies concluded that the use of ionic polishing instead of traditional chemical polishing helps to reduce the rate of oxidation of zirconium alloys. Also studied the effect of alloying elements introduced in the surface layers of claddings by ion mixing on the kinetics of the oxidation of the alloy E110.

  2. Simulation of aggregating particles in complex flows by the lattice kinetic Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Flamm, Matthew H.; Sinno, Talid; Diamond, Scott L.

    2011-01-01

    We develop and validate an efficient lattice kinetic Monte Carlo (LKMC) method for simulating particle aggregation in laminar flows with spatially varying shear rate, such as parabolic flow or flows with standing vortices. A contact time model was developed to describe the particle-particle collision efficiency as a function of the local shear rate, G, and approach angle, θ. This model effectively accounts for the hydrodynamic interactions between approaching particles, which is not explicitly considered in the LKMC framework. For imperfect collisions, the derived collision efficiency [\\varepsilon = 1 - int_0^{{π {π /2} {sin θ exp ( { - 2\\cot θ {{Γ _{agg} }/ { Γ _{agg} } G} )} dθ] was found to depend only on Γagg/G, where Γagg is the specified aggregation rate. For aggregating platelets in tube flow, Γ _{agg} = 0.683 s-1 predicts the experimentally measured ɛ across a physiological range (G = 40-1000 s-1) and is consistent with α2bβ3-fibrinogen bond dynamics. Aggregation in parabolic flow resulted in the largest aggregates forming near the wall where shear rate and residence time were maximal, however intermediate regions between the wall and the center exhibited the highest aggregation rate due to depletion of reactants nearest the wall. Then, motivated by stenotic or valvular flows, we employed the LKMC simulation developed here for baffled geometries that exhibit regions of squeezing flow and standing recirculation zones. In these calculations, the largest aggregates were formed within the vortices (maximal residence time), while squeezing flow regions corresponded to zones of highest aggregation rate.

  3. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    PubMed

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be <8 × 10(-4), at least a factor of 10(4) less than that for HNO3 in water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed. PMID:27043733

  4. Ion beam enhanced emission of charged particles from hot graphite

    NASA Astrophysics Data System (ADS)

    Lozano, J.; Kessel, Q. C.; Pollack, E.; Smith, W. W.

    2001-07-01

    Thermal desorption spectroscopy of ions from positively biased graphite (grafoil) has been investigated by measuring the energies of the emitted ions with a hemispherical electrostatic analyzer and the masses with a residual gas analyzer under ultra-high vacuum conditions. Potassium is one of the ions emitted at temperatures above 800 °C. The present data show that under near threshold conditions (4V), ions appear with well-defined energies equal approximately to the bias voltage minus 4V. This phenomenon can be greatly enhanced by prior bombardment with an ion beam. It is not clear whether these energies are the result of resonant process on the hot surface or simply due to a process attributable to surface chemistry. At higher biases the peaks broaden in energy and the energy deficit increases.

  5. Determination of char combustion kinetics parameters: Comparison of point detector and imaging-based particle-sizing pyrometry

    NASA Astrophysics Data System (ADS)

    Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R.; Vorobiev, Nikita; Scherer, Viktor

    2014-07-01

    In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 μm particles.

  6. Adsorption of Pb(II) ions onto biomass from Trifolium resupinatum: equilibrium and kinetic studies

    NASA Astrophysics Data System (ADS)

    Athar, Makshoof; Farooq, Umar; Aslam, Muhammad; Salman, M.

    2013-09-01

    The present study provides information about the binding of Pb(II) ions on an eco-friendly and easily available biodegradable biomass Trifolium resupinatum. The powdered biomass was characterized by FTIR, potentiometric titration and surface area analyses. The FTIR spectrum showed the presence of hydroxyl, carbonyl and amino functional groups and Pb(II) ions bound with the oxygen- and nitrogen-containing sites (hydroxyl and amino groups). The acidic groups were also confirmed by titrations. Effects of various environmental parameters (time, pH and concentration) have been studied. The biosorption process achieved equilibrium in a very short period of time (25 min). Non-linear approach for Langmuir and Freundlich models was used to study equilibrium process and root mean-square error was used as an indicator to decide the fitness of the mathematical model. The biosorption process was found to follow pseudo-second-order kinetics and was very fast. Thus, the biomass can be cost-effectively used for the binding of Pb(II) ions from aqueous solutions.

  7. Kinetics of copper ion absorption by cross-linked calcium polyacrylate membranes

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; May, C. E.

    1983-01-01

    The absorption of copper ions from aqueous copper acetate solutions by cross-linked calcium acrylate membranes was found to obey parabolic kinetics similar to that found for oxidation of metals that form protective oxide layers. For pure calcium polyacrylate membranes the rate constant was essentially independent of copper acetate concentration and film thickness. For a cross-linked copolymer film of polyvinyl alcohol and calcium polyacrylate, the rate constant was much greater and dependent on the concentration of copper acetate. The proposed mechanism in each case involves the formation of a copper polyacrylate phase on the surface of the membrane. The diffusion of the copper ion through this phase appears to be the rate controlling step for the copolymer film. The diffusion of the calcium ion is apparently the rate controlling step for the calcium polyacrylate. At low pH, the copper polyacrylate phase consists of the normal copper salt; at higher pH, the phase appears to be the basic copper salt.

  8. Charged particle flows in the beam extraction region of a negative ion source for NBI

    NASA Astrophysics Data System (ADS)

    Geng, S.; Tsumori, K.; Nakano, H.; Kisaki, M.; Ikeda, K.; Osakabe, M.; Nagaoka, K.; Takeiri, Y.; Shibuya, M.; Kaneko, O.

    2016-02-01

    Experiments by a four-pin probe and photodetachment technique were carried out to investigate the charged particle flows in the beam extraction region of a negative hydrogen ion source for neutral beam injector. Electron and positive ion flows were obtained from the polar distribution of the probe saturation current. Negative hydrogen ion flow velocity and temperature were obtained by comparing the recovery times of the photodetachment signals at opposite probe tips. Electron and positive ions flows are dominated by crossed field drift and ambipolar diffusion. Negative hydrogen ion temperature is evaluated to be 0.12 eV.

  9. Charged particle flows in the beam extraction region of a negative ion source for NBI.

    PubMed

    Geng, S; Tsumori, K; Nakano, H; Kisaki, M; Ikeda, K; Osakabe, M; Nagaoka, K; Takeiri, Y; Shibuya, M; Kaneko, O

    2016-02-01

    Experiments by a four-pin probe and photodetachment technique were carried out to investigate the charged particle flows in the beam extraction region of a negative hydrogen ion source for neutral beam injector. Electron and positive ion flows were obtained from the polar distribution of the probe saturation current. Negative hydrogen ion flow velocity and temperature were obtained by comparing the recovery times of the photodetachment signals at opposite probe tips. Electron and positive ions flows are dominated by crossed field drift and ambipolar diffusion. Negative hydrogen ion temperature is evaluated to be 0.12 eV. PMID:26931985

  10. Exploration of kinetic and multiple-ion-fluids effects in D3He and T3He gas-filled ICF implosions using multiple nuclear reaction histories

    NASA Astrophysics Data System (ADS)

    Sio, Hong; Rinderknecht, Hans; Rosenberg, Michael; Zylstra, Alex; Séguin, Fredrick; Gatu Johnson, Maria; Li, Chikang; Petrasso, Richard; Hoffman, Nelson; Kagan, Krigory; Molvig, Kim; Amendt, Peter; Bellei, Claudio; Wilks, Scott; Stoeckl, Christian; Glebov, Vladimir; Betti, Riccardo; Sangster, Thomas; Katz, Joseph

    2014-10-01

    To explore kinetic and multi-ion-fluid effects in D3He and T3He gas-filled shock-driven implosions, multiple nuclear reaction histories were measured using the upgraded Particle Temporal Diagnostic (PTD) on OMEGA. For D3He gas-filled implosions, the relative timing of the DD and D3He reaction histories were measured with 20 ps precision. For T3He gas-filled implosions (with 1-2% deuterium), the relative timing of the DT and D3He reaction histories were measured with 10 ps precision. The observed differences between the reaction histories on these two OMEGA experiments are contrasted to 1-D single-ion hydro simulations for different gas-fill pressure and gas mixture. This work is supported in part by the U.S. DOE, LLNL, LLE, and NNSA SSGF.

  11. IonCCD™ for direct position-sensitive charged-particle detection: from electrons and keV ions to hyperthermal biomolecular ions

    SciTech Connect

    Hadjar, Omar; Johnson, Grant E.; Laskin, Julia; Kibelka, Gottfried; Shill, Scott M.; Kuhn, Ken; Cameron, Chad; Kassan, Scott

    2011-04-01

    A novel charged-particle sensitive, pixel based detector array is described and its usage is demonstrated for a variety of applications, from detection of elemental particles (electrons) to hyper-thermal large biomolecular positive and negative ions including keV light atomic and molecular ions. The array detector is a modified light-sensitive charged coupled device (CCD). The IonCCDTM was engineered for direct charged particle detection by replacing the semi-conductor part of the CCD pixel by a conductor1. In contrast with the CCD, where the semi-conductive pixel is responsible for electron-hole pair formation upon photon bombardment, the IonCCD uses a capacitor coupled to the conductive electrode for direct charge integration. The detector can be operated from atmospheric pressure to high vacuum since no high voltages are needed. The IonCCD, presented in this work is an array of 2126 active pixels with 21 um pixel width and 3 um pixel gap. The detection area is 1.5x51mm2 where 1.5 mm and 51 mm are pixel and detector array length, respectively. The result is a one-dimensional position-sensitive detector with 24 um spatial resolution and 88 % pixel area ratio (PAR). In this work we demonstrate the capabilities and the performance of the detector. For the first time we show the direct detection of 250 eV electrons providing linearity response and detection efficiency of the IonCCD as function of electron beam current. Using positive ions from and electron impact source (E-I), we demonstrate that the detection efficiency of the IonCCD is virtually independent of particle energy [250 eV, 1250 eV], particle impact angle [45o, 90o] and particle flux. By combining the IonCCD with a double focusing sector field of Mattauch-Herzog geometry (M-H), we demonstrate fast acquisition of mass spectra in direct air sniffing mode. A first step towards fast in vivo breath analysis is presented. Detection of hyper-thermal biomolecular ions produced using an electrospray ionization

  12. Charged-Particle Bean Transport for Ion Trapping Experiments.

    NASA Astrophysics Data System (ADS)

    Raichle, Brian W.; Wingfield, Love M.

    2001-11-01

    Electrostatic Einsel lenses are being developed for beam transport for use in two distinct metastable atomic lifetime experiments using two separate rf-ion traps. Each system has been modeled using Simion software, and the lenses have been designed from commercially available eV-parts. The first application is part of an electron gun source. Electrons are produced by a conventional dispenser cathode and are transported 25 cm to the trap. The design goal is to create a beam divergence to fully illuminate the active trap volume, and to provide tunable electron energies from 50 to 500 eV. The second application is to transport ions 1 m from a laser ablation ion source to an rf ion trap. Laser ablation involves essentially boiling ions from a solid target with intense laser pulses. Here, the design goal is to maximize flux by maximizing the solid angle of acceptance to the trap, minimize radial velocity, and minimize the spread in axial velocity. Development of a laser ablation ion source external to the trap volume will allow a very low base pressure in the trap region, which will make possible the study of species with lifetimes approaching 1 s. In addition, laser ablation will produce intermediately-charged ions from non-conductive solid targets.

  13. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

    SciTech Connect

    Veltri, P. Serianni, G.; Cavenago, M.

    2014-02-15

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λ{sub D}. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  14. Energetics, kinetics and dynamics of decaying metastable ions studied with a high-resolution three-sector field mass spectrometer

    NASA Astrophysics Data System (ADS)

    Matt-Leubner, S.; Feil, S.; Gluch, K.; Fedor, J.; Stamatovic, A.; Echt, O.; Scheier, P.; Becker, K.; Märk, T. D.

    2005-05-01

    Mass spectrometric analysis of metastable decay reactions is devoted to the measurements of the kinetic energy release distribution (KERD) for the decay of singly charged rare gas dimer ions Xe_{2}^{ + } and Kr_{2}^{ + } , the doubly charged acetylene parent ion C_{2}H_{2^{ 2+ }} and the singly and doubly charged SF6 fragment ions, like for example SF_{3}^{ + } , SF_{3}^{ 2 + } and SF_{4}^{ 2 + } . The KERDs are obtained either from high-resolution mass analysed ion kinetic energy spectra or the measurement of ion beam profiles using a specially improved mass spectrometric system. Due to the high energy resolution measurements and theoretical studies based on ab initio calculations of potential energy curves it is possible to assign the reaction products of the rare gas dimer decays to electronic transitions in the excited parent ion. The C_{2}H_{2^{ 2 + }} and also the SF_{4}^{ 2 + } ions are investigated because of obscurities in the production of their fragment ions. The unusual shape of the SF_{3}^{ + } ionization cross section indicates that at sufficiently high electron energies the fragmentation channel of doubly charged SF_{4}^{ 2 + } contributes significantly to the ion yield. Additional measurements of the corresponding appearance energies confirm the existence of this second production channel.

  15. Orientational kinetics of dipolar particles in a Maxwell fluid matrix: inertialess limit for the rotary microrheology.

    PubMed

    Raikher, Yu L; Rusakov, V V

    2005-12-01

    We study magnetic response of an assembly of ferroparticles suspended in a viscoelastic matrix which is modeled by a Maxwell fluid with a unique stress relaxation time. The problem refers to the magnetic microrheology approach where deformational properties of a complex fluid are tested with the aid of embedded nanoparticle probes set to motion by an external ac magnetic field. A possibility is considered to simplify the description of the orientational kinetics of the system at the expense of neglecting inertia effects in particle rotary motion. It is shown that in this aspect a Maxwell matrix differs essentially from the Newtonian one. In the latter the inertialess approximation for the particles of the approximately 10nm size is valid practically unboundedly. For a viscoelastic matrix the inertialess approximation means an important restriction on the value of the stress relaxation time. Assuming weak nonequilibrium, the magneto-orientational relaxation times are found and low-frequency magnetic spectra of a viscoelastic suspension are determined in the presence of a constant (magnetizing) field. PMID:16485946

  16. Position and energy-resolved particle detection using phonon-mediated microwave kinetic inductance detectors

    SciTech Connect

    Moore, D. C.; Golwala, S. R.; Cornell, B.; Bumble, B.; Day, P. K.; LeDuc, H. G.; Zmuidzinas, J.

    2012-06-04

    We demonstrate position and energy-resolved phonon-mediated detection of particle interactions in a silicon substrate instrumented with an array of microwave kinetic inductance detectors (MKIDs). The relative magnitude and delay of the signal received in each sensor allow the location of the interaction to be determined with < or approx. 1mm resolution at 30 keV. Using this position information, variations in the detector response with position can be removed, and an energy resolution of {sigma}{sub E} = 0.55 keV at 30 keV was measured. Since MKIDs can be fabricated from a single deposited film and are naturally multiplexed in the frequency domain, this technology can be extended to provide highly pixelized athermal phonon sensors for {approx}1 kg scale detector elements. Such high-resolution, massive particle detectors would be applicable to rare-event searches such as the direct detection of dark matter, neutrinoless double-beta decay, or coherent neutrino-nucleus scattering.

  17. Pegasus: A new hybrid-kinetic particle-in-cell code for astrophysical plasma dynamics

    NASA Astrophysics Data System (ADS)

    Kunz, Matthew W.; Stone, James M.; Bai, Xue-Ning

    2014-02-01

    We describe Pegasus, a new hybrid-kinetic particle-in-cell code tailored for the study of astrophysical plasma dynamics. The code incorporates an energy-conserving particle integrator into a stable, second-order-accurate, three-stage predictor-predictor-corrector integration algorithm. The constrained transport method is used to enforce the divergence-free constraint on the magnetic field. A δf scheme is included to facilitate a reduced-noise study of systems in which only small departures from an initial distribution function are anticipated. The effects of rotation and shear are implemented through the shearing-sheet formalism with orbital advection. These algorithms are embedded within an architecture similar to that used in the popular astrophysical magnetohydrodynamics code Athena, one that is modular, well-documented, easy to use, and efficiently parallelized for use on thousands of processors. We present a series of tests in one, two, and three spatial dimensions that demonstrate the fidelity and versatility of the code.

  18. Kinetic Monte Carlo and cellular particle dynamics simulations of multicellular systems

    NASA Astrophysics Data System (ADS)

    Flenner, Elijah; Janosi, Lorant; Barz, Bogdan; Neagu, Adrian; Forgacs, Gabor; Kosztin, Ioan

    2012-03-01

    Computer modeling of multicellular systems has been a valuable tool for interpreting and guiding in vitro experiments relevant to embryonic morphogenesis, tumor growth, angiogenesis and, lately, structure formation following the printing of cell aggregates as bioink particles. Here we formulate two computer simulation methods: (1) a kinetic Monte Carlo (KMC) and (2) a cellular particle dynamics (CPD) method, which are capable of describing and predicting the shape evolution in time of three-dimensional multicellular systems during their biomechanical relaxation. Our work is motivated by the need of developing quantitative methods for optimizing postprinting structure formation in bioprinting-assisted tissue engineering. The KMC and CPD model parameters are determined and calibrated by using an original computational-theoretical-experimental framework applied to the fusion of two spherical cell aggregates. The two methods are used to predict the (1) formation of a toroidal structure through fusion of spherical aggregates and (2) cell sorting within an aggregate formed by two types of cells with different adhesivities.

  19. Effects of He and Ar ion kinetic energies in protection of organosilicate glass from O{sub 2} plasma damage

    SciTech Connect

    Lee, Joe; Graves, David B.; Kazi, Haseeb; Gaddam, Sneha; Kelber, Jeffry A.

    2013-07-15

    In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Fourier transform infrared studies of He plasma and Ar{sup +} ion bombardment pretreatments of organosilicate glass demonstrate that such pretreatments inhibit subsequent O{sub 2} plasma-induced carbon loss by forming a SiO{sub 2}-like damaged overlayer, and that the degree of protection correlates directly with increased ion kinetic energies, but not with the thickness of the SiO{sub 2} overlayer. This thickness is observed by XPS to be roughly constant and <1 nm regardless of ion energies involved. The data indicate that ion kinetic energies are an important parameter in protective noble gas plasma pretreatments to inhibit O{sub 2} plasma-induced carbon loss.

  20. Adsorption of Zn2+ ions onto NaA and NaX zeolites: kinetic, equilibrium and thermodynamic studies.

    PubMed

    Nibou, D; Mekatel, H; Amokrane, S; Barkat, M; Trari, M

    2010-01-15

    The adsorption of Zn(2+) onto NaA and NaX zeolites was investigated. The samples were synthesized according to a hydrothermal crystallization using aluminium isopropoxide (Al[OCH(CH(3))(2)](3)) as a new alumina source. The effects of pH, initial concentration, solid/liquid ratio and temperature were studied in batch experiments. The Freundlich and the Langmuir models were applied and the adsorption equilibrium followed Langmuir adsorption isotherm. The uptake distribution coefficient (K(d)) indicated that the Zn(2+) removal was the highest at minimum concentration. Thermodynamic parameters were calculated. The negative values of standard enthalpy of adsorption revealed the exothermic nature of the adsorption process whereas the negative activation entropies reflected that no significant change occurs in the internal structure of the zeolites solid matrix during the sorption of Zn(2+). The negative values of Gibbs free energy were indicative of the spontaneity of the adsorption process. Analysis of the kinetic and rate data revealed that the pseudo second-order sorption mechanism is predominant and the intra particle diffusion was the determining step for the sorption of zinc ions. The obtained optimal parameters have been applied to wastewater from the industrial zone (Algeria) in order to remove the contained zinc effluents. PMID:19773115

  1. Nonlinear kinetic simulations of ion cyclotron emission from fusion products in large tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Dendy, Richard; Cook, James; Chapman, Sandra

    2012-10-01

    Ion cyclotron emission (ICE) was the only collective radiative instability, driven by fusion-born ions, observed from deuterium-tritium plasmas in both JET and TFTR (R O Dendy et al., Nucl. Fusion 35, 1733 (1995)). Suprathermal emission, peaked at sequential ion cyclotron harmonics at the outer mid-plane edge, was detected using heating antennas as receivers on JET and using probes in TFTR. The intensity of ICE spectral peaks scaled linearly with fusion reactivity. The underlying emission mechanism appears to be the magnetoacoustic cyclotron instability (MCI), which involves resonance between: the fast Alfv'en wave; cyclotron harmonic waves supported by the energetic ions and by the background thermal plasma; and a set of centrally born fusion products, lying on barely trapped orbits, which undergo large drift excursions. Analytical studies show that the linear growth rate of the MCI corresponds well with certain observational features of ICE, including ones where a nonlinear treatment might be thought essential. To help explain this, we have carried out direct numerical simulations using a particle-in-cell (PIC) code. We focus on the results of extending MCI theory from the linear into the nonlinear regime for large tokamak parameters.

