Science.gov

Sample records for kinetic ion particle

  1. Kinetic modeling of particle dynamics in H(-) negative ion sources (invited).

    PubMed

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

    2014-02-01

    Progress in the kinetic modeling of particle dynamics in H(-) 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(-) ion beams: (i) Effects of non-equilibrium features of EEDF (electron energy distribution function) on H(-) production, and (ii) extraction physics of H(-) ions and beam optics.

  2. Toroidal Electromagnetic Particle-in-Cell Code with Gyro-kinetic Electron and Fully-kinetic ion

    NASA Astrophysics Data System (ADS)

    Lin, Jingbo; Zhang, Wenlu; Liu, Pengfei; Li, Ding

    2016-10-01

    A kinetic simulation model has been developed using gyro-kinetic electron and fully-kinetic ion by removing fast gyro motion of electrons using the Lie-transform perturbation theory. A particle-in-cell kinetic code is developed based on this model in general magnetic flux coordinate systems, which is particularly suitable for simulations of toroidally confined plasma. Single particle motion and field solver are successfully verified respectively. Integrated electrostatic benchmark, for example the lower-hybrid wave (LHW) and ion Bernstein wave (IBW), shows a good agreement with theoretical results. Preliminary electromagnetic benchmark of fast wave at lower hybrid frequency range is also presented. This code can be a first-principal tool to investigate high frequency nonlinear phenomenon, such as parametric decay instability, during lower-hybrid current drive (LHCD) and ion cyclotron radio frequency heating (ICRF) with complex geometry effect included. Supported by National Special Research Program of China For ITER and National Natural Science Foundation of China.

  3. 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.

  4. Kinetic Alfvén Turbulence: Electron and Ion Heating by Particle-in-cell Simulations

    NASA Astrophysics Data System (ADS)

    Hughes, R. Scott; Gary, S. Peter; Wang, Joseph; Parashar, Tulasi N.

    2017-10-01

    Three-dimensional particle-in-cell simulations of the forward cascade of decaying kinetic Alfvén turbulence have been carried out as an initial-value problem on a collisionless, homogeneous, magnetized, electron–ion plasma model with {β }{{e}}={β }{{i}}=0.50 and m i/m e = 100, where subscripts e and i represent electrons and ions, respectively. Initial anisotropic narrowband spectra of relatively long-wavelength modes with approximately gyrotropic distributions in {k}\\perp undergo a forward cascade to broadband spectra of magnetic fluctuations at shorter wavelengths. Maximum electron and ion heating rates are computed as functions of the initial fluctuating magnetic field energy density {\\varepsilon }o on the range 0.05< {\\varepsilon }{{o}}< 0.50. In contrast to dissipation by whistler turbulence, the maximum ion heating rate due to kinetic Alfvén turbulence is substantially greater than the maximum electron heating rate. Furthermore, ion heating as well as electron heating due to kinetic Alfvén turbulence scale approximately with ε o. Finally, electron heating leads to anisotropies of the type {T}\\parallel {{e}}> {T}\\perp {{e}}, where the parallel and perpendicular symbols refer to directions parallel and perpendicular, respectively, to the background magnetic field, whereas the heated ions remain relatively isotropic. This implies that, for the range of ε o values considered, the Landau wave–particle resonance is a likely heating mechanism for the electrons and may also contribute to ion heating.

  5. Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

    SciTech Connect

    Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

    2009-08-11

    Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test

  6. Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

    DOE PAGES

    Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

    2016-11-10

    In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field.more » It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.« less

  7. Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

    SciTech Connect

    Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

    2016-11-10

    In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field. It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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).

  13. A unified theory of resonant excitation of kinetic ballooning modes by energetic ions/alpha particles in tokamaks

    SciTech Connect

    Biglari, H.; Chen, L.

    1991-10-01

    A complete theory of wave-particle interactions is presented whereby both circulating and trapped energetic ions can destabilize kinetic ballooning modes in tokamaks. Four qualitatively different types of resonances, involving wave-precessional drift, wave-transit, wave-bounce, and precessional drift-bounce interactions, are identified, and the destabilization potential of each is assessed. For a characteristic slowing-down distribution function, the dominant interaction is that which taps those resonant ions with the highest energy. Implications of the theory for present and future generation fusion experiments are discussed. 16 refs.

  14. Ion gyroradius effects on particle trapping in kinetic Alfvén waves along auroral field lines

    NASA Astrophysics Data System (ADS)

    Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

    2016-11-01

    In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfvén wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfvén waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field. It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfvén wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfvén wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Even in the cold ion limit, trapping effects in kinetic Alfvén waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.

  15. Plasma turbulence at ion scales: a comparison between particle in cell and Eulerian hybrid-kinetic approaches

    NASA Astrophysics Data System (ADS)

    Cerri, S. S.; Franci, L.; Califano, F.; Landi, S.; Hellinger, P.

    2017-04-01

    Kinetic-range turbulence in magnetized plasmas and, in particular, in the context of solar wind turbulence has been extensively investigated over the past decades via numerical simulations. Among others, one of the widely adopted reduced plasma models is the so-called hybrid-kinetic model, where the ions are fully kinetic and the electrons are treated as a neutralizing (inertial or massless) fluid. Within the same model, different numerical methods and/or approaches to turbulence development have been employed. In the present work, we present a comparison between two-dimensional hybrid-kinetic simulations of plasma turbulence obtained with two complementary approaches spanning approximately two decades in wavenumber - from the magnetohydrodynamics inertial range to scales well below the ion gyroradius - with a state-of-the-art accuracy. One approach employs hybrid particle-in-cell simulations of freely decaying Alfvénic turbulence, whereas the other consists of Eulerian hybrid Vlasov-Maxwell simulations of turbulence continuously driven with partially compressible large-scale fluctuations. Despite the completely different initialization and injection/drive at large scales, the same properties of turbulent fluctuations at \\bot \\unicode[STIX]{x1D70C}i\\gtrsim 1$ are observed, where \\bot $ is the fluctuations' wavenumber perpendicular to the background magnetic field and i$ is the ion Larmor radius. The system indeed self-consistently `reprocesses' the turbulent fluctuations while they are cascading towards smaller and smaller scales, in a way which actually depends on the plasma beta parameter ( is the ratio between the thermal and the magnetic pressures). Small-scale turbulence has been found to be mainly populated by kinetic Alfvén wave (KAW) fluctuations for , whereas KAW fluctuations are only sub-dominant for low- .

  16. Kinetics of electrons and neutral particles in radio-frequency transformer coupled plasma H- ion source at Seoul National University

    NASA Astrophysics Data System (ADS)

    Chung, K. J.; Dang, J. J.; Kim, J. Y.; Cho, W. H.; Hwang, Y. S.

    2016-10-01

    In volume production H- ion sources, control of electron temperature is essential due to its close correlation with the generation of vibrationally-excited hydrogen molecules in the driver region as well as the generation of H- ions by dissociative attachment in the extraction region. In the ion source group at Seoul National University (SNU) in Korea, a lot of research effort has been made to the development of a volume production H- ion source based on radio-frequency (RF) transformer-coupled plasma (TCP) for long lifetime continuous wave (CW) operation. It has a spiral RF antenna located outside the discharge chamber to generate a plasma with high electron temperature in the driver region and employs a magnetic filter field to prevent high energy electrons from being transported to the extraction region. In this paper, we present the recent progress on understanding of the underlying physics of the RF TCP H- ion source at SNU. Special attention is paid to the characterization of electron kinetics regime for controlling electron energy distribution and the influence of relaxation of neutral particles during the transport across the magnetic filter region. Effect of the degree of dissociation on the production of H- ions is also discussed.

  17. The inverse problem of the kinetics of redox sorption taking into account the size of ultradisperse metal particles in an electron-ion exchanger

    NASA Astrophysics Data System (ADS)

    Konev, D. V.; Fertikov, V. V.; Kravchenko, T. A.; Kalinichev, A. I.

    2008-08-01

    The inverse kinetic problem of reducing sorption of molecular oxygen by a copper-containing electron-ion exchanger was formulated and solved taking into account the influence of the size of ultradisperse metal particles on the total rate of the process. These results were used to determine the inside diffusion coefficient of oxygen and rate constants for its interaction with disperse copper from the experimental kinetic curves. The diffusion coefficient obtained was compared with the result of an independent experiment. The kinetic parameters found were used to perform a theoretical analysis of the contributions of various factors influencing the rate of the process under consideration. The reason for the experimentally observed acceleration of the reducing sorption of oxygen by a high-dispersity electron-ion exchanger sample was shown to be an increase in the surface area of metal because of a decrease in the size of its particles and a comparatively high copper content in the surface layer of grains.

  18. Ion Kinetics in Silane Plasmas

    DTIC Science & Technology

    1988-02-01

    reaction are determined not only by the chemical reactivity but by the electrical properties of the plasma. Current continuity, impedence match- ing...conventional kinetic theory. Since the chemical and physical properties of the noble-gases vary monotonically down the periods of Mendeleev’s table, one...formation. Most literature with the phrase ion chemistry in its title is concerned only with the properties and reactions of positively charged species

  19. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited).

    PubMed

    Sio, H; Frenje, J A; Katz, J; Stoeckl, C; Weiner, D; Bedzyk, M; Glebov, V; Sorce, C; Gatu Johnson, M; Rinderknecht, H G; Zylstra, A B; Sangster, T C; Regan, S P; Kwan, T; Le, A; Simakov, A N; Taitano, W T; Chacòn, L; Keenan, B; Shah, R; Sutcliffe, G; Petrasso, R D

    2016-11-01

    A Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D(3)He, and T(3)He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  20. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    DOE PAGES

    Sio, H.; Frenje, J. A.; Katz, J.; ...

    2016-09-14

    Here, a Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences,more » and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.« less

  1. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    SciTech Connect

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; Zylstra, A. B.; Sangster, T. C.; Regan, S. P.; Kwan, T.; Le, A.; Simakov, A. N.; Taitano, W. T.; Chacòn, L.; Keenan, B.; Shah, R.; Sutcliffe, G.; Petrasso, R. D.

    2016-09-14

    A Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  2. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    NASA Astrophysics Data System (ADS)

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; Zylstra, A. B.; Sangster, T. C.; Regan, S. P.; Kwan, T.; Le, A.; Simakov, A. N.; Taitano, W. T.; Chacòn, L.; Keenan, B.; Shah, R.; Sutcliffe, G.; Petrasso, R. D.

    2016-11-01

    A Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  3. Ion kinetic transport in TJ-II

    SciTech Connect

    Velasco, J. L.; Tarancon, A.; Castejon, F.; Fernandez, L. A.; Martin-Mayor, V.

    2008-11-02

    The ion Drift Kinetic Equation (DKE) which describes the ion collisional transport is solved for the TJ-II device plasmas. This non-linear equation is computed by performing a mean field iterative calculation. In each step of the calculation, a Fokker-Planck equation is solved by means of the Langevin approach: one million particles are followed in a realistic TJ-II magnetic configuration, taking into account collisions and electric field. This allows to avoid the assumptions made in the usual neoclassical approach, namely considering radially narrow particle trajectories, diffusive transport, energy conservation and infinite parallel transport. As a consequence, global features of transport, not present in the customary neoclassical models, appear: non-diffusive transport and asymmetries on the magnetic surfaces.

  4. Differential kinetic physics of solar-wind minor ions

    NASA Astrophysics Data System (ADS)

    Perrone, Denise; Valentini, Francesco; Servidio, Sergio; Stabile, Sara; Pezzi, Oreste; Sorriso-Valvo, Luca; De Marco, Rossana; Marcucci, Federica; Brienza, Daniele; Bruno, Roberto; Lavraud, Benoit; Retinò, Alessandro; Vaivads, Andris; Consolini, Giuseppe; De Keyser, Johan; Salatti, Mario; Veltri, Pierluigi

    2017-04-01

    The solar wind, although predominantly constituted of protons, is also made up of a finite amount of alpha particles, together with a few percent of heavier ions. The kinetic properties of heavy ions in the solar wind are known to behave in a well organized way under most solar-wind flow conditions: their speeds are faster than that of hydrogen by about the local Alfvén speed, and their kinetic temperatures are more than proportional to their mass. Preferential heating and acceleration of heavy ions in the solar wind and corona represent a long-standing theoretical problem in space physics, and are distinct experimental signatures of kinetic processes occurring in collisionless plasmas. However, due to very scarce measurements of heavy ions at time resolutions comparable with their kinetic scales, energy partition between species in turbulent plasma dissipation is basically unexplored. For the moment, most of the information comes from numerical simulations and a crucial support is given by self-consistent, fully nonlinear Vlasov models. Here, hybrid Vlasov-Maxwell simulations are used to investigate the role of kinetic effects in a two-dimensional turbulent multi-ion plasma, composed of kinetic protons and alpha particles, and fluid electrons. The response of different ion species to the fluctuating electromagnetic fields appears to be different. In particular, a significant differential heating of alpha particles with respect to protons is observed, localized nearby the peaks of ion vorticity and where strong deviations from thermodynamic equilibrium are recovered. Then, the understanding of the complex process of particle heating results strongly related to the study of the non-Maxwellian features on the three-dimensional ion velocity distributions. These numerical results highlight the importance for the future space missions to provide detailed ion measurements to make a significant step forward in the problem of heating in turbulent space plasmas.

  5. 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.

  6. [Particle therapy: carbon ions].

    PubMed

    Pommier, Pascal; Hu, Yi; Baron, Marie-Hélène; Chapet, Olivier; Balosso, Jacques

    2010-07-01

    Carbon ion therapy is an innovative radiation therapy. It has been first proposed in the forties by Robert Wilson, however the first dedicated centres for human care have been build up only recently in Japan and Germany. The interest of carbon ion is twofold: 1) the very sharp targeting of the tumour with the so called spread out Bragg peak that delivers most of the beam energy in the tumour and nothing beyond it, sparing very efficiently the healthy tissues; 2) the higher relative biological efficiency compared to X rays or protons, able to kill radioresistant tumour cells. Both properties make carbon ions the elective therapy for non resectable radioresistant tumours loco-regionally threatening. The technical and clinical experience accumulated during the recent decades is summarized in this paper along with a detailed presentation of the elective indications. A short comparison between conventional radiotherapy and hadrontherapy is proposed for the indications which are considered as priority for carbon ions.

  7. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    SciTech Connect

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; Zylstra, A. B.; Sangster, T. C.; Regan, S. P.; Kwan, T.; Le, A.; Simakov, A. N.; Taitano, W. T.; Chacòn, L.; Keenan, B.; Shah, R.; Sutcliffe, G.; Petrasso, R. D.

    2016-09-14

    Here, a Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  8. A Particle X-ray Temporal Diagnostic (PXTD) for studies of kinetic, multi-ion effects, and ion-electron equilibration rates in Inertial Confinement Fusion plasmas at OMEGA (invited)

    SciTech Connect

    Sio, H.; Frenje, J. A.; Katz, J.; Stoeckl, C.; Weiner, D.; Bedzyk, M.; Glebov, V.; Sorce, C.; Gatu Johnson, M.; Rinderknecht, H. G.; Zylstra, A. B.; Sangster, T. C.; Regan, S. P.; Kwan, T.; Le, A.; Simakov, A. N.; Taitano, W. T.; Chacòn, L.; Keenan, B.; Shah, R.; Sutcliffe, G.; Petrasso, R. D.

    2016-09-14

    Here, a Particle X-ray Temporal Diagnostic (PXTD) has been implemented on OMEGA for simultaneous time-resolved measurements of several nuclear products as well as the x-ray continuum produced in High Energy Density Plasmas and Inertial Confinement Fusion implosions. The PXTD removes systematic timing uncertainties typically introduced by using multiple instruments, and it has been used to measure DD, DT, D3He, and T3He reaction histories and the emission history of the x-ray core continuum with relative timing uncertainties within ±10-20 ps. This enables, for the first time, accurate and simultaneous measurements of the x-ray emission histories, nuclear reaction histories, their time differences, and measurements of Ti(t) and Te(t) from which an assessment of multiple-ion-fluid effects, kinetic effects during the shock-burn phase, and ion-electron equilibration rates can be made.

  9. Carbon Nanofibers Heavy Laden with Li3V2(PO4)3 Particles Featuring Superb Kinetics for High-Power Lithium Ion Battery.

    PubMed

    Shin, Jeongyim; Yang, Junghoon; Sergey, Chernov; Song, Min-Sang; Kang, Yong-Mook

    2017-09-01

    Fast lithium ion and electron transport inside electrode materials are essential to realize its superb electrochemical performances for lithium rechargeable batteries. Herein, a distinctive structure of cathode material is proposed, which can simultaneously satisfy these requirements. Nanosized Li3V2(PO4)3 (LVP) particles can be successfully grown up on the carbon nanofiber via electrospinning method followed by a controlled heat-treatment. Herein, LVP particles are anchored onto the surface of carbon nanofiber, and with this growing process, the size of LVP particles as well as the thickness of carbon nanofiber can be regulated together. The morphological features of this composite structure enable not only direct contact between electrolytes and LVP particles that can enhance lithium ion diffusivity, but also fast electron transport through 1D carbon network along nanofibers simultaneously. Finally, it is demonstrated that this unique structure is an ideal one to realize high electron transport and ion diffusivity together, which are essential for enhancing the electrochemical performances of electrode materials.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  12. 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.

  13. Fluorine negative ion detachment kinetics

    NASA Technical Reports Server (NTRS)

    Burke, R. R.; Miller, W. J.; Gould, R. K.

    1971-01-01

    A study of the rate of F(-) detachment by O and H atoms via the reactions F(-) + O yields FO + e and F(-) + H yields FH+ e was undertaken using a drift tube to produce F(-) ions at various drift velocities and therefore different ion temperatures. Preliminary mobility measurements of F(-) ions in Ar were made, indicating that ion temperatures in the 300 K to 5000 K range could be achieved; however due to numerous difficulties experienced in obtaining a reliable F(-) ion source, the study could not be completed.

  14. Electron and ion kinetics in magnetized capacitively coupled plasma source

    SciTech Connect

    Lee, S. H.; You, S. J.; Chang, H. Y.; Lee, J. K.

    2007-05-15

    One-dimensional particle-in-cell Monte Carlo collision simulations of magnetized argon plasmas in an asymmetric capacitively coupled plasma reactor are presented. At low pressure (10 mTorr), electron kinetics are strongly affected by the magnetic field and transitions from nonlocal to local kinetic property occur with increasing magnetic field which are reflected in spatially resolved calculations of the electron-energy probability function. For high-energy electrons, the transition takes place when the energy-relaxation length is smaller than the system length. For low-energy electrons, however, the transition occurs when the electron-diffusion time scale in the energy space is shorter than the spatial-diffusion time scale in coordinate space. These observations are in agreement with experimental data and theoretical calculations deduced from the Boltzmann equation. The ion energy distribution function (IEDF) on the driven electrode changes from the ion-neutral collisional type to the ion-neutral collisionless type with increasing magnetic field strength. The maximum ion energy in the IEDF decreases and the angular spread in the ion angle distribution function slightly increases with increasing magnetic field strength. These changes are explained in terms of the ratio of the ion-transit time to rf frequency, the sheath length, and the mean potential difference between the driven electrode and the plasma. At high pressure (218 mTorr), electron-neutral collisions disrupt electron gyromotion so that the effects of the magnetic field on electron and ion kinetics are greatly reduced.

  15. 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.

  16. Particle growth kinetics over the Amazon rainforest

    NASA Astrophysics Data System (ADS)

    Pinterich, T.; Andreae, M. O.; Artaxo, P.; Kuang, C.; Longo, K.; Machado, L.; Manzi, A. O.; Martin, S. T.; Mei, F.; Pöhlker, C.; Pöhlker, M. L.; Poeschl, U.; Shilling, J. E.; Shiraiwa, M.; Tomlinson, J. M.; Zaveri, R. A.; Wang, J.

    2016-12-01

    Aerosol particles larger than 100 nm play a key role in global climate by acting as cloud condensation nuclei (CCN). Most of these particles, originated from new particle formation or directly emitted into the atmospheric, are initially too small to serve as CCN. These small particles grow to CCN size mainly through condensation of secondary species. In one extreme, the growth is dictated by kinetic condensation of very low-volatility compounds, favoring the growth of the smallest particles; in the other extreme, the process is driven by Raoult's law-based equilibrium partitioning of semi-volatile organic compound, favoring the growth of larger particles. These two mechanisms can lead to very different production rates of CCN. The growth of particles depends on a number of parameters, including the volatility of condensing species, particle phase, and diffusivity inside the particles, and this process is not well understood in part due to lack of ambient data. Here we examine atmospheric particle growth using high-resolution size distributions measured onboard the DOE G-1 aircraft during GoAmazon campaign, which took place from January 2014 to December 2015 near Manaus, Brazil, a city surrounded by natural forest for over 1000 km in every direction. City plumes are clearly identified by the strong enhancement of nucleation and Aitken mode particle concentrations over the clean background. As the plume traveled downwind, particle growth was observed, and is attributed to condensation of secondary species and coagulation (Fig.1). Observed aerosol growth is modeled using MOSAIC (Model for Simulating Aerosol Interactions and Chemistry), which dynamically partitions multiple compounds to all particle size bins by taking into account compound volatility, gas-phase diffusion, interfacial mass accommodation, particle-phase diffusion, and particle-phase reaction. The results from both wet and dry seasons will be discussed.

  17. Ion Kinetics in Silane Plasmas

    DTIC Science & Technology

    1988-04-20

    reactivity but by the electrical properties of the plasma. Current continuity, impedance matching, and the cou- pling between total charged particle fluxes...theory. Since the chemical and physical properties of the noble-gases vary monotonically down the periods of Mendeleev’s table, one might anticipate a...chemistry in its title is concerned only with the properties and reactions of positively charged species. Anions play a qualitatively different and important

  18. 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.

  19. 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.

  20. 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.

  1. Kinetic aspects of the ion current layer in a reconnection outflow exhaust

    SciTech Connect

    Zenitani, Seiji; Wada, Tomohide; Shinohara, Iku; Nagai, Tsugunobu

    2013-09-15

    Kinetic aspects of the ion current layer at the center of a reconnection outflow exhaust near the X-type region are investigated by a two-dimensional particle-in-cell (PIC) simulation. The layer consists of magnetized electrons and unmagnetized ions that carry a perpendicular electric current. The ion fluid appears to be nonideal, sub-Alfvénic, and nondissipative. The ion velocity distribution functions contain multiple populations, such as global Speiser ions, local Speiser ions, and trapped ions. The particle motion of the local Speiser ions in an appropriately rotated coordinate system explains the ion fluid properties very well. The trapped ions are the first demonstration of the regular orbits in the chaotic particle dynamics [Chen and Palmadesso, J. Geophys. Res. 91, 1499 (1986)] in self-consistent PIC simulations. They would be observational signatures in the ion current layer near reconnection sites.

  2. A unified kinetic model for particle aggregation

    SciTech Connect

    Gardner, K.H.; Theis, T.L.

    1996-06-01

    Aggregation of submicrometer particles is a process with significant implications for the fate and transport of contaminants and major nutrients in many coastal, estuarine, and freshwater bodies as well as groundwater systems. A unified model has been developed that describes the kinetics of particle aggregation. The model is unique in the incorporation of surface chemical phenomena along with solution chemistry in the determination of the stability of a colloidal dispersion. The aggregation process is treated in a truly kinetic fashion, the main output from the model being the evolution of complete particle size distributions over time. The model was developed to interpret laboratory data and, as such, has the capacity to estimate a (variable) set of system parameters by fitting the size distribution over time data to that measured. It was found that the attachment distance, a parameter frequently approximated in practice, has a profound influence on the predicted aggregation kinetics as does the choice of a solid/solution interfacial model. Furthermore, simulation of relatively long-term aggregation, which was the principal focus of this work, indicates that values of the collision efficiency factor should be much smaller than those reported elsewhere in the literature.

  3. Diffusion Limit of Kinetic Equations for Multiple Species Charged Particles

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Lin, Tai-Chia; Liu, Chun

    2015-02-01

    In ionic solutions, there are multi-species charged particles (ions) with different properties like mass, charge etc. Macroscopic continuum models like the Poisson-Nernst-Planck (PNP) systems have been extensively used to describe the transport and distribution of ionic species in the solvent. Starting from the kinetic theory for the ion transport, we study a Vlasov-Poisson-Fokker-Planck (VPFP) system in a bounded domain with reflection boundary conditions for charge distributions and prove that the global renormalized solutions of the VPFP system converge to the global weak solutions of the PNP system, as the small parameter related to the scaled thermal velocity and mean free path tends to zero. Our results may justify the PNP system as a macroscopic model for the transport of multi-species ions in dilute solutions.

  4. 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.

  5. 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.

  6. Kinetic aspects of ion transport through neural membrane

    NASA Astrophysics Data System (ADS)

    Clay, John R.; Shlesinger, Michael F.

    1984-02-01

    The Hodgkin-Huxley model for the nerve membrane action potential is reviewed. The model can be described in terms of channels and gates. That is, ions permeate the nerve membrane through narrow ion specific pores, or channels, which are modulated by a voltage dependent gating process. The Hodgkin-Huxley model provides a detailed kinetic scheme for channel gating, but not for channel permeation. Radioactive tracer flux experiments suggest that permeation occurs via single file motion of ions through a channel. We have modeled this process as a random walk with internal states. The theory leads to expressions for one way fluxes which can be compared with experimental tracer flux data. Recent experiments on channel gating have indicated that the Hodgkin-Huxley model of the gating process requires certain modifications. We present a class of modifications involving temporal memory of gating and interactions between gating particles of any single channel. Thses models can also be described in terms of random walks.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Kinetic models of sub-ion cylindrical magnetic hole

    NASA Astrophysics Data System (ADS)

    Shustov, P. I.; Artemyev, A. V.; Vasko, I. Y.; Yushkov, E. V.

    2016-12-01

    Magnetic holes are magnetoplasma structures very similar to the classical θ-pinch. They are widely observed in the space plasma and identified by the substantial magnetic field depressions on scales from magnetohydrodynamic range to electron scales. In this paper, we develop the kinetic models of cylindrically symmetric magnetic holes with sub-ion scales using two types of charged particle distribution functions (both current-carrying and background plasma populations are included). We demonstrate that developed magnetic holes have configurations very similar to those revealed in the recent spacecraft observations in the Earth magnetosphere: both localized electron currents and strong radial electric fields are found at the magnetic hole boundary. We demonstrate that for realistic plasma parameters, the inclusion of ion currents into the model produces magnetic holes with double-scale magnetic field profile. We find that the magnetic hole depth (amplitude of the magnetic field depression) depends on the magnetic hole typical radius. Possible applications of developed models are discussed.

  13. Selective recognition of neodymium (III) using ion imprinted polymer particles.

    PubMed

    Krishna, Paramesamangalam Gopi; Gladis, Joseph Mary; Rao, Talasila Prasada; Naidu, Gurijala Ramakrishna

    2005-01-01

    Neodymium (III) ion-imprinted polymer (IIP) materials were prepared by the copolymerization of neodymium (III)-5,7-dichloroquinoline-8-ol-4-vinylpyridine ternary complex with styrene(monomer), divinyl benzene (crosslinking monomer) in the presence of 2,2'-azobisisobutyronitrile (initiator). The synthesis was carried out in 2-methoxy ethanol medium (porogen) and the resultant material was filtered, washed, dried and powdered to form unleached IIP particles. The imprint ion was removed by stirring the above particles with 50% (v/v) HCl for 6 h to obtain leached IIP particles with cavities in the polymer particles. Control polymer (CP) particles were similarly prepared without imprint ion, i.e. neodymium (III). CP, unleached and leached IIP particles were characterized by TLC, IR, microanalysis, XRD and UV-visible spectrophotometric studies. The preconcentration of 5-150 microg of neodymium (III) ions present in 500 ml of solution was possible with as little as 40 mg of neodymium (III) IIP particles in the pH range 7.5-8.0 with a detection limit of 50 ng/l. Five replicate determinations of 25 microg of neodymium (III) present in 500 ml of solution gave a mean absorbance of 0.120 with a relative standard deviation of 2.65%. The imprinting effect of IIP particles was noticed in all preconcentration and selectivity studies when compared with CP particles. Furthermore, the selectivity coefficients of neodymium (III) IIP particles were much higher compared with the reported separation factors for the best liquid-liquid extractants, viz. di-2-ethylhexyl phosphoric acid and 2-ethylhexyl-ethylhexyl phosphonate. Kinetic and isotherm studies during rebinding of neodymium (III) onto IIP particles were also carried out.

  14. 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.

  15. A Simulation Model for the Toroidal Ion Temperature Gradient Instability with Fully Kinetic Ions

    NASA Astrophysics Data System (ADS)

    Sturdevant, Benjamin; Parker, Scott; Chen, Yang

    2016-10-01

    A simulation model for the toroidal ITG mode in which the ions follow the primitive Lorentz force equations of motion is presented. Such a model can provide an important validation tool or replacement for gyrokinetic ion models in applications where higher order terms may be important. A number of multiple-scale simulation techniques are employed in this work, based on the previous success in slab geometry with an implicit orbit averaged and sub-cycled δf model. For the toroidal geometry model, we have derived a particle integration scheme based on variational principles, which is demonstrated to produce stable and accurate ion trajectories on long time scales. Orbit averaging and sub-cycling will be implemented with the variational integration scheme. The inclusion of equilibrium gradients in the fully kinetic δf formulation is achieved through the use of a guiding center coordinate transformation of the weight equation. Simulation results for the fully kinetic ion model will be presented for the cyclone base case and comparisons will be made with gyrokinetic ion models.

  16. Antibacterial activity of nanosilver ions and particles.

    PubMed

    Sotiriou, Georgios A; Pratsinis, Sotiris E

    2010-07-15

    The antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO(2) nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction the exposed Ag surface area was measured qualitatively by O(2) chemisorption. Furthermore, the fraction of dissolved nanosilver was determined by measuring the released (leached) Ag(+) ion concentration in aqueous suspensions of such Ag/SiO(2) particles. The antibacterial effect of Ag(+) ions was distinguished from that of nanosilver particles by monitoring the growth of E. coli populations in the presence and absence of Ag/SiO(2) particles. The antibacterial activity of nanosilver was dominated by Ag(+) ions when fine Ag nanoparticles (less than about 10 nm in average diameter) were employed that release high concentrations of Ag(+) ions. In contrast, when relatively larger Ag nanoparticles were used, the concentration of the released Ag(+) ions was lower. Then the antibacterial activity of the released Ag(+) ions and nanosilver particles was comparable.

  17. Kinetic simulation of asymmetric magnetic reconnection with cold ions

    NASA Astrophysics Data System (ADS)

    Dargent, J.; Aunai, N.; Lavraud, B.; Toledo-Redondo, S.; Shay, M. A.; Cassak, P. A.; Malakit, K.

    2017-05-01

    At the dayside magnetopause, the magnetosphere often contains a cold ion population of ionospheric origin. This population is not always detectable by particle instruments due to its low energy, despite having an important contribution to the total ion density and therefore an impact on key plasma processes such as magnetic reconnection. The exact role and implications of this low-temperature population are still not well known and has not been addressed with numerical simulation before. We present 2-D fully kinetic simulations of asymmetric magnetic reconnection with and without a cold ion population on the magnetospheric side of the magnetopause, but sharing the same total density, temperature, and magnetic field profiles. The comparison of the simulations suggests that cold ions directly impact signatures recently suggested as a good marker of the X line region: the Larmor electric field. Our simulations reveal that this electric field, initially present all along the magnetospheric separatrix, is related to the bounce of magnetosheath ions at the magnetopause magnetic field reversal through Speiser-like orbits. Once reconnection widens the current sheet away from the X line, the bouncing stops and the electric field signature remains solely confined near the X line. When cold ions are present, however, their very low temperature enables them to E × B drift in the electric field structure. If their density is large enough compared to other ions, their contribution to the momentum equation is capable of maintaining the signature away from the X line. This effect must be taken into account when analyzing in situ spacecraft measurements.

  18. Preparation and properties of ion-imprinted hollow particles for the selective adsorption of silver ions.

    PubMed

    Hou, Hongbin; Yu, Demei; Hu, Guohe

    2015-02-03

    Four kinds of silver ion-imprinted particles (Ag-IIPs) with different morphologies were prepared by the surface ion-imprinting technology (SIIT) and were used for the selective removal and concentration of silver ions from wastewater. The favorable adsorptivity and selectivity of Ag-IIPs for Ag(+) were confirmed by a series of adsorption experiments at a suitable pH value. The adsorption mechanism was elucidated by analyzing the adsorption isotherms, adsorption thermodynamics, and adsorption kinetics systematically. The Ag(+) adsorption onto the Ag-IIPs was well-described by the Langmuir isotherm model, and it was likely to be a monolayer chemical adsorption. This conclusion was also confirmed by the thermodynamic parameters. Moreover, the adsorption kinetics indicated that the adsorption rate would be controlled jointly by the intraparticle diffusion and the inner surface adsorption process, and the latter process was generally associated with the formation and breaking of chemical bonds. Finally, the effects of different morphologies of the Ag-IIPs for Ag(+) adsorption were also investigated. In aqueous solution, the adsorptivity of the Ag(+) ion-imprinting single-hole hollow particles (Ag-IISHPs) for Ag(+) was highest (80.5 mg g(-1)) because of a specific morphology that features a single hole in the shell. In an oil-water mixture, Ag(+) in the water phase could be adsorbed efficiently by the Ag(+) ion-imprinting Janus hollow particles (Ag-IIJHPs), with emulsifiability originating from the Janus structure.

  19. 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.

  20. 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.

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

    SciTech Connect

    Manley, N.B.

    1988-01-01

    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. The decrease in the values of the labeling indices 1 week after charged particle irradiation was dose- and ion-dependent. Mitotic indices 1 week after 10 and 25 Gy helium and after 10 Gy neon were the same as those seen in the control mice. Analysis of cell kinetics 1 week after 10 Gy helium and 10 Gy neon irradiation suggests the presence of a progenitor subpopulation that is proliferating with a shorter cell cycle. Comparison of the responses to the different charged particle beams indicates that neon ions are more effective in producing direct cellular damage than the helium ions, but the surviving proliferating cells several divisions later continue to maintain active cell renewal. Based on the 1 week post-irradiation H{sup 3}-TdR labeling indices, a rough estimate of the RBE for neon ions is at least 2.5 when compared to helium ions.

  2. Kinetic modeling of auroral ion Outflows observed by the VISIONS sounding rocket

    NASA Astrophysics Data System (ADS)

    Albarran, R. M.; Zettergren, M. D.; Rowland, D. E.; Klenzing, J.; Clemmons, J. H.

    2016-12-01

    The VISIONS (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) sounding rocket was launched on Feb. 7, 2013 at 8:21 UTC from Poker Flat, Alaska, into an auroral substorm with the objective of identifying the drivers and dynamics of the ion outflow below 1000km. Energetic ion data from the VISIONS polar cap boundary crossing show evidence of an ion "pressure cooker" effect whereby ions energized via transverse heating in the topside ionosphere travel upward and are impeded by a parallel potential structure at higher altitudes. VISIONS was also instrumented with an energetic neutral atom (ENA) detector which measured neutral particles ( 50-100 eV energy) presumably produced by charge-exchange with the energized outflowing ions. Hence, inferences about ion outflow may be made via remotely-sensing measurements of ENAs. This investigation focuses on modeling energetic outflowing ion distributions observed by VISIONS using a kinetic model. This kinetic model traces large numbers of individual particles, using a guiding-center approximation, in order to allow calculation of ion distribution functions and moments. For the present study we include mirror and parallel electric field forces, and a source of ion cyclotron resonance (ICR) wave heating, thought to be central to the transverse energization of ions. The model is initiated with a steady-state ion density altitude profile and Maxwellian velocity distribution characterizing the initial phase-space conditions for multiple particle trajectories. This project serves to advance our understanding of the drivers and particle dynamics in the auroral ionosphere and to improve data analysis methods for future sounding rocket and satellite missions.

  3. Ion source studies for particle beam accelerators

    SciTech Connect

    Bieg, K.W.; Burns, E.J.T.; Olsen, J.N.; Dorrell, L.R.

    1985-05-01

    High power particle beam accelerators are being developed for use in inertial confinement fusion applications. These pulsed power accelerators require sources of low atomic number ions (e.g., protons, deuterons, carbon, or lithium). The sources must be of high purity for efficient accelerator operation and proper target coupling, must have a rapid ''turn-on,'' and must be compatible with ion diode configurations under development. A particular type of source presently being investigated is the flashover ion source which generates ions by means of the vacuum flashover of an insulating anode material when the high voltage pulse arrives at the diode. We have developed an applied-magnetic-field, extraction ion diode for the 0.03 TW Nereus accelerator specifically to investigate these sources. Extracted ion species are measured by means of a Thomson-parabola ion analyzer, dB/dt current monitors, and Faraday cups. Experiments have been performed to investigate the surface flashover mechanism and the effects of various dielectric source materials, anode preparation methods (including rf glow discharge cleaning), and vacuum conditions on ion species and diode operation.

  4. 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.

  5. Two-dimensional implosion simulations with a kinetic particle code

    NASA Astrophysics Data System (ADS)

    Sagert, I.; Even, W. P.; Strother, T. T.

    2017-05-01

    We perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focus on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.

  6. Janus particle rotator-to-lamellar nucleation and growth kinetics

    NASA Astrophysics Data System (ADS)

    Beltran-Villegas, Daniel J.; Zhang, Yulei; Larson, Ronald G.

    2017-03-01

    We determine the free energy barrier, critical nucleus size, and kinetics of a Janus particle solid-solid transition by nucleation and growth of lamellar clusters within a metastable rotator phase. The transition involves negligible change in particle position and phase volume and entails only particle orientational ordering. Fast kinetics enable the analysis of unbiased crystal growth and shrinkage trajectories from Brownian dynamic simulations. By fitting simulation trajectories to a diffusion-migration equation, the nucleus free energy and growth coefficient as a function of nucleus size are extracted. Observed transition times are on the order of hundreds of characteristic particle rotation times. Lamellar crystal nuclei are oblate rather than spherical, but otherwise classical nucleation theory applies, with the bulk free energy contribution following closely the Maier-Saupe theory for purely orientational transitions and the interfacial energy contribution following trends from 3-dimensional Ising spin kinetics.

  7. Two-dimensional implosion simulations with a kinetic particle code [2D implosion simulations with a kinetic particle code

    DOE PAGES

    Sagert, Irina; Even, Wesley Paul; Strother, Terrance Timothy

    2017-05-17

    Here, we perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focusmore » on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.« less

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

    PubMed

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

    2013-10-01

    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. The particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic. Conversely, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drugs. 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 article. A large portion of this article deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: (i) the physical characteristics of particles, (ii) particle behavior in gas flow, and (iii) 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 article concludes with a summary and a brief discussion of areas of future research.

  9. 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

  10. Fishbone mode excitation in the ion kinetic regime

    SciTech Connect

    Shi, B.; Sui, G. |

    1997-08-01

    By solving the dispersion relation in the ion kinetic regime, it is found that the threshold of the plasma beta value for exciting the ion-fishbone mode is lowered. Thus, for most of the present-day tokamaks where the Bussac criterion [Bussac {ital et al.}, Phys. Rev. Lett. {bold 35}, 1638 (1975)] is not satisfied, it will still be possible to excite the ion-fishbone mode. {copyright} {ital 1997 American Institute of Physics.}

  11. Nonexponential kinetics of ion pair dissociation in electrofreezing water.

    PubMed

    Alaghemandi, Mohammad; Koller, Volkmar; Green, Jason R

    2017-10-04

    Temporally- or spatially-heterogeneous environments can participate in many kinetic processes, from chemical reactions and self-assembly to the forced dissociation of biomolecules. Here, we simulate the molecular dynamics of a model ion pair forced to dissociate in an explicit, aqueous solution. Triggering dissociation with an external electric field causes the surrounding water to electrofreeze and the ion pair population to decay nonexponentially. To further probe the role of the aqueous environment in the kinetics, we also simulate dissociation events under a purely mechanical force on the ion pair. In this case, regardless of whether the surrounding water is a liquid or already electrofrozen, the ion pair population decays exponentially with a well-defined rate constant that is specific to the medium and applied force. These simulation data, and the rate parameters we extract, suggest the disordered kinetics in an electrofreezing medium are a result of the comparable time scales of two concurrent processes, electrofreezing and dissociation.

  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. Clustering of low-valence particles: structure and kinetics.

    PubMed

    Markova, Olga; Alberts, Jonathan; Munro, Edwin; Lenne, Pierre-François

    2014-08-01

    We compute the structure and kinetics of two systems of low-valence particles with three or six freely oriented bonds in two dimensions. The structure of clusters formed by trivalent particles is complex with loops and holes, while hexavalent particles self-organize into regular and compact structures. We identify the elementary structures which compose the clusters of trivalent particles. At initial stages of clustering, the clusters of trivalent particles grow with a power-law time dependence. Yet at longer times fusion and fission of clusters equilibrates and clusters form a heterogeneous phase with polydispersed sizes. These results emphasize the role of valence in the kinetics and stability of finite-size clusters.

  14. Kinetic energy distributions of ions after surface collisions

    SciTech Connect

    Short, R.T.; Todd, P.J.; Grimm, C.C.

    1991-01-01

    As a part of the development of an organic ion microprobe, to be used for imaging of particular organic compounds in biological tissue, various methods of quadrupole-based tandem mass spectroscopy (MS/MS) have been investigated. High transmission efficiency is essential for the success of the organic ion microprobe, due to expected low analyte concentrations in biological tissue and the potential for sample damage from prolonged exposure to the primary ion beam. MS/MS is necessary for organic ion imaging because of the complex nature of the biological matrices. The goal of these studies of was to optimize the efficiency of daughter ion production and transmission by first determining daughter ion properties and then designing ion optics based on those properties. The properties of main interest are daughter ion kinetic energy and angular distribution. 1 fig.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

    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 envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope 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. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. We believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilites in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented.

  2. 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

  3. 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

  4. Impact of particle formation on atmospheric ions and particle number concentrations in an urban environment

    NASA Astrophysics Data System (ADS)

    Cheung, H. C.; Chou, C. C.-K.; Jayaratne, E. R.; Morawska, L.

    2015-04-01

    A measurement campaign was conducted from 3 to 19 December 2012 at an urban site of Brisbane, Australia. Size distribution of ions and particle number concentrations were measured to investigate the influence of particle formation and biomass burning on atmospheric ion and particle concentrations. Overall ion and particle number concentrations during the measurement period were found to be (- 1.2 × 103 cm- 3 | + 1.6 × 103 cm- 3) and 4.4 × 103, respectively. The results of correlation analysis between concentrations of ions and nitrogen oxides indicated that positive and negative ions originated from similar sources, and that vehicle exhaust emissions had a more significant influence on intermediate/large ions, while cluster ions rapidly attached to larger particles once emitted into the atmosphere. Diurnal variations in ion concentration suggested the enrichment of intermediate and large ions on new particle formation event days, indicating that they were involved in the particle formation processes. Elevated total ions, particularly larger ions, and particle number concentrations were found during biomass burning episodes. This could be due to the attachment of cluster ions onto accumulation mode particles or production of charged particles from biomass burning, which were in turn transported to the measurement site. The results of this work enhance scientific understanding of the sources of atmospheric ions in an urban environment, as well as their interactions with particles during particle formation processes.

  5. Inflight Particle Behavior in the Vacuum Kinetic Spray Process

    NASA Astrophysics Data System (ADS)

    Park, Hyungkwon; Kwon, Hansol; Lee, Changhee

    2017-08-01

    The vacuum kinetic spray (VKS) process, also-called aerosol deposition, is a promising spray technology by which a thin or thick film can be fabricated at room temperature. Although a number of relevant studies have been performed, almost all have focused on the development of various applications, and unfortunately, the deposition mechanism has not yet been clarified. In this respect, the particle velocity in the flow field in VKS is investigated as a first stage of research into the VKS deposition mechanism. In this research, after a simulation prototype was derived based on the experimental results, the particle average and impact velocities were estimated. In addition, the change in particle velocities with gas flow rates, particle size, and working distance was analyzed based on simulation analyses and microstructural evidence. As a result, the gas flow rate, particle size, and working distance affect the particle impact velocity and further deposition behavior and film microstructure.

  6. Inflight Particle Behavior in the Vacuum Kinetic Spray Process

    NASA Astrophysics Data System (ADS)

    Park, Hyungkwon; Kwon, Hansol; Lee, Changhee

    2017-10-01

    The vacuum kinetic spray (VKS) process, also-called aerosol deposition, is a promising spray technology by which a thin or thick film can be fabricated at room temperature. Although a number of relevant studies have been performed, almost all have focused on the development of various applications, and unfortunately, the deposition mechanism has not yet been clarified. In this respect, the particle velocity in the flow field in VKS is investigated as a first stage of research into the VKS deposition mechanism. In this research, after a simulation prototype was derived based on the experimental results, the particle average and impact velocities were estimated. In addition, the change in particle velocities with gas flow rates, particle size, and working distance was analyzed based on simulation analyses and microstructural evidence. As a result, the gas flow rate, particle size, and working distance affect the particle impact velocity and further deposition behavior and film microstructure.

  7. 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…

  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. Gyro-Kinetic Electron and Fully-Kinetic Ion Simulations of Fast Magnetosonic Waves in the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, X.; Liu, K.; Wang, X.; Min, K.; Lin, Y.

    2016-12-01

    Two-dimensional simulations using a gyro-kinetic electron and fully-kinetic ion (GeFi) scheme are preformed to study the excitation of fast magnetosonic waves in the magnetosphere, which arise from the ion Bernstein instability driven by ring-like proton velocity distributions (with a positive slope with respect to the perpendicular velocity). Since both ion and electron kinetics are relevant, particle-in-cell (PIC) simulations have often been employed to study the wave excitation. However, such simulations are limited to reduced ion-to-electron mass ratio (mi/me) and light-to-Alfvén speed ratio (c/VA) due to the computationally expensive nature of PIC codes. The present study exploits a GeFi scheme that can break through these limitations and use larger/more realistic mi/me and c/VA. The capability of the GeFi code in simulating the ion Bernstein instability is first demonstrated by comparing a GeFi simulation using reduced mass ratio (mi/me=100) and speed ratio (c/VA=15) to a corresponding PIC simulation. A realistic speed ratio (c/VA=400) and a larger mass ratio (mi/me=400) are then adopted in the GeFi code to explore how the results vary. It is shown that the increased mi/me and c/VA lead to a larger lower hybrid frequency and allow waves to arise at more ion cyclotron harmonics, consistent with the general prediction of linear dispersion theory.

  11. 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

  12. The cleft ion fountain - A two-dimensional kinetic model

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.; Lockwood, M.

    1985-01-01

    The transport of ionospheric ions from a source in the polar cleft ionosphere through the polar magnetosphere is investigated using a two-dimensional, kinetic, trajectory-based code. The transport model includes the effects of gravitation, longitudinal magnetic gradient force, convection electric fields, and parallel electric fields. Individual ion trajectories as well as distribution functions and resulting bulk parameters of density, parallel average energy, and parallel flux for a presumed cleft ionosphere source distribution are presented for various conditions to illustrate parametrically the dependences on source energies, convection electric field strengths, ion masses, and parallel electric field strengths. The essential features of the model are consistent with the concept of a cleft-based ion fountain supplying ionospheric ions to the polar magnetosphere, and the resulting plasma distributions and parameters are in general agreement with recent low-energy ion measurements from the DE 1 satellite.

  13. Sorption kinetics of ofloxacin in soils and mineral particles.

    PubMed

    Pan, Bo; Wang, Peng; Wu, Min; Li, Jing; Zhang, Di; Xiao, Di

    2012-12-01

    The environmental behavior of antibiotics is not well known and the precise environmental risk assessment is not practical. This study investigated the sorption kinetics of ofloxacin, a widely used antibiotics, on soil particles with different organic carbon contents as well as soil components (a humic acid, ferric oxide and kaolinite). Two-compartment sorption kinetics were mathematically recognized (except ferric oxide because of its very fast sorption). The apparent sorption rate and the contribution of fast sorption compartment decreased with the increased organic carbon content with the exception of humic acid, suggesting that the slow sorption sites were partially located in organo-mineral complex. The OFL concentration-dependent sorption kinetics suggested that the slow sorption compartment was not controlled by diffusion process as indicated by slower sorption at higher OFL loading. The difference between OFL sorption kinetics and those of hydrophobic organic contaminants was discussed and possible mechanism of OFL two-compartment sorption was proposed.

  14. 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.

  15. Analytical solutions for coagulation and condensation kinetics of composite particles

    NASA Astrophysics Data System (ADS)

    Piskunov, Vladimir N.

    2013-04-01

    The processes of composite particles formation consisting of a mixture of different materials are essential for many practical problems: for analysis of the consequences of accidental releases in atmosphere; for simulation of precipitation formation in clouds; for description of multi-phase processes in chemical reactors and industrial facilities. Computer codes developed for numerical simulation of these processes require optimization of computational methods and verification of numerical programs. Kinetic equations of composite particle formation are given in this work in a concise form (impurity integrated). Coagulation, condensation and external sources associated with nucleation are taken into account. Analytical solutions were obtained in a number of model cases. The general laws for fraction redistribution of impurities were defined. The results can be applied to develop numerical algorithms considerably reducing the simulation effort, as well as to verify the numerical programs for calculation of the formation kinetics of composite particles in the problems of practical importance.

  16. The kinetics of composite particle formation during mechanical alloying

    NASA Technical Reports Server (NTRS)

    Aikin, B. J. M.; Courtney, T. H.

    1993-01-01

    The kinetics of composite particle formation during attritor milling of insoluble binary elemental powders have been examined. The effects of processing conditions (i.e., mill power, temperature, and charge ratio) on these kinetics were studied. Particle size distributions and fractions of elemental and composite particles were determined as functions of milling time and processing conditions. This allowed the deduction of phenomenological rate constants describing the propensity for fracture and welding during processing. For the mill-operating conditions investigated, the number of particles in the mill generally decreased with milling time, indicating a greater tendency for particle welding than fracture. Moreover, a bimodal size distribution is often obtained as a result of preferential welding. Copper and chromium 'alloy' primarily by encapsulation of Cr particles within Cu. This form of alloying also occurs in Cu-Nb alloys processed at low mill power and/or for short milling times. For other conditions, however, Cu-Nb alloys develop a lamellar morphology characteristic of mechanically alloyed two-phase ductile metals. Increasing mill power or charge (ball-to-powder weight) ratio (CR) increases the rate of composite particle formation.

  17. Kinetic treatment of nonlinear ion-acoustic waves in multi-ion plasma

    NASA Astrophysics Data System (ADS)

    Ahmad, Zulfiqar; Ahmad, Mushtaq; Qamar, A.

    2017-09-01

    By applying the kinetic theory of the Valsove-Poisson model and the reductive perturbation technique, a Korteweg-de Vries (KdV) equation is derived for small but finite amplitude ion acoustic waves in multi-ion plasma composed of positive and negative ions along with the fraction of electrons. A correspondent equation is also derived from the basic set of fluid equations of adiabatic ions and isothermal electrons. Both kinetic and fluid KdV equations are stationary solved with different nature of coefficients. Their differences are discussed both analytically and numerically. The criteria of the fluid approach as a limiting case of kinetic theory are also discussed. The presence of negative ion makes some modification in the solitary structure that has also been discussed with its implication at the laboratory level.

  18. Differential kinetic dynamics and heating of ions in the turbulent solar wind

    NASA Astrophysics Data System (ADS)

    Valentini, F.; Perrone, D.; Stabile, S.; Pezzi, O.; Servidio, S.; De Marco, R.; Marcucci, F.; Bruno, R.; Lavraud, B.; De Keyser, J.; Consolini, G.; Brienza, D.; Sorriso-Valvo, L.; Retinò, A.; Vaivads, A.; Salatti, M.; Veltri, P.

    2016-12-01

    The solar wind plasma is a fully ionized and turbulent gas ejected by the outer layers of the solar corona at very high speed, mainly composed by protons and electrons, with a small percentage of helium nuclei and a significantly lower abundance of heavier ions. Since particle collisions are practically negligible, the solar wind is typically not in a state of thermodynamic equilibrium. Such a complex system must be described through self-consistent and fully nonlinear models, taking into account its multi-species composition and turbulence. We use a kinetic hybrid Vlasov-Maxwell numerical code to reproduce the turbulent energy cascade down to ion kinetic scales, in typical conditions of the uncontaminated solar wind plasma, with the aim of exploring the differential kinetic dynamics of the dominant ion species, namely protons and alpha particles. We show that the response of different species to the fluctuating electromagnetic fields is different. In particular, a significant differential heating of alphas with respect to protons is observed. Interestingly, the preferential heating process occurs in spatial regions nearby the peaks of ion vorticity and where strong deviations from thermodynamic equilibrium are recovered. Moreover, by feeding a simulator of a top-hat ion spectrometer with the output of the kinetic simulations, we show that measurements by such spectrometer planned on board the Turbulence Heating ObserveR (THOR mission), a candidate for the next M4 space mission of the European Space Agency, can provide detailed three-dimensional ion velocity distributions, highlighting important non-Maxwellian features. These results support the idea that future space missions will allow a deeper understanding of the physics of the interplanetary medium.

  19. 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.

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

    SciTech Connect

    Rubab, N.; Jaffer, G.

    2016-05-15

    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.

  1. RNA folding: structure prediction, folding kinetics and ion electrostatics.

    PubMed

    Tan, Zhijie; Zhang, Wenbing; Shi, Yazhou; Wang, Fenghua

    2015-01-01

    Beyond the "traditional" functions such as gene storage, transport and protein synthesis, recent discoveries reveal that RNAs have important "new" biological functions including the RNA silence and gene regulation of riboswitch. Such functions of noncoding RNAs are strongly coupled to the RNA structures and proper structure change, which naturally leads to the RNA folding problem including structure prediction and folding kinetics. Due to the polyanionic nature of RNAs, RNA folding structure, stability and kinetics are strongly coupled to the ion condition of solution. The main focus of this chapter is to review the recent progress in the three major aspects in RNA folding problem: structure prediction, folding kinetics and ion electrostatics. This chapter will introduce both the recent experimental and theoretical progress, while emphasize the theoretical modelling on the three aspects in RNA folding.