  2. Removal of fine and ultrafine particles from indoor air environments by the unipolar ion emission

    NASA Astrophysics Data System (ADS)

    Uk Lee, Byung; Yermakov, Mikhail; Grinshpun, Sergey A.

    2004-09-01

    The continuous emission of unipolar ions was evaluated in order to determine its ability to remove fine and ultrafine particles from indoor air environments. The evolution of the indoor aerosol concentration and particle size distribution was measured in real time with the ELPI in a room-size (24.3 m3) test chamber where the ion emitter was operating. After the results were compared with the natural decay, the air cleaning factor was determined. The particle aerodynamic size range of ∼0.04-2 μm was targeted because it represents many bioaerosol agents that cause emerging diseases, as well as those that can be used for biological warfare or in the event of bioterrorism. The particle electric charge distribution (also measured in the test chamber with the ELPI) was rapidly affected by the ion emission. It was concluded that the corona discharge ion emitters (either positive or negative), which are capable of creating an ion density of 105-106 e± cm-3, can be efficient in controlling fine and ultrafine aerosol pollutants in indoor air environments, such as a typical office or residential room. At a high ion emission rate, the particle mobility becomes sufficient so that the particle migration results in their deposition on the walls and other indoor surfaces. Within the tested ranges of the particle size and ion density, the particles were charged primarily due to the diffusion charging mechanism. The particle removal efficiency was not significantly affected by the particle size, while it increased with increasing ion emission rate and the time of emission. The performance characteristics of three commercially available ionic air purifiers, which produce unipolar ions by corona discharge at relatively high emission rates, were evaluated. A 30-minute operation of the most powerful device among those tested resulted in the removal of about 97% of 0.1 μm particles and about 95% of 1 μm particles from the air in addition to the natural decay effect.

  3. A High Efficiency, Kinetic-Ejection Negative Ion Source for RIB Generation

    SciTech Connect

    Alton, G.D.; Liu, Y.; Murray, S.N.; Williams, C.

    1998-10-05

    Chemically active radioactive species, diffused from RIB target materials, often arrive at the ionization chamber of the source in a variety of molecular forms. Because of the low probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules with conventional hot-cathode electron-impact ion sources, the species of interest are often distributed in several mass channels in the form of molecular side-band beams and consequently, their intensities are diluted. The sputter negative ion beam generation technique offers an efficient means for simultaneously dissociating and ionizing highly electronegative atomic species present in molecular carriers. We have incorporated these principles in the design and fabrication of a kinetic ejection negative ion source and evaluated its potential for generating {sup 17,18}F{sup {minus}} beams for the Holifield Radioactive Ion Beam Facility astrophysics research program. The source utilizes Cs{sup +} beams to bombard condensable fluorine compounds that emanate from a target material, such as Al{sub 2}O{sub 3}, and are transported to the cooled inner surface of a conical-geometry cathode where they are adsorbed. The energetic Cs{sup +} beams efficiently dissociate these molecules and sputter their constituents. Since the work functions of cesiated surfaces are low, highly electronegative species such as fluorine are efficiently ionized in the sputter-injection process. Measured efficiencies for ionizing atomic fluorine, dissociated from condensable compounds that are formed by reactions of SF{sub 6} with fibrous Al{sub 2}O{sub 3} material, exceed 6.5%. In this report, we describe the mechanical design features and principles of operation, and present emittance, F{sup {minus}} yield and ionization efficiency data derived from off-line, experimental evaluation of the source.

  4. A linear dispersion relation for the hybrid kinetic-ion/fluid-electron model of plasma physics

    NASA Astrophysics Data System (ADS)

    Told, D.; Cookmeyer, J.; Astfalk, P.; Jenko, F.

    2016-07-01

    A dispersion relation for a commonly used hybrid model of plasma physics is developed, which combines fully kinetic ions and a massless-electron fluid description. Although this model and variations of it have been used to describe plasma phenomena for about 40 years, to date there exists no general dispersion relation to describe the linear wave physics contained in the model. Previous efforts along these lines are extended here to retain arbitrary wave propagation angles, temperature anisotropy effects, as well as additional terms in the generalized Ohm’s law which determines the electric field. A numerical solver for the dispersion relation is developed, and linear wave physics is benchmarked against solutions of a full Vlasov–Maxwell dispersion relation solver. This work opens the door to a more accurate interpretation of existing and future wave and turbulence simulations using this type of hybrid model.

  5. Hydrogen micro-kinetics in titanium under mechanical stress studied by ion beam analysis

    NASA Astrophysics Data System (ADS)

    Wang, T. S.; Lv, H. Y.; Grambole, D.; Yang, Z.; Peng, H. B.; Han, Y. C.

    2009-04-01

    Hydrogen (H) is continuously produced by the large dose fast neutron irradiation on fusion reactor material. The concentration, diffusion and evolution of H in the structure material may cause H-embrittlement. Ion beam analysis is one of the most useful methods for studying the micro-kinetics of H in solids. In this work, the H-distribution in titanium (Ti) has been studied by resonance nuclear reaction analysis (resonance-NRA) and micro-elastic recoil detection analysis (micro-ERDA). The evolution of H-depth-profile in titanium samples has been studied versus the change of normal stress. Evident H diffusion has been observed, while a normal stress is changed in the range of 107-963 MPa. The H diffusion is related to the concentration of H in samples.

  6. Kinetic evolution of the glasma and thermalization in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Huang, Xu-Guang; Liao, Jinfeng

    2014-03-01

    In relativistic heavy-ion collisions, a highly occupied gluonic matter is created shortly after initial impact, which is in a nonthermal state and often referred to as the Glasma. Successful phenomenology suggests that the glasma evolves rather quickly toward the thermal quark-gluon plasma (QGP) and a hydrodynamic behavior emerges at a very early time ô(1) fm/c. Exactly how such "apparent thermalization" occurs and connects the initial conditions to the hydrodynamic onset, remains a significant challenge for theory as well as phenomenology. We briefly review various ideas and recent progress in understanding the approach of the glasma to the thermalized QGP, with an emphasis on the kinetic theory description for the evolution of such far-from-equilibrium and highly overpopulated, thus weakly-coupled yet strongly interacting glasma.

  7. Systematics of Charged Particle Production in Heavy-Ion Collisions with the PHOBOS Detector at Rhic

    NASA Astrophysics Data System (ADS)

    Steinberg, Peter A.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Corbo, J.; Decowski, M. P.; Garcia, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Henderson, C.; Hicks, D.; Hofman, D.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A.; Mülmenstädt, J.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Rafelski, M.; Rbeiz, M.; 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.

    2002-03-01

    The multiplicity of charged particles produced in Au+Au collisions as a function of energy, centrality, rapidity and azimuthal angle has been measured with the PHOBOS detector at RHIC. These results contribute to our understanding of the initial state of heavy ion collisions and provide a means to compare basic features of particle production in nuclear collisions with more elementary systems.

  8. Light particle emission measurements in heavy ion reactions: Progress report, June 1, 1987-May 31, 1988

    SciTech Connect

    Petitt, G.A.

    1988-01-01

    This paper discusses work on heavy ion reactions done at Georgia State University. Topics and experiments discussed are: energy division in damped reactions between /sup 58/Ni projectiles and /sup 165/Ho and /sup 58/Ni targets using time-of-flight methods; particle-particle correlations; and development works on the Hili detector system. 10 refs., 9 figs. (DWL

  9. Light Induced Degradation of Eight Commonly Used Pesticides Adsorbed on Atmospheric Particles: Kinetics and Product Study

    NASA Astrophysics Data System (ADS)

    Socorro, J.; Durand, A.; Gligorovski, S.; Wortham, H.; Quivet, E.

    2014-12-01

    Pesticides are widely used all over the world whether in agricultural production or in non-agricultural settings. They may pose a potential human health effects and environmental risks due to their physico-chemical properties and their extensive use which is growing every year. Pesticides are found in the atmosphere removed from the target area by volatilization or wind erosion, and carried over long distances. These compounds are partitioned between the gaseous and particulate atmospheric phases. The increasingly used pesticides are semi-volatile compounds which are usually adsorbed on the surface of the atmospheric particles. These pesticides may undergo chemical and photo-chemical transformation. New compounds may then be formed that could be more hazardous than the primary pesticides. The atmospheric fate and lifetime of adsorbed pesticides on particles are controlled by the these (photo)chemical processes. However, there is a lack of kinetic data regarding the pesticides in the particle phase. This current work focuses on the photolytic degradation of commonly used pesticides in particulate phase. It aims at estimating the photolytic rates and thus the lifetimes of pesticides adsorbed on silica particles as a proxy of atmospheric particles. The following eight commonly used pesticides, cyprodinil, deltamethrin, difenoconazole, fipronil, oxadiazon, pendimethalin, permethrin, tetraconazole, were chosen because of their physico-chemical properties. The photolysis rates of tetraconazole and permethrin were extremely slow ≤ 1.2 · 10-6 s-1. The photolysis rates for the other pesticides were determined in the range of: (5.9 ± 0.3) · 10-6 < k < (1.7 ± 0.1) · 10-4 s-1 from slowest to the fastest: pendimethalin < cyprodinil < deltamethrin < difenoconazole < oxadiazon < fipronil. Finally, the identification of the surface products upon light irradiation was performed, using GC-(QqQ)-MS/MS and LC-(Q-IMS-ToF)-MS/MS. The potentially formed gas-phase products during

  10. Nonlinear interaction of kinetic Alfvén waves and ion acoustic waves in coronal loops

    NASA Astrophysics Data System (ADS)

    Sharma, Prachi; Yadav, Nitin; Sharma, R. P.

    2016-05-01

    Over the years, coronal heating has been the most fascinating question among the scientific community. In the present article, a heating mechanism has been proposed based on the wave-wave interaction. Under this wave-wave interaction, the high frequency kinetic Alfvén wave interacts with the low frequency ion acoustic wave. These waves are three dimensionally propagating and nonlinearly coupled through ponderomotive nonlinearity. A numerical code based on pseudo-spectral technique has been developed for solving these normalized dynamical equations. Localization of kinetic Alfvén wave field has been examined, and magnetic power spectrum has also been analyzed which shows the cascading of energy to higher wavenumbers, and this cascading has been found to have Kolmogorov scaling, i.e., k-5 /3 . A breakpoint appears after Kolmogorov scaling and next to this spectral break; a steeper scaling has been obtained. The presented nonlinear interaction for coronal loops plasmas is suggested to generate turbulent spectrum having Kolmogorov scaling in the inertial range and steepened scaling in the dissipation range. Since Kolmogorov turbulence is considered as the main source for coronal heating; therefore, the suggested mechanism will be a useful tool to understand the mystery of coronal loop heating through Kolmogorov turbulence and dissipation.

  11. Overall kinetics of heterogeneous elemental mercury reactions on TiO2 sorbent particles with UV radiation

    EPA Science Inventory

    A system consisting of a photochemical reaction was used to evaluate the kinetic parameters, such as reaction order and rate constant for the elemental mercury uptake by TiO2 in the presence of uv irradiation. TiO2 particles generated by an aerosol route were used in a fixed bed...

  12. Destabilization of the shear Alfven mode by alpha particles and other high energy ions

    NASA Astrophysics Data System (ADS)

    Belikov, V. S.; Kolesnichenko, Ya. I.; Silivra, O. A.

    1992-08-01

    Toroidal Alfven eigenmode (TAE) and elliptical Alfven eigenmode (EAE) instabilities in plasmas with high energy ions are considered in the context of local theory. The instability growth rate is found for cases when waves are excited by alpha particles or by ions produced as a result of neutral injection or RF heating. Electron and ion Landau damping due to the toroidal sideband wave-particle interaction is also calculated. The electron damping rate is shown to be much lower than the generally accepted value. The TAE instability observed in the experiment with neutral beam injection on TFTR is analysed and the principal experimental features of TAE instability are explained

  13. A Kinetic-fluid Model

    SciTech Connect

    First Author = C.Z. Cheng; Jay R. Johnson

    1998-07-10

    A nonlinear kinetic-fluid model for high-beta plasmas with multiple ion species which can be applied to multiscale phenomena is presented. The model embeds important kinetic effects due to finite ion Larmor radius (FLR), wave-particle resonances, magnetic particle trapping, etc. in the framework of simple fluid descriptions. When further restricting to low frequency phenomena with frequencies less than the ion cyclotron frequency the kinetic-fluid model takes a simpler form in which the fluid equations of multiple ion species collapse into single-fluid density and momentum equations and a low frequency generalized Ohm's law. The kinetic effects are introduced via plasma pressure tensors for ions and electrons which are computed from particle distribution functions that are governed by the Vlasov equation or simplified plasma dynamics equations such as the gyrokinetic equation. The ion FLR effects provide a finite parallel electric field, a perpendicular velocity that modifies the ExB drift, and a gyroviscosity tensor, all of which are neglected in the usual one-fluid MHD description. Eigenmode equations are derived which include magnetosphere-ionosphere coupling effects for low frequency waves (e.g., kinetic/inertial Alfven waves and ballooning-mirror instabilities).

  14. Charge state, angular distribution, and kinetic energy of ions from multicomponent-cathodes in vacuum arc devices

    SciTech Connect

    Nikolaev, A. G. Savkin, K. P.; Yushkov, G. Yu.; Frolova, V. P.; Barengolts, S. A.

    2014-12-07

    We present research results on vacuum arc plasma produced with multicomponent cathode made of several different elements. The ion mass-to-charge-state spectra of the plasmas were studied by time-of-flight spectrometry. The angular distributions of different ion species were measured, and the kinetic energy of their directed (streaming) motion was determined. It is shown that the fractional composition of ions of different cathode components in the plasma flow from the cathode spot closely matches the fractional content of these components in the composite cathode. The charge states of ions of the various cathode components are determined by the average electron temperature in the cathode spot plasma. The angular distribution of lower mass ions in the plasma from a multicomponent cathode is less isotropic and broader than for the plasma from a single-component cathode of the same light element. The directed kinetic energies of the ions of the different components for plasma from a multicomponent cathode are lower for lighter elements and greater for heavier elements compared to the ion directed energy for plasmas from single-component cathodes made of the same materials. The physical processes responsible for these changes in the ion charge states in multicomponent-cathode vacuum arc plasma are discussed.

  15. Azimuthal structures of produced particles in heavy-ion interactions

    SciTech Connect

    Vokal, S. Orlova, G. I.; Lehocka, S.

    2009-02-15

    The angular structures of particles produced in {sup 208}Pb at 158 A GeV/c and {sup 197}Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined.

  16. The influence of dust particles on electromagnetic ion cyclotron waves in a bi-Lorentzian plasma

    SciTech Connect

    Venugopal, C.; Varughese, J.K.; Antony, S.; Anilkumar, C.P.; Renuka, G.

    1997-10-01

    The influence of dust particles on electromagnetic ion cyclotron (EMIC) waves, propagating parallel to the magnetic field, in a plasma where the hot ions are modelled by a bi-Lorentzian or Kappa distribution has been studied. The electrons and dust particles have been treated as cold. Expressions for the dispersion relations and growth/damping rates in both high- and low-{beta} plasmas have been derived. For the low-{beta} case temperature anisotropy is the source of instability in an electron{endash}ion plasma. This instability is strongly influenced by the temperature anisotropy of the hot ions and the charge and density of the dust particles; the instability increases with these parameters. However, in high-{beta} plasmas, the instability is driven by the dust. The growth rate increases with the charge on the dust; but with increasing dust densities the EMIC wave propagates almost freely. {copyright} {ital 1997 American Institute of Physics.}

  17. Analysis of the response of silicon detectors to α particles and 16O ions

    NASA Astrophysics Data System (ADS)

    Kirsebom, O. S.; Fynbo, H. O. U.; Riisager, K.; Raabe, R.; Roger, T.

    2014-09-01

    We clarify basic concepts concerning the response of silicon detectors to ionizing radiation, focusing on light ions with energies ranging from a few hundred keV to a few MeV. Through reanalysis of existing experimental data, we quantify the difference in the response of silicon detectors to α particles and 16O ions, and we determine the correction that must be made before an energy calibration obtained with α particles can be applied to the measurement of 16O ions. Finally, we show that an apparent disagreement among three recent measurements of the decay spectrum of 8B can be explained by a failure to correctly take into account the different response of silicon detectors to α particles and 16O ions.

  18. Orbit-averaged drift kinetic equation for the study of alpha-particle transport in tokamaks

    SciTech Connect

    Sager, G.T.; Miley, G.H. . Fusion Studies Lab.); Burrell, K.H. )

    1990-11-01

    Neoclassical transport of minority suprathermal alpha particles is investigated. This paper departs from previous investigations in that (a) the banana-width ordering parameter {rho}{sub {theta}}/L is not formally restricted to be a small parameter and (b) a linearized collision operator that retains the effects of pitch-angle scattering, electron and ion drag, and speed diffusion is used. A step model approximation for the large-aspect-ratio, circular-cross-section tokamak magnetic field is adopted to simplify the orbit-averaging procedure. Assuming that the suprathermal alphas are in the banana regime, an asymptotic expansion in {tau}{sub B}/{tau}{sub S} {much lt} l is carried out.

  19. Response to “Comment on ‘The ion-kinetic D'Angelo mode’” [Phys. Plasmas 22, 044703 (2015)

    SciTech Connect

    Chibisov, D. V.; Mikhailenko, V. S.

    2015-04-15

    A response to “Comment on ‘The ion-kinetic D'Angelo mode’” by Aman-ur-Rehman, Shaukat Ali Shan, and Hamid Saleem is given. We find that all Comments are grounded on the misinterpretations of the results of our paper “The ion-kinetic D'Angelo mode” and are erroneous.

  20. First observation of alpha particle loss induced by kinetic ballooning modes in TFTR deuterium-tritium experiments

    SciTech Connect

    Chang, Z.; Budny, R.V.; Chen, L.; Darrow, D.; Fredrickson, E.D.; Janos, A.; Mansfield, D.; Mazzucato, E.; McGuire, K.M.; Nazikian, R.; Rewoldt, G.; Strachan, J.D.; Tang, W.M.; Taylor, G.; White, R.B.; Zweben, S. |; TFTR group

    1996-02-01

    A correlation between the measured alpha particle loss and high frequency ({approximately}100{endash}200 kHz) magnetohydrodynamic (MHD) modes has been observed in some high {beta} (= plasma pressure/magnetic pressure) DT plasmas in TFTR. These modes are localized around the peak plasma pressure gradient and have ballooning characteristics. Particle simulation shows that the loss is due to wave-particle resonances. Linear instability analysis indicates that the plasma is unstable to the kinetic MHD ballooning modes driven by strong local pressure gradients. {copyright} {ital 1996 The American Physical Society.}

  1. Kinetic Alfvén turbulence below and above ion cyclotron frequency

    NASA Astrophysics Data System (ADS)

    Zhao, J. S.; Voitenko, Y. M.; Wu, D. J.; Yu, M. Y.