  2. Kinetics of small single particle combustion of zirconium alloy

    SciTech Connect

    Wei Haoyan; Yoo, Choong-Shik

    2012-01-15

    We present quantitative kinetic information regarding small, 1-10 {mu}m in diameter, single particle combustion of Zr-rich metal alloy foils subjected to either mechanical impacts or laser-ablation. The lights from combustion of metal fragments were recorded on a high-speed camera. The particle size was determined by the motion analysis of individual particle trajectory based on an aerodynamic drag law and further verified by the microstructure and chemical composition analysis of recovered post-burn particles. The measured particle sizes show a log-normal distribution centered at around 3.1 {mu}m in diameter, and the composition of recovered particles is that of fully oxidized ZrO{sub 2}. The temperature evolution of each particle along the space/time-trajectory is determined based on the thermal emission from combustion using a single-color photographic spectro-pyrometry. The result indicates that the particle has reached the maximum combustion temperature of 4000 K, well beyond the melting temperature of ZrO{sub 2}, and undergone the solidification of molten ZrO{sub 2} during the cooling stage. It also shows that the maximum combustion temperature decreases linearly with increasing the particle diameter, following the correlation t aD{sup 1.5-1.8} between the burn time (t) and the particle diameter (D). Combining the particle size, the burn time, and the particle temperature, both temperature and mass burn rates are obtained as a function of particle size. As the particle size increases, the temperature burn rate decreases, whereas the mass burn rate goes in the opposite direction.

  3. A non-Maxwellian kinetic approach for charging of dust particles in discharge plasmas

    NASA Astrophysics Data System (ADS)

    Alexandrov, A. L.; Schweigert, I. V.; Peeters, F. M.

    2008-09-01

    Nanoparticle charging in a capacitively coupled radio frequency discharge in argon is studied using a particle in cell Monte Carlo collisions method. The plasma parameters and dust potential were calculated self-consistently for different unmovable dust profiles. A new method for definition of the dust floating potential is proposed, based on the information about electron and ion energy distribution functions, obtained during the kinetic simulations. This approach provides an accurate balance of the electron and ion currents on the dust particle surface and allows us to precisely calculate the dust floating potential. A comparison of the obtained floating potentials with the results of the traditional orbital motion limit (OML) theory shows that in the presence of the ion resonant charge exchange collisions, even when the OML approximation is valid, its results are correct only in the region of a weak electric field, where the ion drift velocity is much smaller than the thermal one. With increasing ion drift velocity, the absolute value of the calculated dust potential becomes significantly smaller than the theory predicts. This is explained by a non-Maxwellian shape of the ion energy distribution function for the case of fast ion drift.

  4. 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

  5. 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.

  6. 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.

  7. Quantum kinetics and thermalization in a particle bath model.

    PubMed

    Alamoudi, S M; Boyanovsky, D; de Vega, H J

    1999-07-01

    We study the dynamics of relaxation and thermalization in an exactly solvable model of a particle interacting with a harmonic oscillator bath. Our goal is to understand the effects of non-Markovian processes on the relaxational dynamics and to compare the exact evolution of the distribution function with approximate Markovian and non-Markovian quantum kinetics. There are two different cases that are studied in detail: (i) a quasiparticle (resonance) when the renormalized frequency of the particle is above the frequency threshold of the bath and (ii) a stable renormalized "particle" state below this threshold. The time evolution of the occupation number for the particle is evaluated exactly using different approaches that yield to complementary insights. The exact solution allows us to investigate the concept of the formation time of a quasiparticle and to study the difference between the relaxation of the distribution of bare particles and that of quasiparticles. For the case of quasiparticles, the exact occupation number asymptotically tends to a statistical equilibrium distribution that differs from a simple Bose-Einstein form as a result of off-shell processes whereas in the stable particle case, the distribution of particles does not thermalize with the bath. We derive a non-Markovian quantum kinetic equation which resums the perturbative series and includes off-shell effects. A Markovian approximation that includes off-shell contributions and the usual Boltzmann equation (energy conserving) are obtained from the quantum kinetic equation in the limit of wide separation of time scales upon different coarse-graining assumptions. The relaxational dynamics predicted by the non-Markovian, Markovian, and Boltzmann approximations are compared to the exact result. The Boltzmann approach is seen to fail in the case of wide resonances and when threshold and renormalization effects are important.

  8. Fluid and kinetic models of negative ion sheaths

    SciTech Connect

    Cavenago, M.

    2011-09-26

    Due to the presence of a large transverse magnetic field (B{sub x} and B{sub y} where z is the extraction axis), the extraction of electrons from a negative ion source is likely to happen with a large angle with respect to z axis. The negative ion and electron sheaths are here studied both with kinetic and with fluid models. First, Vlasov-Poisson models are reduced to one dimensional integrodifferential equations, discussing also trapped orbits. The integrodifferential equations for electron transport are analytically solved for a variety of extraction potentials (in 1D). Collision frequency dependency from electron flow speed and temperature is discussed. Then both ion and electron space charge and fluid motion are solved, using electron densities expression consistent with kinetic model. Results for the sheath charge profile and extraction field as a function of B{sub x} are shown.

  9. Ion and velocity map imaging for surface dynamics and kinetics

    NASA Astrophysics Data System (ADS)

    Harding, Dan J.; Neugebohren, Jannis; Hahn, Hinrich; Auerbach, D. J.; Kitsopoulos, T. N.; Wodtke, Alec M.

    2017-07-01

    We describe a new instrument that uses ion imaging to study molecular beam-surface scattering and surface desorption kinetics, allowing independent determination of both residence times on the surface and scattering velocities of desorbing molecules. This instrument thus provides the capability to derive true kinetic traces, i.e., product flux versus residence time, and allows dramatically accelerated data acquisition compared to previous molecular beam kinetics methods. The experiment exploits non-resonant multiphoton ionization in the near-IR using a powerful 150-fs laser pulse, making detection more general than previous experiments using resonance enhanced multiphoton ionization. We demonstrate the capabilities of the new instrument by examining the desorption kinetics of CO on Pd(111) and Pt(111) and obtain both pre-exponential factors and activation energies of desorption. We also show that the new approach is compatible with velocity map imaging.

  10. Ion Dynamics during Substorm Events Modeled with Coupled Global MHD and Kinetic Models

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Ashour-Abdalla, M.; Walker, R. J.; El-Alaoui, M.

    2014-12-01

    We have studied ion dynamics during a substorm by using a coupled fluid-kinetic approach. The UCLA global magnetospheric model was applied first and its results in a region encompassing a magnetotail reconnection site and earthward propagating dipolarization fronts was selected as input state for a full kinetic simulation based on the iPic3D code [1]. The coupling is one-way: the MHD result is used to create a full kinetic initial state by using the approach described by [2] and to force the boundary conditions. The kinetic results are not fed back into the MHD run. This approach previously has been shown [3] to provide correctly the large scale picture for a kinetic approach when the duration of the kinetic run is not so long as to alter significantly the macroscopic state captured by MHD. Here we focus especially on the ions. The electrons were described in [3]. Three aspects are analyzed. First, the ions are accelerated during the event and we track the localization of the energy exchanged, separating the contributions to the directed energy and those to the thermal energy. Second, we consider the ion motion to identify the regions where the finite Larmor radius effects violate the drift approximation and the frozen-in condition, thereby identifying the ion diffusion region. Our approach follows individual electrons and ions fully kinetically and no approximation is made in the particle orbit, so our code is equipped to study accurately the regions where the drift approximation is valid. Finally, we consider the ion distribution as a possible source of instabilities, focusing especially on temperature anisotropy instabilities and on the firehose instability. The novelty of the approach is this kinetic study is done for a specific substorm by using the global state of the magnetosphere as provided by a global MHD simulation. This differs sharply from previous approaches based on analytical approximations such as the Harris or the (quasi)-parabolic equilibria. [1

  11. 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.

  12. A bounce-averaged kinetic model of the ring current ion population

    NASA Technical Reports Server (NTRS)

    Jordanova, V. K.; Kozyra, J. U.; Khazanov, G. V.; Nagy, A. F.; Rasmussen, C. E.; Fok, M.-C.

    1994-01-01

    A bounced-averaged ring current kinetic model for arbitrary pitch angle, including losses due to charge exchange and Coulomb collisions along ion drift paths, is developed and solved numerically. Results from simplifield model runs, intended to illustrate the effects of adiabatic drifts and collisional losses on the proton population, are presented. The processes of: (1) particle acceleration under the conditions of time-independent magnetospheric electric fields; (2) a predominant loss of particles with small pitch angles due to charge exchange; and (3) a buildup of a low-energy population caused by the Coulomb drag energy degradation, are discussed.

  13. A kinetic electron-neutral collision model for particle-in-cell plasma simulation

    NASA Astrophysics Data System (ADS)

    Pointon, Timothy; Cartwright, Keith

    2014-10-01

    Details of a kinetic electron-neutral collision model for particle-in-cell plasma simulation codes are presented. The model uses an efficient scheme to randomly select collision events - elastic, excitation and ionization - with the appropriate probability Ionization events create electron-ion pairs, and the secondary electrons can themselves ionize the gas. To maintain a manageable particle count, a particle merger algorithm can be used to periodically replace all particles of a given species in a cell with a new, smaller set that conserves charge, momentum, and energy Small-scale tests show that results with the merger are in good agreement with non-merged runs. Large simulations can only be done with the merger on, and typically show excellent merger efficiency (>90%). Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. DOE's NNSA under Contract DE-AC04-94-AL85000.

  14. Shock wave, fluid instability and implosion studies with a kinetic particle approach

    NASA Astrophysics Data System (ADS)

    Sagert, Irina; Even, Wesley P.; Strother, Terrance T.

    2016-10-01

    Many problems in laboratory plasma physics are subject to flows that move between the continuum and the kinetic regime. The correct description of these flows is crucial in order to capture their impact on the system's dynamical evolution. Examples are capsule implosions in inertial confinement fusion (ICF). Although their dynamics is predominantly shaped by shock waves and fluid instabilities, non-equilibrium flows in form of deuterium/tritium ions have been shown to play a significant role. We present recent studies with our Monte Carlo kinetic particle code that is designed to capture continuum and kinetic flows in large physical systems with possible applications in ICF studies. Discussed results will include standard shock wave and fluid instability tests and simulations that are adapted towards future ICF studies with comparisons to hydrodynamic simulations. This work used the Wolf TriLAB Capacity Cluster at LANL. I.S. acknowledges support through a Director's fellowship (20150741PRD3) from Los Alamos National Laboratory.

  15. 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.

  16. Kinetics of silica particle formation in nonionic W/O microemulsions from TEOS

    SciTech Connect

    Chang, C.L.; Fogler, H.S.

    1996-11-01

    The kinetics of silica particle formation by the ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil (W/O) microemulsions containing a nonionic surfactant was investigated using Fourier-transform infrared spectroscopy, transmission electron microscopy, and light-scattering techniques. The results show that TEOS hydrolysis and silica-particle growth occur at the same rate, indicating the growth of silica particles is rate-controlled by the hydrolysis of TEOS. The rate of TEOS hydrolysis in microemulsions is first order with respect to the concentration of aqueous ammonia (29 wt. % NH{sub 3}), but depends weakly on the concentration of water. Based on the fact that TEOS hydrolysis follows a nucleophilic substitution of the TEOS`s ethoxy group with hydroxyl ion, the kinetic data suggest that both water and ammonia remain predominantly in W/O microemulsion droplets. The rate of TEOS hydrolysis also depends on the surfactant concentration that controls the molecular contact between hydroxyl ions and TEOS in the solution. Due to the reaction-controlled growth mechanism, the silica-particle size distribution retains virtually the same shape over the growth period. The final average size of silica particles can be varied from 26 to 43 nm by adjusting concentrations of water and surfactant. Increasing the water concentration decreases the average size and uniformity of silica particles. For a given water concentration, the smallest and most uniform silica particles are produced at intermediate water-to-surfactant molar ratios (about 1.9). The results are discussed in terms of the effect of water concentration on the stability of the hydrolyzed silica reacting species during the nucleation of particles and of the water-to-surfactant molar ratio on the compartmentalization of silica species in microemulsions.

  17. 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.

  18. 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

    2017-05-01

    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.

  19. Ion kinetic scale in the solar wind observed.

    PubMed

    Śafránková, Jana; Němeček, Zdeněk; Přech, Lubomír; Zastenker, Georgy N

    2013-01-11

    This Letter shows the first results from the solar wind monitor onboard the Spektr-R spacecraft which measures plasma moments with a time resolution of 31 ms. This high-time resolution allows us to make direct observations of solar wind turbulence below ion kinetic length scales. We present examples of the frequency spectra of the density, velocity, and thermal velocity. Our study reveals that although these parameters exhibit the same behavior at the magnetohydrodynamic scale, their spectra are remarkably different at the kinetic scale.

  20. Inelastic processes in ion/surface collisions: Direct recoil ion fractions as a function of kinetic energy

    NASA Astrophysics Data System (ADS)

    Rabalais, J. Wayne; Chen, Jie-Nan

    1986-09-01

    Time-of-flight (TOF) spectra of the scattered and recoiled particles resulting from 1-10 keV Ar+ ions impingent on surfaces of MgO, Mg(OH)2, graphite, Si, and SiO2 have been obtained. Measurements of directly recoiled (DR) neutrals plus ions and neutrals only are used to calculate positive and negative ion fractions Y+,- from DR events. These positive and negative ion yields observed for DR of H, C, O, and Si have distinctly different behavior as a function of ion kinetic energy. The Y+ values exhibit a ``threshold-type'' behavior with a steep rise followed by a slowly rising or plateau region at higher energy. The Y- values exhibit a maximum in the low energy region followed by a decreasing yield as energy increases. The Y-/Y+ ratio for C and O is very sensitive to the amount of hydrogen present, with the Y+ yields dropping as hydrogen concentration increases. The recently developed model for electronic transitions in keV ion/surface collisions which considers Auger and resonant transitions along the ion trajectory and electron promotions in the quasidiatomic molecule of the close atomic encounter is extended to include DR events. Analytical expressions for Y+,- are derived for the case of surface atoms in positive, neutral, and negative bonding environments. These model expressions are fitted to the experimental data, allowing determination of the probabilities of ionization in the close atomic encounter and of electron capture along the outgoing trajectory.

  1. Global simulation of field-reversed configuration using fully kinetic ion and drift kinetic electron

    NASA Astrophysics Data System (ADS)

    Lau, Calvin; Fulton, Daniel; Kuley, Animesh; Bao, Jian; Lin, Zhihong; Binderbauer, Michael; Tajima, Toshiki; Schmitz, Lothar; the TAE Team Team

    2016-10-01

    In the last several years, the C-2/C-2U advanced beam-driven field-reversed configuration (FRC) experiments at Tri Alpha Energy have progressed to consistent, reproducible plasma lifetimes of 10+ ms, i.e. FRCs have reached transport limited regimes. In FRC geometry, the thermal ion gyroradius is on the order of the size of the plasma near the magnetic null-point. Fast ion orbits intersect both the FRC core and the scrape-off layer (SOL) regions. Previous local simulations of electrostatic drift-wave instabilities using the Gyrokinetic Toroidal Code (GTC) find the core to be robustly stable with driftwave instability only in the SOL at frequencies approaching the ion cyclotron frequency. Therefore, FRC transport studies require fully kinetic ion simulations with cross-separatrix coupling between the core and SOL. Here we report progress of such global simulations using fully kinetic ions and drift kinetic electrons, including the implementation of the Boris push scheme for cyclotron motion and cylindrical coordinates for the separatrix. Supported by the Norman Rostoker Fellowship.

  2. Estimation of ion channel kinetics from fluctuations of macroscopic currents.

    PubMed

    Moffatt, Luciano

    2007-07-01

    For single channel recordings, the maximum likelihood estimation (MLE) of kinetic rates and conductance is well established. A direct extrapolation of this method to macroscopic currents is computationally prohibitive: it scales as a power of the number of channels. An approximated MLE that ignored the local time correlation of the data has been shown to provide estimates of the kinetic parameters. In this article, an improved approximated MLE that takes into account the local time correlation is proposed. This method estimates the channel kinetics using both the time course and the random fluctuations of the macroscopic current generated by a homogeneous population of ion channels under white noise. It allows arbitrary kinetic models and stimulation protocols. The application of the proposed algorithm to simulated data from a simple three-state model on nonstationary conditions showed reliable estimates of all the kinetic constants, the conductance and the number of channels, and reliable values for the standard error of those estimates. Compared to the previous approximated MLE, it reduces by a factor of 10 the amount of data needed to secure a given accuracy and it can even determine the kinetic rates in macroscopic stationary conditions.

  3. Estimation of Ion Channel Kinetics from Fluctuations of Macroscopic Currents

    PubMed Central

    Moffatt, Luciano

    2007-01-01

    For single channel recordings, the maximum likelihood estimation (MLE) of kinetic rates and conductance is well established. A direct extrapolation of this method to macroscopic currents is computationally prohibitive: it scales as a power of the number of channels. An approximated MLE that ignored the local time correlation of the data has been shown to provide estimates of the kinetic parameters. In this article, an improved approximated MLE that takes into account the local time correlation is proposed. This method estimates the channel kinetics using both the time course and the random fluctuations of the macroscopic current generated by a homogeneous population of ion channels under white noise. It allows arbitrary kinetic models and stimulation protocols. The application of the proposed algorithm to simulated data from a simple three-state model on nonstationary conditions showed reliable estimates of all the kinetic constants, the conductance and the number of channels, and reliable values for the standard error of those estimates. Compared to the previous approximated MLE, it reduces by a factor of 10 the amount of data needed to secure a given accuracy and it can even determine the kinetic rates in macroscopic stationary conditions. PMID:17416622

  4. Kinetics of ice particles growth in the polar summer mesosphere

    NASA Astrophysics Data System (ADS)

    Zasetsky, A. Y.; Petelina, S. V.

    2009-05-01

    The growth kinetics of ice particles in the polar summer mesosphere is discussed. The particle growth time is calculated using the temperature, water vapor density, and ice number density simultaneously measured by the infrared Fourier Transform Spectrometer on the Atmospheric Chemistry Experiment (ACE-FTS) satellite. The formation rate for ice particles is a very strong function of temperature and water vapor concentration. We found the equilibrium radius of ice particles to be in the range from 20 to 70 nm, and the formation time - from about 2 hours at 150 K to about 18 hours at 125 K. Our results imply that in addition to the commonly accepted particle growth during their sedimentation from higher altitudes, in-situ growth to radii of 50-70 nm at mesospheric temperatures near 150 K in two hours or less may also be possible. Our analysis of possible shapes for mesospheric ice particles using the band shape of ice absorption feature measured by ACE-FTS suggests that cubes or compact hexagonal prisms (with an aspect ratio of 1.1) are the best candidates to represent the crystalline ice particles in the polar summer mesosphere.

  5. 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.

  6. Kinetic Structures of Quasi-Perpendicular Shocks in Global Particle-in-Cell Simulations

    NASA Astrophysics Data System (ADS)

    Peng, I. B.; Markidis, S.; Laure, E.; Johlander, A.; Vaivads, A.; Khotyaintsev, Y. V.; Pierre, H.; Lapenta, G.

    2015-12-01

    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.

  7. The Role of Kinetic Effects, Including Plasma Rotation and Energetic Particles, in Resistive Wall Mode Stability

    NASA Astrophysics Data System (ADS)

    Berkery, John W.

    2009-11-01

    Continuous, disruption-free operation of tokamaks requires stabilization of the resistive wall mode (RWM). Theoretically, the RWM is thought to be stabilized by energy dissipation mechanisms that depend on plasma rotation and other parameters, with kinetic effects being emphasized.footnotetextB. Hu et al., Phys. Plasmas 12 (2005) 057301. Experiments in NSTX show that the RWM can be destabilized in high rotation plasmas while low rotation plasmas can be stable, which calls into question the concept of a simple critical plasma rotation threshold for stability. The present work tests theoretical stabilization mechanisms against experimental discharges with various plasma rotation profiles created by applying non-resonant n=3 braking, and with various fast particle fractions. Kinetic modification of ideal stability is calculated with the MISK code, using experimental equilibrium reconstructions. Analysis of NSTX discharges with unstable RWMs predicts near-marginal mode growth rates. Trapped ions provide the dominant kinetic resonances, while fast particles contribute an important stabilizing effect. Increasing or decreasing rotation in the calculation drives the prediction farther from the marginal point, showing that unlike simpler critical rotation theories, kinetic theory allows a more complex relationship between plasma rotation and RWM stability. Results from JT-60U show that energetic particle modes can trigger RWMsfootnotetextG. Matsunaga et al., IAEA FEC 2008 Paper EX/5-2.. Kinetic theory may explain how fast particle loss can trigger RWMs through the loss of an important stabilization mechanism. These results are applied to ITER advanced scenario equilibria to determine the impact on RWM stability.

  8. 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.

  9. Kinetics of dust particles around the scrape off layer in fusion devices

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Misra, Shikha; Sodha, M. S.

    2014-05-01

    A kinetic model based on the balance of charge and energy over the dust particle surface around the scrape off layer (SOL) region in fusion devices has been developed; for describing the dust mass diminution, its temperature evolution and phase change process have been taken into account. The formulation has been utilized to determine the lifetime of cylindrical and spherical dust particles. A realistic situation in fusion devices, when the plasma exhibits meso-thermal flow, has been taken into account; for this purpose a rigorous approach, pioneered by Mott-Smith and Langmuir (1926 Phys. Rev. 28 727), has been adopted to derive the general expressions for the electron (ion) current on cylindrical dust surfaces and the corresponding mean energy of accreting electrons/ions in a flowing plasma. On the basis of analytical modelling the numerical results for the dust electric potential energy and the lifetime of the dust particles corresponding to a typical plasma environment near the SOL region of Mega Ampere Spherical tokamak (MAST)/Joint European Torus (JET) fusion devices have been evaluated for graphite and tungsten dust particles. The results are graphically illustrated as functions of particle size, electron/ion temperature and plasma ionization. It is seen that a large dust particle immersed in low temperature plasma can survive for long time; as an important outcome it is also noticed that the cylindrical particles of tungsten last longer than spherical particles. The findings are of relevance in characterizing and simulating the effects of a variety of dusts for experimental campaigns in large scale (ITER/Demo-like) fusion devices.

  10. Ion composition and kinetics in Mercury's magnetotail (Invited)

    NASA Astrophysics Data System (ADS)

    Gershman, D. J.; Slavin, J. A.; Raines, J. M.; Zurbuchen, T.; Anderson, B. J.; Korth, H.; Baker, D. N.; Solomon, S. C.

    2013-12-01

    We present the first targeted study of the kinetic properties of Mercury's magnetotail plasmas using three-dimensional data from the Fast Imaging Plasma Spectrometer sensor on the MESSENGER spacecraft. The average velocity distribution functions of both solar wind and planetary ions in the plasma sheet are consistent with hot, near-isotropic Maxwellian distributions, enabling an estimation of both density and temperature for each species. Although the temperature and density of the H+-dominated plasma sheet vary over the ranges ~2-20 cm-3 and ~5-30 MK, respectively, they maintain a nearly constant thermal pressure of ~0.75 nPa, sufficient to balance the observed diamagnetic depressions in Mercury's magnetotail magnetic field. Solar wind ions, namely He2+ and O6++C5+, retain near-solar-wind abundances with respect to H+ and exhibit mass-proportional ion temperatures. Conversely, planetary ion species such as He+, O+, and Na+ are accelerated to approximately the same average energies. Substantial heavy ion plasma content in the pre-midnight plasma sheet suggests that planetary ions may asymmetrically mass-load Mercury's magnetotail, though it remains to be seen whether the predicted quasi-adiabaticity of these ions permits them to dynamically influence the ambient plasma. No such asymmetry with respect to local midnight is evident in the measured planetary ion temperatures. The temperature of He2+ is strongly correlated with that of H+ in the plasma sheet, which scales linearly with upstream solar wind speed (vsw) due to the conversion of solar wind ram pressure to plasma thermal pressure across Mercury's bow shock. The temperature of Na+-group ions, however, increases only linearly with solar wind speed for vsw < 500 km/s. For vsw > 500 km/s, the temperature of Na+ remains near ~25 MK, suggesting the presence of a saturation effect in the energization process of planetary ions at Mercury.

  11. 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.

  12. Kinetic energy offsets for multicharged ions from an electron beam ion source.

    PubMed

    Kulkarni, D D; Ahl, C D; Shore, A M; Miller, A J; Harriss, J E; Sosolik, C E; Marler, J P

    2017-08-01

    Using a retarding field analyzer, we have measured offsets between the nominal and measured kinetic energy of multicharged ions extracted from an electron beam ion source (EBIS). By varying source parameters, a shift in ion kinetic energy was attributed to the trapping potential produced by the space charge of the electron beam within the EBIS. The space charge of the electron beam depends on its charge density, which in turn depends on the amount of negative charge (electron beam current) and its velocity (electron beam energy). The electron beam current and electron beam energy were both varied to obtain electron beams of varying space charge and these were related to the observed kinetic energy offsets for Ar(4+) and Ar(8+) ion beams. Knowledge of these offsets is important for studies that seek to utilize slow, i.e., low kinetic energy, multicharged ions to exploit their high potential energies for processes such as surface modification. In addition, we show that these offsets can be utilized to estimate the effective radius of the electron beam inside the trap.

  13. Kinetic energy offsets for multicharged ions from an electron beam ion source

    NASA Astrophysics Data System (ADS)

    Kulkarni, D. D.; Ahl, C. D.; Shore, A. M.; Miller, A. J.; Harriss, J. E.; Sosolik, C. E.; Marler, J. P.

    2017-08-01

    Using a retarding field analyzer, we have measured offsets between the nominal and measured kinetic energy of multicharged ions extracted from an electron beam ion source (EBIS). By varying source parameters, a shift in ion kinetic energy was attributed to the trapping potential produced by the space charge of the electron beam within the EBIS. The space charge of the electron beam depends on its charge density, which in turn depends on the amount of negative charge (electron beam current) and its velocity (electron beam energy). The electron beam current and electron beam energy were both varied to obtain electron beams of varying space charge and these were related to the observed kinetic energy offsets for Ar4+ and Ar8+ ion beams. Knowledge of these offsets is important for studies that seek to utilize slow, i.e., low kinetic energy, multicharged ions to exploit their high potential energies for processes such as surface modification. In addition, we show that these offsets can be utilized to estimate the effective radius of the electron beam inside the trap.

  14. Annealing kinetics of latent particle tracks in Durango apatite

    SciTech Connect

    Afra, B.; Rodriguez, M. D.; Giulian, R.; Kluth, P.; Lang, M.; Zhang, J.; Ewing, R. C.; Kirby, N.; Trautmann, C.; Toulemonde, M.

    2011-02-01

    Using synchrotron small-angle x-ray scattering we determine the ''latent'' track morphology and the track annealing kinetics in the Durango apatite. The latter, measured during ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallization of the damaged material. The resolution of fractions of a nanometer with which the track radii are determined, as well as the nondestructive, artefact-free measurement methodology shown here, provides an effective means for in-depth studies of ion-track formation in natural minerals under a wide variety of geological conditions.

  15. Strange Particles and Heavy Ion Physics

    SciTech Connect

    Bassalleck, Bernd; Fields, Douglas

    2016-04-28

    This very long-running grant has supported many experiments in nuclear and particle physics by a group from the University of New Mexico. The gamut of these experiments runs from many aspects of Strangeness Nuclear Physics, to rare Kaon decays, to searches for exotic Hadrons such as Pentaquark or H-Dibaryon, and finally to Spin Physics within the PHENIX collaboration at RHIC. These experiments were performed at a number of laboratories worldwide: first and foremost at Brookhaven National Lab (BNL), but also at CERN, KEK, and most recently at J-PARC. In this Final Technical Report we summarize progress and achievements for this award since our last Progress Report, i.e. for the period of fall 2013 until the award’s termination on November 30, 2015. The report consists of two parts, representing our two most recent experimental efforts, participation in the Nucleon Spin Physics program of the PHENIX experiment at RHIC, the Relativistic Heavy Ion Collider at BNL – Task 1, led by Douglas Fields; and participation in several Strangeness Nuclear Physics experiments at J-PARC, the Japan Proton Accelerator Research Center in Tokai-mura, Japan – Task 2, led by Bernd Bassalleck.