    2016-01-01

    Alfvénic turbulent cascade perpendicular and parallel to the background magnetic field is studied accounting for anisotropic dispersive effects and turbulent intermittency. The perpendicular dispersion and intermittency make the perpendicular-wave-number magnetic spectra steeper and speed up production of high ion cyclotron frequencies by the turbulent cascade. On the contrary, the parallel dispersion makes the spectra flatter and decelerate the frequency cascade above the ion cyclotron frequency. Competition of these factors results in spectral indices distributed in the interval [-2, -3], where -2 is the index of high-frequency space-filling turbulence and -3 is the index of low-frequency intermittent turbulence formed by tube-like fluctuations. Spectra of fully intermittent turbulence fill a narrower range of spectral indices [-7/3, -3], which almost coincides with the range of indexes measured in the solar wind. This suggests that the kinetic-scale turbulent spectra are mainly shaped by the dispersion and intermittency. A small mismatch with measured indexes of about 0.1 can be associated with damping effects not studied here.

  2. Early stage of the electron kinetics in swift heavy ion tracks in dielectrics

    SciTech Connect

    Medvedev, N. A.; Rethfeld, B.; Volkov, A. E.; Shcheblanov, N. S.

    2010-09-15

    A Monte Carlo approach was applied for simulations of the early stage (first tens of femtosecond) of kinetics of the electronic subsystem of silica (SiO{sub 2}) in tracks of swift heavy ions (SHIs) decelerated in the electronic stopping regime. At the first step multiple ionizations of target atoms by a projectile (Ca{sup +19}, E=11.4 MeV/amu) were described that gave the initial spatial distributions of free electrons having different momenta as well as distributions of holes in different atomic shells. Spatial propagation of fast electrons results in secondary ionizations of target atoms as well as in energy transfer to the lattice at times much shorter than the times of atomic oscillations (phonons). The well detected front of excitation in the electronic and ionic subsystems is formed due to this propagation which cannot be described by models based on diffusion mechanisms (e.g., parabolic equations of heat diffusion). At times {approx}10 fs after the projectile passage, about {approx}0.1% of the energy is already transferred to the lattice. About 63% of the energy deposited by the ion is accumulated in holes at these times. Calculated distributions of these holes through the atomic shells are in excellent agreement with the spectroscopy experiments. Comparison with these experiments demonstrated also that relaxation of the electronic subsystem in SHI tracks in solids cannot be described adequately without taking into account intra-atomic and interatomic Auger (Knotek-Feibelman) processes.

  3. Surface-Coating Regulated Lithiation Kinetics and Degradation in Silicon Nanowires for Lithium Ion Battery

    SciTech Connect

    Luo, Langli; Yang, Hui; Yan, Pengfei; Travis, Jonathan J.; Lee, Younghee; Liu, Nian; Piper, Daniela M.; Lee, Se-Hee; Zhao, Peng; George, Steven M.; Zhang, Jiguang; Cui, Yi; Zhang, Sulin; Ban, Chunmei; Wang, Chong M.

    2015-05-26

    Silicon (Si)-based materials hold promise as the next-generation anodes for high-energy lithium (Li)-ion batteries. Enormous research efforts have been undertaken to mitigate the chemo-mechanical failure due to the large volume changes of Si during lithiation and delithiation cycles. It has been found nanostructured Si coated with carbon or other functional materials can lead to significantly improved cyclability. However, the underlying mechanism and comparative performance of different coatings remain poorly understood. Herein, using in situ transmission electron microscopy (TEM) through a nanoscale half-cell battery, in combination with chemo-mechanical simulation, we explored the effect of thin (~5 nm) alucone and Al2O3 coatings on the lithiation kinetics of Si nanowires (SiNWs). We observed that the alucone coating leads to a “V-shaped” lithiation front of the SiNWs , while the Al2O3 coating yields an “H-shaped” lithiation front. These observations indicate that the difference between the Li surface diffusivity and bulk diffusivity of the coatings dictates lithiation induced morphological evolution in the nanowires. Our experiments also indicate that the reaction rate in the coating layer can be the limiting step for lithiation and therefore critically influences the rate performance of the battery. Further, the failure mechanism of the Al2O3 coated SiNWs was also explored. Our studies shed light on the design of high capacity, high rate and long cycle life Li-ion batteries.

  4. Constraining Solar Wind Heating Processes by Kinetic Properties of Heavy Ions

    NASA Astrophysics Data System (ADS)

    Tracy, Patrick J.; Kasper, Justin C.; Raines, Jim M.; Shearer, Paul; Gilbert, Jason A.; Zurbuchen, Thomas H.

    2016-06-01

    We analyze the heavy ion components (A >4 amu ) in collisionally young solar wind plasma and show that there is a clear, stable dependence of temperature on mass, probably reflecting the conditions in the solar corona. We consider both linear and power law forms for the dependence and find that a simple linear fit of the form Ti/Tp=(1.35 ±.02 )mi/mp describes the observations twice as well as the equivalent best fit power law of the form Ti/Tp=(mi/mp) 1.07 ±.01 . Most importantly we find that current model predictions based on turbulent transport and kinetic dissipation are in agreement with observed nonthermal heating in intermediate collisional age plasma for m /q <3.5 , but are not in quantitative or qualitative agreement with the lowest collisional age results. These dependencies provide new constraints on the physics of ion heating in multispecies plasmas, along with predictions to be tested by the upcoming Solar Probe Plus and Solar Orbiter missions to the near-Sun environment.

  5. Constraining Solar Wind Heating Processes by Kinetic Properties of Heavy Ions.

    PubMed

    Tracy, Patrick J; Kasper, Justin C; Raines, Jim M; Shearer, Paul; Gilbert, Jason A; Zurbuchen, Thomas H

    2016-06-24

    We analyze the heavy ion components (A>4  amu) in collisionally young solar wind plasma and show that there is a clear, stable dependence of temperature on mass, probably reflecting the conditions in the solar corona. We consider both linear and power law forms for the dependence and find that a simple linear fit of the form T_{i}/T_{p}=(1.35±.02)m_{i}/m_{p} describes the observations twice as well as the equivalent best fit power law of the form T_{i}/T_{p}=(m_{i}/m_{p})^{1.07±.01}. Most importantly we find that current model predictions based on turbulent transport and kinetic dissipation are in agreement with observed nonthermal heating in intermediate collisional age plasma for m/q<3.5, but are not in quantitative or qualitative agreement with the lowest collisional age results. These dependencies provide new constraints on the physics of ion heating in multispecies plasmas, along with predictions to be tested by the upcoming Solar Probe Plus and Solar Orbiter missions to the near-Sun environment. PMID:27391732

  6. Responses of a direct ion storage dosimeter (DIS-1) to heavy charged particles.

    PubMed

    Yasuda, H

    2001-12-01

    The responses of a direct ion storage dosimeter (DIS-1) to energetic heavy charged particles were examined using (4)He, (12)C, (40)Ar and (56)Fe ion beams at the HIMAC at the National Institute of Radiological Sciences. The efficiency of the DIS-1 on the basis of absorbed dose was almost unity for the helium and carbon ions and was slightly decreased for the argon and iron ions. The linearity in the dose response and the angular independence for these heavy ions were fairly good. Although further studies are necessary, these results suggest that the DIS-1 would be a suitable passive dosimeter for measurements of absorbed dose in a field dominated by heavy charged particles such as the space environment. PMID:11741505

  7. Inside versus Outside: Ion Redistribution in Nitric Acid Reacted Sea Spray Aerosol Particles as Determined by Single Particle Analysis (Invited)

    NASA Astrophysics Data System (ADS)

    Ault, A. P.; Guasco, T.; Ryder, O. S.; Baltrusaitis, J.; Cuadra-Rodriguez, L. A.; Collins, D. B.; Ruppel, M. J.; Bertram, T. H.; Prather, K. A.; Grassian, V. H.

    2013-12-01

    Sea spray aerosol (SSA) particles were generated under real-world conditions using natural seawater and a unique ocean-atmosphere facility equipped with actual breaking waves or a marine aerosol reference tank (MART) that replicates those conditions. The SSA particles were exposed to nitric acid in situ in a flow tube and the well-known chloride displacement and nitrate formation reaction was observed. However, as discussed here, little is known about how this anion displacement reaction affects the distribution of cations and other chemical constituents within and phase state of individual SSA particles. Single particle analysis of individual SSA particles shows that cations (Na+, K+, Mg2+ and Ca2+) within individual particles undergo a spatial redistribution after heterogeneous reaction with nitric acid, along with a more concentrated layer of organic matter at the surface of the particle. These data suggest that specific ion and aerosol pH effects play an important role in aerosol particle structure in ways that have not been previously recognized. The ordering of organic coatings can impact trace gas uptake, and subsequently impact trace gas budgets of O3 and NOx.

  8. Characterizing particle-scale equilibrium adsorption and kinetics of uranium(VI) desorption from U-contaminated sediments

    USGS Publications Warehouse

    Stoliker, Deborah L.; Liu, Chongxuan; Kent, Douglas B.; Zachara, John M.

    2013-01-01

    Rates of U(VI) release from individual dry-sieved size fractions of a field-aggregated, field-contaminated composite sediment from the seasonally saturated lower vadose zone of the Hanford 300-Area were examined in flow-through reactors to maintain quasi-constant chemical conditions. The principal source of variability in equilibrium U(VI) adsorption properties of the various size fractions was the impact of variable chemistry on adsorption. This source of variability was represented using surface complexation models (SCMs) with different stoichiometric coefficients with respect to hydrogen ion and carbonate concentrations for the different size fractions. A reactive transport model incorporating equilibrium expressions for cation exchange and calcite dissolution, along with rate expressions for aerobic respiration and silica dissolution, described the temporal evolution of solute concentrations observed during the flow-through reactor experiments. Kinetic U(VI) desorption was well described using a multirate SCM with an assumed lognormal distribution for the mass-transfer rate coefficients. The estimated mean and standard deviation of the rate coefficients were the same for all <2 mm size fractions but differed for the 2–8 mm size fraction. Micropore volumes, assessed using t-plots to analyze N2 desorption data, were also the same for all dry-sieved <2 mm size fractions, indicating a link between micropore volumes and mass-transfer rate properties. Pore volumes for dry-sieved size fractions exceeded values for the corresponding wet-sieved fractions. We hypothesize that repeated field wetting and drying cycles lead to the formation of aggregates and/or coatings containing (micro)pore networks which provided an additional mass-transfer resistance over that associated with individual particles. The 2–8 mm fraction exhibited a larger average and standard deviation in the distribution of mass-transfer rate coefficients, possibly caused by the abundance of

  9. Simulation study of the role of ion kinetics in low-frequency wave train evolution

    NASA Technical Reports Server (NTRS)

    Vasquez, Bernard J.

    1995-01-01

    The evolution of uniform, parallel propagating, low-frequency (less than or approx. ion cyclotron) wave trains is followed with a one-dimensional hybrid numerical code with fluid electrons and particle ions. We show that moderate amplitude (delta B/B less than 1/2) wave trains give instabilities and saturated states which differ completely from pure fluid evolution. This is most clearly seen when beta greater than 1 and instability exists for wavenumbers both below and above the wavenumber of an inital, left-handed wave train or pump wave. For corresponding parameters a fluid theory gives only a narrow range of instability above the pump wavenumber where decay and beat instabilities can occur. in simulations wave energy inverse cascades to smaller wavenumbers and into a greater number of forward than backward going waves. In fluids energy by decay goes mostly to backward ones of smaller wavenumber, and energy by beat goes mostly to forward ones of larger wavenumber. Neither fluid instability explains simulation results. The instability is saturated by thermalizing ions and sometimes exciting small wavenumber electrostatic or acoustic modes. In contrast, saturation in fluids first occurs by generating the harmonics of the growing linear modes. Harmonic generation is mostly absent in simulations. Simulations are carried out to long times and mostly reach a limit beyond which no further significant evolution can occur. Application to Alfvenic fluctuations in the solar wind is discussed.

  10. Effect of valence holes kinetics on material excitation in tracks of swift heavy ions

    NASA Astrophysics Data System (ADS)

    Rymzhanov, R. A.; Medvedev, N. A.; Volkov, A. E.

    2015-12-01

    A considerable part of the excess energy of the electronic subsystem of a solid penetrated by a swift heavy ion (SHI) is accumulated in valence holes. Spatial redistribution of these holes can affect subsequent relaxation, resulting in ionizations of new electrons by hole impacts as well as energy transfer to the target lattice. A new version of the Monte Carlo code TREKIS is applied to study this effect in Al2O3 for SHI tracks. The complex dielectric function (CDF) formalism is used to calculate the cross sections of interaction of involved charged particles (an ion, electrons, holes) with the target giving us ability to take into account collective response of a target to excitations. We compare the radial distributions of the densities and energies of excited electrons and valence holes at different times to those obtained under the assumption of immobile holes used in earlier works. The comparison shows a significant difference between these distributions within the track core, where the majority of slow electrons and valence holes are located at femtosecond timescales after the ion impact. The study demonstrates that the energy deposited by valence holes into the lattice in nanometric tracks is comparable to the energy transferred by excited electrons. Radii of structure transformations in tracks produced by these energy exchange channels are in a good agreement with experiments.

  11. Effects of H+, He+ ion reflection at the lunar surface and pickup ion dynamics in case of oblique/quasi-parallel magnetic field: 3-D hybrid kinetic modeling

    NASA Astrophysics Data System (ADS)

    Lipatov, A. S.; Cooper, J. F.; Sittler, E. C.; Hartle, R. E.; Sarantos, M.

    2013-12-01

    The hybrid kinetic model used here supports comprehensive simulation of the interaction between different spatial and energetic elements of the moon-solar wind-magnetosphere of the Earth system. This involves variable upstream magnetic field and solar wind plasma, including energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of existing measurements for surface and atmospheric composition from previous missions and planning future missions. Recently, MAP-PAGE-IMA (Plasma energy Angle and Composition Experiment, and Ion Mass Analyzer) onboard Japanese lunar orbiter SELENE (KAGUYA) detected Moon originating ions at 100 km altitude. Ion species of H+, He++, He+, C+, O+, Na+, K+, and Ar+ were definitively identified. The first portion of our modeling devotes to a study of the H+, H2+, He+, Na+ pickup ion dynamics in cases of flow with a oblique and quasi-parallel magnetic field. In the second series of modeling we also take into account collisions between ions and the surface of the moon and further sputtering of fragments from the surface of the moon. The ion reflection at the lunar surface is also responsible for wave activity in the upstream flow. The solar wind parameters are chosen from ARTEMIS observations. The hybrid kinetic model allows us to take into account the finite gyroradius effects of pickup ions and to estimate correctly the ions velocity distribution and the fluxes along the magnetic field. Modeling shows the asymmetric Mach cone, pickup and reflected ion tails, and presents another type of lunar-solar wind interaction. Our simulation may be also important for the study of the interaction between the solar wind and very weak comets, Mercury and Pluto.

  12. Dissolution kinetics of sub-millimeter Composition B detonation residues: role of particle size and particle wetting.

    PubMed

    Fuller, Mark E; Schaefer, Charles E; Andaya, Christina; Lazouskaya, Volha; Fallis, Steve; Wang, Chao; Jin, Yan

    2012-07-01

    The dissolution of the 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from microscale particles (<250μm) of the explosive formulation Composition B was examined and compared to dissolution from macroscopic particles (>0.5mm). The dissolution of explosives from detonation soot was also examined. The measured mass transfer coefficients for the microscale particles were one to two orders of magnitude greater than the macroscopic particles. When normalized to particle surface area, mass transfer coefficients of microscale and macroscale particles were similar, indicating that the bulk dissolution processes were similar throughout the examined size range. However, an inverse relationship was observed between the particle diameter and the RDX:TNT mass transfer rate coefficient ratio for dry-attritted particles, which suggests that RDX may be more readily dissolved (relative to TNT) in microscale particles compared to macroscale particles. Aqueous weathering of larger Composition B residues generated particles that possessed mass transfer coefficients that were on the order of 5- to 20-fold higher than dry-attritted particles of all sizes, even when normalized to particle surface area. These aqueous weathered particles also possessed a fourfold lower absolute zeta-potential than dry-attritted particles, which is indicative that they were less hydrophobic (and hence, more wettable) than dry-attritted particles. The increased wettability of these particles provides a plausible explanation for the observed enhanced dissolution. The wetting history and the processes by which particles are produced (e.g., dry physical attrition vs. aqueous weathering) of Composition B residues should be considered when calculating mass transfer rates for fate and transport modeling. PMID:22483856

  13. Particle Accelerator Applications: Ion and Electron Irradiation in Materials Science, Biology and Medicine

    NASA Astrophysics Data System (ADS)

    Rodríguez-Fernández, Luis

    2010-09-01

    Although the developments of particle accelerators are devoted to basic study of matter constituents, since the beginning these machines have been applied with different purposes in many areas also. Today particle accelerators are essential instruments for science and technology. This work presents an overview of the main application for direct particle irradiation with accelerator in material science, biology and medicine. They are used for material synthesis by ion implantation and charged particle irradiation; to make coatings and micromachining; to characterize broad kind of samples by ion beam analysis techniques; as mass spectrometers for atomic isotopes determination. In biomedicine the accelerators are applied for the study of effects by charged particles on cells. In medicine the radiotherapy by electron irradiation is widely used, while hadrontherapy is still under development. Also, they are necessary for short life radioisotopes production required in radiodiagnostic.

  14. Kinetics of first-order phase transitions initiated by diffusion of particles from the surface into the bulk

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. P.; Krozer, A.; Kasemo, B.

    1993-05-01

    The kinetic equations are formulated and solved to describe a first-order phase transition initiated by diffusion of particles from the surface into the bulk. The scenario of phase transformation is assumed to involve the following three stages. At first, the particles diffuse in the bulk almost freely because the grain concentration is low. Then, with increasing grain concentration, the particles are trapped predominantly near the interface and the space distribution of particles shifts to the interface. Finally, the dense phase formed near the interface blocks diffusion of particles from the interface into the bulk and prevents further uptake. General results are used to interpret the experimental data on the hydrogen uptake by Pd-coated Mg at low temperatures. In this system, the asymptotic hydrogen uptake as a function of time decreases with increasing hydrogen pressure. This unusual feature of the hydrogen uptake is shown to be qualitatively explained by hydride nucleation and growth near the Pd/Mg interface.

  15. Modeling aerosol surface chemistry and gas-particle interaction kinetics with K2-SURF: PAH oxidation

    NASA Astrophysics Data System (ADS)

    Shiraiwa, M.; Garland, R.; Pöschl, U.

    2009-04-01

    Atmospheric aerosols are ubiquitous in the atmosphere. They have the ability to impact cloud properties, radiative balance and provide surfaces for heterogeneous reactions. The uptake of gaseous species on aerosol surfaces impacts both the aerosol particles and the atmospheric budget of trace gases. These subsequent changes to the aerosol can in turn impact the aerosol chemical and physical properties. However, this uptake, as well as the impact on the aerosol, is not fully understood. This uncertainty is due not only to limited measurement data, but also a dearth of comprehensive and applicable modeling formalizations used for the analysis, interpretation and description of these heterogeneous processes. Without a common model framework, comparing and extrapolating experimental data is difficult. In this study, a novel kinetic surface model (K2-SURF) [Ammann & Pöschl, 2007; Pöschl et al., 2007] was used to describe the oxidation of a variety of polycyclic aromatic hydrocarbons (PAHs). Integrated into this consistent and universally applicable kinetic and thermodynamic process model are the concepts, terminologies and mathematical formalizations essential to the description of atmospherically relevant physicochemical processes involving organic and mixed organic-inorganic aerosols. Within this process model framework, a detailed master mechanism, simplified mechanism and parameterizations of atmospheric aerosol chemistry are being developed and integrated in analogy to existing mechanisms and parameterizations of atmospheric gas-phase chemistry. One of the key aspects to this model is the defining of a clear distinction between various layers of the particle and surrounding gas phase. The processes occurring at each layer can be fully described using known fluxes and kinetic parameters. Using this system there is a clear separation of gas phase, gas-surface and surface bulk transport and reactions. The partitioning of compounds can be calculated using the flux

  16. Internal composition of atmospheric dust particles from focused ion-beam scanning electron microscopy.

    PubMed

    Conny, Joseph M

    2013-08-01

    Use of focused ion-beam scanning electron microscopy (FIB-SEM) to investigate the internal composition of atmospheric particles is demonstrated for assessing particle optical properties. In the FIB-SEM instrument equipped with an X-ray detector, a gallium-ion beam mills the particle, while the electron beam images the slice faces and energy-dispersive X-ray spectroscopy provides element maps of the particle. Differences in assessments of optical behavior based on FIB-SEM and conventional SEM were shown for five selected urban dust particles. The benefit of FIB-SEM for accurately determining the depth and size of optically important phases within particles was shown. FIB-SEM revealed that iron oxide grains left undetected by conventional SEM could potentially shift the single-scattering albedo of the particle from negative to positive radiative forcing. Analysis of a coke-like particle showed that 73% of the light-scattering inclusion went undetected with conventional SEM, causing the bulk absorption coefficient to vary by as much as 25%. Optical property calculations for particles as volume-equivalent spheres and as spheroids that approximated actual particle shapes revealed that the largest effect between conventional SEM and FIB-SEM analyses was on backscattering efficiency, in some cases varying several-fold. PMID:23763344

  17. Rate laws of the self-induced aggregation kinetics of Brownian particles

    NASA Astrophysics Data System (ADS)

    Mondal, Shrabani; Sen, Monoj Kumar; Baura, Alendu; Bag, Bidhan Chandra

    2016-03-01

    In this paper we have studied the self induced aggregation kinetics of Brownian particles in the presence of both multiplicative and additive noises. In addition to the drift due to the self aggregation process, the environment may induce a drift term in the presence of a multiplicative noise. Then there would be an interplay between the two drift terms. It may account qualitatively the appearance of the different laws of aggregation process. At low strength of white multiplicative noise, the cluster number decreases as a Gaussian function of time. If the noise strength becomes appreciably large then the variation of cluster number with time is fitted well by the mono exponentially decaying function of time. For additive noise driven case, the decrease of cluster number can be described by the power law. But in case of multiplicative colored driven process, cluster number decays multi exponentially. However, we have explored how the rate constant (in the mono exponentially cluster number decaying case) depends on strength of interference of the noises and their intensity. We have also explored how the structure factor at long time depends on the strength of the cross correlation (CC) between the additive and the multiplicative noises.

  18. Study of electron transport in a Hall thruster by axial-radial fully kinetic particle simulation

    NASA Astrophysics Data System (ADS)

    Cho, Shinatora; Watanabe, Hiroki; Kubota, Kenichi; Iihara, Shigeyasu; Fuchigami, Kenji; Uematsu, Kazuo; Funaki, Ikkoh

    2015-10-01

    Electron transport across a magnetic field in a magnetic-layer-type Hall thruster was numerically investigated for the future predictive modeling of Hall thrusters. The discharge of a 1-kW-class magnetic-layer-type Hall thruster designed for high-specific-impulse operation was modeled using an r-z two-dimensional fully kinetic particle code with and without artificial electron-diffusion models. The thruster performance results showed that both electron transport models captured the experimental result within discrepancies less than 20% in thrust and discharge current for all the simulated operation conditions. The electron cross-field transport mechanism of the so-called anomalous diffusion was self-consistently observed in the simulation without artificial diffusion models; the effective electron mobility was two orders of magnitude higher than the value obtained using the classical diffusion theory. To account for the self-consistently observed anomalous transport, the oscillation of plasma properties was speculated. It was suggested that the enhanced random-walk diffusion due to the velocity oscillation of low-frequency electron flow could explain the observed anomalous diffusion within an order of magnitude. The dominant oscillation mode of the electron flow velocity was found to be 20 kHz, which was coupled to electrostatic oscillation excited by global ionization instability.

  19. Study of electron transport in a Hall thruster by axial–radial fully kinetic particle simulation

    SciTech Connect

    Cho, Shinatora Kubota, Kenichi; Funaki, Ikkoh; Watanabe, Hiroki; Iihara, Shigeyasu; Fuchigami, Kenji; Uematsu, Kazuo

    2015-10-15

    Electron transport across a magnetic field in a magnetic-layer-type Hall thruster was numerically investigated for the future predictive modeling of Hall thrusters. The discharge of a 1-kW-class magnetic-layer-type Hall thruster designed for high-specific-impulse operation was modeled using an r-z two-dimensional fully kinetic particle code with and without artificial electron-diffusion models. The thruster performance results showed that both electron transport models captured the experimental result within discrepancies less than 20% in thrust and discharge current for all the simulated operation conditions. The electron cross-field transport mechanism of the so-called anomalous diffusion was self-consistently observed in the simulation without artificial diffusion models; the effective electron mobility was two orders of magnitude higher than the value obtained using the classical diffusion theory. To account for the self-consistently observed anomalous transport, the oscillation of plasma properties was speculated. It was suggested that the enhanced random-walk diffusion due to the velocity oscillation of low-frequency electron flow could explain the observed anomalous diffusion within an order of magnitude. The dominant oscillation mode of the electron flow velocity was found to be 20 kHz, which was coupled to electrostatic oscillation excited by global ionization instability.

  20. The heavy-ion compositional signature in He-3-rich solar particle events

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Reames, D. V.; Von Rosenvinge, T. T.; Klecker, B.; Hovestadt, D.

    1986-01-01

    A survey of the approx. 1 MeV/nucleon heavy ion abundances in 66 He-3-rich solar particle events was performed using the Max-Planck-Institut/University of Maryland and Goddard Space Flight Center instruments on the ISEE-3 spacecraft. The observations were carried out in interplanetary space over the period 1978 October through 1982 June. Earlier observations were confirmed which show an enrichment of heavy ions in He-3-rich events, relative to the average solar energetic particle composition in large particle events. For the survey near 1.5 MeV/nucleon the enrichments compared to large solar particle events are approximately He4:C:O:Ne:Mg:Si:Fe = 0.44:0.66:1.:3.4:3.5:4.1:9.6. Surprising new results emerging from the present broad survey are that the heavy ion enrichment pattern is the same within a factor of approx. 2 for almost all cases, and the degree of heavy ion enrichment is uncorrelated with the He-3 enrichment. Overall, the features established appear to be best explained by an acceleration mechanism in which the He-3 enrichment process is not responsible for the heavy ion enrichment, but rather the heavy ion enrichment is a measure of the ambient coronal composition at the sites where the He-3-rich events occur.

  1. The heavy ion compositional signature in 3He-rich solar particle events

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Reames, D. V.; Klecker, B.; Hovestadt, D.; Vonrosenvinge, T. T.

    1985-01-01

    A survey of the approx. 1 MeV/nucleon heavy ion abundances in 66 He3-rich solar particle events was performed using the Max-Planck-Institut/University of Maryland and Goddard Space Flight Center instruments on the ISEE-3 spacecraft. The observations were carried out in interplanetary space over the period 1978 October through 1982 June. Earlier observations were confirmed which show an enrichment of heavy ions in HE3-rich events, relative to the average solar energetic particle composition in large particle events. For the survey near 1.5 MeV/nucleon the enrichments compared to large solar particle events are approximately He4:C:O:Ne:Mg:Si:Fe = 0.44:0.66:1.:3.4:3.5:4.1:9.6. Surprising new results emerging from the present broad survey are that the heavy ion enrichment pattern is the same within a factor of approx. 2 for almost all cases, and the degree of heavy ion enrichment is uncorrelated with the He3 enrichment. Overall, the features established appear to be best explained by an acceleration mechanism in which the He3 enrichment process is not responsible for the heavy ion enrichment, but rather the heavy ion enrichment is a measure of the ambient coronal composition at the sites where the He3-rich events occur.

  2. Improved dispensing targets for ion beam particle generators

    NASA Technical Reports Server (NTRS)

    Miller, C. G.

    1974-01-01

    Beam impinges on palladium-silver tube, which is target, and heats impinged surface causing local hot spot. Contained gas diffuses through hot spot to meet incoming beam and produce desired particles. When beam is turned off, target spot cools and stops dispensing contained gas.

  3. Interaction of energized bacteria cells with particles of colloidal gold: peculiarities and kinetic model of the process.

    PubMed

    Ulberg, Z R; Karamushka, V I; Vidybida, A K; Sericov, A A; Dukhin, A S; Gruzina, T G; Pechenaya, V I

    1992-03-16

    It is found that the cells of Bacillus cereus B-4368 at energized state can concentrate the colloidal gold particles on their surface. It is shown that the process depends on metabolic reactions proceeding on the plasma membrane. The inhibitory analysis permits to suppose that the metal concentration is due to the functioning of ATP-dependent generator of the transmembrane potential, apparently, of proton ATPase. Kinetic characteristics of the process show the presence of an intermediate state in the formation of biomineral aggregates. A kinetic model of the studied process is suggested which describes the experimental data well. PMID:1532513

  4. Kinetic energy distributions in ion-induced CO fragmentation: Signature of shallow states in multiply charged CO

    NASA Astrophysics Data System (ADS)

    Rajput, Jyoti; Safvan, C. P.

    2007-06-01

    Ion-induced molecular fragmentation of CO has been studied using time-of-flight mass spectroscopy with position sensitive detectors in multihit coincidence mode. Ar8+ ions having a velocity of 1.1 a.u. were used as projectiles. The features observed in the kinetic energy release (KER) spectra for all the detected fragmentation channels are discussed in light of the existing and calculated ab initio potential energy curves. The preference of the symmetric breakup over the asymmetric one is clearly observed. For fragmentation channels originating from the same parent molecular ion, it is observed that the most probable KER value is higher for the dissociation channel having a higher charge on the oxygen ion. Occurrence of sharp peaks in KER spectra of some of the fragmentation channels hints towards the existence of shallow (possibly metastable) excited states of COq+ (q=4,5) molecular ions and calls for further theoretical investigations.

  5. Ion Exchange Equilibrium and Kinetic Properties of Polyacrylate Films and Applications to Chemical Analysis and Environmental Decontamination

    NASA Technical Reports Server (NTRS)

    Tanner, Stephen P.

    1997-01-01

    One of the goals of the original proposal was to study how cross-linking affects the properties of an ion exchange material(IEM) developed at Lewis Research Center. However, prior to the start of this work, other workers at LERC investigated the effect of cross-linking on the properties of this material. Other than variation in the ion exchange capacity, the chemical characteristics were shown to be independent of the cross-linking agent, and the degree of cross-linking. New physical forms of the film were developed (film, supported film, various sizes of beads, and powder). All showed similar properties with respect to ion exchange equilibria but the kinetics of ion exchange depended on the surface area per unit mass; the powder form of the IEM exchanging much more rapidly than the other forms. The research performed under this grant was directed towards the application of the IEM to the analysis of metal ions at environmental concentrations.

  6. kinetics and mechanism of the oxidation of uranium(iv) by persulfate ions in perchloric acid solutions

    SciTech Connect

    Ermakov, V.A.

    1986-07-01

    The kinetics of the oxidation of uranium(IV) by persulfate ions in perchloric acid solutions was studied by a spectrophotometric method. It was established that the oxidation of uranium(IV) ions occurs along three pathways: directly by S/sub 2/O /SUP 2/8/ /sup -/ ions, by products of their thermal decomposition, and intramolecularly in a persulfate complex. It was shown that the contribution of each of the three pathways to the overall rate of oxidation of uranium(IV) depends on the initial reagent concentrations, the hydrogen ion concentration, and the temperature. The activation energies of the oxidation of uranium(IV) directly by persulfate ions, by products of their thermal decomposition, as well as in a persulfate complex, were determined.

  7. An investigation of electrostatic interactions between organically functionalized silica particles, surfaces, and metal ions

    NASA Astrophysics Data System (ADS)

    Stahl, Sarah Margaret

    This research focuses on the electrostatic interactions between silica particles and either coated surfaces or metal ions. This work has two objectives: to begin a preliminary investigation into particle-surface systems that may be ideal for further investigation as a sensor and to investigate metal-ligand interactions for the potential use of metal ions to aid in the self assembly of silica particles. Silica particles with various organic functionalizations were synthesized from trialkoxysilane precursors using variations of the Stöber synthesis method, a well-known colloidal suspensions technique. The functional groups that were used in this work include mercaptopropyl (MPTMS), ethylenediamine (enTMOS), and aminopropyl groups (APTES). The aminopropyl functionalized particles were synthesized by varying the mol% of APTES in a tetraethoxyorthosilicate (TEOS) particle formulation. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used to analyze the particles for size, shape, and composition. Silica particles with all three functionalizations were used for the particle-surface study, whereas only MPTMS particles were used in the metal-ligand study. The coatings used for the particle-surface study were synthesized using standard sol gel chemistry with trialkoxysilane precursors as well. The functional groups used in this study include methyl (MTMOS) and aminopropyl groups (TEOS/APTES). Sol gel coatings incorporating carboxy and ammonium groups were also investigated but were not suitable for further study. FTIR was used to analyze the MTMOS and TEOS/APTES coatings. The adsorption of the MPTMS particles onto TEOS/APTES coatings and enTMOS or TEOS/APTES particles onto MTMOS coatings over time was monitored using fluorescence spectroscopy. Since silica particles are not fluorescent in the visible light range, a fluorescent dye was incorporated into the particles, either rhodamine (MPTMS particles) or pyranine dye (enTMOS, TEOS

  8. Particle-in-cell simulations of ion-acoustic waves with application to Saturn's magnetosphere

    SciTech Connect

    Koen, Etienne J.; Collier, Andrew B.; Hellberg, Manfred A.; Maharaj, Shimul K.

    2014-07-15

    Using a particle-in-cell simulation, the dispersion and growth rate of the ion-acoustic mode are investigated for a plasma containing two ion and two electron components. The electron velocities are modelled by a combination of two kappa distributions, as found in Saturn's magnetosphere. The ion components consist of adiabatic ions and an ultra-low density ion beam to drive a very weak instability, thereby ensuring observable waves. The ion-acoustic mode is explored for a range of parameter values such as κ, temperature ratio, and density ratio of the two electron components. The phase speed, frequency range, and growth rate of the mode are investigated. Simulations of double-kappa two-temperature plasmas typical of the three regions of Saturn's magnetosphere are also presented and analysed.

  9. Mass spectrometry of refractory black carbon particles from six sources: carbon-cluster and oxygenated ions

    NASA Astrophysics Data System (ADS)

    Corbin, J. C.; Sierau, B.; Gysel, M.; Laborde, M.; Keller, A.; Kim, J.; Petzold, A.; Onasch, T. B.; Lohmann, U.; Mensah, A. A.

    2013-10-01

    We discuss the major mass spectral features of different types of refractory carbonaceous particles, ionized after laser vapourization with an Aerodyne High-Resolution Soot-Particle Aerosol Mass Spectrometer (SP-AMS). The SP-AMS was operated with a switchable 1064 nm laser and a 600 °C thermal vapourizer, yielding respective measurements of the refractory and non-refractory particle components. Six samples were investigated, all of which were composed primarily of refractory material: fuel-rich and fuel-lean propane/air diffusion-flame combustion particles; graphite-spark-generated particles; a commercial Fullerene-enriched Soot; Regal Black, a commercial carbon black; and nascent aircraft-turbine combustion particles. All samples exhibited a spectrum of carbon-cluster ions Cxn+ in their refractory mass spectrum. Smaller clusters (x<6) were found to dominate the Cxn+ distribution. For Fullerene Soot, fuel-rich-flame particles and spark-generated particles, significant Cxn+ clusters at x≫6 were present, with significant contributions from multiply-charged ions (n>1). In all six cases, the ions C1+ and C3+ contributed over 60% to the total C1ions C1+/C3+ could be used to predict whether significant Cxn+ signals with x>5 were present. When such signals were present, C1+/C3+ was close to 1. When absent, C1+/C3+ was <0.8. This ratio may therefore serve as a proxy to distinguish between the two types of spectra in atmospheric SP-AMS measurements. Significant refractory oxygenated ions such as CO+ and CO2+ were also observed for all samples. We discuss these signals in detail for Regal Black, and describe their formation via decomposition of oxygenated moieties incorporated into the refractory carbon structure. These species may be of importance in atmospheric processes such as water uptake, aging and heterogeneous chemistry.

  10. Unimolecular reactions of halogeno phenylarsenium ions: Kinetic energy release during the elimination of halogen hydride

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Dirk; Grützmacher, Hans-Friedrich; Grützmacher, Hansjörg

    2006-03-01

    The four dihalogeno phenylarsanes C6H5AsF2, 1, C6H5AsCl2, 2, C6H5AsBr2, 3, and C6H5AsI2, 4, produce in the 70 eV-EI mass spectra by loss of a halogen atom abundant halogeno phenylarseniun ions C6H5As+-X, 1a+-4a+. The further fragmentation reactions of ions 1a+-4a+ are elimination of a molecule halogen hydride HX and/or loss of a halogen atom X. The preferred route of fragmentation depends clearly on the strength of the As-X bond. The metastable fluoro ion 1a+ and chloro ion 2a+, respectively, fragment only by loss of HF and HCl, the metastable bromo derivative 3a+ exhibits losses of HBr and Br of about equal intensity, and the metastable iodo ion 4a+ fragments only by loss of an I atom. The loss of HX is associated with a large kinetic energy release (KER) which yield a dish-topped peak in the MIKE spectrum of 1a+ ( = 845 meV) and 2a+ ( = 550 meV) and a broad round-topped peak on the MIKE spectrum of 3a+ ( = 369 meV). Theoretical calculations (UBHLYP/6-311 + G(2d,p)/-/UBHLYP/6-31 + G(d)) confirm that the elimination of HX requires an enthalpy of activation [Delta]H#, and that in the case of 3a+ this [Delta]H# and the reaction enthalpy for loss of Br are of similar size. The [Delta]H# of HX elimination is also responsible for the reverse enthalpy of activation and the KER during this process. The observed amounts to 78% (1a+), 55% (2a+), and 40% (3a+) of the calculated value of . Thus, the KER as well as the distribution of the KER (KERD) and the competition between elimination of HX and loss of X are very specific for the halogen ligand at the As atom. Metastable (4-fluorophenyl) arsenium ions 1b+, F-C6H4As+-H, and (4-chlorophenyl) arsenium ions 2b+, Cl-C6H4As+-H+, eliminate HF or HCl with virtually identical KERD as metastable 1a+ or 2a+, C6H5As+-Cl, proving an identical transition state for both isomers. Accordingly, 1b+ and 2b+ rearrange to 1a+ and 2a+ prior to HCl elimination. Such a rearrangement by a reductive elimination/oxidative insertion of

  11. Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas

    NASA Astrophysics Data System (ADS)

    Field, A. R.; Dunai, D.; Ghim, Y.-c.; Hill, P.; McMillan, B.; Roach, C. M.; Saarelma, S.; Schekochihin, A. A.; Zoletnik, S.; the MAST Team

    2014-02-01

    Observations of ion-scale (kyρi ⩽ 1) density turbulence of relative amplitude ≳0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplitude and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be ‘critically balanced’, the simulated turbulence is weak.