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

    PubMed

    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); J. Stat. Phys. 149, 643 (2012); J. Stat. Phys. 152, 159 (2013); Phys. Rev. E 83, 041125 (2011)] 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.

  17. Microfluidic rheology of active particle suspensions: Kinetic theory

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    We analyze the effective rheology of a dilute suspension of self-propelled slender particles between two infinite parallel plates in a pressure-driven flow. We use a continuum kinetic model to study the dynamics and transport of particles, where hydrodynamic interactions induced by the swimmers are taken into account. Using finite volume simulations we study how the activity of the swimmer and the external flow modify the rheological properties of the system. Results indicate that at low flow rates, activity decreases the value of the viscosity for pushers and increases its value for pullers. Both effects become weaker with increasing the flow strength due to the alignment of the particles with the flow. In the case of puller particles, shear thinning is observed over the entire range of flow rates. Pusher particles exhibit shear thickening at intermediate flow rates, where passive stresses start dominating over active stresses, reaching a viscosity greater than that of the Newtonian fluid. Finally shear thinning is observed at high flow rates. Both pushers and pullers exhibit a Newtonian plateau at very high flow rates. We demonstrate a good agreement between numerical results and experiments.

  18. Kinetic effects of energetic particles on resistive MHD stability.

    PubMed

    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(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 deltaf 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)10.1063/1.2949704]. It is observed that energetic particles have significant damping and stabilizing effects at experimentally relevant beta, beta(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.

  19. 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.

  20. Fully kinetic particle simulations of high pressure streamer propagation

    NASA Astrophysics Data System (ADS)

    Rose, David; Welch, Dale; Thoma, Carsten; Clark, Robert

    2012-10-01

    Streamer and leader formation in high pressure devices is a dynamic process involving a hierarchy of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. We have performed 2D and 3D fully EM implicit particle-in-cell simulation model of gas breakdown leading to streamer formation under DC and RF fields. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm [D. R. Welch, et al., J. Comp. Phys. 227, 143 (2007)] that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge. These models are being applied to the analysis of high-pressure gas switches [D. V. Rose, et al., Phys. Plasmas 18, 093501 (2011)] and gas-filled RF accelerator cavities [D. V. Rose, et al. Proc. IPAC12, to appear].

  1. Influence of Co-Ion Nature on the Gelation Kinetics of Colloidal Silica Suspensions.

    PubMed

    Trompette, Jean-Luc

    2017-06-08

    The influence of the nature of three representative monovalent co-ions on the gelation kinetics of Ludox suspensions has been investigated. At a given Ludox volume fraction and for the same concentration of potassium salt, the gelation time is longer as the studied anion presents a more pronounced kosmotrope character. As the screening of the silica surface charge is similar since the same cationic counterion is taken, these results highlight the unexpected role played by hydration effects imparted by the co-ions when particles are pushed together as gelation proceeds. This reveals that jamming transitions of nanoparticle fluids may be finely tuned by changing the co-ion nature in spite of the fact that the cationic counterion is the same.

  2. Continuum Theory of Phase Separation Kinetics for Active Brownian Particles

    NASA Astrophysics Data System (ADS)

    Stenhammar, Joakim; Tiribocchi, Adriano; Allen, Rosalind J.; Marenduzzo, Davide; Cates, Michael E.

    2013-10-01

    Active Brownian particles (ABPs), when subject to purely repulsive interactions, are known to undergo activity-induced phase separation broadly resembling an equilibrium (attraction-induced) gas-liquid coexistence. Here we present an accurate continuum theory for the dynamics of phase-separating ABPs, derived by direct coarse graining, capturing leading-order density gradient terms alongside an effective bulk free energy. Such gradient terms do not obey detailed balance; yet we find coarsening dynamics closely resembling that of equilibrium phase separation. Our continuum theory is numerically compared to large-scale direct simulations of ABPs and accurately accounts for domain growth kinetics, domain topologies, and coexistence densities.

  3. Dipole-Potential-Mediated Effects on Ion Pump Kinetics

    PubMed Central

    Clarke, Ronald J.

    2015-01-01

    The kinetics of conformational changes of P-type ATPases necessary for the occlusion or deocclusion of transported ions are known to be sensitive to the composition of the surrounding membrane, e.g., phospholipid content, mole percentage of cholesterol, and the presence of lipid-bound anions. Research has shown that many membrane components modify the dipole potential of the lipid head-group region. Based on the observation that occlusion/deocclusion reactions of ion pumps perturb the membrane surrounding the protein, a mechanism is suggested whereby dipole potential modifiers induce preferential stabilization or destabilization of occluded or nonoccluded states of the protein, leading to changes in the forward and backward rate constants for the transition. The mechanism relies on the assumption that conformational changes of the protein are associated with changes in its hydrophobic thickness that requires a change in local lipid packing density to allow hydrophobic matching with the membrane. The changes in lipid packing density cause changes in local lipid dipole potential that are responsible for the dependence of conformational kinetics on dipole potential modifiers. The proposed mechanism has the potential to explain effects of lipid composition on the kinetics of any membrane protein undergoing significant changes in its membrane cross-sectional area during its activity. PMID:26488640

  4. Low frequency fully kinetic simulation of the toroidal ion temperature gradient instability

    NASA Astrophysics Data System (ADS)

    Sturdevant, B. J.; Chen, Y.; Parker, S. E.

    2017-08-01

    A fully kinetic ion model is useful for the verification of gyrokinetic turbulence simulations in certain regimes, where the gyrokinetic model may break down due to the lack of small ordering parameters. However, for a fully kinetic model to be of value, it must first be able to accurately simulate low frequency drift-type instabilities typically well within the domain of gyrokinetics. Here, a fully kinetic ion model is formulated with weak gradient drive terms and applied to the toroidal ion-temperature-gradient (ITG) instability for the first time. Implementation in toroidal geometry is discussed, where orthogonal coordinates are used for particle dynamics, but field-line-following coordinates are used for the field equation allowing for high resolution of the field-aligned mode structure. Variational methods are formulated for integrating the equation of motion allowing for accuracy at a modest time-step size. Linear results are reported for both the slab and toroidal ITG instabilities. Good agreement with full Vlasov and gyrokinetic theory is demonstrated in slab geometry. Good agreement with global gyrokinetic simulation is also shown in toroidal geometry.

  5. Ion specificity in α-helical folding kinetics.

    PubMed

    von Hansen, Yann; Kalcher, Immanuel; Dzubiella, Joachim

    2010-11-04

    The influence of the salts KCl, NaCl, and NaI at molar concentrations on the α-helical folding kinetics of the alanine-based oligopeptide Ace-AEAAAKEAAAKA-Nme is investigated by means of (explicit-water) molecular dynamics simulations and a diffusional analysis. The mean first passage times for folding and unfolding are found to be highly salt-specific. In particular, the folding times increase about 1 order of magnitude for the sodium salts. The drastic slowing can be traced to long-lived, compact configurations of the partially folded peptide, in which sodium ions are tightly bound by several carbonyl and carboxylate groups. This multiple trapping leads to a nonexponential residence time distribution of the cations in the first solvation shell of the peptide. The analysis of α-helical folding in the framework of diffusion in a reduced (one-dimensional) free energy landscape further shows that the salt not only specifically modifies equilibrium properties but also induces kinetic barriers due to individual ion binding. In the sodium salts, for instance, the peptide's configurational mobility (or "diffusivity") can decrease about 1 order of magnitude. This study demonstrates the highly specific action of ions and highlights the intimate coupling of intramolecular friction and solvent effects in protein folding.

  6. Kinetic Theory Model for Ion Movement through Biological Membranes

    PubMed Central

    Mackey, Michael C.

    1971-01-01

    A model for ion movement through specialized sites in the plasma membrane is presented and analyzed using techniques from nonequilibrium kinetic theory. It is assumed that ions traversing these specialized regions interact with membrane molecules through central conservative forces. The membrane molecules are approximated as massive spherical scattering centers so that ionic fractional energy losses per collision are much less than one. Equations for steady-state membrane ionic currents and conductances as functions of externally applied electric field strength are derived and numerically analyzed, under the restriction of identical solutions on each size of the membrane and constant electric fields within the membrane. The analysis is carried through for a number of idealized ion-membrane molecule central force interactions. For any interaction leading to a velocity-dependent ion-membrane molecule collision frequency, the membrane chord conductance is a function of the externally applied electric field. Interactions leading to a collision frequency that is an increasing (decreasing) function of ionic velocity are characterized by chord conductances that are decreasing (increasing) functions of field strength. For ion-neutral molecule interactions, the conductance is such a rapidly decreasing function of field strength that the slope conductance becomes negative for all field strengths above a certain value. PMID:5539001

  7. Gated ion spectrometer for spectroscopy of neutral particles

    NASA Astrophysics Data System (ADS)

    Sharif, S.; Braenzel, J.; Schnürer, M.; Prasad, R.; Borghesi, M.; Tikhonchuk, V.; Ter-Avetisyan, S.

    2017-08-01

    A new design of an ion mass spectrometer for the laser-plasma particle diagnostic, which is capable to detect simultaneously also neutral particles, is described. The particles are detected with micro-channel-plate detector operating in a gated mode. This allows us to separate x-rays and energetic electrons from other stray plasma emissions, e.g., neutral particles, which hit the detector in the same place. The ion energies are measured with the spectrometer in energy intervals corresponding to their time-of-flight within the gating window. The latter also defines the energy interval of neutrals recorded with the same time-of-flight. The spectrum of neutral particles can be reconstructed by subsequently collecting different parts of the spectrum while applying different delays on the gate pulse. That separation-in-time technique (time-of-flight mass spectrometry) in combination with the spatially separating mass analyzer (ion mass spectrometer) is used for the neutral particles spectroscopy.

  8. Kinetic equation for classical particles obeying an exclusion principle

    NASA Astrophysics Data System (ADS)

    Kaniadakis, G.; Quarati, P.

    1993-12-01

    In this paper we analyze the kinetics of classical particles which obey an exclusion principle (EP) in the only-individual-transitions (OIT) approximation, and separately in the more rigorous contemporary-transitions (CT) description. In order to be able to include the EP into the kinetics equations we consider a discrete, one-dimensional, heterogeneous and anisotropic phase space and, after defining the reduced transition probabilities, we write a master equation. As a limit to the continuum of this master equation we obtain a generalized Fokker-Planck (FP) equation. This last is a nonlinear partial differential equation and reduces to the standard FP equation if the nonlinear term, which takes into account the EP, is neglected. The steady states of this equation, both in the OIT approximation and CT description, are considered. In the particularly interesting case of Brownian particles as a steady state in the OIT approximation we obtain the Fermi-Dirac (FD) distribution, while in the CT description we obtain another distribution which differs slightly from that of the FD. Moreover, our approach permits us to treat in an alternative and efficient way the problem of the determination of an effective potential to simulate the exclusion principle in classical many-body equations of motion.

  9. Understanding memory effects in Li-ion batteries: evidence of a kinetic origin in TiO2 upon hydrogen annealing.

    PubMed

    Ventosa, E; Löffler, T; La Mantia, F; Schuhmann, W

    2016-09-20

    Memory effects in Li-ion battery materials have been explained on the basis of the thermodynamics of many-particles body, however the role of the (de-)intercalation kinetics is not yet clear. We demonstrate that kinetic aspects, specifically Li-ion mobility, are determining the magnitude of the memory effect in TiO2 by studying samples with different levels of oxygen vacancies.

  10. Particle simulation of ion heating in the ring current

    NASA Technical Reports Server (NTRS)

    Qian, S.; Hudson, M. K.; Roth, I.

    1990-01-01

    Heating of heavy ions has been observed in the equatorial magnetosphere in GEOS 1 and 2 and ATS 6 data due to ion cyclotron waves generated by anisotropic hot ring current ions. A one-dimensional hybrid-Darwin code has been developed to study ion heating in the ring current. Here, a strong instability and heating of thermal ions is investigated in a plasma with a los cone distribution of hot ions. The linear growth rate calculation and particle simulations are conducted for cases with different loss cones and relative ion densities. The linear instability of the waves, the quasi-linear heating of cold ions and dependence on the thermal H(+)/He(+) density ratio are analyzed, as well as nonlinear parallel heating of thermal ions. Effects of thermal oxygen and hot oxygen are also studied.

  11. 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.

  12. Ion acceleration and heating by kinetic Alfvén waves associated with magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Liang, Ji; Lin, Yu; Johnson, Jay R.; Wang, Zheng-Xiong; Wang, Xueyi

    2017-10-01

    Our previous study on the generation and signatures of kinetic Alfvén waves (KAWs) associated with magnetic reconnection in a current sheet revealed that KAWs are a common feature during reconnection [Liang et al. J. Geophys. Res.: Space Phys. 121, 6526 (2016)]. In this paper, ion acceleration and heating by the KAWs generated during magnetic reconnection are investigated with a three-dimensional (3-D) hybrid model. It is found that in the outflow region, a fraction of inflow ions are accelerated by the KAWs generated in the leading bulge region of reconnection, and their parallel velocities gradually increase up to slightly super-Alfvénic. As a result of wave-particle interactions, an accelerated ion beam forms in the direction of the anti-parallel magnetic field, in addition to the core ion population, leading to the development of non-Maxwellian velocity distributions, which include a trapped population with parallel velocities consistent with the wave speed. The ions are heated in both parallel and perpendicular directions. In the parallel direction, the heating results from nonlinear Landau resonance of trapped ions. In the perpendicular direction, however, evidence of stochastic heating by the KAWs is found during the acceleration stage, with an increase of magnetic moment μ. The coherence in the perpendicular ion temperature T⊥ and the perpendicular electric and magnetic fields of KAWs also provides evidence for perpendicular heating by KAWs. The parallel and perpendicular heating of the accelerated beam occur simultaneously, leading to the development of temperature anisotropy with T⊥>T∥ . The heating rate agrees with the damping rate of the KAWs, and the heating is dominated by the accelerated ion beam. In the later stage, with the increase of the fraction of the accelerated ions, interaction between the accelerated beam and the core population also contributes to the ion heating, ultimately leading to overlap of the beams and an overall

  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. 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…

  15. Charged particles and cluster ions produced during cooking activities.

    PubMed

    Stabile, L; Jayaratne, E R; Buonanno, G; Morawska, L

    2014-11-01

    Previous studies showed that a significant number of the particles present in indoor air are generated by cooking activities, and measured particle concentrations and exposures have been used to estimate the related human dose. The dose evaluation can be affected by the particle charge level which is usually not considered in particle deposition models. To this purpose, in this paper we show, for the very first time, the electric charge of particles generated during cooking activities and thus extending the interest on particle charging characterization to indoor micro-environments, so far essentially focused on outdoors. Particle number, together with positive and negative cluster ion concentrations, was monitored using a condensation particle counter and two air ion counters, respectively, during different cooking events. Positively-charged particle distribution fractions during gas combustion, bacon grilling, and eggplant grilling events were measured by two Scanning Mobility Particle Sizer spectrometers, used with and without a neutralizer. Finally, a Tandem Differential Mobility Analyzer was used to measure the charge specific particle distributions of bacon and eggplant grilling experiments, selecting particles of 30, 50, 80 and 100 nm in mobility diameter. The total fraction of positively-charged particles was 4.0%, 7.9%, and 5.6% for gas combustion, bacon grilling, and eggplant grilling events, respectively, then lower than other typical outdoor combustion-generated particles.

  16. Dual signal amplification for bioassays using ion release from nanolabels and ion-activated enzyme kinetics.

    PubMed

    Cowles, Chad L; Zhu, Xiaoshan

    2012-10-21

    A dual signal amplification technique was developed for bioassays. The technique consists of zinc-ion release from ZnS nanoparticle labels and enzyme kinetics activated by the released zinc ions as cofactors. In the ion release process, each ZnS nanoparticle label liberates a high number of zinc ions by acidic dissolution. After the ion release, at appropriate pH levels, the released zinc ions are used as cofactors to trigger the enzymatic activity of carbonic anhydrase. The fluorescence produced from the activated enzyme kinetics is measured for bioassay signal quantification. A model bioassay on mouse IgG adopting this technique presents a detection limit around 0.5 pM and a detection range over at least two orders of magnitude. This technique was also successfully applied to the detection of human cardiac troponin I (cTnI) in human serum samples to demonstrate a clinical diagnosis application. The developed immunoassay is capable of distinguishing clinically critical levels of cTnI. This technique possesses a high detection resolution and offers the advantage of straightforward operation (simple preparation of ZnS nanoparticles and no enzyme immobilization).

  17. Kinetics of particle deposition in the oblique impinging jet cell.

    PubMed

    Adamczyk, Zbigniew; Musiał, Elizeusz; Siwek, Barbara

    2004-01-01

    A new oblique impinging-jet (OBIJ) cell was developed, suitable for colloid deposition studies at various interfaces. In contrast to previously used orthogonal cells, the OBIJ construction makes possible direct microscope observations of particle deposition on nontransparent substrates. The cell performance was tested by studying kinetics of polystyrene latex particle deposition on mica. Two limiting cell configuration were used in the experiments: (i) the lower position (inverted microscope observation of substrate surface through air) and (ii) the upper position (observation of the substrate surface with adsorbed particles through the suspension layer). The dependence of local mass transfer rate (particle flux) on the position over the substrate surface was studied for various flow Reynolds numbers. It was demonstrated that deposition rate attained maximum at the flow stagnation point whose position was dependent on Re number. Moreover, it was shown that the local flux decreased at much slower rate when moving in the downstream direction, than for previously used impinging-jet cells. Consequently, the area of uniform transport conditions was larger, enabling more precise determination of the limiting particle flux at the stagnation-point. The dependence of the flux on Re number was systematically studied for various ionic strength of the suspension. It was demonstrated, in accordance with previous results for the ordinary impinging-jet, that the flux increased significantly for low ionic strength and high Re number. This phenomenon, referred to as the inverse salt effect, was interpreted in terms of the convective diffusion theory. The governing transport equation originating from this theory was solved numerically, for the region near the stagnation point, using the finite-difference method. These numerical solutions were used for nonlinear fitting of the flow intensity parameter dependence on the Re number. In this way the flow field in the vicinity of the

  18. 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.

  19. The influence of particle size on latex colloid deposition kinetics

    SciTech Connect

    Litton, G.M.; Olson, T.M.

    1995-12-01

    The influence of particle size on the deposition kinetics of latex colloids in packed-bed columns was investigated in the presence of sodium dodecyl sulfate. Deposition rates, expressed as attachment efficiencies, were determined with 245, 481, and 755 nm carboxyl and 248 and 753 nm sulfate latex microspheres in granular quartz beds as a function of ionic strength. Experiments were performed at pH 10 in the presence of 10{sup -3} M sodium dodecyl sulfate to mask possible hydrophobic regions on the interacting surfaces. The onset of unfavorable filtration conditions and the sensitivity of the experimental attachment efficiencies, {alpha}{sub exp}, to changes in the ionic strength were both particle size dependent. However, both effects were opposite to that predicted by DLVO theory based on the primary interaction energy barrier height. Correlations of {alpha}{sub exp} with the secondary minimum showed that as attachment efficiencies approached 1 the depth of the secondary well increased. These observations suggest that particles may be retained within the secondary minimum even when a primary energy barrier is sufficient to inhibit attachment.

  20. 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)

  1. Kinetic ion-acoustic solitary waves in collisional plasmas

    NASA Astrophysics Data System (ADS)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2014-05-01

    The excitation and the propagation of solitary waves of ion-acoustic nature are analyzed by means of kinetic Eulerian simulations, in both collision-free and collisional plasmas, composed of kinetic warm protons and linear Boltzmannian electrons. The process of soliton formation is discussed in detail through the description of the time evolution of the electrostatic potential and of the associated phase space portraits of the proton distribution function. We study the effects of collisions on the propagation of solitary waves, by modeling proton-proton interactions through the one-dimensional nonlinear Dougherty operator, which is a collisional operator of the Fokker-Planck type. We show how, in a case of non-negligible collisionality, short spatial scales in the electrostatic potential are dissipated in time and the phase space structures, observed in the distribution function in absence of collisions, are significantly smoothed out. Finally, by exploiting the analogy between ion-acoustic waves in neutral infinite plasma and Trivelpiece-Gould waves in nonneutral plasmas columns, a recipe to observe solitary structures in nonneutral plasma devices is proposed.

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

    PubMed

    Bicknell, Brendan A; Goodhill, Geoffrey J

    2016-09-06

    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.

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

    PubMed Central

    Bicknell, Brendan A.

    2016-01-01

    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 Ca2+ 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

  4. Ion-release kinetics and ecotoxicity effects of silver nanoparticles.

    PubMed

    Lee, Yong-Ju; Kim, Jiwon; Oh, Jeehyun; Bae, Sujin; Lee, Sungkyu; Hong, In Seok; Kim, Sang-Ho

    2012-01-01

    The environmental toxicity associated with silver nanoparticles (AgNPs) has been a major focus in nanotoxicology. The Ag(+) released from AgNPs may affect ecotoxicity, although whether the major toxic effect is governed by Ag(+) ions or by AgNPs themselves is unclear. In the present study, we have examined the ecotoxicity of AgNPs in aquatic organisms, silver ion-release kinetics of AgNPs, and their relationship. The 48-h median effective concentration (EC50) values for Daphnia magna of powder-type AgNP suspensions were 0.75 µg/L (95% confidence interval [CI] = 0.71-0.78) total Ag and 0.37 µg/L (95% CI = 0.36-0.38) dissolved Ag. For sol-type AgNP suspension, the 48-h EC50 values for D. magna were 7.98 µg/L (95% CI = 7.04-9.03) total Ag and 0.88 µg/L (95% CI = 0.80-0.97) dissolved Ag. The EC50 values for the dissolved Ag of powder-type and sol-type AgNPs for D. magna showed similar results (0.37 µg/L and 0.88 µg/L) despite their differences of EC50 values in total Ag. We observed that the first-order rate constant (k) of Ag(+) ions released from AgNPs was 0.0734/h at 0.05 mg/L total Ag at 22°C within 6 h. The kinetic experiments and the toxicity test showed that 36% and 11% of sol-type AgNPs were converted to the Ag(+) ion form under oxidation conditions, respectively. Powder-type AgNPs showed 49% conversion rate of Ag(+) ion from AgNPs. We also confirmed that Ag(+) ion concentration in AgNP suspension reaches an equilibrium concentration after 48 h, which is an exposure time of the acute aquatic toxicity test.

  5. 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.

  6. 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.

  7. Stopping power of charged particles due to ion wave excitations.

    PubMed

    Nitta, H; Muroki, C; Nambu, M

    2002-08-01

    Stopping power due to ion wave excitations is derived for a charged particle moving in a two-component plasma. Unlike previous theories based on ion-acoustic-wave approximation (IAWA), the excitation of short-wavelength ion waves is taken into account. The obtained stopping power has a magnitude larger than that of IAWA. Stopping power at subsonic velocities, where stopping power in IAWA disappears, is even larger than that of supersonic velocities.

  8. Stopping power of charged particles due to ion wave excitations

    NASA Astrophysics Data System (ADS)

    Nitta, H.; Muroki, C.; Nambu, M.

    2002-08-01

    Stopping power due to ion wave excitations is derived for a charged particle moving in a two-component plasma. Unlike previous theories based on ion-acoustic-wave approximation (IAWA), the excitation of short-wavelength ion waves is taken into account. The obtained stopping power has a magnitude larger than that of IAWA. Stopping power at subsonic velocities, where stopping power in IAWA disappears, is even larger than that of supersonic velocities.

  9. 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.

  10. A survey of the cusp ion outflow's kinetic energy flux measured by Polar and FAST during conjunction events

    NASA Astrophysics Data System (ADS)

    Tian, S.; Wygant, J. R.; Cattell, C. A.; Scudder, J. D.; McFadden, J. P.; Mozer, F.; Russell, C. T.

    2014-12-01

    Polar and FAST conjunction events are selected from Polar cusp crossings in 1997. These conjunction events reveal a common pattern in which Polar observed significant ion kinetic energy flux in the upward direction at mid-altitudes (below 6 Re). Depending on the magnetic activity level, the maximum ion kinetic energy flux is on the order of 10-100 mW/m^2, when mapped to the ionosphere. It is an order of magnitude or more larger than the ion kinetic energy flux observed by FAST in conjunction at altitudes of <1 Re. Therefore, the ion outflows are significantly energized within the mid-latitude cusp. Also shown in the conjunction events is that the downward Poynting flux has enough wave energy to power the ion energization. The observed pattern suggests that the cusp at ionosphere altitudes is not a simple mapping of higher altitude particles. Instead, the mid-latitude cusp receives significant downward Poynting flux from higher altitude due to the solar wind/magnetosphere coupling. Within the mid-altitude cusp, the Poynting flux then supplies energy to power the ionosphere/magnetosphere coupling. Ion outflows are triggered and energized, forming a planetary wind that feeds the magnetosphere with ionospheric ions. During southward IMF, the wind convects anti-sunward and can affect the tail lobe, the nightside auroral region and the nightside plasma sheet.

  11. Effect of ion streaming on particle-particle interactions in a dusty plasma

    SciTech Connect

    Vyas, Vivek; Kushner, Mark J.

    2005-02-15

    Dust particles in low-temperature, low-pressure plasmas form Coulomb crystals and display collective behavior under select conditions. The trajectories of ions can be perturbed as they pass by negatively charged dust particles and, in some cases, will converge beyond the particle. This process, called ion streaming, produces a positive potential in the wakefield of the particle that can be large enough to perturb interparticle dynamics. In this paper, we discuss results from a three-dimensional model for dust particle transport in plasma processing reactors with which we investigated the effects of ion streaming on particle-particle interactions. When including the wakefield potential produced by ion streaming, dust particles can form vertically correlated pairs when trapped in electrical potential wells. The ion-streaming force was found to be significant only over a select range of pressures and for given combinations of particle sizes and mass densities. The formation of vertically correlated pairs critically depends on the shape of the potential well. Wakefield forces can also affect the order of multilayer lattices by producing vertical correlations between particles in adjacent layers.

  12. 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.

  13. 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.

  14. A multi-ion particle sensor.

    PubMed

    Ruedas-Rama, Maria Jose; Wang, Xiaojuan; Hall, Elizabeth A H

    2007-04-21

    The first sub-micron polyacrylic sensor containing two independent ion-sensing systems is shown, that uses a single excitation wavelength and separates signals by using quantum dot donors to form FRET pairs with other fluorophores.

  15. 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.

  16. Kinetic and thermodynamic evaluation of phosphate ions binding onto sevelamer hydrochloride.

    PubMed

    Elsiddig, Reem; Hughes, Helen; Owens, Eleanor; O' Reilly, Niall J; O'Grady, David; McLoughlin, Peter

    2014-10-20

    Sevelamer hydrochloride is the first non-aluminium, non-calcium-based phosphate binder developed for the management of hyperphosphatemia in end stage renal diseases. It is a synthetic ion-exchange polymer which binds and removes phosphate ions due to the high content of cationic charge associated with protonated amine groups on the polymer matrix. This is the first in-depth study investigating phosphate removal in vitro from aqueous solutions using commercially available sevelamer hydrochloride at physiological conditions of phosphate level, pH and temperature. The kinetic and thermodynamic parameters of phosphate binding onto the sevelamer hydrochloride particles were evaluated in order to define the binding process. A series of kinetic studies were carried out in order to delineate the effect of initial phosphate concentration, absorbent dose and temperature on the rate of binding. The results were analysed using three kinetic models with the best-fit of the experimental data obtained using a pseudo-second order model. Thermodynamic parameters provide in-depth information on inherent energetic changes that are associated with binding. Free energy ΔG°, enthalpy ΔH°, and entropy ΔS° changes were calculated in this study in order to assess the relationship of these parameters to polymer morphology. The binding reaction was found to be a spontaneous endothermic process with increasing entropy at the solid-liquid interface.