  12. Measuring kinetics of complex single ion channel data using mean-variance histograms.

    PubMed Central

    Patlak, J B

    1993-01-01

    The measurement of single ion channel kinetics is difficult when those channels exhibit subconductance events. When the kinetics are fast, and when the current magnitudes are small, as is the case for Na+, Ca2+, and some K+ channels, these difficulties can lead to serious errors in the estimation of channel kinetics. I present here a method, based on the construction and analysis of mean-variance histograms, that can overcome these problems. A mean-variance histogram is constructed by calculating the mean current and the current variance within a brief "window" (a set of N consecutive data samples) superimposed on the digitized raw channel data. Systematic movement of this window over the data produces large numbers of mean-variance pairs which can be assembled into a two-dimensional histogram. Defined current levels (open, closed, or sublevel) appear in such plots as low variance regions. The total number of events in such low variance regions is estimated by curve fitting and plotted as a function of window width. This function decreases with the same time constants as the original dwell time probability distribution for each of the regions. The method can therefore be used: 1) to present a qualitative summary of the single channel data from which the signal-to-noise ratio, open channel noise, steadiness of the baseline, and number of conductance levels can be quickly determined; 2) to quantify the dwell time distribution in each of the levels exhibited. In this paper I present the analysis of a Na+ channel recording that had a number of complexities. The signal-to-noise ratio was only about 8 for the main open state, open channel noise, and fast flickers to other states were present, as were a substantial number of subconductance states. "Standard" half-amplitude threshold analysis of these data produce open and closed time histograms that were well fitted by the sum of two exponentials, but with apparently erroneous time constants, whereas the mean

  13. Modelling of the physico-chemical behaviour of clay minerals with a thermo-kinetic model taking into account particles morphology in compacted material.

    NASA Astrophysics Data System (ADS)

    Sali, D.; Fritz, B.; Clément, C.; Michau, N.

    2003-04-01

    Modelling of fluid-mineral interactions is largely used in Earth Sciences studies to better understand the involved physicochemical processes and their long-term effect on the materials behaviour. Numerical models simplify the processes but try to preserve their main characteristics. Therefore the modelling results strongly depend on the data quality describing initial physicochemical conditions for rock materials, fluids and gases, and on the realistic way of processes representations. The current geo-chemical models do not well take into account rock porosity and permeability and the particle morphology of clay minerals. In compacted materials like those considered as barriers in waste repositories, low permeability rocks like mudstones or compacted powders will be used : they contain mainly fine particles and the geochemical models used for predicting their interactions with fluids tend to misjudge their surface areas, which are fundamental parameters in kinetic modelling. The purpose of this study was to improve how to take into account the particles morphology in the thermo-kinetic code KINDIS and the reactive transport code KIRMAT. A new function was integrated in these codes, considering the reaction surface area as a volume depending parameter and the calculated evolution of the mass balance in the system was coupled with the evolution of reactive surface areas. We made application exercises for numerical validation of these new versions of the codes and the results were compared with those of the pre-existing thermo-kinetic code KINDIS. Several points are highlighted. Taking into account reactive surface area evolution during simulation modifies the predicted mass transfers related to fluid-minerals interactions. Different secondary mineral phases are also observed during modelling. The evolution of the reactive surface parameter helps to solve the competition effects between different phases present in the system which are all able to fix the chemical

  14. The role of ions in the self-healing behavior of soft particle suspensions

    NASA Astrophysics Data System (ADS)

    Scotti, Andrea; Gasser, Urs; Herman, Emily S.; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L. Andrew; Fernández-Nieves, Alberto

    2016-05-01

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562–4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior.

  15. Evaluation of Dielectric Properties of Ferroelectric Fine Particles Fabricated by Focused Ion Beam Technique

    NASA Astrophysics Data System (ADS)

    Ogiso, Hisato; Yoshida, Mikiko; Akedo, Jun

    2007-10-01

    In this study, we propose a method for evaluating the dielectric property of a single fine particle using the focused ion beam technieque. Lead zirconate titanate (PZT) particles (Sakai Chemical Industry LQ) were sintered at 1473 K for 2 h to fabricate bulk PZT. The bulk PZT was milled to fabricate sample particles. The particles were dispersed on a Au surface substrate, and were shaped into a parallel-plate capacitor using the focused ion beam (FIB) technique. The FIB technique was used to deposite tungsten, W, with a square shape on top of the particle sample as an upper electrode, and the particles were shaved into a rectangular shape; the area of the electrode was 2× 10-12 m2 and the thickness of the PZT segment was 2× 10-6 m. The capacitance of the fabricated PZT particle sample was successfully measured by compensating the parasitic capacitance of the experimental setup. Consequently, the relative permittivity of the PZT particle sample was 1250 at 105 Hz. This value was comparably close to the 1750 of the bulk PZT. The issue of electric contact between the particles and the substrate should be overcome in order to discuss permittivity quantitatively.

  16. Ion precipitation in planetary upper atmospheres: test particle simulations and implications for escape

    NASA Astrophysics Data System (ADS)

    Parkinson, Christopher; Liemohn; Fang, Xiaohua

    A 3-D Monte Carlo energetic particle transport model has been developed and successfully applied to ion precipitation into planetary upper atmospheres in our solar system (viz., Earth, Mars, Jupiter, and Saturn), and can be readily be extended using a full Lorentz motion formu-lation in the absence of strong dipole planetary magnetic fields. This model can be used with a variety of other models to assess the influence of hot ion precipitation on the thermosphere and exosphere of planetary atmospheres and the subsequent sputtering and escape. For instance in the case of Mars, a pick-up ion transport model already exists to allow for particle acceleration exerted by the convection electric field used in conjunction with existing model results from the Mars Thermosphere General Circulation Model (MTGCM) and the BATS-R-US global MHD model. The loss of exospheric neutrals through ionization, in which they become pick-up ions in the solar wind, can be calculated to examine the relative contribution of the various ionization processes. Solar wind protons as well as pick-up ions from a planetary exosphere routinely enter and alter their upper atmosphere. A study of the pick-up ion escape, sputtering, ion-ization, excitation, and energy deposition will be reviewed and discussed, resulting in a robust examination of the influence of energetic ion transport on planetary upper atmospheres.

  17. Review of heavy-ion induced desorption studies for particle accelerators

    NASA Astrophysics Data System (ADS)

    Mahner, Edgar

    2008-10-01

    During high-intensity heavy-ion operation of several particle accelerators worldwide, large dynamic pressure rises of orders of magnitude were caused by lost beam ions that impacted under grazing angle onto the vacuum chamber walls. This ion-induced desorption, observed, for example, at CERN, GSI, and BNL, can seriously limit the ion intensity, luminosity, and beam lifetime of the accelerator. For the heavy-ion program at CERN’s Large Hadron Collider collisions between beams of fully stripped lead (Pb82+208) ions with a beam energy of 2.76TeV/u and a nominal luminosity of 1027cm-2s-1 are foreseen. The GSI future project FAIR (Facility for Antiproton and Ion Research) aims at a beam intensity of 1012 uranium (U28+238) ions per second to be extracted from the synchrotron SIS18. Over the past years an experimental effort has been made to study the observed dynamic vacuum degradations, which are important to understand and overcome for present and future particle accelerators. The paper reviews the results obtained in several laboratories using dedicated test setups, the mitigation techniques found, and their implementation in accelerators.

  18. Energy deposition by heavy ions: additivity of kinetic and potential energy contributions in hillock formation on CaF2.

    PubMed

    Wang, Y Y; Grygiel, C; Dufour, C; Sun, J R; Wang, Z G; Zhao, Y T; Xiao, G Q; Cheng, R; Zhou, X M; Ren, J R; Liu, S D; Lei, Y; Sun, Y B; Ritter, R; Gruber, E; Cassimi, A; Monnet, I; Bouffard, S; Aumayr, F; Toulemonde, M

    2014-01-01

    Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe(22+) to Xe(30+)) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface. PMID:25034006

  19. Kinetics of Heterogeneous Reaction of CaCO3 Particles with Gaseous HNO3 Over a Wide Range of Humidity

    SciTech Connect

    Liu, Yong; Gibson, Elizabeth R.; Cain, Jeremy P.; Wang, Hai; Grassian, Vicki H.; Laskin, Alexander

    2008-02-21

    Heterogeneous reaction kinetics of gaseous nitric acid (HNO3) with calcium carbonate (CaCO3) particles was investigated using the Particle-on-Substrate Stagnation Flow Reactor (PS-SFR). The technique utilizes the exposure of substrate deposited, isolated, and narrowly dispersed particles to a gas mixture of HNO3/H2O/N2 followed by microanalysis of individual reacted particles using computer-controlled scanning electron microscopy with energy-dispersive X-ray analysis (CCSEM/EDX). The first series of experiment was conducted at atmospheric pressure, room temperature and constant relative humidity (40%) with a median dry particle diameter pD = 0.85 μm, particle loading densities 2×104 ≤ Ns ≤ 6×106 cm–2 and free stream HNO3 concentrations of 7, 14 and 25 ppb. The apparent, pseudo first-order rate constant for the reaction was determined from oxygen enrichment in individual particles as a function of particle loading. Quantitative treatment of the data using a diffusion-kinetic model yields lower limit to the net reaction probability γnet ≥ 0.06 (×3/÷2). In the second series of experiments, HNO3 uptake on CaCO3 of the same particle size was examined over a wide range of relative humidity, from 10 to 80%. The lower limit for the net reaction probability was found to increase with an increase in the relative humidity, from γnet ≥ 0.003 at RH = 10% to 0.21 at 80%.

  20. Single-droplet evaporation kinetics and particle formation in an acoustic levitator. Part 2: drying kinetics and particle formation from microdroplets of aqueous mannitol, trehalose, or catalase.

    PubMed

    Schiffter, Heiko; Lee, Geoffrey

    2007-09-01

    A single droplet drying acoustic levitator has been used to examine the drying behavior of droplets of pharmaceutically relevant solutes used to produce protein-loaded particles via spray-drying. The drying behavior of solution droplets of mannitol, trehalose, or catalase was determined. Evidence of super-saturation of the solute in the droplet surface up to the critical point of drying was obtained. The trehalose achieves a lower degree of super-saturation than does the mannitol before precipitating at the droplet surface. This results in a shorter duration of the constant-rate period, but protracted further drying of this amorphous material. Mannitol achieved a higher degree of super-saturation, and a later critical point with shorter falling-rate period. Measurements of dried particle radius showed that both solutes form hollow particles. The catalase formed holed, hollow particles with characteristic drying rate profiles that correlated well with developing particle morphology. A strong similarity between the morphologies of dried particles of mannitol, trehalose, or catalase produced either in the levitator or in a spray-dryer was found. PMID:17523166

  1. Three-dimensional plasma particle-in-cell calculations of ion thruster backflow contamination

    SciTech Connect

    Roy, R.I.S.; Hastings, D.E.; Taylor, S.

    1996-10-01

    A fully three-dimensional hybrid plasma particle-in-cell model for multi-computer environments was developed to assess the spacecraft backflow contamination of an ion thruster. Results of plume backflow are presented for a 13-cm xenon ion thruster operating with a current level of 0.4 A on a model spacecraft. The computational domain was over 40 m{sup 3} in volume, and used over 35 million particles representing charge-exchange (CEX) xenon ions produced in the plume. Results obtained on a massively parallel 256-node Cray T3D clearly show the plasma density enhancement around the spacecraft due to the CEX ions. Three-dimensional results are compared with the results of a two-dimensional axisymmetric model to explore the three-dimensionality of the backstreaming flowfield. 15 refs., 14 figs., 1 tab.

  2. Alignment of dust particles by ion drag forces in subsonic flows

    SciTech Connect

    Piel, Alexander

    2011-07-15

    The role of ion drag forces for the alignment of dust particles is studied for subsonic flows. While alignment by wake-field attraction is a well known mechanism for supersonic flows, it is argued here that ion-scattering forces become more important in subsonic ion flows. A model of non-overlapping collisions is introduced and numerical results are discussed. For typical conditions of dusty plasma experiments, alignment by drag forces is found strong enough to overcome the destabilizing force from Coulomb repulsion between dust particles. It turns out that the major contribution to the horizontal restoring force originates from the transverse momentum transfer, which is usually neglected in ion drag force calculations because of an assumed rotational symmetry of the flow.

  3. Influence of ion movement in a particle trap on the bound electron g factor

    NASA Astrophysics Data System (ADS)

    Michel, Niklas; Zatorski, Jacek; Keitel, Christoph H.

    2015-11-01

    In the relativistic description of atomic systems in external fields, the total momentum and the external electric field couple to the angular momentum of the individual particles. Therefore, the motional state of an ion in a particle trap influences measurements of internal observables such as energy levels or the g factor. We calculate the resulting relativistic shift of the Larmor frequency and the corresponding g -factor correction for a bound electron in a hydrogenlike ion in the 1 S state due to the ion moving in a Penning trap and show that it is negligible at the current precision of measurements. We also show that the analogous energy shift for measurements with an ion in the ground state of a Paul trap vanishes in leading order.

  4. Determination of triacylglycerol regioisomers using electrospray ionization-quadrupole ion trap mass spectrometry with a kinetic method.

    PubMed

    Leveque, Nathalie L; Acheampong, Akwasi; Heron, Sylvie; Tchapla, Alain

    2012-04-13

    The kinetic method was applied to differentiate and quantify mixtures of regioisomeric triacylglycerols (TAGs) by generating and mass selecting alkali ion bound metal dimeric clusters with a TAG chosen as reference (ref) and examining their competitive dissociations in a quadrupole ion trap mass spectrometer. This methodology readily distinguished pairs of regioisomers (AAB/ABA) such as LLO/LOL, OOP/OPO and SSP/SPS and consequently distinguished sn-1/sn-3, sn-2 substituents on the glycerol backbone. The dimeric complex ions [ref, Li, TAG((AAB and/or ABA))](+) generated by electrospray ionization mass spectrometry were subjected to collision induced dissociation causing competitive loss of either the neutral TAG reference (ref) leading to [Li(AAB and/or ABA)](+) or the neutral TAG molecule (TAG((AAB and/or ABA))) leading to [ref, Li](+). The ratio of the two competitive dissociation rates, defined by the product ion branching ratio (R(iso)), was related via the kinetic method to the regioisomeric composition of the investigated TAG mixture. In this work, a linear correlation was established between composition of the mixture of each TAG regioisomer and the logarithm of the branching ratio for competitive fragmentation. Depending on the availability of at least one TAG regioisomer as standard, the kinetic method and the standard additions method led to the quantitative analysis of natural TAG mixtures. PMID:22444537

  5. Differential retention of 212Pb ions and insoluble particles in nasal mucosa of the rat.

    PubMed

    Greenhalgh, J R; Birchall, A; James, A C; Smith, H; Hodgson, A

    1982-06-01

    The time course of retention of 212Pb ions in ciliated nasal epithelium and of tagged insoluble particles, which served both as a deposition vector and marker for mucus, was measured in 13 rats by counting the head externally at 2 min intervals up to 100 min after deposition. On average, 70-75% of insoluble particles introduced onto ciliated epithelium in 3 microliters of distilled water were cleared to the gut with a half-time of approximately 15 min (range 6-35 min). A smaller fraction of lead ions (averaging about 60%) introduced in the same water sample was cleared to the gut with a half-time in each rat similar to that of particle clearance. Rapid uptake of about 8% of deposited 212Pb into blood was also observed. A compartment model consistent with the observed nasal retention and appearance of 212Pb in blood showed that, on average, 8% of deposited lead ions were transferred to the blood with a half-time of 15 min. For about 35% of the deposited lead ions and 25% of the particles, no clearance was detected up to 60-100 min after deposition. It is probable that a fraction of the lead ions are retained by epithelial tissue. PMID:7111392

  6. Universal behavior of charged particle production in heavy ion collisions at RHIC energies

    NASA Astrophysics Data System (ADS)

    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.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holyński, 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.; Phobos Collaboration

    2003-04-01

    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 √ SNN = 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/ overlinepp and e +e - data. < Nch>/< Npart/2> in nuclear collisions at high energy scales with √ s in a similar way as Nch 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.

  7. Fully kinetic particle-in-cell simulations of a deuterium gas puff z pinch.

    PubMed

    Welch, D R; Rose, D V; Clark, R E; Mostrom, C B; Stygar, W A; Leeper, R J

    2009-12-18

    We present the first fully kinetic, collisional, and electromagnetic simulations of the complete time evolution of a deuterium gas puff z pinch. Recent experiments with 15-MA current pinches have suggested that the dominant neutron-production mechanism is thermonuclear. We observe distinct differences between the kinetic and magnetohydrodynamic simulations in the pinch evolution with the kinetic simulations producing both thermonuclear and beam-target neutrons. The kinetic approach demonstrated in this Letter represents a viable alternative for performing future plasma physics calculations. PMID:20366259

  8. Kinetic Study of Radiation-Reaction-Limited Particle Acceleration During the Relaxation of Force-Free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Blandford, Roger D.; East, William E.; Zrake, Jonathan

    2016-01-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over short time scales. This might be due to prodigal dissipation in a highly magnetized outflow. In order to understand the generic behavior of relativistic plasma with high magnetization, we consider a class of prototypical force-free equilibria which are shown to be unstable to ideal modes (East et al 2015 PRL 115, 095002). Kinetic simulations are carried out to follow the evolution of the instability and to study the basic mechanisms of particle acceleration, especially in the radiation-reaction-limited regime. We find that the instability naturally produces current layers and these are sites for efficient particle acceleration. Detailed calculations of the gamma ray spectrum, the evolution of the particle distribution function and the dynamical consequences of radiation reaction will be presented.

  9. Nanoalginate based biosorbent for the removal of lead ions from aqueous solutions: Equilibrium and kinetic studies.

    PubMed

    Geetha, P; Latha, M S; Pillai, Saumya S; Koshy, Mathew

    2015-12-01

    Population explosion, depletion of water resources and prolonged droughts and floods due to climatic change lead to scarcity of pure and hygienic drinking water in most of the developing countries. Recently nanomaterials attained considerable attention as biosorbent for water purification purpose. However difficulties in removing polymeric surfactants and organic solvents used for nanoproduction and instability of the generated nanoparticles limit the scope of this approach in water cleanup. Here, we describe a novel green method for synthesizing polysaccharide nanoparticles in aqueous medium using honey as the capping agent. The highly stable alginate nanoparticles, characterized by various microscopic and spectroscopic techniques, exhibited a maximum uptake capacity of 333 mg g (-1)of Pb(II) ions from aqueous solution. The effect of various parameters such as initial metal concentration, pH, contact time, temperature and adsorbent dose on sorption process was investigated in batch mode technique. The maximum removal percentage was 94.81 at 45 °C and at pH 4.5 in 60 min contact time. The biosorption followed Freundlich model indicating multilayer adsorption and pseudo second order kinetics. The mechanism involves both surface adsorption and pore diffusion. The positive values of ΔH°, ∆S° and the negative value of ΔG°, confirmed the endothermic nature, randomness and spontaneity of biosorption process. PMID:26164724

  10. Influence of Oxygen Ion Implantation on the Damage and Annealing Kinetics of Iron-Implanted Sapphire

    SciTech Connect

    Hunn, J.D.; McHargue, C.J.

    1999-11-14

    The effects of implanted oxygen on the damage accumulation in sapphire which was previously implanted with iron was studied for (0001) sapphire implanted with iron and then with oxygen. The energies were chosen to give similar projected ranges. One series was implanted with a 1:l ratio (4x10{sup 16} ions/cm{sup 2} each) and another with a ratio of 2:3 (4x10{sup 16} fe{sup +}/cm{sup 2}; 6x10{sup 16} O{sup +}/cm{sup 2}). Retained damage, X, in the Al-sublattice, was compared to that produced by implantation of iron alone. The observed disorder was less for the dual implantations suggesting that implantation of oxygen enhanced dynamic recovery during implantation. Samples were annealed for one hour at 800 and 1200 C in an oxidizing and in a reducing atmosphere. No difference was found in the kinetics of recovery in the Al-sublattice between the two dual implant conditions. However, the rate of recovery was different for each from samples implanted with iron alone.

  11. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  12. Test particle study of ion transport in drift type turbulence

    SciTech Connect

    Vlad, M.; Spineanu, F.

    2013-12-15

    Ion transport regimes in drift type turbulence are determined in the frame of a realistic model for the turbulence spectrum based on numerical simulations. The model includes the drift of the potential with the effective diamagnetic velocity, turbulence anisotropy, and dominant waves. The effects of the zonal flow modes are also analyzed. A semi-analytical method that is able to describe trajectory stochastic trapping or eddying is used for obtaining the transport coefficients as function of the parameters of the turbulence. Analytical approximations of the transport coefficients are derived from the results. They show the transition from Bohm to gyro-Bohm scaling as plasma size increases in very good agreement with the numerical simulations.

  13. Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change

    NASA Astrophysics Data System (ADS)

    George, I. J.; Vlasenko, A.; Slowik, J. G.; Broekhuizen, K.; Abbatt, J. P. D.

    2007-08-01

    The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl) sebacate (BES) particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ0=1.3 (±0.4), confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

  14. Ion beam generation and focusing on PBFA (Particle Beam Fusion Accelerator) II

    SciTech Connect

    Stinnett, R.W.; Bailey, J.E.; Bieg, K.W.; Coats, R.S.; Chandler, G.; Derzon, M.S.; Desjarlais, M.P.; Dreike, P.L.; Gerber, R.A.; Johnson, D.J.; Leeper, R.J.; Lockner, T.R.; Maenchen, J.; Mehlhorn, T.A.; Pregenzer, A.L.; Quintenz, J.P.; Renk, T.J.; Rosenthal, S.E.; Ruiz, C.L.; Slutz, S.A.; Stygar, W.A.; Tisone, G.C.; Woodworth, J.R. ); Maron, Y. (Weizmann Inst. of Science, R

    1990-01-01

    During the past year we have succeeded in obtaining a 5 TW/cm{sup 2} proton focus on Sandia National Laboratories' Particle Beam Fusion Accelerator (PBFA) II. This has allowed us to shift our experimental emphasis to the implementation of an improved ion diode geometry for higher voltage operation, full azimuthal beam characterization, and especially lithium ion source experiments. We have made significant progress in each of these areas during the past year, demonstrating 10 MV diode operation, {plus minus}10% azimuthal beam symmetry, and promising initial results from lithium ion source experiments. 8 refs., 6 figs.

  15. Effects of meteoric smoke particles on the D region ion chemistry

    NASA Astrophysics Data System (ADS)

    Baumann, Carsten; Rapp, Markus; Anttila, Milla; Kero, Antti; Verronen, Pekka T.

    2015-12-01

    This study focuses on meteor smoke particle (MSP) induced effects on the D region ion chemistry. Hereby, MSPs, represented with an 11 bin size distribution, have been included as an active component into the Sodankyä Ion and Neutral Chemistry model. By doing that, we model the diurnal variation of the negatively and positively charged MSPs as well as ions and the electron density under quiet ionospheric conditions. Two distinct points in time are studied in more detail, i.e., one for sunlit conditions (Solar zenith angle is 72°) and one for dark conditions (Solar zenith angle is 103°). We find nightly decrease of free electrons and negative ions, the positive ion density is enhanced at altitudes above 80 km and reduced below. During sunlit conditions the electron density is enhanced between 60 and 70 km altitude, while there is a reduction in negative and positive ions densities. In general, the MSP influence on the ion chemistry is caused by changes in the electron density. On the one hand, these changes occur due to nightly electron scavenging by MSPs resulting in a reduced electron-ion recombination. As a consequence positive ion density increase, especially water cluster ions are highly affected. On the other hand, the electron density is slightly increased during daytime by a MSP-related production due to solar radiation. Thus, more electrons attach to neutrals and short-lived negative ions increase in number density. The direct attachment of ions to MSPs is a minor process, but important for long living ions.

  16. Emission properties of Tb3 + ions in LYSO: evidence of a cross relaxation mechanism explained by a kinetic model

    NASA Astrophysics Data System (ADS)

    Ricci, P. C.; Salis, M.; Corpino, R.; Carbonaro, C. M.; Fortin, E.; Anedda, A.

    2010-09-01

    The optical properties of Tb3 + ions in oxyorthosilicates of lutetium and yttrium (LYSO) are reported. The introduction of a small number of terbium ions (nominal content 10 ppm) generates, in the otherwise transparent absorption spectrum of the matrix, an ultraviolet absorption band peaked at about 240 nm. By exciting within the reported UV band, line shaped emissions in the 350-600 nm range are detected. These transitions are related to the 5D3 and 5D4 levels of the Tb3 + ions and are characterized by decay times in the millisecond time domain. Analysis of the decay time measurements allows us to individuate a cross relaxation mechanism among terbium ions even at the low dopant concentration investigated. We propose a three-level kinetic model which is able to successfully reproduce the experimental data, allowing us to discriminate among the radiative and non-radiative contributions to the observed emissions.

  17. Emission properties of Tb3+ ions in LYSO: evidence of a cross relaxation mechanism explained by a kinetic model.

    PubMed

    Ricci, P C; Salis, M; Corpino, R; Carbonaro, C M; Fortin, E; Anedda, A

    2010-09-01

    The optical properties of Tb(3+) ions in oxyorthosilicates of lutetium and yttrium (LYSO) are reported. The introduction of a small number of terbium ions (nominal content 10 ppm) generates, in the otherwise transparent absorption spectrum of the matrix, an ultraviolet absorption band peaked at about 240 nm. By exciting within the reported UV band, line shaped emissions in the 350-600 nm range are detected. These transitions are related to the (5)D(3) and (5)D(4) levels of the Tb(3+) ions and are characterized by decay times in the millisecond time domain. Analysis of the decay time measurements allows us to individuate a cross relaxation mechanism among terbium ions even at the low dopant concentration investigated. We propose a three-level kinetic model which is able to successfully reproduce the experimental data, allowing us to discriminate among the radiative and non-radiative contributions to the observed emissions. PMID:21403256

  18. Activation of oxygen-mediating pathway using copper ions: fine-tuning of growth kinetics in gold nanorod overgrowth.

    PubMed

    Liu, Wenqi; Zhang, Hui; Wen, Tao; Yan, Jiao; Hou, Shuai; Shi, Xiaowei; Hu, Zhijian; Ji, Yinglu; Wu, Xiaochun

    2014-10-21

    Growth kinetics plays an important role in the shape control of nanocrystals (NCs). Herein, we presented a unique way to fine-tune the growth kinetics via oxidative etching activated by copper ions. For the overgrowth of gold nanorods (Au NRs), competitive adsorption of dissolved oxygen on rod surface was found to slow down the overgrowth rate. Copper ions were able to remove the adsorbed oxygen species from the Au surface via oxidative etching, thus exposing more reaction sites for Au deposition. In this way, copper ions facilitated the overgrowth process. Furthermore, Cu(2+) rather than Cu(+) acted as the catalyst for the oxidative etching. Comparative study with Ag(+) indicated that Cu(2+) cannot regulate NC shapes via an underpotential deposition mechanism. In contrast, Ag(+) led to the formation of Au tetrahexahedra (THH) and a slight decrease of the growth rate at similar growth conditions. Combining the distinct roles of the two ions enabled elongated THH to be produced. Copper ions activating the O2 pathway suggested that dissolved oxygen has a strong affinity for the Au surface. Moreover, the results of NC-sensitized singlet oxygen ((1)O2) indicated that the absorbed oxygen species on the surface of Au NCs bounded with low-index facets mainly existed in the form of molecular O2. PMID:25244407

  19. Universality of Poisson indicator and Fano factor of transport event statistics in ion channels and enzyme kinetics.

    PubMed

    Chaudhury, Srabanti; Cao, Jianshu; Sinitsyn, Nikolai A

    2013-01-17

    We consider a generic stochastic model of ion transport through a single channel with arbitrary internal structure and kinetic rates of transitions between internal states. This model is also applicable to describe kinetics of a class of enzymes in which turnover events correspond to conversion of substrate into product by a single enzyme molecule. We show that measurement of statistics of single molecule transition time through the channel contains only restricted information about internal structure of the channel. In particular, the most accessible flux fluctuation characteristics, such as the Poisson indicator (P) and the Fano factor (F) as function of solute concentration, depend only on three parameters in addition to the parameters of the Michaelis-Menten curve that characterizes average current through the channel. Nevertheless, measurement of Poisson indicator or Fano factor for such renewal processes can discriminate reactions with multiple intermediate steps as well as provide valuable information about the internal kinetic rates. PMID:23198705

  20. Comparing equilibrium and kinetic protein unfolding using time-resolved electrospray-coupled ion mobility mass spectrometry.

    PubMed

    Liuni, Peter; Deng, Bin; Wilson, Derek J

    2015-10-21

    Protein unfolding intermediates are thought to play a critical role in conformational pathogenesis, acting as a 'gateway' to inactivation or pathogenic aggregation. Unfolding intermediates have long been studied either by populating partially-folded species at equilibrium using incresingly denaturing conditions, or by transiently populating 'kinetic' intermediates under fully denaturing conditions using a time-resolved approach (e.g. stopped-flow fluorescence). However, it is not clear that the folding intermediates populated under equilibrium conditions are comparable to intermediates transiently populated in kinetic experiments. In this work, we combine time-resolved electrospray (TRESI) with travelling wave Ion Mobility Spectrometry (IMS) for the first time to directly compare equilibrium and kinetic unfolding intermediates of cytochrome c. Our results show a high degree of correlation between all species populated under these substantially different regimes. PMID:26115375

  1. Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

    SciTech Connect

    Lin, L.; Brower, D. L.; Ding, W. X.; Anderson, J. K.; Capecchi, W.; Eilerman, S.; Forest, C. B.; Koliner, J. J.; Nornberg, M. D.; Reusch, J.; Sarff, J. S.; Liu, D.

    2014-05-15

    Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboard-outboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfvén frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n=5 to n=6 while retaining the same poloidal mode number m=1. The transition occurs when the m=1, n=5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (q{sub fi}) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes.

  2. Tuning of platinum nano-particles by Au usage in their binary alloy for direct ethanol fuel cell: Controlled synthesis, electrode kinetics and mechanistic interpretation

    NASA Astrophysics Data System (ADS)

    Dutta, Abhijit; Mondal, Achintya; Datta, Jayati

    2015-06-01

    Understanding of the electrode-kinetics and mechanism of ethanol oxidation reaction (EOR) is of considerable interest for optimizing electro-catalysis in direct ethanol fuel cell (DEFC). This work attempts to design Pt based electro-catalyst on carbon support, tuned with gold nano-particles (NPs), for their use in DEFC operating in alkaline medium. The platinum-gold alloyed NPs are synthesized at desired compositions and size (2-10 nm) by controlled borohydride reduction method and successfully characterized by XRD, TEM, EDS and XPS techniques. The kinetic parameters along with the activation energies for the EOR are evaluated over the temperature range 20-80 °C and the oxidation reaction products estimated through ion chromatographic analysis. Compared to single Pt/C catalyst, the over potential of EOR is reduced by ca. 500 mV, at the onset during the reaction, for PtAu/C alloy with only 23% Pt content demonstrating the ability of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pt. Furthermore, a considerable increase in the peak power density (>191%) is observed in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC using the best performing Au covered Pt electrode (23% Pt) compared to the monometallic Pt catalyst.

  3. The (kinetic) theory of active particles applied to learning dynamics. Comment on "Collective learning modeling based on the kinetic theory of active particles" by D. Burini et al.

    NASA Astrophysics Data System (ADS)

    Nieto, J.

    2016-03-01

    The learning phenomena, their complexity, concepts, structure, suitable theories and models, have been extensively treated in the mathematical literature in the last century, and [4] contains a very good introduction to the literature describing the many approaches and lines of research developed about them. Two main schools have to be pointed out [5] in order to understand the two -not exclusive- kinds of existing models: the stimulus sampling models and the stochastic learning models. Also [6] should be mentioned as a survey where two methods of learning are pointed out, the cognitive and the social, and where the knowledge looks like a mathematical unknown. Finally, as the authors do, we refer to the works [9,10], where the concept of population thinking was introduced and which motivate the game theory rules as a tool (both included in [4] to develop their theory) and [7], where the ideas of developing a mathematical kinetic theory of perception and learning were proposed.

  4. Concentration of Methylamine and Ethylamine Salts measured by a particle into liquid sampler and Ion Chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A Particle-Into-Liquid Sampler (PILS) and ion chromatographs (ICs) were used to detect the concentration of methylamine salts associated with atmospheric particulate matter reactions in a smog chamber. The smog chamber is located at U.C. Riverside’s College of Engineering Center for Environmental Re...

  5. Can Bose condensation of alpha particles be observed in heavy ion collisions?

    NASA Technical Reports Server (NTRS)

    Tripathi, Ram K.; Townsend, Lawrence W.

    1993-01-01

    Using a fully self-consistent quantum statistical model, we demonstrate the possibility of Bose condensation of alpha particles with a concomitant phase transition in heavy ion collisions. Suggestions for the experimental observation of the signature of the onset of this phenomenon are made.

  6. Specific spacecraft evaluation: Special report. [charged particle transport from a mercury ion thruster to spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1978-01-01

    Charged and neutral particle transport from an 8 cm mercury ion thruster to the surfaces of the P 80-1 spacecraft and to the Teal Ruby sensor and the ECOM-501 sensor of that spacecraft were investigated. Laboratory measurements and analyses were used to examine line-of-sight and nonline-of sight particle transport modes. The recirculation of Hg(+) ions in the magnetic field of the earth was analyzed for spacecraft velocity and Earth magnetic field vector configurations which are expected to occur in near Earth, circular, high inclination orbits. For these magnetic field and orbit conditions and for expected ion release distribution functions, in both angles and energies, the recirculation/re-interception of ions on spacecraft surfaces was evaluated. The refraction of weakly energetic ions in the electric fields of the thruster plasma plume and in the electric fields between this plasma plume and the material boundaries of the thruster, the thruster sputter shield, and the various spacecraft surfaces were examined. The neutral particle transport modes of interest were identified as sputtered metal atoms from the thruster beam shield. Results, conclusions, and future considerations are presented.

  7. A time-dependent gyro-kinetic model of thermal ion upflows in the high-latitude F region

    NASA Technical Reports Server (NTRS)

    Loranc, M.; St.-Maurice, J.-P.

    1994-01-01

    Ample evidence supports the significance of the high-latitude ionospheric contribution to magnetospheric plasma. Assuming flux conservation along a flux tube, the upward field-aligned ion flows observed in the magnetosphere require high-latitude ionospheric field-aligned ion upflows of the order of 10(exp 8) to 10(exp 9)/sq cm/s. Since radar and satellite observations of high-latitude F region flows at times exceed this flux requirement by an order of magnitude, the thermal ionospheric upflows are not simply the ionospheric response to a magnetospheric flux requirement. Several ionospheric ion upflow mechanisms have been proposed, but simulations based on fluid theory do not reproduce all the observed features of ionospheric ion upflows. Certain asymmetries in the statistical morphology of high-latitude F region ion upflows suggest that the ion upflows may be generated by ion-neutral frictional heating. We developed a single-component (O(+)), time-dependent gyro-kinetic model of the high-latitude F region response to frictional heating in which the neutral exobase is a discontinuous boundary between fully collisional and collisionless plasmas. The concept of a discontinuous neutreal exobase and the assumption of a constant and uniform polarization electric field reduce the ion velocity distribution function, from which we can compute the ion density, parallel velocity, parallel and perpendicular temperature, and parallel flux. Using our model, we simulated the response of a convecting flux tube between 500 km and 2500 km to various frictional heating inputs; the results were both qualitatively and quantitatively different from fluid model results, which may indicate an inadequacy of the fluid theory approach. The gyro-kinetic frictional heating model responses to the various simulations were qualitatively similar: (1) initial perturbations of all the modeled parameters propagated rapidly up the flux tube, (2) transient values of the ion parallel velocity

  8. Kinetic energy deficit in the symmetric fission of /sup 259/Md. [Light particle emission in /sup 256/Fm fission

    SciTech Connect

    Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Dougan, R.J.; Mustafa, M.G.

    1980-10-01

    The fragment energies of about 725 coincidence events have now been observed in the spontaneous fission (SF) decay of 105-min /sup 259/Md since its discovery in 1977. The fission of /sup 259/Md is characterized by a symmetric mass distribution, similar to those of /sup 258/Fm and /sup 259/Fm, but with a broad total kinetic energy (anti TKE) distribution which peaks at about 195 MeV, in contrast to those of /sup 258/Fm and /sup 259/Fm, for which the anti TKE is about 240 MeV. This kinetic energy deficit, approx. 40 MeV, has been postulated to be due to the emission of hydrogen-like particles by /sup 259/Md at the scission point in a large fraction of the fissions, leaving the residual fissioning nucleus with 100 protons. The residual nucleus would then be able to divide into two ultrastable tin-like fission fragments, but with less kinetic energy than that observed in the SF of /sup 258/Fm and /sup 259/Fm, because of binding-energy losses and a reduction in the Coulomb repulsion of the major fragments. To test this hypothesis, counter-telescope experiments aimed at detecting and identifying these light particles were performed. In 439 SF events 3 + 3 protons of the appropriate energy were observed, too few to account for the kinetic energy deficit in the fission of /sup 259/Md. There seems to be no explanation for this problem within the framework of current fission theory. These results are discussed along with preliminary measurements of light-particle emission in the SF of /sup 256/Fm. 5 figures.

  9. Non-modal theory of the kinetic ion temperature gradient driven instability of plasma shear flows across the magnetic field

    NASA Astrophysics Data System (ADS)

    Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June

    2016-06-01

    The temporal evolution of the kinetic ion temperature gradient driven instability and of the related anomalous transport of the ion thermal energy of plasma shear flow across the magnetic field is investigated analytically. This instability develops in a steady plasma due to the inverse ion Landau damping and has the growth rate of the order of the frequency when the ion temperature is equal to or above the electron temperature. The investigation is performed employing the non-modal methodology of the shearing modes which are the waves that have a static spatial structure in the frame of the background flow. The solution of the governing linear integral equation for the perturbed potential displays that the instability experiences the non-modal temporal evolution in the shearing flow during which the unstable perturbation becomes very different from a canonical modal form. It transforms into the non-modal structure with vanishing frequency and growth rate with time. The obtained solution of the nonlinear integral equation, which accounts for the random scattering of the angle of the ion gyro-motion due to the interaction of ions with ensemble of shearing waves, reveals similar but accelerated process of the transformations of the perturbations into the zero frequency structures. It was obtained that in the shear flow the anomalous ion thermal conductivity decays with time. It is a strictly non-modal effect, which originates from the temporal evolution of the shearing modes turbulence.

  10. Kinetic theory of geomagnetic pulsations: I. Internal excitations by energetic particles

    SciTech Connect

    Chen, Liu . Plasma Physics Lab. Princeton Univ., NJ . Dept. of Astrophysical Sciences); Hasegawa, Akira )

    1990-05-01

    Motivated by recent satellite observations, we have carried out a comprehensive theoretical analysis on the generation of hydromagnetic Alfven waves in a realistic magnetospheric plasma environment consisting of a core and an energetic components. Our theoretical formulation employs the gyrokinetic equations and, thus, retains nonuniform plasma equilibria, anisotropy, finite Larmor radii, magnetic trapping as well as wave-particle interactions. A set of coupled equations for transverse and compressional magnetic perturbations is derived and analyzed for its stabilities assuming interchange stable equilibrium distribution functions. Our findings are compressional and tranverse shear Alfven oscillations are generally coupled in realistic plasmas. In the decoupled limit, for the compressional wave branch, one recovers the drift-mirror instability due to the Landau resonances and {tau} {equivalent to} 1 + 4 {pi}({partial derivative}P{sub {perpendicular}}/B{partial derivative}B) < 0. Here, P{sub {perpendicular}} = P{sub {perpendicular}}({psi},B) is the perpendicular pressure and {psi} is the magnetic flux function. For the decoupled transverse shear Alfven branch, one obtains the drift Alfven ballooning instability due to the Landau resonances and free energy of the pressure gradient for {tau} > 0. For both branches, the most unstable modes have antisymmetric structures and propagate in the diamagnetic drift direction of the energetic ions. Finite coupling can be shown to further enhance the drift Alfven ballooning instabilities. Thus, we conclude that for {tau} {ge} 0, the coupled drift Alfven ballooning-mirror instability constitutes an important internal generating mechanism of geomagnetic pulsations. The various predicted features of this instability are also found to be consistent with satellite observations.