  17. Design Conception of a Solution Ion Source Based Particle Accelerator

    NASA Astrophysics Data System (ADS)

    Ashis, Das

    2004-05-01

    Particle accelerators till date have been based on several ion source principles such as thermal ionization, stripping etc. Such methods of ion source enabling is very limited by high temperature of ionization required in cases of very heavy ions generation. Heavy ions speeding in accelerator may lead to experiments with such ions in both accelerators and colliders, that is believed capable of opening new regimes of particle accelerator studies that is very heavy very heavy collision. Literature indicate that many yet-unknown mysteries of atomic and subnuclear Physics, creation and fate of Universe, new element synthesis all lie in this regime of investigation. In this paper, I outline a simpler and less energetic manner of creating, particularly, speeding very heavy ions using a solution ion stripping source such as with liquid ammonia which has ability to dissolve many heavy metals in form of ammonia-metal ion clusters, that can be led to a specially designed accelerator chamber as detailed in the paper. It is surprising indeed why such easy road to ions source generation was not conceived by particle accelerator Physicists earlier.

  18. 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.

  19. Gyrokinetic electron and fully kinetic ion simulations of fast magnetosonic waves in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, Xiaotian; Liu, Kaijun; Wang, Xueyi; Min, Kyungguk; Lin, Yu; Wang, Xiaogang

    2017-06-01

    Two-dimensional simulations using a gyrokinetic electron and fully kinetic ion (GeFi) scheme are preformed to study the excitation of fast magnetosonic waves in the terrestrial magnetosphere, which arise from the ion Bernstein instability driven by proton velocity distributions with a positive slope with respect to the perpendicular velocity. Since both ion and electron kinetics are relevant, particle-in-cell (PIC) simulations have often been employed to study the wave excitation. However, the full particle-in-cell scheme is computationally expensive for simulating waves in the ion scale because the electron scale must be fully resolved. Therefore, such simulations are limited to reduced proton-to-electron mass ratio ( m p / m e) and light-to-Alfvén speed ratio ( c / v A). The present study exploits the GeFi scheme that can break through these limitations to some extent, so larger m p / m e and c / v A can be used. In the simulations presented, the ion Bernstein instability is driven by a proton velocity distribution composed of 10% energetic protons with a shell distribution and 90% relatively cool, background protons with a Maxwellian distribution. The capability of the GeFi code in simulating the ion Bernstein instability is first demonstrated by comparing a GeFi simulation using reduced mass ratio ( m p / m e = 100) and speed ratio ( c / v A = 15) to a corresponding PIC simulation as well as linear dispersion analysis. A realistic speed ratio ( c / v A = 400) and a larger mass ratio ( m p / m e = 400) are then adopted in the GeFi code to explore how the results vary. It is shown that, as the increased m p / m e and c / v A lead to a larger lower hybrid frequency, ion Bernstein waves are excited at more ion cyclotron harmonics, consistent with the general prediction of linear dispersion theory. On the other hand, the GeFi simulations also revealed some interesting features after the instability saturation, which are likely related to nonlinear wave

  20. Study of the ion kinetic effects in ICF run-away burn using a quasi-1D hybrid model

    DOE PAGES

    Huang, Cheng -Kun; Molvig, Kim; Albright, Brian James; ...

    2017-02-21

    Here, the loss of fuel ions in the Gamow peak and other kinetic effects related to the α particles during ignition, run-away burn, and disassembly stages of an inertial confinement fusion D-T capsule are investigated with a quasi-1D hybrid volume ignition model that includes kinetic ions, fluid electrons, Planckian radiation photons, and a metallic pusher. The fuel ion loss due to the Knudsen effect at the fuel-pusher interface is accounted for by a local-loss model by with an albedo model for ions returning from the pusher wall. The tail refilling and relaxation of the fuel ion distribution are captured withmore » a nonlinear Fokker-Planck solver. Alpha heating of the fuel ions is modeled kinetically while simple models for finite alpha range and electron heating are used. This dynamical model is benchmarked with a 3 T hydrodynamic burn model employing similar assumptions. For an energetic pusher (~40 kJ) that compresses the fuel to an areal density of ~1.07g/cm2 at ignition, the simulation shows that the Knudsen effect can substantially limit ion temperature rise in runaway burn. While the final yield decreases modestly from kinetic effects of the α particles, large reduction of the fuel reactivity during ignition and runaway burn may require a higher Knudsen loss rate compared to the rise time of the temperatures above ~25 keV when the broad D-T Gamow peak merges into the bulk Maxwellian distribution.« less

  1. Study of the ion kinetic effects in ICF run-away burn using a quasi-1D hybrid model

    NASA Astrophysics Data System (ADS)

    Huang, C.-K.; Molvig, K.; Albright, B. J.; Dodd, E. S.; Vold, E. L.; Kagan, G.; Hoffman, N. M.

    2017-02-01

    The loss of fuel ions in the Gamow peak and other kinetic effects related to the α particles during ignition, run-away burn, and disassembly stages of an inertial confinement fusion D-T capsule are investigated with a quasi-1D hybrid volume ignition model that includes kinetic ions, fluid electrons, Planckian radiation photons, and a metallic pusher. The fuel ion loss due to the Knudsen effect at the fuel-pusher interface is accounted for by a local-loss model by Molvig et al. [Phys. Rev. Lett. 109, 095001 (2012)] with an albedo model for ions returning from the pusher wall. The tail refilling and relaxation of the fuel ion distribution are captured with a nonlinear Fokker-Planck solver. Alpha heating of the fuel ions is modeled kinetically while simple models for finite alpha range and electron heating are used. This dynamical model is benchmarked with a 3 T hydrodynamic burn model employing similar assumptions. For an energetic pusher (˜40 kJ) that compresses the fuel to an areal density of ˜1.07 g/cm 2 at ignition, the simulation shows that the Knudsen effect can substantially limit ion temperature rise in runaway burn. While the final yield decreases modestly from kinetic effects of the α particles, large reduction of the fuel reactivity during ignition and runaway burn may require a higher Knudsen loss rate compared to the rise time of the temperatures above ˜25 keV when the broad D-T Gamow peak merges into the bulk Maxwellian distribution.

  2. A particle dynamic model of red blood cell aggregation kinetics.

    PubMed

    Fenech, Marianne; Garcia, Damien; Meiselman, Herbert J; Cloutier, Guy

    2009-11-01

    To elucidate the relationship between microscopic red blood cell (RBC) interactions and macroscopic rheological behavior, we propose a two-dimensional particle model capable of mimicking the main characteristics of RBC aggregation kinetics. The mechanical model of RBCs sheared in Couette flow is based on Newton law. We assumed a hydrodynamic force to move particles, a force to describe aggregation and an elasticity force. The role of molecular mass and concentration of neutral polymers on aggregation [Neu, B., and H. J. Meiselman. Biophys. J. 83:2482-2490, 2002] could be mimicked. Specifically, it was shown that for any shear rate (SR), the mean aggregate size (MAS) grew with time until it reached a constant value, which is consistent with in vitro experiments. It was also demonstrated that we could mimic the modal relationship between MAS and SR and the occurrence of maximum aggregation at about 0.1 s(-1). As anticipated, simulations indicated that an increase in aggregation force augmented MAS. Further, augmentation of the depletion layer thickness influenced MAS only for SR close to zero, which is a new finding. To conclude, our contribution reveals that the aggregation force intensity and SR influence the steady state MAS, and that the depletion and layer thickness affect the aggregation speed.

  3. Probing the oxidation kinetics of small permalloy particles

    NASA Astrophysics Data System (ADS)

    Dong, Xiaolei; Song, Xiao; Yin, Shiliu; Shirolkar, Mandar M.; Li, Ming; Wang, Haiqian

    2017-02-01

    The oxidation of permalloys is important to apply in a wide range. The oxidation and diffusion mechanisms of small permalloy particles with different Fe content are studied by using thermal gravimetric analysis (TGA) and microstructure characterizations. Fe2O3/(Ni, Fe)3O4 plays a key role in the morphology evolution and diffusion mechanisms of small NiFe particles upon oxidation. The activation energies of grain boundary diffusion for the NiFe alloys increase from 141 kJ/mol to 208 kJ/mol as the Fe content increases from 0 to 50 wt%. We have developed a diffusion process resolved temperature programed oxidation (PR-TPO) analysis method. Three diffusion mechanisms have been recognized by using this method: In addition to the grain boundary diffusion and lattice diffusion, our TGA analysis suggests that the phase conversion from Fe2O3 to (Ni, Fe)3O4 induces diffusion change and affects the diffusion process at the intermediate temperature. Relevant oxidation kinetics and diffusion mechanisms are discussed.

  4. 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.

  5. Negative ion-driven associated particle neutron generator

    DOE PAGES

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; ...

    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

  6. 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.

  7. Particle radiotherapy with carbon ion beams

    PubMed Central

    2013-01-01

    Carbon ion radiotherapy offers superior dose conformity in the treatment of deep-seated malignant tumours compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. The algorithm of treatment planning and beam delivery system is tailored to the individual parameters of the patient. The present article reviews the available literatures for various disease sites including the head and neck, skull base, lung, liver, prostate, bone and soft tissues and pelvic recurrence of rectal cancer as well as physical and biological properties. PMID:23497542

  8. Kinetic-MHD hybrid simulation of fishbone modes excited by fast ions on the experimental advanced superconducting tokamak (EAST)

    NASA Astrophysics Data System (ADS)

    Pei, Youbin; Xiang, Nong; Hu, Youjun; Todo, Y.; Li, Guoqiang; Shen, Wei; Xu, Liqing

    2017-03-01

    Kinetic-MagnetoHydroDynamic hybrid simulations are carried out to investigate fishbone modes excited by fast ions on the Experimental Advanced Superconducting Tokamak. The simulations use realistic equilibrium reconstructed from experiment data with the constraint of the q = 1 surface location (q is the safety factor). Anisotropic slowing down distribution is used to model the distribution of the fast ions from neutral beam injection. The resonance condition is used to identify the interaction between the fishbone mode and the fast ions, which shows that the fishbone mode is simultaneously in resonance with the bounce motion of the trapped particles and the transit motion of the passing particles. Both the passing and trapped particles are important in destabilizing the fishbone mode. The simulations show that the mode frequency chirps down as the mode reaches the nonlinear stage, during which there is a substantial flattening of the perpendicular pressure of fast ions, compared with that of the parallel pressure. For passing particles, the resonance remains within the q = 1 surface, while, for trapped particles, the resonant location moves out radially during the nonlinear evolution. In addition, parameter scanning is performed to examine the dependence of the linear frequency and growth rate of fishbones on the pressure and injection velocity of fast ions.

  9. Probing kinetic and multi-ion-fluid effects in ICF implosions using DT and D He reaction histories on OMEGA

    NASA Astrophysics Data System (ADS)

    Sio, H. W.; Frenje, J. A.; Gatu Johnson, M.; Li, C. K.; Petrasso, R. D.; Katz, J.; Stoeckl, C.; Kwan, T.; Le, A.; Bellei, C.

    2016-10-01

    To explore kinetic and multi-ion-fluid effects in D3He-gas-filled shock-driven implosions (with a trace amount of T2) , D3He and DT reaction histories were measured using the upgraded Particle X-ray Temporal Diagnostic (PXTD) on OMEGA. The relative timing between the D3He and DT reaction histories was measured with 10-ps precision. The initial gas-fill density of the thin-glass targets was varied from 0.3 - 2.2 mg/cc, spanning highly-kinetic to more hydrodynamic-like plasma conditions during shock burn. Multi-ion-fluid simulations of similar implosions show reaction histories that are quantitatively different than those from average-ion-fluid simulations, including differences in burn onset, burn width, and relative bang-time. The measured differences between the reaction histories will be contrasted to average-ion-fluid hydrodynamic simulations, as well as multi-ion-fluid and kinetic-ion simulations, using LSP. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  10. Kinetic temperature of dust particle motion in gas-discharge plasma.

    PubMed

    Norman, G E; Timofeev, A V

    2011-11-01

    A system of equations describing motion of dust particles in gas discharge plasma is formulated. This system is developed for a monolayer of dust particles with an account of dust particle charge fluctuations and features of the discharge near-electrode layer. Molecular dynamics simulation of the dust particles system is performed. A mechanism of dust particle average kinetic energy increase is suggested on the basis of theoretical analysis of the simulation results. It is shown that heating of dust particles' vertical motion is initiated by forced oscillations caused by the dust particles' charge fluctuations. The process of energy transfer from vertical to horizontal motion is based on the phenomenon of the parametric resonance. The combination of parametric and forced resonances explains the abnormally high values of the dust particles' kinetic energy. Estimates of frequency, amplitude, and kinetic energy of dust particles are close to the experimental values.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Cho, Shinatora; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2013-06-01

    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.

  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. Phosphate recovery from wastewater using engineered superparamagnetic particles modified with layered double hydroxide ion exchangers.

    PubMed

    Drenkova-Tuhtan, Asya; Mandel, Karl; Paulus, Anja; Meyer, Carsten; Hutter, Frank; Gellermann, Carsten; Sextl, Gerhard; Franzreb, Matthias; Steinmetz, Heidrun

    2013-10-01

    An innovative nanocomposite material is proposed for phosphate recovery from wastewater using magnetic assistance. Superparamagnetic microparticles modified with layered double hydroxide (LDH) ion exchangers of various compositions act as phosphate adsorbers. Magnetic separation and chemical regeneration of the particles allows their reuse, leading to the successful recovery of phosphate. Based upon the preliminary screening of different LDH ion exchanger modifications for phosphate selectivity and uptake capacity, MgFe-Zr LDH coated magnetic particles were chosen for further characterization and application. The adsorption kinetics of phosphate from municipal wastewater was studied in dependence with particle concentration, contact time and pH. Adsorption isotherms were then determined for the selected particle system. Recovery of phosphate and regeneration of the particles was examined via testing a variety of desorption solutions. Reusability of the particles was demonstrated for 15 adsorption/desorption cycles. Adsorption in the range of 75-97% was achieved in each cycle after 1 h contact time. Phosphate recovery and enrichment was possible through repetitive application of the desorption solution. Finally, a pilot scale experiment was carried out by treating 125 L of wastewater with the particles in five subsequent 25 L batches. Solid-liquid separation on this scale was carried out with a high-gradient magnetic filter (HGMF).

  15. Kinetic description of Bose-Einstein condensation with test particle simulations

    NASA Astrophysics Data System (ADS)

    Zhou, Kai; Xu, Zhe; Zhuang, Pengfei; Greiner, Carsten

    2017-07-01

    We present a kinetic description of Bose-Einstein condensation for particle systems being out of thermal equilibrium, which may happen for gluons produced in the early stage of ultrarelativistic heavy-ion collisions. The dynamics of bosons towards equilibrium is described by a Boltzmann equation including Bose factors. To solve the Boltzmann equation with the presence of a Bose-Einstein condensate we make further developments of the kinetic transport model BAMPS (Boltzmann approach of multiparton scatterings). In this work we demonstrate the correct numerical implementations by comparing the final numerical results to the expected solutions at thermal equilibrium for systems with and without the presence of Bose-Einstein condensate. In addition, the onset of the condensation in an overpopulated gluon system is studied in more details. We find that both expected power-law scalings denoted by the particle and energy cascade are observed in the calculated gluon distribution function at infrared and intermediate momentum regions, respectively. Also, the time evolution of the hard scale exhibits a power-law scaling in a time window, which indicates that the distribution function is approximately self-similar during that time.

  16. 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.

  17. Kinetic Effects on the Ion Sound Waves Generated by Stimulated Brillouin Scattering of a Spatially Smoothed Laser Beam

    NASA Astrophysics Data System (ADS)

    Riconda, Caterina; Hüller, Stefan; Myatt, Jason; Pesme, Denise

    Stimulated Brillouin Scattering (SBS) can drive ion sound waves to amplitudes such that steepening and particle kinetic effects occur. Such phenomena have been studied recently in spatial volumes corresponding to a single laser speckle, in two [Cohen, B. I. et al. Phys. Plasmas 4, 956 (1997)], and three spatial dimensions [Vu, H. X., Phys. Plasmas 4, 1841 (1997)]. We analyze the results of 2D kinetic simulations modeling the evolution of SBS in the case of a spatially smoothed laser beam interacting with a plasma containing many speckles. For this purpose, we have coupled a 2D particle-in-cell code to a 2D non-paraxial electromagnetic wave solver. The generation of a fast ion population is observed to initially take place in the most intense hot spots, resulting in a decrease of the amplitude of the ion sound wave amplitude generated by SBS in these hot spots. SBS activity is consequently reduced in the most intense laser speckles, so that the overall backscattering SBS reflectivity drops considerably below the values expected from models that do not account for particle kinetics and/or nonlinear hydrodynamics.

  18. 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.

  19. Kinetic characteristics of mixed conductive electrodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Wang, Chunsheng; Wroblewski, Shannon

    The rate performances of four mixed conductive electrodes (Li 4/3Ti 5/3O 4, LiFePO 4, LiCoO 2 and LiCo 1/3Ni 1/3Mn 1/3O 2) were investigated using galvanostatic charge/discharge, electrochemical impedance Spectroscopy (EIS) and galvanostatic intermittent titration (GITT). These four electrode materials can be roughly divided into two groups according to the structure change during Li intercalation/extraction, i.e. the phase transition materials (Li 4/3Ti 5/3O 4 and LiFePO 4) and mixed phase transformation and solid solution materials (LiNi 1/3Mn 1/3Co 1/3O 2 and LiCoO 2). Both the ionic conductivity and phase transition kinetics have a strong impact on the rate capability of the electrode material in addition to the generally accepted factors such as particle size and electronic conductivity. The rate capabilities of Li 4/3Ti 5/3O 4 and LiFePO 4, which have an extended flat region in the charge/discharge curves, mainly depended on their phase transition kinetics. The rate performance of the solid solution materials were controlled by the ionic conductivity, with some influence from the electronic conductivity.

  20. Ion Pre-acceleration in Fully Self-consistent Particle-in-cell Simulations of Supercritical Perpendicular Reforming Shocks in Multiple Ion Species Plasmas

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    Supernova remnant and heliopause termination shock plasmas may contain significant populations of minority heavy ions, with relative number densities n α/ni 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 α/ni . 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 (np ) and α-particles (n α), with differing mass and charge-to-mass ratios, that spans the entire range of n α/ni 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 α/ni . We show how the overall energization changes with n α/ni , 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 α/ni = 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.

  1. 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.

  2. 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.

  3. Preparation of zirconium oxy ion-imprinted particle for the selective separation of trace zirconium ion from water.

    PubMed

    Ren, Yueming; Liu, Pingxin; Liu, Xiaoli; Feng, Jing; Fan, Zhuangjun; Luan, Tianzhu

    2014-10-01

    Zr(IV) oxy ion-imprinted particle (Zr-IIP) was prepared using the metal ion imprinting technique in a sol-gel process on the surface of amino-silica. The dosages of zirconium ions as imprinted target, (3-aminopropyl) triethoxysilane (APTES) as a functional monomer and teraethyl orthosilicate (TEOS) as a cross-linker were optimized. The prepared Zr-IIP and Zr(IV) oxy ion non-imprinted particle (Zr-NIP) were characterized. pH effect, binding ability and the selectivity were investigated in detail. The results showed that the Zr-IIP had an excellent binding capacity and selectivity in the water. The equilibrium data fitted well to the pseudo-second-order kinetic and the Langmuir model for Zr(IV) binding onto Zr-IIP, respectively. The saturate binding capacity of Zr-IIP was found to be 196.08 μmol g(-1), which was 18 times higher than that of Zr-NIP. The sequence of binding efficiency of Zr-IIP for various ions was Zr(IV)>Cu(II)>Sb(III)>Eu(III). The coordination number has an important effect on the dimensional binding capacity. The equilibrium binding capacity of Zr-IIP for Zr(IV) decreased little under various concentrations of Pb(II) ions. The analysis of relative selectivity coefficient (Kr) indicated that the Zr-IIP had an appreciable binding specificity towards Zr(IV) although the competitive ions coexisted in the water. The Zr-IIP could serve as an efficient selective material for recovering or removing zirconium from the water environment.

  4. 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

  5. Dust particle diffusion in ion beam transport region

    SciTech Connect

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

    2016-02-15

    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.

  6. Ion probe beam experiments and kinetic modeling in a dense plasma focus Z-pinch

    SciTech Connect

    Schmidt, A. Ellsworth, J. Falabella, S. Link, A. McLean, H. Rusnak, B. Sears, J. Tang, V.; Welch, D.

    2014-12-15

    The Z-pinch phase of a dense plasma focus (DPF) emits multiple-MeV ions in a ∼cm length. The mechanisms through which these physically simple devices generate such high energy beams in a relatively short distance are not fully understood. We are exploring the origins of these large gradients using measurements of an ion probe beam injected into a DPF during the pinch phase and the first kinetic simulations of a DPF Z-pinch. To probe the accelerating fields in our table top experiment, we inject a 4 MeV deuteron beam along the z-axis and then sample the beam energy distribution after it passes through the pinch region. Using this technique, we have directly measured for the first time the acceleration of an injected ion beam. Our particle-in-cell simulations have been benchmarked on both a kJ-scale DPF and a MJ-scale DPF. They have reproduced experimentally measured neutron yields as well as ion beams and EM oscillations which fluid simulations do not exhibit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for accelerator and neutron source applications.

  7. TOPICAL REVIEW: Particle and fluid simulations of low-temperature plasma discharges: benchmarks and kinetic effects

    NASA Astrophysics Data System (ADS)

    Kim, H. C.; Iza, F.; Yang, S. S.; Radmilovic-Radjenovic, M.; Lee, J. K.

    2005-10-01

    Fluid, particle-in-cell and hybrid models are the numerical simulation techniques commonly used for simulating low-temperature plasma discharges. Despite the complexity of plasma systems and the challenges in describing and modelling them, well-organized simulation methods can provide physical information often difficult to obtain from experiments. Simulation results can also be used to identify research guidelines, find optimum operating conditions or propose novel designs for performance improvements. In this paper, we present an overview of the principles, strengths and limitations of the three simulation models, including a brief history and the recent status of their development. The three modelling techniques are benchmarked by comparing simulation results in different plasma systems (plasma display panels, capacitively coupled plasmas and inductively coupled plasmas) with experimentally measured data. In addition, different aspects of the electron and ion kinetics in these systems are discussed based upon simulation results.

  8. 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

  9. Kinetics of lipid mixing between bicelles and nanolipoprotein particles

    PubMed Central

    Lai, Ginny; Forti, Kevin Muñoz; Renthal, Robert

    2015-01-01

    Nanolipoprotein particles (NLPs), also known as nanodiscs, are lipid bilayers bounded by apolipoprotein. Lipids and membrane proteins cannot exchange between NLPs. However, addition of bicelles opens NLPs and transfers their contents to bicelles, which freely exchange lipids and proteins. NLP-bicelle interactions may provide a new method for studying membrane protein oligomerization. The interaction mechanism was investigated by stopped flow fluorometry. NLP lipids included fluorescence resonance energy transfer donors and acceptors. NLPs were mixed with a 200-fold molar excess of dihexanoyl phosphatidylcholine (DHPC)/dimyristoyl phosphatidylcholine bicelles, and the rate of lipid transfer was monitored by the appearance of dequenched lipid donor fluorescence. The observed pseudo-first-order rate constant was surprisingly small. NLPs did not react with DHPC alone below its critical micelle concentration (cmc). Above the cmc, the reaction was complete within the instrument dead time. Thus, the rate-limiting step is not the reaction of NLPs with DHPC monomers or micelles. Added MSP1E3D1 had no effect on the rate, ruling out free apolipoprotein involvement. The NLP-bicelle mixing rate showed a strong temperature dependence (activation energy = 28 kcal/mol). Near or below the DMPC phase transition temperature, the kinetics were sigmoidal. Models are proposed for the NLP-bicelle mixing, including one involving fusion pores. PMID:25660392

  10. Kinetic simulation of neutral particle transport in sputtering processes

    NASA Astrophysics Data System (ADS)

    Trieschmann, Jan; Gallian, Sara; Brinkmann, Ralf Peter; Mussenbrock, Thomas; Ries, Stefan; Bibinov, Nikita; Awakowicz, Peter

    2013-09-01

    For many physical vapor deposition applications using sputtering processes, knowledge about the detailed spatial and temporal evolution of the involved gas species is of great importance. Modeling of the involved gas dynamic and plasma processes is however challenging, because the operating pressure is typically below 1 Pa. In consequence, only kinetic descriptions are appropriate. In order to approach this problem, the dynamics of sputtered particle transport through a neutral gas background is simulated. For this study, a modified version of the three-dimensional Direct Simulation Monte Carlo (DSMC) code dsmcFoam is utilized. The impact of a transient sputtering wind is investigated in a generic reactor geometry, which may be used for dc Magnetron Sputtering (dcMS), High Power Impulse Magnetron Sputtering (HiPIMS), as well as sputtering in capacitively coupled discharges. In the present work a rarefaction of the background gas is observed. Moreover in pulsed mode the temporal dynamics of the rarefaction and subsequent recovery of the background gas is investigated. This work is supported by the German Research Foundation in the frame of TRR 87.

  11. 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.

  12. Analysis of VX on soil particles using ion trap secondary ion mass spectrometry.

    PubMed

    Groenewold, G S; Appelhans, A D; Gresham, G L; Olson, J E; Jeffery, M; Wright, J B

    1999-07-01

    The direct detection of the nerve agent VX (methylphosphonothioic acid, S-[2-[bis(1-methylethyl)amino]ethyl] O-ethyl ester) on milligram quantities of soil particles has been achieved using ion trap secondary ion mass spectrometry (IT-SIMS). VX is highly adsorptive toward a wide variety of surfaces; this attribute makes detection using gas-phase approaches difficult but renders the compound very amenable to surface detection. An ion trap mass spectrometer, modified to perform SIMS, was employed in the present study. A primary ion beam (ReO4-) was fired on axis through the ion trap, where it impacted the soil particle samples. [VX + H]+, [VX + H]+ fragment ions, and ions from the chemical background were sputtered into the gas-phase environment of the ion trap, where they were either scanned out or isolated and fragmented (MS2). At a surface concentration of 0.4 monolayer, intact [VX + H]+, and its fragment ions, were readily observable above background. However, at lower concentrations, the secondary ion signal from VX became obscured by ions derived from the chemical background on the surface of the soil particles. MS2 analysis using the ion trap was employed to improve detection of lower concentrations of VX: detection of the 34S isotopic ion of [VX + H]+, present at a surface concentration of approximately 0.002 monolayer, was accomplished. The study afforded the opportunity to investigate the fragmentation chemistry of VX. Semiempirical calculations suggest strongly that the molecule is protonated at the N atom. Deuterium labeling showed that formation of the base peak ion (C2H4)N(i-C3H7)2+ involves transfer of the amino proton to the phosphonothioate moiety prior to, or concurrent with, C-S bond cleavage. To manage the risk associated with working with the compound, the vacuum unit of the IT-SIMS was located in a hood, connected by cables to the externally located electronics and computer.

  13. Kinetic Alfven wave instability in a Lorentzian dusty plasma: Non-resonant particle approach

    SciTech Connect

    Rubab, N.; Biernat, H. K.; Erkaev, V.; Langmayr, D.