  11. Kinetic theory of geomagnetic pulsations 1. Internal excitations by energetic particles

    SciTech Connect

    Liu Chen ); Hasegawa, Akira )

    1991-02-01

    Motivated by recent satellite observations. the authors have carried out a comprehensive theoretical analysis on the generation of hydromagnetic Alfven waves in a realistic magnetospheric plasma environment consisting of a core ({approximately}100 eV) component and an energetic ({approximately}10 keV) component. The theoretical formulation employs the gyrokinetic equations and, thus, retains anisotropy, finite Larmor radii, magnetic trapping, and wave-particle interactions in addition to nonuniform plasma equilibria. A set of coupled equations for transverse and compressional magnetic perturbations is derived and analyzed for its stabilities assuming equilibrium distribution functions which are interchange stable. The findings are as follows: (1) compressional and transverse shear Alfven oscillations are generally coupled in realistic plasmas; (2) in the decoupled limit, for the compressional wave branch, one recovers the drift mirror instability due to the Landau resonances and {tau}{triple bond} 1 + 4{pi}({partial derivative}P{sub {perpendicular}}/B{partial derivative}B) < 0; here, P{sub {perpendicular}}=P{sub {perpendicular}}({psi},B) is the perpendicular pressure and {psi} is the magnetic flux function; (3) for the decoupled transverse shear Alfven branch, one obtains the drift Alfven ballooning instability due to the Landau resonances and free energy of the pressure gradient for {tau} > 0; (4) for both branches, the most unstable modes have antisymmetric structures and propagate in the diamagnetic drift direction of the energetic ions; and (5) finite coupling can be shown to further enhance the drift Alfven ballooning instabilities. Thus they conclude that for {tau}{ge}0, the coupled drift Alfven ballooning mirror instability constitutes an important internal generating mechanism of geomagnetic pulsations. The various predicted features of this instability are consistent with satellite observations.

  12. A Computationally-Efficient Kinetic Approach for Gas/Particle Mass Transfer Treatments: Development, Testing, and 3-D Application

    NASA Astrophysics Data System (ADS)

    Hu, X.; Zhang, Y.

    2007-05-01

    The Weather Research and Forecast/Chemistry Model (WRF/Chem) that simulates chemistry simultaneously with meteorology has recently been developed for real-time forecasting by the U.S. National Center for Atmospheric Research (NCAR) and National Oceanic & Atmospheric Administration (NOAA). As one of the six air quality models, WRF/Chem with a modal aerosol module has been applied for ozone and PM2.5 ensemble forecasts over eastern North America as part of the 2004 New England Air Quality Study (NEAQS) program (NEAQS-2004). Significant differences exist in the partitioning of volatile species (e.g., ammonium and nitrate) simulated by the six models. Model biases are partially attributed to the equilibrium assumption used in the gas/particles mass transfer approach in some models. Development of a more accurate, yet computationally- efficient gas/particle mass transfer approach for three-dimensional (3-D) applications, in particular, real-time forecasting, is therefore warranted. Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID) has been implemented into WRF/Chem (referred to as WRF/Chem-MADRID). WRF/Chem-MADRID offers three gas/particle partitioning treatments: equilibrium, kinetic, and hybrid approaches. The equilibrium approach is computationally-efficient and commonly used in 3-D air quality models but less accurate under certain conditions (e.g., in the presence of coarse, reactive particles such as PM containing sea-salts in the coastal areas). The kinetic approach is accurate but computationally-expensive, limiting its 3-D applications. The hybrid approach attempts to provide a compromise between merits and drawbacks of the two approaches by treating fine PM (typically < ~ 1 μm) with the equilibrium approach and coarse PM with the kinetic approach. A computationally-efficient kinetic gas/particle mass transfer approach in MADRID has recently been developed for 3-D applications based on an Analytical Predictor of Condensation (referred

  13. Role of solution chemistry and ion valence on the adhesion kinetics of groundwater and marine bacteria.

    PubMed

    Chen, Gexin; Walker, Sharon L

    2007-06-19

    The role of solution chemistry on bacterial adhesion has been investigated using a radial stagnation point flow (RSPF) system. This experimental system utilized an optical microscope and an image-capturing device to directly observe the deposition kinetics of a groundwater bacterium, Burkholderia cepacia G4g, and a marine bacterium, Halomonas pacifica g. Experiments were carried out under well-controlled hydrodynamic and solution chemistry conditions, allowing for the sensitivity of bacterial adhesion behavior to be examined under a range of ionic strength and valence (KCl vs CaCl2) simulating groundwater and marine environments. Complimentary cell characterization techniques were conducted to evaluate the electrophoretic mobility, hydrophobicity, surface charge density, and viability of the bacteria under the same range of conditions. Solution chemistry was found to have a marked effect on the electrokinetic and surface properties of bacteria and the quartz collector, as well as on the resulting rate of bacterial deposition. Comparable adhesion trends were observed for B. cepacia G4g and H. pacifica g. Specifically, the deposition rates of the two bacteria species in both KCl and CaCl2 solutions increased with ionic strength, a trend consistent with traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which considers the combination of van der Waals and electrostatic double-layer interaction forces. However, in some cases, experimental results showed bacterial deposition behavior to deviate from DLVO predictions. On the basis of the systematic investigation of bacterial cell characteristics, it was found that Ca2+ ions play a distinct role on bacterial surface charge, hydrophobicity, and deposition behaviors. It is further suggested that bacterial adhesion is determined by the combined influence of DLVO interactions, electrosteric interactions associated with solution chemistry, and the hydrodynamics of the deposition system. PMID:17523680

  14. Adsorption of metal ions onto Moroccan stevensite: kinetic and isotherm studies.

    PubMed

    Benhammou, A; Yaacoubi, A; Nibou, L; Tanouti, B

    2005-02-15

    The aim of this paper is to study the adsorption of the heavy metals (Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II)) from aqueous solutions by a natural Moroccan stevensite called locally rhassoul. We carried out, first, a mineralogical and physicochemical characterization of stevensite. The surface area is 134 m2/g and the cation exchange capacity (CEC) is 76.5 meq/100 g. The chemical formula of stevensite is Si3.78Al0.22Mg2.92Fe0.09Na0.08K0.08O10(OH)2.4H2O. Adsorption tests of Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II) in batch reactors were carried out at ambient temperature and at constant pH. Two simplified models including pseudo-first-order and pseudo-second- order were used to test the adsorption kinetics. The equilibrium time and adsorption rate of adsorption were determined. The increasing order of the adsorption rates follows the sequence Mn(II) > Pb(II) > Zn(II) > Cu(II) > Cd(II). The Dubinin-Radushkevich (D-R), Langmuir, and Redlich-Peterson (R-P) models were adopted to describe the adsorption isotherms. The maximal adsorption capacities at pH 4.0 determined from the D-R and Langmuir models vary in the following order: Cu(II) > Mn(II) > Cd(II) > Zn(II) > Pb(II). The equilibrium data fitted well with the three-parameter Redlich-Peterson model. The values of mean energy of adsorption show mainly an ion-exchange mechanism. Also, the influence of solution pH on the adsorption onto stevensite was studied in the pH range 1.5-7.0. PMID:15589536

  15. Characteristics of new particle formation events in Nanjing, China: Effect of water-soluble ions

    NASA Astrophysics Data System (ADS)

    An, Junlin; Wang, Honglei; Shen, Lijuan; Zhu, Bin; Zou, Jianan; Gao, Jinhui; Kang, Hanqing

    2015-05-01

    New particle formation (NPF) events and water-soluble ions were studied at the meteorological building on the campus of the Nanjing University of Information Science and Technology (NUIST), which is located in the western part of the Yangtze River Delta (YRD). A wide-range particle spectrometer (WPS) provided particle number size distributions between 10 nm and 10 μm, whereas water-soluble ions for particles with diameters between 10 nm and 18 μm were measured using a 13-stage Nano-MOUDI aerosol sampler and 850 professional Ion Chromatography (IC). Additionally, meteorological data, trace gas concentrations and mass concentration were recorded. Ten NPF days were captured during the measurement period from 08 July to 02 August 2012. The mean aerosol number concentration, which was primarily composed of Aitken-mode particles, i.e., with diameters of 20-100 nm, was 13,664 cm-3, which was 1.9 times larger than that on non-NPF days. The results suggest that the NPF events were only slightly affected by O3, SO2, and NO2; the primary factors affecting NPF events were meteorological factors and air mass directions. NPF events were found to be favorable during the summer in the presence of high temperatures, strong radiation, low humidity, strong winds and clean air masses originating from the southeastern coast. The mean growth rate (GR), formation rate (J10), condensational sink (CS), condensing vapor rate (Q), and condensation vapor (C) were determined to be 7.6 nm h-1, 3.7 cm-3 s-1, 2.8 × 10-2 s-1, 2.9 × 106 cm-3 s-1, and 10.5 × 107 cm-3, respectively, on NPF days. The largest effects of the studied NPF events were on the mass and water-soluble ion concentrations of Aitken-mode particles, followed by nuclei-mode particles; few contributions to accumulation- and coarse-mode particles were observed. Different water-soluble ions were observed to have distinct interactions with the NPF events. The proportions of NH4+, SO42-, NO3-, K+ and Mg2+ in nuclei- and Aitken

  16. Excitation of kinetic Alfven waves by resonant mode conversion and longitudinal heating of magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Tanaka, Motohiko; Sato, Tetsuya; Hasegawa, A.

    1989-01-01

    The excitation of the kinetic Alfven wave by resonant mode conversion and longitudinal heating of the plasma by the kinetic Alfven wave were demonstrated on the basis of a macroscale particle simulation. The longitudinal electron current was shown to be cancelled by the ions. The kinetic Alfven wave produced an ordered motion of the plasma particles in the wave propagation direction. The electrons were pushed forward along the ambient magnetic field by absorbing the kinetic Alfven wave through the Landau resonance.

  17. Gyrokinetic-ion drift-kinetic-electron simulation of the (m = 2, n = 1) cylindrical tearing mode

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Chowdhury, J.; Maksimovic, N.; Parker, S. E.; Wan, W.

    2016-05-01

    Particle-in-cell simulations of (m =2 ,n =1 ) tearing mode in cylindrical plasmas are carried out with kinetic electrons using the split-weight control-variate algorithm [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)]. Radially, global simulation shows global mode structure in agreement with reduced-magnetohydrodynamic eigenmode calculation. Simulations of the tearing layer are verified with analytic results for the collisionless, semi-collisional, and drift-tearing mode.

  18. Electron-Anode Interactions in Particle-in-Cell Simulations of Applied-B Ion Diodes

    SciTech Connect

    Bailey, J.E.; Cuneo, M.D.; Johnson, D.J.; Mehlhorn, T.A.; Pointon, T.D.; Renk, T.J.; Stygar, W.A.; Vesey, R.A.

    1998-11-12

    Particle-in-cell simulations of applied-B ion diodes using the QUICKSILVER code have been augmented with Monte Carlo calculations of electron-anode interactions (reflection and energy deposition). Extraction diode simulations demonstrate a link between the instability evolution and increased electron loss and anode heating. Simulations of radial and extraction ion diodes show spatial non-uniformity in the predicted electron loss profile leading to hot spots on the anode that rapidly exceed the 350-450 {degree}C range, known to be sufficient for plasma formation on electron-bombarded surfaces. Thermal resorption calculations indicate complete resorption of contaminants with 15-20 kcal/mole binding energies in high-dose regions of the anode during the power pulse. Comparisons of parasitic ion emission simulations and experiment show agreement in some aspects; but also highlight the need for better ion source, plasma, and neutral gas models.

  19. A Core-Particle Model for Periodically Focused Ion Beams with Intense Space-Charge

    SciTech Connect

    Lund, S M; Barnard, J J; Bukh, B; Chawla, S R; Chilton, S H

    2006-08-02

    A core-particle model is derived to analyze transverse orbits of test particles evolving in the presence of a core ion beam described by the KV distribution. The core beam has uniform density within an elliptical cross-section and can be applied to model both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image charge nonlinearities. Transformations are employed to remove coherent utter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied focusing forces. Diagnostics for particle trajectories, Poincare phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The core-particle model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms matched beam in a periodic quadrupole focusing channel [Lund and Chawla, Nuc. Instr. and Meth. A 561, 203 (2006)]. Further characteristics of these processes are presented here.

  20. A core-particle model for periodically focused ion beams withintense space-charge

    SciTech Connect

    Lund, Steven M.; Barnard, John J.; Bukh, Boris; Chawla, SurgreevR.; Chilton, Sven H.

    2006-08-28

    A core-particle model is derived to analyze transverse orbits of test particles evolving in the presence of a core ion beam that has uniform density within an elliptical cross-section. The model can be applied to both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image charge nonlinearities. Transformations are employed to remove coherent flutter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied focusing forces. Diagnostics for particle trajectories, Poincare phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The core-particle model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms matched beam in a periodic quadrupole focusing channel. Further characteristics of these processes are presented here.

  1. The role of ions in the self-healing behavior of soft particle suspensions.

    PubMed

    Scotti, Andrea; Gasser, Urs; Herman, Emily S; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L Andrew; Fernández-Nieves, Alberto

    2016-05-17

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562-4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior. PMID:27125854

  2. Mass spectrometry of refractory black carbon particles from six sources: carbon-cluster and oxygenated ions

    NASA Astrophysics Data System (ADS)

    Corbin, J. C.; Sierau, B.; Gysel, M.; Laborde, M.; Keller, A.; Kim, J.; Petzold, A.; Onasch, T. B.; Lohmann, U.; Mensah, A. A.

    2014-03-01

    We discuss the major mass spectral features of different types of refractory carbonaceous particles, ionized after laser vaporization with an Aerodyne high-resolution soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated with a switchable 1064 nm laser and a 600 °C thermal vaporizer, yielding respective measurements of the refractory and non-refractory particle components. Six samples were investigated, all of which were composed primarily of refractory material: fuel-rich and fuel-lean propane/air diffusion-flame combustion particles; graphite-spark-generated particles; a commercial fullerene-enriched soot; Regal Black, a commercial carbon black; and nascent aircraft-turbine combustion particles. All samples exhibited a spectrum of carbon-cluster ions Cxn+ in their refractory mass spectrum. Smaller clusters (x < 6) were found to dominate the Cxn+ distribution. For fullerene soot, fuel-rich-flame particles and spark-generated particles, significant Cxn+ clusters at x ≫ 6 were present, with significant contributions from multiply charged ions (n > 1). In all six cases, the ions C1+ and C3+ contributed over 60% to the total C1ions C1+ / C3+ could be used to predict whether significant Cxn+ signals with x > 5 were present. When such signals were present, C1+ / C3+ was close to 1. When absent, C1+ / C3+ was < 0.8. This ratio may therefore serve as a proxy to distinguish between the two types of spectra in atmospheric SP-AMS measurements. Significant refractory oxygenated ions such as CO+ and CO2+ were also observed for all samples. We discuss these signals in detail for Regal Black, and describe their formation via decomposition of oxygenated moieties incorporated into the refractory carbon structure. These species may be of importance in atmospheric processes such as water uptake and heterogeneous chemistry. If atmospherically stable, these oxidized species may be useful for distinguishing

  3. A study of lithium ion intercalation induced fracture of silicon particles used as anode material in Li-ion battery

    SciTech Connect

    Daniel, Claus; Kalnaus, Sergiy; Rhodes, Kevin

    2011-01-01

    The fracture of Si particles due to internal stresses formed during the intercalation of lithium ions was described by means of thermal analogy model and brittle fracture damage parameter. The stresses were calculated following the diffusion equation and equations of elasticity with appropriate volumetric expansion term. The damage parameter takes into account triaxiality of the stress state and change in elasticity upon tension and compression, and represents the probability of fracture under given stress state, - an approach suitable for brittle materials. The results were compared with the acoustic emission data from the experiments on electrochemical cycling of Li ion half-cells with silicon electrodes. A good correlation between experiment and prediction was observed.

  4. First Observation of Switch-Off Slow Shocks in Fully Kinetic Particle in Cell Simulation of Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Sanna, L.; Goldman, M. V.; Newman, D. L.; Markidis, S.

    2014-12-01

    A perduring challenge in the study of reconnection it has long been the failing attempts to reconcile the large scale MHD view based on the Petschek model with the small scale view based on kinetic theory. The first is based on the existence of standing switch off slow shocks (SSS) that eliminate the horizontal (the x component in the usual GSM coordinates) reconnecting magnetic field component forming vertical magnetic field lines. The second is based on nested diffusion regions where the magnetic field lines become decoupled first from ions and then from electrons. The kinetic picture when observed superficially does seem to have seem resemblance to the Petschek topology, despite the nested boxes being more of a Sweet-Parker concept. Nevertheless, the question has always been: if expanded to sufficiently large scales, does the kinetic description eventually lead tot the formation os SSS? The question remains answered. Recently a first negative answer has been proposed in Ref. [1]. The proposed answer is in essence that SSS are made impossible by the presence of a firehose instability in the reconnection exhaust and by the formation of a plateau in the firehose parameter at a value of 0.25 corresponding to the condition where nonlinear slow and intermediate wave become degenerate. We report a new series of simulations where we demonstrate that this is not the case in general. While for the specific case used in Ref [1], we indeed re-obtain the same conclusions reached by the authors. But our study demonstrates that case to be very peculiar and not representative of the more general kinetic answer. We will report direct evidence of the presence of extended SSS (over regions of hundreds of ion inertial lengths) in fully kinetic simulations for parameters typical of the magntotail and of the solar wind. Our results indicate that SSS are the natural extension of kinetic reconnection to large scales. The simulations required for the study are heroic and were conducted

  5. Comparison of structural, thermodynamic, kinetic and mass transport properties of Mg2+ ion models commonly used in biomolecular simulations

    PubMed Central

    Panteva, Maria T.; GiambaȈsu, George M.; York, Darrin M.

    2015-01-01

    The prevalence of Mg2+ ions in biology and their essential role in nucleic acid structure and function has motivated the development of various Mg2+ ion models for use in molecular simulations. Currently the most widely used models in biomolecular simulations represent a non-bonded metal ion as an ion-centered point charge surrounded by a non-electrostatic pairwise potential that takes into account dispersion interactions and exchange effects that give rise to the ion's excluded volume. One strategy toward developing improved models for biomolecular simulations is to first identify a Mg2+ model that is consistent with the simulation force fields that closely reproduces a range of properties in aqueous solution, and then, in a second step, balance the ion-water and ion-solute interactions by tuning parameters in a pairwise fashion where necessary. The present work addresses the first step in which we compare 17 different non-bonded single-site Mg2+ ion models with respect to their ability to simultaneously reproduce structural, thermodynamic, kinetic and mass transport properties in aqueous solution. None of the models based on a 12-6 non-electrostatic non-bonded potential was able to reproduce the experimental radial distribution function, solvation free energy, exchange barrier and diffusion constant. The models based on a 12-6-4 potential offered improvement, and one model in particular, in conjunction with the SPC/E water model, performed exceptionally well for all properties. The results reported here establish useful benchmark calculations for Mg2+ ion models that provide insight into the origin of the behavior in aqueous solution, and may aid in the development of next-generation models that target specific binding sites in biomolecules. PMID:25736394

  6. Comparison of structural, thermodynamic, kinetic and mass transport properties of Mg(2+) ion models commonly used in biomolecular simulations.