    2011-07-15

    Analysis of the electromagnetic streaming instability is carried out which is related to the cross field drift of kappa distributed ions. The linear dispersion relation for electromagnetic wave using Vlasov-fluid equations in a dusty plasma is derived. Modified two stream instability (MTSI) in a dusty plasma has been discussed in the limit {omega}{sub pd}{sup 2}/c{sup 2}k{sub perpendicular}{sup 2}<<1. Numerical calculations of the growth rate of instability have been carried out. Growth rates of kinetic Alfven instability are found to be small as compared to MTSI. Maximum growth rates for both instabilities occur in oblique directions for V{sub 0}{>=}V{sub A}. It is shown that the presence of both the charged dust particles and perpendicular ion beam sensibly modify the dispersion relation of low-frequency electromagnetic wave. The dispersion characteristics are found to be insensible to the superthermal character of the ion distribution function. Applications to different intersteller regions are discussed.

  14. Kramers' diffusion theory applied to gating kinetics of voltage-dependent ion channels.

    PubMed Central

    Sigg, D; Qian, H; Bezanilla, F

    1999-01-01

    Kramers' diffusion theory of reaction rates in the condensed phase is considered as an alternative to the traditional discrete-state Markov (DSM) model in describing ion channel gating current kinetics. Diffusion theory can be expected to be particularly relevant in describing high-frequency (>100 kHz) events in channel activation. The generalized voltage sensor of a voltage-dependent ion channel is treated as a Brownian motion particle undergoing spatial diffusion along a one-dimensional energy landscape. Two classes of energy landscapes are considered. The first class contains large barriers, which give rise to gating currents with two distinct time scales: the usual low-frequency decay, which can modeled with a DSM scheme, and a high-frequency component arising from intrastate relaxation. Large depolarizations reduce potential barriers to such a degree that activation rates are diffusion limited, causing the two time scales to merge. Landscapes of the second class are either featureless or contain barriers that are small compared to kT; these are termed "drift landscapes." These landscapes require a larger friction coefficient to generate slow gating kinetics. The high-frequency component that appears with barrier models is not present in pure drift motion. The presence of a high-frequency component can be tested experimentally with large-bandwidth recordings of gating currents. Topics such as frequency domain analysis, spatial dependence of the friction coefficient, methods for determining the adequacy of a DSM model, and the development of physical models of gating are explored. PMID:9929481

  15. 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.

  16. 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

  17. Incorporation of terbium(III) ion into mesoporous silica particles

    NASA Astrophysics Data System (ADS)

    Kataoka, Takuya; Wang, Liyin; Kobayashi, Kouhei; Nishikawa, Masami; Tagaya, Motohiro

    2016-10-01

    Terbium(III)-doped mesoporous silicas were synthesized, and the states of terbium ions in the silica frameworks were investigated. The mesopores were preserved upon doping at terbium ion molar concentrations relative to (Si+Tb) up to 15 mol %, indicating the interaction of terbium ions with Si-O bonds. Significant morphological changes of the particles were observed with increasing the doping concentration. The shapes of the photoluminescence spectra due to the transitions of 5D4 → 7F6 and 5D4 → 7F5 were indicative of the presence of terbium ions in the silica matrix, and the quantum efficiency (2.1-2.8%) and lifetime (1.6-1.9 ms) decreased with increasing the doping concentration up to 15 mol %. Therefore, the terbium ions are considered to be located inside the amorphous silica frameworks, where they electrostatically interact with the O atoms of silanol and siloxane groups.

  18. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. 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

  20. 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.

  1. Increase of ion kinetic temperature across a collisionless shock. I - A new mechanism

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Wu, C. S.; Hu, X. W.

    1986-01-01

    A simple but effective mechanism is proposed to account for the increase of ion kinetic temperature across an oblique or perpendicular shock. This mechanism is based on the nonadiabatic motion of the transmitted ions across the shock ramp, which can lead to an ion gyrophase-bunching behind the shock.

  2. 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.

  3. Ion microprobe isotopic measurements of individual interplanetary dust particles

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  4. Kinetic studies on the cupric ion oxidation of sheep hemoglobin.

    PubMed

    Brittain, T; Ivanetich, K M

    1980-11-01

    The oxidation of sheep hemoglobin, in both the oxygenated and deoxygenated forms, by cuprous ions have been studied by spectrophotometric and stopped-flow techniques. Mixing of both the oxy and deoxy forms with excess Cu2+ leads to the rapid oxidation of the iron atoms of all four of the hem groups of the tetrameric protein, followed by the slow formation of hemichromes (low spin FeIII forms of hemoglobin). Stopped-flow studies show that the oxidations follow simple monophasic kinetics with second-order rate constants of 65 and 310 M-1 sec-1 for the oxy and deoxy forms, respectively. Variable temperature studies yield Arrhenius activation energies of 43 for the oxy form and 113 kJ mole-1 for the deoxy form. For each form of the protein the activation energy is very similar to the activation enthalpy. While the deoxy form is characterized by an activation energy and enthalpy that is more than twice the corresponding value in the oxy form. The activation entropies show highly significant differences being -128 e.u. and 136 e.u. at 25 degrees C for the oxy and deoxy forms, respectively.

  5. 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.

  6. 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.

  7. Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: kinetic, equilibrium and thermodynamic study.

    PubMed

    Kul, Ali Riza; Koyuncu, Hülya

    2010-07-15

    In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore-size distributions of the samples were fully characterized. The adsorption efficiency of Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol(-1) for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R(L) separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy (DeltaG), the enthalpy (DeltaH) and the entropy change of sorption (DeltaS) were determined as about -5.06, 10.29 and 0.017 kJ mol(-1) K(-1), respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously.

  8. 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.

  9. Kinetic freeze-out, particle spectra, and harmonic-flow coefficients from mode-by-mode hydrodynamics

    NASA Astrophysics Data System (ADS)

    Floerchinger, Stefan; Wiedemann, Urs Achim

    2014-03-01

    The kinetic freeze-out for the hydrodynamical description of relativistic heavy-ion collisions is discussed using a background-fluctuation splitting of the hydrodynamical fields. For a single event, the particle spectrum, or its logarithm, can be written as the sum of the background part that is symmetric with respect to azimuthal rotations and longitudinal boosts and a part containing the contribution of fluctuations or deviations from the background. Using a complete orthonormal basis to characterize the initial state allows one to write the double differential harmonic-flow coefficients determined by the two-particle correlation method as matrix expressions involving the initial fluid correlations. We discuss the use of these expressions for a mode-by-mode analysis of fluctuating initial conditions in heavy-ion collisions.

  10. A hybrid kinetic hot ion PIC module for the M3D-C1 Code

    NASA Astrophysics Data System (ADS)

    Breslau, J. A.; Ferraro, N.; Jardin, S. C.; Kalyanaraman, K.

    2016-10-01

    Building on the success of the original M3D code with the addition of efficient high-order, high-continuity finite elements and a fully implicit time advance making use of cutting-edge numerical techniques, M3D-C1 has become a flagship code for realistic time-dependent 3D MHD and two-fluid calculations of the nonlinear evolution of macroinstabilities in tokamak plasmas. It is therefore highly desirable to introduce to M3D-C1 one of the most-used features of its predecessor: the option to use a drift-kinetic delta- f PIC model for a minority population of energetic ions (representing, e.g., beam ions or fusion alpha particles) coupled with the usual finite element advance of the bulk ion and electron fluids through its pressure tensor. We describe the implementation of a module for this purpose using high-order-of-accuracy numerical integration and carefully tuned to take advantage of state-of-the-art multicore processing elements. Verification results for a toroidal Alfvén eigenmode test problem will be presented, along with a demonstration of favorable parallel scaling to large numbers of supercomputer nodes.

  11. Kinetic Modeling of Ion Beams in Dense Plasma Focus Z-Pinches

    NASA Astrophysics Data System (ADS)

    Link, A.; Bennett, N.; Falabella, S.; Higginson, D. P.; Olsen, R.; Podpaly, Y. A.; Povilus, A.; Shaw, B.; Sipes, N.; Welch, D. R.; Schmidt, A.

    2016-10-01

    Dense plasma focus (DPF) Z-pinches are compact devices capable of producing MeV ion beams, x-rays, and (for D or DT gas fill) neutrons. We report on predictions of ion beam generation using the particle-in-cell code LSP. These simulations include full-scale electrodes, an external pulse power circuit and model through the run-down phase as a fluid, transitioning to a fully kinetic simulation during the run-in phase and through the pinch. Simulations of a deuterium filled DPF predict a substantial number of ions accelerated to energies greater than 50 keV escape the dense plasma in the pinch region and could be used to enhance total neutron yield by employing a solid target. Results of the simulations will be presented and compared to experimental observations. LLNL-ABS-697617 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344 and with support from the Computing Grand Challenge program at LLNL.

  12. Optimization and adsorption kinetic studies of aqueous manganese ion removal using chitin extracted from shells of edible Philippine crabs

    NASA Astrophysics Data System (ADS)

    Quimque, Mark Tristan J.; Jimenez, Marvin C.; Acas, Meg Ina S.; Indoc, Danrelle Keth L.; Gomez, Enjelyn C.; Tabuñag, Jenny Syl D.

    2017-01-01

    Manganese is a common contaminant in drinking water along with other metal pollutants. This paper investigates the use of chitin, extracted from crab shells obtained as restaurant throwaway, as an adsorbent in removing manganese ions from aqueous medium. In particular, this aims to optimize the adsorption parameters and look into the kinetics of the process. The adsorption experiments done in this study employed the batch equilibration method. In the optimization, the following parameters were considered: pH and concentration of Mn (II) sorbate solution, particle size and dosage of adsorbent chitin, and adsorbent-adsorbate contact time. At the optimal condition, the order of the adsorption reaction was estimated using kinetic models which describes the process best. It was found out that the adsorption of aqueous Mn (II) ions onto chitin obeys the pseudo-second order model. This model assumes that the adsorption occurred via chemisorption

  13. Kinetic modelling for neoclassical transport of high-Z impurity particles using a binary collision method

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Yamoto, S.; Sawada, Y.; Inoue, H.; Hatayama, A.

    2016-03-01

    A new kinetic model for neoclassical impurity particle transport simulation has been developed. Our model is able to simulate the following two effects, which have been theoretically predicted, but neglected in most of the existing kinetic impurity transport simulations in the SOL (scrape-off layer)/Divertor plasmas of tokamak; (1) the neoclassical inward pinch (NC IWP) due to the density gradient of background plasmas and (2) the neoclassical temperature screening effect (NC TSE, outward transport) caused by the plasma temperature gradient. The IWP and TSE, both proportional to the impurity charge number Z, become especially important for higher-Z impurities such as tungsten. In this paper we focus on the case where background plasmas are in the Pfirsch-Schlüter regime. The velocity distribution of background plasma ions is modelled by a distorted Maxwellian distribution, which includes the Pfirsch-Schlüter flow velocity and the Pfirsch-Schlüter heat flux density, in order to reproduce the NC IWP and NC TSE. A series of test simulations have been performed for a toroidal magnetic field geometry. Characteristics of the neoclassical transport, such as dependencies on the safety factor and on the impurity charge number, have been confirmed.

  14. Fluid electron, gyrokinetic ion simulations of linear internal kink and energetic particle modes

    NASA Astrophysics Data System (ADS)

    Cole, Michael; Mishchenko, Alexey; Könies, Axel; Kleiber, Ralf; Borchardt, Matthias

    2014-07-01

    The internal kink mode is an important plasma instability responsible for a broad class of undesirable phenomena in tokamaks, including the sawtooth cycle and fishbones. To predict and discover ways to mitigate this behaviour in current and future devices, numerical simulations are necessary. The internal kink mode can be modelled by reduced magnetohydrodynamics (MHD). Fishbone modes are an inherently kinetic and non-linear phenomenon based on the n = 1 Energetic Particle Mode (EPM), and have been studied using hybrid codes that combine a reduced MHD bulk plasma model with a kinetic treatment of fast ions. In this work, linear simulations are presented using a hybrid model which couples a fluid treatment of electrons with a gyrokinetic treatment of both bulk and fast ions. Studies of the internal kink mode in geometry relevant to large tokamak experiments are presented and the effect of gyrokinetic ions is considered. Interaction of the kink with gyrokinetic fast ions is also considered, including the destabilisation of the linear n = 1 EPM underlying the fishbone.

  15. Fluid electron, gyrokinetic ion simulations of linear internal kink and energetic particle modes

    SciTech Connect

    Cole, Michael Mishchenko, Alexey; Könies, Axel; Kleiber, Ralf; Borchardt, Matthias

    2014-07-15

    The internal kink mode is an important plasma instability responsible for a broad class of undesirable phenomena in tokamaks, including the sawtooth cycle and fishbones. To predict and discover ways to mitigate this behaviour in current and future devices, numerical simulations are necessary. The internal kink mode can be modelled by reduced magnetohydrodynamics (MHD). Fishbone modes are an inherently kinetic and non-linear phenomenon based on the n = 1 Energetic Particle Mode (EPM), and have been studied using hybrid codes that combine a reduced MHD bulk plasma model with a kinetic treatment of fast ions. In this work, linear simulations are presented using a hybrid model which couples a fluid treatment of electrons with a gyrokinetic treatment of both bulk and fast ions. Studies of the internal kink mode in geometry relevant to large tokamak experiments are presented and the effect of gyrokinetic ions is considered. Interaction of the kink with gyrokinetic fast ions is also considered, including the destabilisation of the linear n = 1 EPM underlying the fishbone.

  16. 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.

  17. 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.

  18. Particle Simulations of Ion Rings for Magnetic Fusion.

    NASA Astrophysics Data System (ADS)

    Lyster, Peter Michael

    1987-09-01

    This thesis contains a numerical study of the dynamics of axis encircling charged particles in ion rings and layers. Part of this work deals with the coalescence of ion rings to form field reversed rings, which may be useful for Compact Torus magnetic fusion reactors. The coalescence of weak ion rings with Compact Toroids is also investigated. This is important because a component of energetic particles may help to maintain the flux or stabilize these configurations against a number of macroscopic magnetohydrodynamic instabilities. Several different types of particle codes are used. RINGA and CIDER are two and one half-dimensional codes in cylindrical axisymmetric geometry. For the RINGA code, a simple Ohm's law is used for modeling a resistive background plasma. For CIDER, the massless electron momentum equation is used for modeling a conductive background plasma. In a resistive plasma, ring coalescence can be achieved if the initial relative translational velocity is not excessive, and if the plasma conductivity is chosen to maximize the dissipation of ring energy. A theoretical and computational study is made of a mechanism by which ring translational energy is transferred to Alfven waves in a conductive plasma. A new collective phenomenon is discussed, whereby the merging of rings is improved if they have stronger initial self fields. A study is made of the coalescence of strong field-reversed ion rings in highly conductive plasmas, in which it is found that magnetic field line reconnection is an important process. Finally, a study of the magnetic compression of ion layers in conductive plasmas is presented. BAGSHAW, a one-dimensional particle code which treats the background plasma in the two fluid approximation, was developed for this purpose. Compression on a timescale which is comparable with the Alfven transit time may create considerable transients in the system. In a one-dimensional system, the plasma return current does not cancel the increase in the

  19. Kinetics of charged particles in a high-voltage gas discharge in a nonuniform electrostatic field

    NASA Astrophysics Data System (ADS)

    Kolpakov, V. A.; Krichevskii, S. V.; Markushin, M. A.

    2017-01-01

    A high-voltage gas discharge is of interest as a possible means of generating directed flows of low-temperature plasma in the off-electrode space distinguished by its original features [1-4]. We propose a model for calculating the trajectories of charges particles in a high-voltage gas discharge in nitrogen at a pressure of 0.15 Torr existing in a nonuniform electrostatic field and the strength of this field. Based on the results of our calculations, we supplement and refine the extensive experimental data concerning the investigation of such a discharge published in [1, 2, 5-8]; good agreement between the theory and experiment has been achieved. The discharge burning is initiated and maintained through bulk electron-impact ionization and ion-electron emission. We have determined the sizes of the cathode surface regions responsible for these processes, including the sizes of the axial zone involved in the discharge generation. The main effect determining the kinetics of charged particles consists in a sharp decrease in the strength of the field under consideration outside the interelectrode space, which allows a free motion of charges with specific energies and trajectories to be generated in it. The simulation results confirm that complex electrode systems that allow directed plasma flows to be generated at a discharge current of hundreds or thousands of milliamperes and a voltage on the electrodes of 0.3-1 kV can be implemented in practice [3, 9, 10].

  20. 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.

  1. Tumor control in ion beam radiotherapy with different ions in presence of hypoxia: an oxygen enhancement ratio model based on the microdosimetric kinetic model.

    PubMed

    Strigari, Lidia; Torriani, Francesca; Manganaro, Lorenzo; Inaniwa, Taku; Dalmasso, Federico; Cirio, Roberto; Attili, Andrea

    2017-09-01

    Few attempts to include the oxygen enhancement ratio (OER) in treatment planning for ion beam therapy have been made and systematic studies to evaluate the impact of hypoxia in treatments with beam of different ion species are missing. The radiobiological models used to quantify the OER in such studies are mainly based on the dose-averaged LET estimates and do not explicitly distinguish between ion species and fractionation schemes. In this study a new OER modelling, based on the microdosimetric kinetic model, taking into account the specificity of the different ions, LET spectra, tissues and fractionation schemes, has been developed. The model has been benchmarked with published in-vitro data, HSG, V79 and CHO cells in aerobic and hypoxic conditions, for different ions irradiation. The model has been included in the simulation of treatments for a clinical case (brain tumor) using proton, lithium, helium, carbon and oxygen ion beams. A study of the tumour control probability (TCP) as a function of oxygen partial pressure, dose per fraction and primary ion type has been performed. The modeled OER depends on both LET and ion type, showing also a decrease for increasing dose per fraction with a slope that depends on the LET and ion type, in good agreement with the experimental data. In the investigated clinical case, a significant increase in TCP by increasing ion charge has been found. Higher OER variations as a function of dose per fraction have been also found for low-LET ions (up to 15% varying from 2 to 8 Gy(RBE) for protons). The model could be exploited for the identification of the treatment condition optimality in presence of hypoxia, including fractionation and primary particles selection. © 2017 Institute of Physics and Engineering in Medicine.

  2. 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)

  3. Kinetic theory of radio frequency quadrupole ion traps. I. Trapping of atomic ions in a pure atomic gas

    NASA Astrophysics Data System (ADS)

    Viehland, Larry A.; Goeringer, Douglas E.

    2004-05-01

    A kinetic theory based on the Boltzmann equation is developed for the trapping of atomic ions in a radio-frequency quadrupole ion trap containing enough neutral atoms that ion-neutral collisions cannot be ignored. The collisions are treated at the same level of sophistication and detail as is used to deal with the time- and space-dependent electric fields in the trap. As a result, microscopic definitions are obtained for the damping and stochastic forces that originate from such collisions. These definitions contrast with corresponding phenomenological terms added ad hoc in previous treatments to create damped Mathieu and Langevin equations, respectively. Furthermore, the theory indicates that either collisional cooling or heating of the ions is possible, depending upon details of the ion-neutral mass ratios and interaction potential. The kinetic theory is not dependent on any special assumptions about the electric field strengths, the ion-neutral interaction potentials, or the ion-neutral mass ratio. It also provides an ab initio way to describe the ion kinetic energies, temperatures, and other properties by a series of successive approximations.

  4. Kinetic Alfvén wave and ion velocity distribution functions in the solar wind

    NASA Astrophysics Data System (ADS)

    Li, X.; Lu, Q.; Chen, Y.; Li, B.; Xia, L.

    2010-12-01

    Using 1D test particle simulations, the effect of a kinetic Alfvén wave on the velocity distribution function of protons in the collisionless solar wind is investigated. We first use linear Vlasov theory to obtain the property of a kinetic Alfvén wave numerically (the wave propagates in the direction almost perpendicular to the background magnetic field). We then numerically simulate how the wave will shape the proton velocity distribution function. It is found that Landau resonance may be able to generate two components in the initially Maxwellian proton velocity distribution function: a tenuous beam component along the direction of the background magnetic field and a core component. The streaming speed of the beam relative to the core proton component is about 1.2 -- 1.3 Alfvén speed. However, no perpendicular ion heating is observed from the simulation. Reference: Li, X., Lu, Q.M., Chen, Y., Li, B., Xia, L.D., ApJ, 719, L190, 2010.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Ion heating by kinetic cross-field streaming instability due to reflected ions at a quasiperpendicular shock

    NASA Technical Reports Server (NTRS)

    Yoon, Peter H.; Wu, C. S.; Mandt, M. E.

    1992-01-01

    The present paper shows that the reflected ion at a supercritical quasi-perpendicular shock wave can excite a purely growing mode propagating parallel to the ambient magnetic field. To discuss the ion heating by such an unstable mode, the self-consistent quasi-linear kinetic equation is solved with the assumption that the present purely growing mode is the dominant unstable mode in the system. In the quasi-linear analysis of the instability, two particular cases are considered: the case of low initial ion beta and that of a high initial ion beta.

  10. Measurement of alpha particle energy using windowless electret ion chambers.

    PubMed

    Dua, S K; Kotrappa, P; Srivastava, R; Ebadian, M A; Stieff, L R

    2002-10-01

    Electret ion chambers are inexpensive, lightweight, robust, commercially available, passive, charge-integrating devices for accurate measurement of different ionizing radiations. In an earlier work a chamber of dimensions larger than the range of alpha particles having aluminized Mylar windows of different thickness was used for measurement of alpha radiation. Correlation between electret mid-point voltage, alpha particle energy, and response was developed and it was shown that this chamber could be used for estimating the effective energy of an unknown alpha source. In the present study, the electret ion chamber is used in the windowless mode so that the alpha particles dissipate their entire energy inside the volume, and the alpha particle energy is determined from the first principles. This requires that alpha disintegration rate be accurately known or measured by an alternate method. The measured energies were within 1 to 4% of the true values for different sources (230Th, 237Np, 239Pu, 241Am, and 224Cm). This method finds application in quantitative determination of alpha energy absorbed in thin membrane and, hence, the absorbed dose.

  11. 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

  12. Nonlinear particle-wave kinetics in weakly unstable plasmas

    SciTech Connect

    Breizman, B.N.; Berk, H.L.; Pekker, M.S.

    1996-12-31

    With the motivation to address the behavior of the fusion produced alpha particles in a thermonuclear reactor, a theory is developed for predicting the wave saturation levels and particle transport in weakly unstable systems with a discrete number of modes in the presence of energetic particle sources and sinks. Conditions are established for either steady state or bursting nonlinear scenarios when several modes are excited for cases where there is and there is not resonance overlap. Depending on parameters, the particles can undergo benign relaxation, with only a small fraction of the available free energy released to waves and with no global transport, or the particles can experience rapid global transport caused by a substantial conversion of their free energy into wave energy. When the resonance condition of the particle-wave interaction is varied adiabatically, the particles trapped in a wave are found to form phase space holes or clumps that enhance the particle-wave energy exchange. This mechanism, which has been experimentally observed when there is frequency chirping, causes increased saturation levels of instabilities. If resonance sweeping is imposed externally, the particle free energy can even be tapped in stable systems where background dissipation suppresses linear instability. Externally applied resonance sweeping can be important for alpha particle energy channeling, as well as for understanding fishbone and some Alfven wave instability experiments. Near instability threshold, that is when the destabilizing drive just exceeds the background dissipation, a more sophisticated analysis is developed to predict the correct saturation. To leading order, this problem reduces to an integral equation for the wave amplitude with a temporally non local cubic term. This equation has a self-similar solution that blows-up in a finite time.

  13. 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.

  14. 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.

  15. The kinetics of energetic O‑ ions in oxygen discharge plasmas

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. A.; Aleksandrov, N. L.

    2017-04-01

    Monte Carlo simulation was used to study the translational relaxation of energetic O‑ ions produced by dissociative electron attachment to O2 molecules in oxygen plasmas in a strong electric field. Initial O‑ ions have rather high energies and are more reactive than the ions reaching equilibrium with the electric field. Therefore, there is a noticeable probability that the energetic O‑ ions participate in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange, electron detachment and ion impact vibrational excitation of O2 molecules were calculated versus the reduced electric field. It was shown that up to 6% of energetic O‑ ions produced in oxygen by dissociative electron attachment to O2 molecules are rapidly transformed to {{{{O}}}2}- ions due to charge exchange collisions. The probability of electron detachment from energetic O‑ ions and the probability of vibrational excitation were smaller that the probability of charge exchange. Estimates showed that the increase in the effective rates of the ion–molecule reactions due to high reactivity of energetic O‑ ions can be important in oxygen plasmas for reduced electric fields of 50–100 Td.

  16. 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.

  17. Simulation and assessment of ion kinetic effects in a direct-drive capsule implosion experiment

    NASA Astrophysics Data System (ADS)

    Le, A.; Kwan, T. J. T.; Schmitt, M. J.; Herrmann, H. W.; Batha, S. H.

    2016-10-01

    The first simulations employing a kinetic treatment of both fuel and shell ions to model inertial confinement fusion experiments are presented, including results showing the importance of kinetic physics processes in altering fusion burn. A pair of direct drive capsule implosions performed at the OMEGA facility with two different gas fills of deuterium, tritium, and helium-3 are analyzed. During implosion shock convergence, highly non-Maxwellian ion velocity distributions and separations in the density and temperature amongst the ion species are observed. Diffusion of fuel into the capsule shell is identified as a principal process that degrades fusion burn performance.

  18. Simulation and assessment of ion kinetic effects in a direct-drive capsule implosion experiment

    SciTech Connect

    Le, Ari Yitzchak; Kwan, Thomas J. T.; Schmitt, Mark J.; Herrmann, Hans W.; Batha, Steven H.

    2016-10-24

    The first simulations employing a kinetic treatment of both fuel and shell ions to model inertial confinement fusion experiments are presented, including results showing the importance of kinetic physics processes in altering fusion burn. A pair of direct drive capsule implosions performed at the OMEGA facility with two different gas fills of deuterium, tritium, and helium-3 are analyzed. During implosion shock convergence, highly non-Maxwellian ion velocity distributions and separations in the density and temperature amongst the ion species are observed. Finally, diffusion of fuel into the capsule shell is identified as a principal process that degrades fusion burn performance.

  19. Measuring and Imaging Metal Ions With Fluorescence-Based Biosensors: Speciation, Selectivity, Kinetics, and Other Issues.

    PubMed

    Thompson, Richard B; Fierke, Carol A

    2017-01-01

    Fluorescence-based biosensors have shown themselves to be a powerful tool for the study of a variety of chemical species in biological systems, notably including metal ions. This chapter provides an overview of several important issues in using such sensors to study metallobiochemistry. These issues include selectivity for the analyte over potential interferents, including those that do not themselves induce a signal, the different forms in which metal ions are found (speciation), the utility of metal ion buffers, and the importance of kinetics in studying metal ion binding reactions. Finally, the chapter briefly discusses some of the issues in understanding whole-organism distribution of metal ions and its control.

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

    SciTech Connect

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

    2016-01-15

    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.

  1. 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.

  2. 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.

  3. Determining Ion-Aerosol Nucleation Rates in the Lower Atmosphere: Thermodynamic and Kinetic Modeling and Data Requirements

    NASA Astrophysics Data System (ADS)

    D'Auria, R.; Turco, R. P.

    2005-12-01

    In situ measurements in the free troposphere [Eichkorn et al., 2002] have detected massive positively charged clusters (up to 2500 amu) that appear to be composed of water, acetone and sulfuric acid. Previous modeling studies have suggested that such ionic clusters participate in a number of atmospheric processes, including aerosol formation [Yu and Turco, 1999] and phase transitions in polar stratospheric clouds [D'Auria and Turco, 2001a]. Other work [Lee et al., 2003] indicates that ultrafine particle bursts detected in the upper troposphere can be explained by negative ion clustering mechanisms constrained by laboratory thermodynamic data [Lovejoy et al., 2004], offering further evidence for ion-mediated nucleation. In the lower troposphere, where charged clusters containing hydrated acids, ammonia and a variety of organic compounds are seen, ion-based modeling can often explain nucleation events observed in this region [Yu and Turco, 2001]. We discuss the thermodynamic and kinetic aspects of ion growth and activation in the atmosphere, and describe a "hybrid" representation for common ion families that integrates laboratory measurements with quantum mechanical simulations of charged cluster structure and energetics [D'Auria and Turco, 2001b]. We show that a kinetic model of ion cluster evolution applicable to atmospheric phenomena, including particle nucleation, can be constructed using a hybrid data approach. We present recent results--based on high-level quantum mechanical geometry optimization and thermochemical calculations--for positive ion clusters composed of water, sulfuric acid and acetone [D'Auria, 2005]. It is argued that ions with ternary compositions provide a high degree of cluster stabilization, and are therefore likely to generate pre-condensation nuclei throughout the lower atmosphere. We also discuss errors in the determination of cluster free energies and entropies under atmospheric conditions, and identify the types and precision of data

  4. 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.

  5. Stormtime Subauroral Density Troughs: Ion-Molecule Kinetics Effects

    DTIC Science & Technology

    2007-11-02

    trap to measure the total ion density (ni); and (4) a coincided with an increase in the energy and intensity of spherical Langmuir probe to measure...Experiments Figure 3. Rate coefficients for the reaction (RI). Circles in a high-temperature flowing afterglow device (HTFA) and squares show the HTFA and...poleward part coincided with strong wave structures, energetic (ring current) ion precipitations, and enhanced vertical ion flows . One or several narrow

  6. Eigen kinetics in surface complexation of aqueous metal ions.

    PubMed

    van Leeuwen, Herman P

    2008-10-21

    The mechanism of chemisorption of aqueous metal ions at surfaces has long been a topical issue in such fields as soil chemistry and bioenvironmental science. Here it is quantitatively demonstrated for the first time that release of water from the inner hydration shell is the rate-limiting step in inner-sphere surface complexation. The reactive intermediate is an outer-sphere complex between metal ion and surface site, with an electrostatically controlled stability defined by Boltzmann statistics. Using tabulated dehydration rate constants for metal ions, the resulting scheme allows for prediction of rates of sorption of aqueous metal ions at any type of complexing surface.

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

    SciTech Connect

    Farid, N.; 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.

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

    NASA Astrophysics Data System (ADS)

    Farid, N.; Harilal, S. S.; Ding, H.; Hassanein, A.

    2013-07-01

    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.

  9. Comparison of the effects of wave-particle interactions and the kinetic suprathermal electron population on the acceleration of the solar wind

    NASA Astrophysics Data System (ADS)

    Tam, S. W. Y.; Chang, T.

    2002-12-01

    Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam & Chang (1999a,b). In this study, we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

  10. Kinetic modeling of charged particle cloud expansion and emission in magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    Ponomarjov, Maxim G.; Gunko, Yuri F.

    1995-02-01

    The kinetic theory of unsteady charged-partitle fluxes in electric and magnetic fields is dealt with. An attempt is made to extend the results of Narasimha ( J. Fluid Meth.12, 294-305, 1962) and Burgan et al. ( J. Plasma Phys.29, 139-142. 1983). These authors studied the neutral and electron gas expansion into a vacuum, respectively. Burgan et al. ( J. Plasma Phys.29, 139-142. 1953) considered the Vlasov equation, coupled self-consistently with the Poisson equation. The magnetic field effects were omitted. Gunko and Ponomarjov ( Vestnik St-Petersburg State Univ. Ser. 1, No. 2. 89-94, 1993; Astron. Nachr.316(1), 17-21, 1995) carried out an analysis of the magnetic field effect for a special case of particle emission. A general method is proposed for simulating the charged-particle cloud expansion and the emission from sources in both electric and magnetic fields based on the kinetic approach. It consists of the representation of any cloud or emission source by the superposition of point-like clouds or sources with the corresponding initial particle distribution. As examples, the expansion of the following spatial domains filled by charged particles are analyzed : the semi-space, the plane layer of finite thickness, the circular cylinder, and the spherically symmetric cloud. In all the cases considered, Maxwell initial velocity distribution has been used for homogeneous magnetic and electric fields. It is found that in the case of the spherical cloud expansion, the cloud configuration at large times tends to an ellipsoid whose major axis expands along the magnetic field. Obtained results support the suggestion that this method has addressed the problem of plasma-cloud expansion into a uniform magnetic. field, with emphasis on the dynamics of lower density parts which appear to be highly structured in the form of field aligned striations (Davis et al., Planet. Space Sci.22, 67-78, 1974). Different specific situations for a small charged-particle source is considered

  11. 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.

  12. On the estimation of cooperativity in ion channel kinetics: activation free energy and kinetic mechanism of Shaker K+ channel.

    PubMed

    Banerjee, Kinshuk; Das, Biswajit; Gangopadhyay, Gautam

    2013-04-28

    In this paper, we have explored generic criteria of cooperative behavior in ion channel kinetics treating it on the same footing with multistate receptor-ligand binding in a compact theoretical framework. We have shown that the characterization of cooperativity of ion channels in terms of the Hill coefficient violates the standard Hill criteria defined for allosteric cooperativity of ligand binding. To resolve the issue, an alternative measure of cooperativity is proposed here in terms of the cooperativity index that sets a unified criteria for both the systems. More importantly, for ion channel this index can be very useful to describe the cooperative kinetics as it can be readily determined from the experimentally measured ionic current combined with theoretical modelling. We have analyzed the correlation between the voltage value and slope of the voltage-activation curve at the half-activation point and consequently determined the standard free energy of activation of the ion channel using two well-established mechanisms of cooperativity, namely, Koshland-Nemethy-Filmer (KNF) and Monod-Wyman-Changeux (MWC) models. Comparison of the theoretical results for both the models with appropriate experimental data of mutational perturbation of Shaker K(+) channel supports the experimental fact that the KNF model is more suitable to describe the cooperative behavior of this class of ion channels, whereas the performance of the MWC model is unsatisfactory. We have also estimated the mechanistic performance through standard free energy of channel activation for both the models and proposed a possible functional disadvantage in the MWC scheme.

  13. A comparative study of ion exchange kinetics in zinc/lead-modified zeolite-clinoptilolite systems.

    PubMed

    Trgo, M; Perić, J; Medvidović, N Vukojević

    2006-08-25

    The kinetics of zinc and lead ions removal by modified zeolite-clinoptilolite has been investigated. The rate of the ion exchange process for lead ions is faster than for zinc ions, as well as the time needed to reach the equilibrium. The ion exchange capacity of zeolite of lead ions is doubly higher than that of zinc ions. Diffusion models according to the Vermeulen's approximation, the parabolic diffusion model and the homogeneous diffusion model have been tested with the experimental data of ion exchange for zinc and lead. For both systems examined, the best fit of the models proposed with the experimental data was shown by the Vermeulen's approximation and the homogeneous diffusion model with t-->t(infinity). The diffusion coefficients are calculated from kinetic models of lead ions they are of the order of 10(-6)cm(2)/min, constant for all examined initial concentrations and not dependent on time. The diffusion coefficients in the system of zinc ions is of the order of 10(-8)cm(2)/min, also independent of initial concentrations, but decreasing with time from the beginning of ion exchange to the equilibrium.

  14. 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.

  15. Luminescent oxygen channeling immunoassay: measurement of particle binding kinetics by chemiluminescence.

    PubMed Central

    Ullman, E F; Kirakossian, H; Singh, S; Wu, Z P; Irvin, B R; Pease, J S; Switchenko, A C; Irvine, J D; Dafforn, A; Skold, C N

    1994-01-01

    A method for monitoring formation of latex particle pairs by chemiluminescence is described. Molecular oxygen is excited by a photosensitizer and an antenna dye that are dissolved in one of the particles. 1 delta gO2 diffuses to the second particle and initiates a high quantum yield chemiluminescent reaction of an olefin that is dissolved in it. The efficiency of 1 delta gO2 transfer between particles is approximately 3.5%. The technique permits real-time measurement of particle binding kinetics. Second-order rate constants increase with the number of receptor binding sites on the particles and approach diffusion control. By using antibody-coated particles, a homogeneous immunoassay capable of detecting approximately 4 amol of thyroid-stimulating hormone in 12 min was demonstrated. Single molecules of analyte produce particle heterodimers that are detected even when no larger aggregates are formed. PMID:8202502

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    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.

  18. 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

  19. 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.

  20. Combined Experimental and Theoretical Approach to the Kinetics of Magnetite Crystal Growth from Primary Particles

    PubMed Central

    2017-01-01

    It is now recognized that nucleation and growth of crystals can occur not only by the addition of solvated ions but also by accretion of nanoparticles, in a process called nonclassical crystallization. The theoretical framework of such processes has only started to be described, partly due to the lack of kinetic or thermodynamic data. Here, we study the growth of magnetite nanoparticles from primary particles—nanometer-sized amorphous iron-rich precursors—in aqueous solution at different temperatures. We propose a theoretical framework to describe the growth of the nanoparticles and model both a diffusion-limited and a reaction-limited pathway to determine which of these best describes the rate-limiting step of the process. We show that, based on the measured iron concentration and the related calculated concentration of primary particles at the steady state, magnetite growth is likely a reaction-limited process, and within the framework of our model, we propose a phase diagram to summarize the observations. PMID:28225626

  1. 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.

  2. The role of multivalency in the association kinetics of patchy particle complexes

    NASA Astrophysics Data System (ADS)

    Newton, Arthur C.; Groenewold, Jan; Kegel, Willem K.; Bolhuis, Peter G.

    2017-06-01

    Association and dissociation of particles are elementary steps in many natural and technological relevant processes. For many such processes, the presence of multiple binding sites is essential. For instance, protein complexes and regular structures such as virus shells are formed from elementary building blocks with multiple binding sites. Here we address a fundamental question concerning the role of multivalency of binding sites in the association kinetics of such complexes. Using single replica transition interface sampling simulations, we investigate the influence of the multivalency on the binding kinetics and the association mechanism of patchy particles that form polyhedral clusters. When the individual bond strength is fixed, the kinetics naturally is very dependent on the multivalency, with dissociation rate constants exponentially decreasing with the number of bonds. In contrast, we find that when the total bond energy per particle is kept constant, association and dissociation rate constants turn out rather independent of multivalency, although of course still very dependent on the total energy. The association and dissociation mechanisms, however, depend on the presence and nature of the intermediate states. For instance, pathways that visit intermediate states are less prevalent for particles with five binding sites compared to the case of particles with only three bonds. The presence of intermediate states can lead to kinetic trapping and malformed aggregates. We discuss implications for natural forming complexes such as virus shells and for the design of artificial colloidal patchy particles.

  3. 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)

  4. Kinetic effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Siminos, Evangelos; Svedung Wettervik, Benjamin; Grech, Mickael; Fülöp, Tünde

    2016-10-01

    We study kinetic effects responsible for the transition to relativistic self-induced transparency in the interaction of a circularly-polarized laser-pulse with an overdense plasma and their relation to hole-boring and ion acceleration. It is shown, using particle-in-cell simulations and an analysis of separatrices in single-particle phase-space, that this transition is mediated by the complex interplay of fast electron dynamics and ion motion at the initial stage of the interaction. It thus depends on the ion charge-to-mass ratio and can be controlled by varying the laser temporal profile. Moreover, we find a new regime in which a transition from relativistic transparency to hole-boring occurs dynamically during the course of the interaction. It is shown that, for a fixed laser intensity, this dynamic transition regime allows optimal ion acceleration in terms of both energy and energy spread. This work was supported by the Knut and Alice Wallenberg Foundation (pliona project) and the European Research Council (ERC-2014-CoG Grant 647121).

  5. 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.

  6. Kinetics of ion carbonitriding of constructional steels with direct hardening

    NASA Astrophysics Data System (ADS)

    Grigor'ev, V. S.; Solodkin, G. A.; Shevchuk, S. A.

    1991-07-01

    The action of a glow discharge plasma in carbonitriding of steel provides high kinetic effectiveness of the process, the parameters of which exceed those of vacuum carburizing by no less than 1.5 times and of gas carburizing by no less than 2.0 times at the same temperatures.

  7. 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. 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. Furthermore, we expect that the success of our simple

  8. 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

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

    DOE PAGES

    Hoffman, Nelson M.; Zimmerman, George B.; Molvig, Kim; ...

    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

  10. 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.

  11. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    DOE PAGES

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; ...

    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

  12. Kinetic characteristics of ions in the gas discharge and on the target surface

    NASA Astrophysics Data System (ADS)

    Maiorov, S. A.; Kodanova, S. K.; Golyatina, R. I.; Ramazanov, T. S.

    2017-06-01

    The drift velocities of ions in a constant homogeneous electric field are calculated using Monte Carlo simulations for noble-gas and some metal vapors. The ion mobility is analyzed as a function of the field strength and gas temperature. A general approximate formula for the dependence of the drift velocity on the reduced field and gas temperature is derived. The results of calculations of kinetic characteristics of ions crossing the surface of the target are presented. The authors focus on the angular and energy distributions of ions and differences between the distributions of the average volume and the average flow on the surface.

  13. The role of kinetic effects, including plasma rotation and energetic particles, in resistive wall mode stability

    SciTech Connect

    Berkery, J. W.; Sabbagh, S. A.; Reimerdes, H.; Betti, R.; Hu, B.; Bell, R. E.; Gerhardt, S. P.; Manickam, J.; Podesta, M.

    2010-08-15

    The resistive wall mode (RWM) instability in high-beta tokamaks is stabilized by energy dissipation mechanisms that depend on plasma rotation and kinetic effects. Kinetic modification of ideal stability calculated with the 'MISK' code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)] is outlined. For an advanced scenario ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)] plasma, the present calculation finds that alpha particles are required for RWM stability at presently expected levels of plasma rotation. Kinetic stabilization theory is tested in an experiment in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] that produced marginally stable plasmas with various energetic particle contents. Plasmas with the highest and lowest energetic particle content agree with calculations predicting that increased energetic particle pressure is stabilizing but does not alter the nonmonotonic dependence of stability on plasma rotation due to thermal particle resonances. Presently, the full MISK model, including thermal particles and an isotropic slowing-down distribution function for energetic particles, overpredicts stability in NSTX experiments. Minor alteration of either effect in the theory may yield agreement; several possibilities are discussed.

  14. 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.

    2016-11-01

    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.

  15. Formation of gas-phase peptide ions and their dissociation in MALDI: insights from kinetic and ion yield studies.

    PubMed

    Moon, Jeong Hee; Yoon, Sohee; Bae, Yong Jin; Kim, Myung Soo

    2015-01-01

    Insights on mechanisms for the generation of gas-phase peptide ions and their dissociation in matrix-assisted laser desorption ionization (MALDI) gained from the kinetic and ion yield studies are presented. Even though the time-resolved photodissociation technique was initially used to determine the dissociation kinetics of peptide ions and their effective temperature, it was replaced by a simpler method utilizing dissociation yields from in-source decay (ISD) and post-source decay (PSD). The ion yields for a matrix and a peptide were measured by repeatedly irradiating a region on a sample and collecting ion signals until the sample in the region was completely depleted. Matrix- and peptide-derived gas-phase cations were found to be generated by pre-formed ion emission or by ion-pair emission followed by anion loss, but not by laser-induced ionization. The total number of ions, that is, matrix plus peptide, was found to be equal to the number of ions emitted from a pure matrix. A matrix plume was found to cool as it expanded, from around 800-1,000 K to 400-500 K. Dissociation of peptide ions along b/y channels was found to occur statistically, that is, following RRKM behavior. Small critical energy (E0  = 0.6-0.7 eV) and highly negative critical entropy (ΔS(‡)  = -30 to -25 eu) suggested that the transition structure was stabilized by multiple intramolecular interactions.

  16. Comparisons of Kinetic Electron Models in Gyrokinetic Particle Simulations

    NASA Astrophysics Data System (ADS)

    Wang, W. X.; Lin, Z.; Lewandowski, J. L. V.; Lee, W. W.

    2001-10-01

    Comparisons of the hybrid [1] and split-weight [2,3] schemes for the electron dynamics in gyrokinetic particle simulations has been carried out. The emphasis here is to understand the regions of validity for these schemes as well as their numerical properties with regard to noise, time step and accuracy. The numerical issues for the implementation of these schemes in our 3D global gyrokinetic particle code (GTC) in general geometry [4] will also be discussed. Work supported by US DoE. [1] Z. Lin and L. Chen, Phys. Plasmas <8>, 1447 (2001). [2] I. Manuilskiy and W. W. Lee, Phys. Plasmas <7>, 1381 (2000). [3] W. W. Lee, J. L. V. Lewandowski, T. S. Hahm and Z. Lin, Phys. Plasmas (to appear). [4] Z. Lin, T. S. Hahm, W. W. Lee, W. M. Tang and R. White, Science <281>, 1835 (1998).

  17. 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.

  18. KINETIC EVOLUTION OF CORONAL HOLE PROTONS BY IMBALANCED ION-CYCLOTRON WAVES: IMPLICATIONS FOR MEASUREMENTS BY SOLAR PROBE PLUS

    SciTech Connect

    Isenberg, Philip A.; Vasquez, Bernard J.

    2015-08-01

    We extend the kinetic guiding-center model of collisionless coronal hole protons presented in Isenberg and Vasquez to consider driving by imbalanced spectra of obliquely propagating ion-cyclotron waves. These waves are assumed to be a small by-product of the imbalanced turbulent cascade to high perpendicular wavenumber, and their total intensity is taken to be 1% of the total fluctuation energy. We also extend the kinetic solutions for the proton distribution function in the resulting fast solar wind to heliocentric distances of 20 solar radii, which will be attainable by the Solar Probe Plus spacecraft. We consider three ratios of outward-propagating to inward-propagating resonant intensities: 1, 4, and 9. The self-consistent bulk flow speed reaches fast solar wind values in all cases, and these speeds are basically independent of the intensity ratio. The steady-state proton distribution is highly organized into nested constant-density shells by the resonant wave-particle interaction. The radial evolution of this kinetic distribution as the coronal hole plasma flows outward is understood as a competition between the inward- and outward-directed large-scale forces, causing an effective circulation of particles through the (v{sub ∥}, v{sub ⊥}) phase space and a characteristic asymmetric shape to the distribution. These asymmetries are substantial and persist to the outer limit of the model computation, where they should be observable by the Solar Probe Plus instruments.

  19. Nonlinear evolution of ion acoustic solitary waves in space plasmas: Fluid and particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Kakad, Bharati; Kakad, Amar; Omura, Yoshiharu

    2014-07-01

    Spacecraft observations revealed the presence of electrostatic solitary waves (ESWs) 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. We find that the number of trapped electrons in the wave potential is higher for the 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 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.

  20. Wave-particle energy exchange directly observed in a kinetic Alfvén-branch wave

    NASA Astrophysics Data System (ADS)

    Gershman, Daniel J.; F-Viñas, Adolfo; Dorelli, John C.; Boardsen, Scott A.; Avanov, Levon A.; Bellan, Paul M.; Schwartz, Steven J.; Lavraud, Benoit; Coffey, Victoria N.; Chandler, Michael O.; Saito, Yoshifumi; Paterson, William R.; Fuselier, Stephen A.; Ergun, Robert E.; Strangeway, Robert J.; Russell, Christopher T.; Giles, Barbara L.; Pollock, Craig J.; Torbert, Roy B.; Burch, James L.

    2017-03-01

    Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA's Magnetospheric Multiscale (MMS) mission, we utilize Earth's magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. The investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.

  1. Wave-particle energy exchange directly observed in a kinetic Alfvén-branch wave

    DOE PAGES

    Gershman, Daniel J.; F-Viñas, Adolfo; Dorelli, John C.; ...

    2017-03-31

    Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA’s Magnetospheric Multiscale (MMS) mission, we utilize Earth’s magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electronsmore » confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. As a result, the investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.« less

  2. Wave-particle energy exchange directly observed in a kinetic Alfvén-branch wave

    PubMed Central

    Gershman, Daniel J.; F-Viñas, Adolfo; Dorelli, John C.; Boardsen, Scott A.; Avanov, Levon A.; Bellan, Paul M.; Schwartz, Steven J.; Lavraud, Benoit; Coffey, Victoria N.; Chandler, Michael O.; Saito, Yoshifumi; Paterson, William R.; Fuselier, Stephen A.; Ergun, Robert E.; Strangeway, Robert J.; Russell, Christopher T.; Giles, Barbara L.; Pollock, Craig J.; Torbert, Roy B.; Burch, James L.

    2017-01-01

    Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA's Magnetospheric Multiscale (MMS) mission, we utilize Earth's magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. The investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations. PMID:28361881

  3. Wave-particle energy exchange directly observed in a kinetic Alfvén-branch wave.

    PubMed

    Gershman, Daniel J; F-Viñas, Adolfo; Dorelli, John C; Boardsen, Scott A; Avanov, Levon A; Bellan, Paul M; Schwartz, Steven J; Lavraud, Benoit; Coffey, Victoria N; Chandler, Michael O; Saito, Yoshifumi; Paterson, William R; Fuselier, Stephen A; Ergun, Robert E; Strangeway, Robert J; Russell, Christopher T; Giles, Barbara L; Pollock, Craig J; Torbert, Roy B; Burch, James L

    2017-03-31

    Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA's Magnetospheric Multiscale (MMS) mission, we utilize Earth's magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. The investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.

  4. Simulation study of overtaking of ion-acoustic solitons in the fully kinetic regime

    NASA Astrophysics Data System (ADS)

    Hosseini Jenab, S. M.; Spanier, F.

    2017-03-01

    The overtaking collisions of ion-acoustic solitons in the presence of trapping effects of electrons are studied based on a fully kinetic simulation approach. The method is able to provide all the kinetic details of the process alongside the fluid-level quantities self consistently. Solitons are produced naturally by utilizing the chain formation phenomenon, and then are arranged in a new simulation box to test the different scenarios of overtaking collisions. Three achievements are reported here. First, simulations prove the long-time life span of the ion-acoustic solitons in the presence of trapping effect of electrons (kinetic effects), which serves as the benchmark of the simulation code. Second, their stability against overtaking mutual collisions is established by creating collisions between solitons with different number and shapes of trapped electrons, i.e., different trapping parameter. Finally, details of solitons during collisions for both ions and electrons are provided on both fluid and kinetic levels. These results show that on the kinetic level, trapped electron population accompanying each of the solitons are exchanged between the solitons during the collision. Furthermore, the behavior of electron holes accompanying solitons contradicts the theory about the electron holes interaction developed based on kinetic theory. They also show behaviors much different from other electron holes witnessed in processes such as nonlinear Landau damping (Bernstein-Greene-Kruskal -BGK- modes) or beam-plasma interaction (like two-beam instability).

  5. The nonlinear evolution of driven nonlinear ion acoustic waves with kinetic electrons

    NASA Astrophysics Data System (ADS)

    Berger, Richard; Brunner, Stephan; Valeo, Ernest; Divol, Laurent; Still, Charles

    2006-10-01

    The stimulated Brillouin scattering (SBS) of laser light from hot plasma drives ion acoustic waves to large amplitudes particularly if the phase velocity is much greater than the ion thermal velocity for all ion species, that is, ZTe/Ti >>1 where Z is the charge state of the ion, and Te and Ti are the electron and ion temperatures. In fluid simulations of the SBS from CO2 and Krypton plasmas, ad hoc limits on the amplitude of the driven ion waves were required to match the measured reflectivity. Because ZTe/Ti >>1, ion kinetics are unlikely to play a role in the saturation of ion waves. Here, we study the effect of electron trapping which produces a positive frequency shift in quantitative agreement with theory (see abstract by S. Brunner et al., this meeting) and the role of electron kinetics on the decay instability of the driven ion wave. Further, we apply these results to modeling of experiments where ZTe/Ti >>1 [e.g., Glenzer et al., PRL 86, 2565 (2001), L. Divol, et al., Physics of Plasmas 10, 1822 (2003)].

  6. 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.

  7. Kinetic instabilities in pulsed operation mode of a 14 GHz electron cyclotron resonance ion source

    SciTech Connect

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

    2016-02-15

    The occurrence of kinetic plasma instabilities is studied in pulsed operation mode of a 14 GHz A-electron cyclotron resonance type electron cyclotron resonance ion source. It is shown that the temporal delay between the plasma breakdown and the appearance of the instabilities is on the order of 10-100 ms. The most important parameters affecting the delay are magnetic field strength and neutral gas pressure. It is demonstrated that kinetic instabilities limit the high charge state ion beam production in the unstable operating regime.

  8. Gating Kinetics and Ion Transfer in Channels of Nerve Membrane.

    DTIC Science & Technology

    1987-10-21

    and sea hare ( Aplysia ). In the classical squid axon preparation a detailed comparison between estimates of the relaxation time obtained via Hodgkin...Mrra nr . r -W, ,.r w -. r- _ ,,- Fishman, H.M. N00014-87-K-0055 Inward K Rectifier Channel Kinetics from Analysis of Complex Conductances in Aplysia ...Neuronal Membrane. The inward K rectifier in Aplysia neuron and Ba* blockade of the recti- fication process were studied by rapid measurement of

  9. Particle-in-cell Simulations with Kinetic Electrons

    SciTech Connect

    J.L.V. Lewandowski

    2004-02-12

    A new scheme, based on an exact separation between adiabatic and nonadiabatic electron responses, for particle-in-cell (PIC) simulations of drift-type modes is presented. The (linear and nonlinear) elliptic equations for the scalar fields are solved using a multi-grid solver. The new scheme yields linear growth rates in excellent agreement with theory and it is shown to conserve energy well into the nonlinear regime. It is also demonstrated that simulations with few electrons are reliable and accurate, suggesting that large-scale, PIC simulations with electron dynamics in toroidal geometry (e.g., tokamaks and stellarators plasmas) are within reach of present-day massively parallel supercomputers.

  10. Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion

    NASA Astrophysics Data System (ADS)

    Tsankov, Tsanko V.; Czarnetzki, Uwe

    2017-05-01

    Non-equilibrium distribution functions of electrons and ions play an important role in plasma physics. A prominent example is the kinetic Bohm criterion. Since its first introduction it has been controversial for theoretical reasons and due to the lack of experimental data, in particular on the ion distribution function. Here we resolve the theoretical as well as the experimental difficulties by an exact solution of the kinetic Boltzmann equation including charge exchange collisions and ionization. This also allows for the first time non-invasive measurement of spatially resolved ion velocity distributions, absolute values of the ion and electron densities, temperatures, and mean energies as well as the electric field and the plasma potential in the entire plasma. The non-invasive access to the spatially resolved distribution functions of electrons and ions is applied to the problem of the kinetic Bohm criterion. Theoretically a so far missing term in the criterion is derived and shown to be of key importance. With the new term the validity of the kinetic criterion at high collisionality and its agreement with the fluid picture are restored. All findings are supported by experimental data, theory and a numerical model with excellent agreement throughout.