    PubMed

    Panteva, Maria T; Giambaşu, George M; York, Darrin M

    2015-05-15

    The prevalence of Mg(2+) ions in biology and their essential role in nucleic acid structure and function has motivated the development of various Mg(2+) ion models for use in molecular simulations. Currently, the most widely used models in biomolecular simulations represent a nonbonded metal ion as an ion-centered point charge surrounded by a nonelectrostatic pairwise potential that takes into account dispersion interactions and exchange effects that give rise to the ion's excluded volume. One strategy toward developing improved models for biomolecular simulations is to first identify a Mg(2+) model that is consistent with the simulation force fields that closely reproduces a range of properties in aqueous solution, and then, in a second step, balance the ion-water and ion-solute interactions by tuning parameters in a pairwise fashion where necessary. The present work addresses the first step in which we compare 17 different nonbonded single-site Mg(2+) ion models with respect to their ability to simultaneously reproduce structural, thermodynamic, kinetic and mass transport properties in aqueous solution. None of the models based on a 12-6 nonelectrostatic nonbonded potential was able to reproduce the experimental radial distribution function, solvation free energy, exchange barrier and diffusion constant. The models based on a 12-6-4 potential offered improvement, and one model in particular, in conjunction with the SPC/E water model, performed exceptionally well for all properties. The results reported here establish useful benchmark calculations for Mg(2+) ion models that provide insight into the origin of the behavior in aqueous solution, and may aid in the development of next-generation models that target specific binding sites in biomolecules. PMID:25736394

  7. A hybrid method for hydrodynamic-kinetic flow Part I: A particle-grid method for reducing stochastic noise in kinetic regimes

    SciTech Connect

    Alaia, Alessandro; Puppo, Gabriella

    2011-06-20

    In this work we present a hybrid particle-grid Monte Carlo method for the Boltzmann equation, which is characterized by a significant reduction of the stochastic noise in the kinetic regime. The hybrid method is based on a first order splitting in time to separate the transport from the relaxation step. The transport step is solved by a deterministic scheme, while a hybrid DSMC-based method is used to solve the collision step. Such a hybrid scheme is based on splitting the solution in a collisional and a non-collisional part at the beginning of the collision step, and the DSMC method is used to solve the relaxation step for the collisional part of the solution only. This is accomplished by sampling only the fraction of particles candidate for collisions from the collisional part of the solution, performing collisions as in a standard DSMC method, and then projecting the particles back onto a velocity grid to compute a piecewise constant reconstruction for the collisional part of the solution. The latter is added to a piecewise constant reconstruction of the non-collisional part of the solution, which in fact remains unchanged during the relaxation step. Numerical results show that the stochastic noise is significantly reduced at large Knudsen numbers with respect to the standard DSMC method. Indeed in this algorithm, the particle scheme is applied only on the collisional part of the solution, so only this fraction of the solution is affected by stochastic fluctuations. But since the collisional part of the solution reduces as the Knudsen number increases, stochastic noise reduces as well at large Knudsen numbers.

  8. PFI-ZEKE (Pulsed Field Ionization-Zero Electron Kinetic Energy) para el estudio de iones

    NASA Astrophysics Data System (ADS)

    Castaño, F.; Fernández, J. A.; Basterretxea, A. Longarte. F.; Sánchez Rayo, M. N.; Martínez, R.

    Entre las áreas hacia donde ha evolucionado la Química en los últimos años están los estudios de sistemas con especies reactivas de alta energía y los dominados por fuerzas intermoleculares débiles, con energías de unas pocas kcal/mol. En efecto, el estudio de las propiedades de los iones, comenzando por su relación con la molécula neutra de la que procede, la energía de ionización, los estados vibracionales y rotacionales, energías de enlace de Van der Waals entre el ión y una amplia variedad de otras moléculas, sus confórmeros o isómeros y sus reacciones o semi-reacciones químicas están en la raíz de la necesidad de la espectroscopía conocida como PFI-ZEKE, Pulsed Field Ionization-Zero Electron Kinetic Energy. Entre las aplicaciones que requieren estos conocimientos se encuentran la generación de plasmas para la fabricación de semiconductores, memorias magnéticas, etc, así como los sistemas astrofísicos, la ionosfera terrestre, etc. La espectroscopía ZEKE es una evolución de las de fluorescencia inducida por láser, LIF, ionización multifotónica acrecentada por resonancia, REMPI, con uno y dos colores y acoplada a un sistema de tiempo de vuelo, REMPI-TOF-MS, y las espectroscopías de doble resonancia IR-UV y UV-UV. Sus espectros y la ayuda de cálculos ab inicio permite determinar las energías de enlace de complejos de van der Waals en estados fundamental y excitados, identificar confórmeros e isómeros, obtener energías de ionización experimentales aproximadas (100 cm-1) y otras variables de interés. Al igual que con LIF, REMPI y dobles resonancias, es posible utilizar muestras gaseosas, pero los espectros están muy saturados de bandas y su interpretación es difícil o imposible. Se evitan estas dificultades estudiando las moléculas o complejos en expansiones supersónicas, donde la T de los grados de libertad solo alcanzan unos pocos K. Para realizar experimentos de ZEKE hay que utilizar una propiedad recientemente

  9. Potential profile near singularity point in kinetic Tonks-Langmuir discharges as a function of the ion sources temperature

    NASA Astrophysics Data System (ADS)

    Kos, L.; Tskhakaya, D. D.; Jelić, N.

    2011-05-01

    A plasma-sheath transition analysis requires a reliable mathematical expression for the plasma potential profile Φ(x) near the sheath edge xs in the limit ɛ ≡λD/ℓ =0 (where λD is the Debye length and ℓ is a proper characteristic length of the discharge). Such expressions have been explicitly calculated for the fluid model and the singular (cold ion source) kinetic model, where exact analytic solutions for plasma equation (ɛ =0) are known, but not for the regular (warm ion source) kinetic model, where no analytic solution of the plasma equation has ever been obtained. For the latter case, Riemann [J. Phys. D: Appl. Phys. 24, 493 (1991)] only predicted a general formula assuming relatively high ion-source temperatures, i.e., much higher than the plasma-sheath potential drop. Riemann's formula, however, according to him, never was confirmed in explicit solutions of particular models (e.g., that of Bissell and Johnson [Phys. Fluids 30, 779 (1987)] and Scheuer and Emmert [Phys. Fluids 31, 3645 (1988)]) since "the accuracy of the classical solutions is not sufficient to analyze the sheath vicinity" [Riemann, in Proceedings of the 62nd Annual Gaseous Electronic Conference, APS Meeting Abstracts, Vol. 54 (APS, 2009)]. Therefore, for many years, there has been a need for explicit calculation that might confirm the Riemann's general formula regarding the potential profile at the sheath edge in the cases of regular very warm ion sources. Fortunately, now we are able to achieve a very high accuracy of results [see, e.g., Kos et al., Phys. Plasmas 16, 093503 (2009)]. We perform this task by using both the analytic and the numerical method with explicit Maxwellian and "water-bag" ion source velocity distributions. We find the potential profile near the plasma-sheath edge in the whole range of ion source temperatures of general interest to plasma physics, from zero to "practical infinity." While within limits of "very low" and "relatively high" ion source temperatures

  10. Single discharge of the matrix source of negative hydrogen ions: Influence of the neutral particle dynamics

    SciTech Connect

    Paunska, Ts.; Todorov, D. Shivarova, A.; Tarnev, Kh.

    2015-04-08

    The study presents two-dimensional (2D) fluid-plasma-model description of a planar-coil inductively-driven discharge, considered as a single element of a matrix source of volume-produced negative hydrogen ions. Whereas the models developed up to now have been directed towards description of the charged particle behavior in the discharge, including that of the negative ions, this model stresses on the role of the neutral particle dynamics and of the surface processes in the formation of the discharge structure. The latter is discussed based on comparison of results obtained for discharges in a flowing gas and at a constant gas pressure as well as for different values of the coefficient of atom recombination on the walls. The conclusions are that the main plasma parameters – electron density and temperature and plasma potential – determining the gas discharge regime stay stable, regardless of changes in the redistribution of the densities of the neutral particles and of the positive ions. With regards to the volume production of the ions, which requires high density of (vibrationally excited) molecules, the impact on the degree of dissociation of the coefficient of atom recombination on the wall is discussed.

  11. Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments

    NASA Astrophysics Data System (ADS)

    Chung, H. K.; MacFarlane, J. J.; Wang, P.; Moses, G. A.; Bailey, J. E.; Olson, C. L.; Welch, D. R.

    1997-01-01

    Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons.

  12. Electrostatic ion-acoustic-like instabilities in the solar wind with a backstreaming alpha particle beam

    SciTech Connect

    Gomberoff, L.; Gomberoff, K.; Deutsch, A.

    2010-06-15

    Nonlinear electrostatic instabilities have been shown to occur frequently and under very different conditions in plasma with two ion beams such as the fast solar wind. These instabilities can be triggered when the phase velocity of electrostatic ion-acoustic waves propagating forward and backward relative to the interplanetary magnetic field overlaps due to the presence of a finite amplitude of circularly polarized wave. The instabilities can be triggered by waves supported by the same ion component, or by waves supported by different ion components. By assuming a beam of alpha particles moving backward relative to the external magnetic field, as observed in some events in the fast solar wind, it is shown that a very small negative drift velocity of the alpha particle beam relative to the core plasma--a few percent of the local Alfven velocity--can trigger a very rich variety of nonlinear electrostatic acousticlike instabilities. Their growth rates can be rather large and they persist for larger negative alpha particles drift velocities and temperatures.

  13. Kinetic-energy release in the dissociative capture-ionization of CO molecules by 97-MeV Ar14+ ions

    NASA Astrophysics Data System (ADS)

    Watson, R. L.; Sampoll, G.; Horvat, V.; Heber, O.

    1996-02-01

    The dissociation of COQ+ molecular ions (Q=4 to 9) produced in multiply ionizing collisions accompanied by the transfer of an electron to the projectile has been studied using time-of-flight techniques. Analysis of the coincident-ion-pair flight-time-difference distributions yielded average values of the kinetic-energy releases for the various dissociation reactions. These values were found to be as much as a factor of 2 greater than the kinetic-energy releases expected for dissociation along Coulombic potential curves. The average kinetic-energy release observed for a given ion pair with charges q1 and q2 are nearly equal to the point-charge Coulomb potential energies for an ion pair with charges q1+1 and q2+1, suggesting that the parent molecular ion is formed with two electrons, on average, in highly excited states that do not contribute to the screening of the nuclei.

  14. Self-Consistent Conversion of a Viscous Fluid to Particles and Heavy-Ion Physics Applications

    NASA Astrophysics Data System (ADS)

    Wolff, Zack J.

    The most widely used theoretical framework to model the early stages of a heavy-ion collision is viscous hydrodynamics. Comparing hydrodynamic simulations to heavy-ion data inevitably requires the conversion of the fluid to particles. This conversion, typically done in the Cooper-Frye formalism, is ambiguous for viscous fluids. In this thesis work, self-consistent phase space corrections are calculated by solving the linearized Boltzmann equation. These species-dependent solutions are contrasted with those obtained using the ad-hoc ''democratic Grad'' ansatz typically employed in the literature in which coefficients are independent of particle dynamics. Solutions are calculated analytically for a massless gas and numerically for the general case of a hadron resonance gas. For example, it is found that for a gas of massless particles interacting via isotropic, energy-independent 2 → 2 scatterings, the shear viscous corrections variationally prefer a momentum dependence close to p3/2 rather than the quadratic dependence assumed in the Grad ansatz. The self-consistent phase space distributions are then used to calculate transverse momentum spectra and differential flow coefficients, v n(pT), to study the effects on heavy-ion identified particle observables. Using additive quark model cross sections, it is found that proton flow coefficients are higher than those for pions at moderately high pT in Pb + Pb collisions at LHC, especially for the coefficients v 4 and v6.

  15. Angular emission distributions of neutrals and ions in laser ablated particle beams

    NASA Astrophysics Data System (ADS)

    Thum-Jager, Andrea; Rohr, Klaus

    1999-11-01

    The present work represents investigations of angular emission distributions in laser-produced particle beams resolved for the different ion groups (up to q=4) and the neutral particle component. The measurements are for a spectrum of target masses: 12 C, 27Al, 48 Ti, 59Ni, 96Mo and 181Ta. The plasma was produced by obliquely incident Q-switched pulses (TAU=5~ns and LAMBDA=1.06~MU m) of a Nd-YAG laser focused to energy densities ranging from about 20 to 180~J~cm-2. For the first time the results reveal in detail that the emission distributions systematically depend on the degree of ionization of the particles in the cloud. While for the neutral particles the angular emission is always dominated by a broad background with an additional, but less pronounced, peaked component, the background component rapidly but continuously diminishes with the increasing charge state of the ions. If, in the usual way, the emission distribution is approximated by the superposition of a cosine and a cosn fit function, the distribution of ions with qgeq 2 can already be well fitted by a cosn function alone. It seems highly probable, that this behaviour essentially is a result of the recombination dynamics during the expansion. It was found that the effect holds for all atomic masses investigated, whereby the mass dependence of the exponent n for all species behaves alike, approximately following a A3/4 law.

  16. Heavy-ion isotopic anomalies in He-3 rich solar particle events

    NASA Astrophysics Data System (ADS)

    Mason, G. M.; Mazur, J. E.; Halmilton, D. C.

    1994-04-01

    We have measured the approximately 1 MeV/nucleon heavy-ion mass composition during a series of (3)He-rich solar particle events during 1992 July using the University of Maryland instrument on the SAMPEX spacecraft. In addition to enhancements of He-3/He-4 of approximately 103 to 104 larger than coronal values, these events also showed typical enhancements of heavy nuclei of up to a factor of approximately 10 compared with large solar particle events. Over the energy range of approximately 0.4 - 4.0 MeV/nucleon the spectra of both he isotopes as well as heavier ions C, N, O, Ne, Mg, Si, S, Ca+Ar, and Fe were found to be power laws in enegy per nucleon with nearly identical spectral indices, indicating that both the He and heavier ions were accelerated by the same mechanism. We obtain upper limits of approximately 15 for possible enrichments of neutron-rich isotopes of C, N, O, and Fe compared to large solar particle events; however, we find Ne-22/Ne-20 = 0.29 +/- 0.10, an enhancement of a factor of 3-4 compared with large solar particle event abundances. We also find evidence of enrichments of approximately 2-3 for Mg-25/Mg-24 and Mg-26/Mg-24, although the uncertainties are large. Thus while at least one of the heavy elements shows isotopic enhancements of neutron-rich isotopes, the mechanisms that produce the extremely large He-3 enrichments apparently do not produce similarly dramatic isotopic anomalies in the heavy nuclei. These observations constrain possible acceleration models and may indicate that the particles are energized in solar coronal locations enhanced in heavy ions.

  17. Particle simulation of collision dynamics for ion beam injection into a rarefied gas

    SciTech Connect

    Giuliano, Paul N.; Boyd, Iain D.

    2013-03-15

    This study details a comparison of ion beam simulations with experimental data from a simplified plasma test cell in order to study and validate numerical models and environments representative of electric propulsion devices and their plumes. The simulations employ a combination of the direct simulation Monte Carlo and particle-in-cell methods representing xenon ions and atoms as macroparticles. An anisotropic collision model is implemented for momentum exchange and charge exchange interactions between atoms and ions in order to validate the post-collision scattering behaviors of dominant collision mechanisms. Cases are simulated in which the environment is either collisionless or non-electrostatic in order to prove that the collision models are the dominant source of low- and high-angle particle scattering and current collection within this environment. Additionally, isotropic cases are run in order to show the importance of anisotropy in these collision models. An analysis of beam divergence leads to better characterization of the ion beam, a parameter that requires careful analysis. Finally, suggestions based on numerical results are made to help guide the experimental design in order to better characterize the ion environment.

  18. Controlled fabrication of nanopores using a direct focused ion beam approach with back face particle detection

    NASA Astrophysics Data System (ADS)

    Patterson, N.; Adams, D. P.; Hodges, V. C.; Vasile, M. J.; Michael, J. R.; Kotula, P. G.

    2008-06-01

    We report a direct, ion drilling technique that enables the reproducible fabrication and placement of nanopores in membranes of different thickness. Using a 30 keV focused Ga ion beam column combined with an in situ, back face, multi-channelplate particle detector, nanopores are sputtered in Si3N4 and W/Si3N4 to have diameters as small as 12 nm. Transmission electron microscopy shows that focused ion beam-drilled holes are near-conical with the diameter decreasing from entry to exit side. By monitoring the detector signal during ion exposure, the drilled hole width can be minimized such that the exit-side diameter is smaller than the full width at half-maximum of the nominally Gaussian-shaped incident beam. Judicious choice of the beam defining aperture combined with back face particle detection allows for reproducible exit-side hole diameters between 18 and 100 nm. The nanopore direct drilling technique does not require potentially damaging broad area exposure to tailor hole sizes. Moreover, this technique successfully achieves breakthrough despite the effects of varying membrane thickness, redeposition, polycrystalline grain structure, and slight ion beam current fluctuations.

  19. Controlled fabrication of nanopores using a direct focused ion beam approach with back face particle detection.

    PubMed

    Patterson, N; Adams, D P; Hodges, V C; Vasile, M J; Michael, J R; Kotula, P G

    2008-06-11

    We report a direct, ion drilling technique that enables the reproducible fabrication and placement of nanopores in membranes of different thickness. Using a 30 keV focused Ga ion beam column combined with an in situ, back face, multi-channelplate particle detector, nanopores are sputtered in Si(3)N(4) and W/Si(3)N(4) to have diameters as small as 12 nm. Transmission electron microscopy shows that focused ion beam-drilled holes are near-conical with the diameter decreasing from entry to exit side. By monitoring the detector signal during ion exposure, the drilled hole width can be minimized such that the exit-side diameter is smaller than the full width at half-maximum of the nominally Gaussian-shaped incident beam. Judicious choice of the beam defining aperture combined with back face particle detection allows for reproducible exit-side hole diameters between 18 and 100 nm. The nanopore direct drilling technique does not require potentially damaging broad area exposure to tailor hole sizes. Moreover, this technique successfully achieves breakthrough despite the effects of varying membrane thickness, redeposition, polycrystalline grain structure, and slight ion beam current fluctuations. PMID:21825787

  20. Comparison of kinetic and extended magnetohydrodynamics computational models for the linear ion temperature gradient instability in slab geometry

    SciTech Connect

    Schnack, D. D.; Cheng, J.; Parker, S. E.; Barnes, D. C.

    2013-06-15

    We perform linear stability studies of the ion temperature gradient (ITG) instability in unsheared slab geometry using kinetic and extended magnetohydrodynamics (MHD) models, in the regime k{sub ∥}/k{sub ⊥}≪1. The ITG is a parallel (to B) sound wave that may be destabilized by finite ion Larmor radius (FLR) effects in the presence of a gradient in the equilibrium ion temperature. The ITG is stable in both ideal and resistive MHD; for a given temperature scale length L{sub Ti0}, instability requires that either k{sub ⊥}ρ{sub i} or ρ{sub i}/L{sub Ti0} be sufficiently large. Kinetic models capture FLR effects to all orders in either parameter. In the extended MHD model, these effects are captured only to lowest order by means of the Braginskii ion gyro-viscous stress tensor and the ion diamagnetic heat flux. We present the linear electrostatic dispersion relations for the ITG for both kinetic Vlasov and extended MHD (two-fluid) models in the local approximation. In the low frequency fluid regime, these reduce to the same cubic equation for the complex eigenvalue ω=ω{sub r}+iγ. An explicit solution is derived for the growth rate and real frequency in this regime. These are found to depend on a single non-dimensional parameter. We also compute the eigenvalues and the eigenfunctions with the extended MHD code NIMROD, and a hybrid kinetic δf code that assumes six-dimensional Vlasov ions and isothermal fluid electrons, as functions of k{sub ⊥}ρ{sub i} and ρ{sub i}/L{sub Ti0} using a spatially dependent equilibrium. These solutions are compared with each other, and with the predictions of the local kinetic and fluid dispersion relations. Kinetic and fluid calculations agree well at and near the marginal stability point, but diverge as k{sub ⊥}ρ{sub i} or ρ{sub i}/L{sub Ti0} increases. There is good qualitative agreement between the models for the shape of the unstable global eigenfunction for L{sub Ti0}/ρ{sub i}=30 and 20. The results quantify how far