  11. Kinetic, Thermochemical, and Photodissociation Studies of Sulfur- Containing Atmospheric Ions

    DTIC Science & Technology

    1987-08-29

    O:KO+ -o IH20’ 0 : K p 3 H2 SO 4+ /. 167 IHSO4 K 13- 0: Kp 6_’K p 12- AH- dssc 28.1 KcaVmole 11- 100 C -’ AHdissoc - 31.6 KcaI,/mole 9. for: H2S0 4(g) V...measurements of the rate of ion -molecule ’E. W McDaniel and E. A Mason. The Mobiliiy and Diffusion v/Ions in reacion yild atecontans avragd oer-man

  12. 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.

  13. Preequilibrium particle emissions and in-medium effects on the pion production in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Feng, Zhao-Qing

    2017-02-01

    Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, pion dynamics in heavy-ion collisions near threshold energies and the emission of preequilibrium particles (nucleons and light complex fragments) have been investigated. A density, momentum and isospin-dependent pion-nucleon potential based on the Δ-hole model is implemented in the transport approach, which slightly leads to the increase of the π-/π+ ratio, but reduces the total pion yields. It is found that a bump structure of the π-/π+ ratio in the kinetic energy spectra appears at the pion energy close to the Δ (1232) resonance region. The yield ratios of neutrons to protons from the squeeze-out particles perpendicular to the reaction plane are sensitive to the stiffness of nuclear symmetry energy, in particular at the high-momentum (kinetic energy) tails.

  14. A kinetic model of NMDA ion channel under varying noise

    NASA Astrophysics Data System (ADS)

    Wang, Rubin; Chen, Hao; Zhang, Zhikang

    2004-05-01

    It is well known that when transmitters are applied to the postsynaptic membrane, the resulting depolarization is noisy that is due to the random opening and closing of the ion channels activated by the transmitters[1]. In other words, the energy of noise is associated with changes in ion channels. On the base of these ideas, we explore a model of relationship between NMDA (n-methyl-D-aspartate) ion channels and LTP (long-term synaptic potentiation). We have proved that NMDA ion channel and calcium-dependent protein kinases, which are the triggers for the inducement of LTP, could be regarded as "molecular machines". In this system all of these molecules require energy and the energy of the system is supplied from the random motion of water molecules generated through heat energy of ATP hydrolysis[2]. So the appropriate framework to describe them comes from bioenergetics. Models of LTP previously reported are all on the macroscopic level [3-7]. Instead, we research a model at the molecular level by applying energy parameters [8].

  15. 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.

  16. 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.

  17. Solitary kinetic Alfvén wave in a bi-ion plasma with superthermal electrons

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Chen, L.

    2017-08-01

    The dispersion relation and the nonlinear solitary structure of kinetic Alfvén waves (KAWs) have been investigated in bi-ion plasma with superthermal electrons modeled by kappa (κ) distribution. A detailed analysis of the existence condition and the structure of solitary KAW (SKAW) is present. Numerical results indicate there is only the sub-Alfvénic hump type SKAW. For the same parallel phase velocity, the amplitude of SKAW will increase with the increase in the charge number of heavy ion, and with the decrease in the suprathermal index κ and the heavy ion number density. Moreover, the width of SKAW will increase with the decrease in the charge number of heavy ion, and with the increase in the super-thermal index κ and the heavy ion number density. The findings of the present study can be applied to low beta space plasma composed of multi-ion components and suprathermal electrons.

  18. Thermodynamics and kinetics of ion speciation in supercritical aqueous solutions: A molecular based study

    SciTech Connect

    Chialvo, A.A.; Cummings, P.T. |; Simonson, J.M.; Mesmer, R.E.

    1997-05-01

    Molecular simulation of infinitely dilute NaCl aqueous solutions are performed to study the Na{sup +}/Cl{sup -} ion pairing in a polarizable and a nonpolarizable solvent at supercritical conditions. The Simple Point Charge, Pettitt-Rossky, and Fumi-Tosi models for the water-water, ion-water, and ion-ion interactions are used in determining the degree of dissociation, its temperature and density dependence, and the kinetics of the interconversion between ion-pair configurations in a nonpolarizable medium. To assess the effect of the solvent polarizability on the stability of the ion-pair configurations, we replace the Simple Point Charge by the Polarizable Point Charge water model and determine the anion-cation potential of mean force at T{sub r}=1.20 and {rho}{sub r}=1.5.

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

    SciTech Connect

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

    2016-05-15

    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. 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.

  1. Interactive Computer Simulation and Animation for Improving Student Learning of Particle Kinetics

    ERIC Educational Resources Information Center

    Fang, N.; Guo, Y.

    2016-01-01

    Computer simulation and animation (CSA) has been receiving growing attention and wide application in engineering education in recent years. A new interactive CSA module was developed in the present study to improve student learning of particle kinetics in an undergraduate engineering dynamics course. The unique feature of this CSA module is that…

  2. Magnetic particle imaging: kinetics of the intravascular signal in vivo

    PubMed Central

    Haegele, Julian; Duschka, Robert L; Graeser, Matthias; Schaecke, Catharina; Panagiotopoulos, Nikolaos; Lüdtke-Buzug, Kerstin; Buzug, Thorsten M; Barkhausen, Jörg; Vogt, Florian M

    2014-01-01

    Background Magnetic particle imaging (MPI) uses magnetic fields to visualize superparamagnetic iron oxide nanoparticles (SPIO). Today, Resovist® is still the reference SPIO for MPI. The objective of this study was to evaluate the in vivo blood half-life of two different types of Resovist (one from Bayer Pharma AG, and one from I’rom Pharmaceutical Co Ltd) in MPI. Methods A Resovist concentration of 50 μmol/kg was injected into the ear artery of ten New Zealand White rabbits. Five animals received Resovist distributed by I’rom Pharmaceutical Co Ltd and five received Resovist by Bayer Pharma AG. Blood samples were drawn before and directly after injection of Resovist, at 5, 10, and 15 minutes, and then every 15 minutes until 120 minutes after the injection. The MPI signal of the blood samples was evaluated using magnetic particle spectroscopy. Results The average decline of the blood MPI signal from the two distributions differed significantly (P=0.0056). Resovist distributed by Bayer Pharma AG showed a slower decline of the MPI signal (39.7% after 5 minutes, 20.5% after 10 minutes, and 12.1% after 15 minutes) compared with Resovist produced by I’rom Pharmaceutical Co Ltd (20.4% after 5 minutes, 7.8% after 10 minutes, no signal above noise level after 15 minutes). Conclusion In MPI, the blood half-life of an SPIO tracer cannot be equalized to the blood half-life of its MPI signal. Resovist shows a very rapid decline of blood MPI signal and is thus not suitable as a long circulating tracer. For cardiovascular applications in MPI, it may be used as a bolus tracer. PMID:25214784

  3. Kinetic characteristics of brush border sucrase activation by Na+ ions in mice intestine.

    PubMed

    Gupta, Shiffalli; Mahmood, Safrun; Mahmood, Akhtar

    2009-10-01

    The kinetics of Na+ activation of brush border sucrase (sucrose D-glucosidase E.C. 3.2.1.48) has been studied in mice intestine. At pH 5.0, 50 mM Na+ ions stimulated sucrase activity by 84%. At pH 7.2, enzyme stimulation was reduced to 16%, whereas, atpH 8.5, 10-100 mMNa+ ions produced 18-45% inhibition of enzyme activity. Kinetic studies revealed that at pH 5.0, the enzyme activation by Na+ ions was V-type, which changed to K-type atpH 7.2, whereas at alkaline pH (8.5), Na+ ions inhibited the enzyme activity non-competitively. Using the non-compulsory model of Na+ ion stimulation of brush border sucrase [Mahmood & Alvarado, Arch Bioch Biophys, 168 (1975) 585] various kinetic constants involved in activation of sucrase by Na ions were determined. It is apparent that Na+ stimulation of brush border sucrase is pH dependent, which is similar to that described for rat, rabbit and other mammalian species and conform to identical mechanisms, at least with reference to the affinity type effects, as observed in mice intestine.

  4. 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

  5. Characteristics of SME biodiesel-fueled diesel particle emissions and the kinetics of oxidation.

    PubMed

    Jung, Heejung; Kittelson, David B; Zachariah, Michael R

    2006-08-15

    Biodiesel is one of the most promising alternative diesel fuels. As diesel emission regulations have become more stringent, the diesel particulate filter (DPF) has become an essential part of the aftertreatment system. Knowledge of kinetics of exhaust particle oxidation for alternative diesel fuels is useful in estimating the change in regeneration behavior of a DPF with such fuels. This study examines the characteristics of diesel particulate emissions as well as kinetics of particle oxidation using a 1996 John Deere T04045TF250 off-highway engine and 100% soy methyl ester (SME) biodiesel (B100) as fuel. Compared to standard D2 fuel, this B100 reduced particle size, number, and volume in the accumulation mode where most of the particle mass is found. At 75% load, number decreased by 38%, DGN decreased from 80 to 62 nm, and volume decreased by 82%. Part of this decrease is likely associated with the fact that the particles were more easily oxidized. Arrhenius parameters for the biodiesel fuel showed a 2-3times greater frequency factor and approximately 6 times higher oxidation rate compared to regular diesel fuel in the range of 700-825 degrees C. The faster oxidation kinetics should facilitate regeneration when used with a DPF.

  6. Kinetic energies of fragment ions produced by dissociative photoionization of NO

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Angel, G. C.; Rstgi, O. P.

    1985-01-01

    The kinetic energies of ions produced by dissociative photoionization of NO have been measured at the discrete resonance lines of He (584A) and Ne (736A), and with undispersed synchrotron radiation. O sup + ions were identified with energies from 0 to approximately 0.5 eV and two groups of N sup + ions one with energy of 0.36 eV and another with energies between 0.9 and 1.5 eV, apparently produced by predissociation of the C sup 3 P 1 and B'1 sigma states respectively.

  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. 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.

  9. 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.

  10. Observation of ions and particles near busy roads using a neutral cluster and air ion spectrometer (NAIS)

    NASA Astrophysics Data System (ADS)

    Jayaratne, E. R.; Ling, X.; Morawska, L.

    2014-02-01

    Motor vehicles emit large quantities of ions in the form of both charged particles and molecular cluster ions. While, the health effects of inhalation of charged particles is largely unexplored, the concentrations near busy roads and the distance to which these particles and ions are carried have important implications for the exposure of the large percentage of the population that lives close to such roadways. We measured ion concentrations using a neutral cluster and air ion spectrometer (NAIS) near seven busy roads carrying on the average approximately 7000 vehicles h-1 including about 15% heavy duty diesel vehicles. In this study, charged particle concentrations were measured as a function of downwind distance from the road for the first time. We show that, at a moderate wind speed of 2.0 m s-1, mean charged particle concentrations at the kerb were of the order of 2 × 104 cm-3 and, more importantly, decreased as d-0.6 where d is the distance from the road. While cluster ions were rapidly depleted by attachment to particles and were not carried to more than about 20 m from the road, elevated concentrations of charged particle were detected up to at least 400 m from the road. Most of the charge on the downwind side was carried on the larger particles, with no excess charge on particles smaller than about 10 nm. At 30 nm, particles carried more than double the charge they would normally carry in equilibrium. There are very few measurements of ions near road traffic and this is the first study of the spatial dispersion of charged particles from a road.

  11. Cobalt, chromium and molybdenum ions kinetics in the human body: data gained from a total hip replacement with massive third body wear of the head and neuropathy by cobalt intoxication.

    PubMed

    Pazzaglia, U E; Apostoli, P; Congiu, T; Catalani, S; Marchese, M; Zarattini, G

    2011-09-01

    A patient with a total hip replacement developed optic, acoustic and peripheral neuropathy from metal ions intoxication, due to the wear products released from the prosthesis. Subsequently the kinetics of the metal ions was studied. Massive wear and acute intoxication allowed a study of the metal ions kinetics and of EDTA treatment. Plasma and other organic fluids were saturated by each of the metal ions released from the exposed surface according to the solubility of each ion; a larger fraction of Co ions was bound within red cells, while the plasmatic fraction appeared more movable. In a patient with a prosthesis subjected to wear, the ions released are from the prosthetic and from the debris surface (spread in the body). The latter is a function of the number and size of particles. Revision of the prosthesis from the point of view of the metal ions kinetics corresponded to a reduction of the releasing surface because of debris washed out by irrigation and tissue excision; however, the metal particles spread by lymphatic circulation continued to release ions even though the source of wear had been removed. Early diagnosis of high metal wear can be ascertained with mass spectrometry and after revision high levels of metal ions can only be reduced with repeated chelating treatment. It is preferable not to revise fractured ceramic components with a polyethylene-metal articulation.

  12. 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.

  13. Ion kinetic energy distributions and cross sections for the electron impact ionization of ethyl tert-butyl ether

    NASA Astrophysics Data System (ADS)

    Di Palma, T. M.; Apicella, B.; Armenante, M.; Velotta, R.; Wang, X.; Spinelli, N.

    2005-11-01

    The kinetic energy distributions and the cross sections of the ions produced in the electron impact of ethyl tert-butyl ether (ETBE) have been studied by time of flight (TOF) mass spectrometry. The kinetic energy distributions have been deduced from the TOF peak shape analysis and a Montecarlo simulation method of the ion trajectories has been used to evaluate the collection efficiency of the spectrometer as a function of the ion initial kinetic energy. The measured ion yields have been corrected for the collection efficiency and the partial and total ionization cross sections of ETBE determined in the range 20-150 eV.

  14. 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.

  15. Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: vibrational kinetics and negative ions control

    NASA Astrophysics Data System (ADS)

    Diomede, P.; Bruneau, B.; Longo, S.; Johnson, E.; Booth, J.-P.

    2017-07-01

    A comprehensive hybrid model of a hydrogen capacitively coupled plasma, including a detailed description of the molecular vibrational kinetics, has been applied to the study of the effect of tailored voltage waveforms (TVWs) on the production kinetics and transport of negative ions in these discharges. Two kinds of TVWs are considered, valleys-to-peaks and saw-tooth, with amplitude and slope asymmetry respectively. By tailoring the voltage waveform only, it is possible to exert substantial control over the peak density and position of negative ions inside the discharge volume. This control is particularly effective for saw-tooth waveforms. Insight into the mechanisms allowing this control is provided by an analysis of the model results. This reveals the roles of the vibrational distribution function and of the electron energy distribution and their correlations, as well as changes in the negative ion transport in the electric field when using different TVWs. Considering the chemical reactivity of H- ions, the possibility of a purely electrical control of the negative ion cloud in a reactor operating with a feedstock gas diluted by hydrogen may find interesting applications. This is the first study of vibrational kinetics in the context of TVWs in molecular gases.

  16. 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

  17. 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

  18. 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.

  19. Three-dimensional particle-in-cell simulation of a miniature plasma source for a microwave discharge ion thruster

    NASA Astrophysics Data System (ADS)

    Takao, Yoshinori; Koizumi, Hiroyuki; Komurasaki, Kimiya; Eriguchi, Koji; Ono, Kouichi

    2014-12-01

    We have developed a three-dimensional particle model for a miniature microwave discharge ion thruster to elucidate the mechanism of ECR discharges confined in a small space. The model consists of a particle-in-cell simulation with a Monte Carlo collision algorithm (PIC-MCC) for the kinetics of charged particles, a finite-difference time-domain method for the electromagnetic fields of 4.2 GHz microwaves, and a finite element analysis for the magnetostatic fields of permanent magnets. The PIC-MCC results have shown that the electrons are well confined owing to the mirror magnetic fields and can be effectively heated in the ECR layer downstream of a ring-shaped antenna. The confinement results in the ring-shaped profiles of the plasma density along the antenna. The visual appearance of the plasma discharge of the thruster in operation was also ring-shaped. Moreover, the ions are expected to be accelerated effectively through the grid electrode without a large loss of ions toward side walls, that is, the plasma source developed here would be desirable in ion thrusters.

  20. A kinetic model for heterogeneous condensation of vapor on an insoluble spherical particle.

    PubMed

    Luo, Xisheng; Fan, Yu; Qin, Fenghua; Gui, Huaqiao; Liu, Jianguo

    2014-01-14

    A kinetic model is developed to describe the heterogeneous condensation of vapor on an insoluble spherical particle. This new model considers two mechanisms of cluster growth: direct addition of water molecules from the vapor and surface diffusion of adsorbed water molecules on the particle. The effect of line tension is also included in the model. For the first time, the exact expression of evaporation coefficient is derived for heterogeneous condensation of vapor on an insoluble spherical particle by using the detailed balance. The obtained expression of evaporation coefficient is proved to be also correct in the homogeneous condensation and the heterogeneous condensation on a planar solid surface. The contributions of the two mechanisms to heterogeneous condensation including the effect of line tension are evaluated and analysed. It is found that the cluster growth via surface diffusion of adsorbed water molecules on the particle is more important than the direct addition from the vapor. As an example of our model applications, the growth rate of the cap shaped droplet on the insoluble spherical particle is derived. Our evaluation shows that the growth rate of droplet in heterogeneous condensation is larger than that in homogeneous condensation. These results indicate that an explicit kinetic model is benefit to the study of heterogeneous condensation on an insoluble spherical particle.

  1. 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.

  2. Automated system for kinetic analysis of particle size distributions for pharmaceutically relevant systems.

    PubMed

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

    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 [Ca(2+)] 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.

  3. 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

  4. 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.

  5. Kinetics of interlayer ion migration in non-swelling clays: An atomic-scale study

    NASA Astrophysics Data System (ADS)

    Lammers, L. N.; Kolluri, K.

    2015-12-01

    Clay-rich geologic repositories serve as hosts for fossil methane reserves and as traps for contaminant radionuclides and sequestered CO2. Despite the abundance of non-swelling clay minerals in sedimentary formations, the mechanisms of ion exchange and mass transport mediated by these minerals are not well understood. Ion exchange kinetics in collapsed clays are characterized by a long tail of slow exchange, which suggests that interlayer ions can exchange with the bulk solution. Recent High-Resolution TEM evidence suggests that Cs+ ion exchange K+ in collapsed interlayers leads to interstratified structures, where entire interlayers are completely exchanged while others remain pristine [Okamura T et al., (2005) Microscopy 6365-72]. This phenomenon could be explained by kinetic feedbacks arising when a larger ion substitutes for a smaller one, although the details of this exchange mechanism are currently unknown. We investigated the kinetics and mechanisms of interlayer cation migration in illite (K0.7Al2[Al0.7Si3.3O10](OH)2) using molecular simulations. A Monte Carlo scheme was used to distribute interlayer K ions, and these ions were found to prefer sites neighboring two or more Al3+ substitutions in the tetrahedral sheets. Interlayer K+ ion migration between stable ditrigonal cavity sites was observed directly in molecular dynamics simulations performed at temperatures ranging from 500 K to 900 K and at constant volume. The Climbing Image Nudged Elastic Band method was used to determine the activation energy barrier on 660 K+ ion migration paths. Interlayer ions were observed to migrate between stable lattice sites with migration barriers of 2.35 ± 1.06 eV. Only about 20% of this variation is statistically explained by the distribution of charge deficit sites in the layer caused by Al3+ substitution for Si4+. Remarkably, we find that migration barriers decrease as we increase interlayer spacing. These results suggest that frayed edge sites - local regions with

  6. 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

  7. 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.

  8. Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering

    NASA Astrophysics Data System (ADS)

    Chan, Wai Lun; Chason, Eric

    2007-06-01

    When collimated beams of low energy ions are used to bombard materials, the surface often develops a periodic pattern or "ripple" structure. Different types of patterns are observed to develop under different conditions, with characteristic features that depend on the substrate material, the ion beam parameters, and the processing conditions. Because the patterns develop spontaneously, without applying any external mask or template, their formation is the expression of a dynamic balance among fundamental surface kinetic processes, e.g., erosion of material from the surface, ion-induced defect creation, and defect-mediated evolution of the surface morphology. In recent years, a comprehensive picture of the different kinetic mechanisms that control the different types of patterns that form has begun to emerge. In this article, we provide a review of different mechanisms that have been proposed and how they fit together in terms of the kinetic regimes in which they dominate. These are grouped into regions of behavior dominated by the directionality of the ion beam, the crystallinity of the surface, the barriers to surface roughening, and nonlinear effects. In sections devoted to each type of behavior, we relate experimental observations of patterning in these regimes to predictions of continuum models and to computer simulations. A comparison between theory and experiment is used to highlight strengths and weaknesses in our understanding. We also discuss the patterning behavior that falls outside the scope of the current understanding and opportunities for advancement.

  9. Combining electromagnetic gyro-kinetic particle-in-cell simulations with collisions

    NASA Astrophysics Data System (ADS)

    Slaby, Christoph; Kleiber, Ralf; Könies, Axel

    2017-09-01

    It has been an open question whether for electromagnetic gyro-kinetic particle-in-cell (PIC) simulations pitch-angle collisions and the recently introduced pullback transformation scheme (Mishchenko et al., 2014; Kleiber et al., 2016) are consistent. This question is positively answered by comparing the PIC code EUTERPE with an approach based on an expansion of the perturbed distribution function in eigenfunctions of the pitch-angle collision operator (Legendre polynomials) to solve the electromagnetic drift-kinetic equation with collisions in slab geometry. It is shown how both approaches yield the same results for the frequency and damping rate of a kinetic Alfvén wave and how the perturbed distribution function is substantially changed by the presence of pitch-angle collisions.

  10. 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

  11. Kinetic modeling of ion conduction in KcsA potassium channel

    NASA Astrophysics Data System (ADS)

    Mafé, Salvador; Pellicer, Julio; Cervera, Javier

    2005-05-01

    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 NH4+ are obtained and compared with those of other ions (the NH4+ 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 could limit conduction at high

  12. Thermal ablation of plasma-facing surfaces in tokamak disruptions: Sensitivity to particle kinetic energy

    SciTech Connect

    Ehst, D.A.; Hassanein, A.

    1996-02-01

    Ablation damage to solid targets with high heat flux impulses is generally greater high-energy electron beam heat sources compared to low-energy plasma guns. This sensitivity to incoming particle kinetic energy is explored with computer modelling; a fast-running routine (DESIRE) is developed for initial scoping analysis and is found to be in reasonable agreement with several experiments on graphite and tungsten targets. If tokamak disruptions are characterized by particle energies less than {approximately}1 keV, then we expect plasma guns are a better analogue than electron beams for simulating disruption behavior and testing candidate plasma-facing materials.

  13. 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.

  14. Brownian particle-kinetics in a superparamagnetic ferrofluid subjected to static magnetic-field

    NASA Astrophysics Data System (ADS)

    Trisnanto, Suko Bagus; Kitamoto, Yoshitaka

    2017-01-01

    The stochastic Brownian particle-kinetics in a superparamagnetic ferrofluid at room temperature is of significance in nullifying total magnetization vectors of the suspended particles. Correspondingly, the apparent magnetization response observed under static magnetic field shows no hysteresis loop, but being linear at a given finite field-difference. Owing to this superparamagnetism, we propose a differential magnetometry to analyze the static field-induced particle-kinetics and further to identify the effective field-strength in reorienting particle-moments toward the applied field direction. A polydispersive ferrofluid containing iron-oxide nanoparticles, in practice, is subjected to a very-low oscillatory-field, immediately after applying the static-field. For a given frequency, we confirm a decreasing ac susceptibility as dc field-strength increases, which suggests a statistically less fluctuating magnetization-vectors. Via numerical integration of ac susceptibility recorded, we furthermore estimate the nonlinear quasi-static magnetization at various measurement frequencies. The resulting nonlinearity is attributable to the contributing relaxation dynamics of the particles. More importantly, the difference between dc and ac susceptibilities is found to be field-strength and frequency-dependent. Its value is further maximized at an effective field-strength, from which we identified the coexisting energy-barriers.

  15. 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.

  16. Nanocrystalline MgMnSiO4 and MgCoSiO4 particles for rechargeable Mg-ion batteries

    NASA Astrophysics Data System (ADS)

    Truong, Quang Duc; Devaraju, Murukanahally Kempaiah; Honma, Itaru

    2017-09-01

    Magnesium-ion batteries hold promise as next-generation secondary battery systems owing to its low cost, safety and high volumetric capacity. Magnesium metal silicates exhibit potential electrode materials with high specific capacities. However, the strong electrostatic interaction between Mg2+ and host lattice due to its divalency as well as antisite cation exchange, induces slow intercalation kinetics of Mg ions within the crystal lattices. Thus, nanocrystalline particles with shortened Mg ion diffusion distance enable the insertion/extraction of Mg ions and improve specific capacities of the batteries. Herein, we report the low-temperature production of crystalline MgMnSiO4 and MgCoSiO4 nanoparticles by a rapid supercritical fluid processing. The extraction of magnesium ions from the olivine framework has been confirmed by X-ray photoelectron spectroscopy, revealing its ability as active materials for magnesium-ion battery.

  17. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    SciTech Connect

    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 where $\\vec{k}$• $\\vec{B}$ =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.

  18. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    SciTech Connect

    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 where $\\vec{k}$• $\\vec{B}$ =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.

  19. 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.

  20. Effect of chloride ion on the kinetics and mechanism of the reaction between chlorite ion and hypochlorous acid.

    PubMed

    Kormányos, Balázs; Nagypál, István; Peintler, Gábor; Horváth, Attila K

    2008-09-01

    The effect of chloride ion on the chlorine dioxide formation in the ClO 2 (-)-HOCl reaction was studied by following .ClO 2 concentration spectrophotometrically at pH 5-6 in 0.5 M sodium acetate. On the basis of the earlier experimental data collected without initially added chloride and on new experiments, the earlier kinetic model was modified and extended to interpret the two series of experiments together. It was found that the chloride ion significantly increases the initial rate of .ClO 2 formation. At the same time, the .ClO 2 yield is increased in HOCl but decreased in ClO 2 (-) excess by the increase of the chloride ion concentration. The two-step hydrolysis of dissolved chlorine through Cl 2 + H 2O left harpoon over right harpoon Cl 2OH (-) + H (+) and Cl 2OH (-) left harpoon over right harpoon HOCl + Cl (-) and the increased reactivity of Cl 2OH (-) compared to HOCl are proposed to explain these phenomena. It is reinforced that the hydrolysis of the transient Cl 2O 2 takes place through a HOCl-catalyzed step instead of the spontaneous hydrolysis. A seven-step kinetic model with six rate parameters (constants and/or ratio of constants) is proposed on the basis of the rigorous least-squares fitting of the parameters simultaneously to 129 absorbance versus time curves measured up to approximately 90% conversion. The advantage of this method of evaluation is briefly outlined.

  1. Langevin equation versus kinetic equation: Subdiffusive behavior of charged particles in a stochastic magnetic field

    SciTech Connect

    Balescu, R.; Wang, H. ); Misguich, J.H. )

    1994-12-01

    The running diffusion coefficient [ital D]([ital t]) is evaluated for a system of charged particles undergoing the effect of a fluctuating magnetic field and of their mutual collisions. The latter coefficient can be expressed either in terms of the mean square displacement (MSD) of a test particle, or in terms of a correlation between a fluctuating distribution function and the magnetic field fluctuation. In the first case a stochastic differential equation of Langevin type for the position of a test particle must be solved; the second problem requires the determination of the distribution function from a kinetic equation. Using suitable simplifications, both problems are amenable to exact analytic solution. The conclusion is that the equivalence of the two approaches is by no means automatically guaranteed. A new type of object, the hybrid kinetic equation'' is constructed: it automatically ensures the equivalence with the Langevin results. The same conclusion holds for the generalized Fokker--Planck equation. The (Bhatnagar--Gross--Krook) (BGK) model for the collisions yields a completely wrong result. A linear approximation to the hybrid kinetic equation yields an inexact behavior, but represents an acceptable approximation in the strongly collisional limit.

  2. Mechanical disassembly of single virus particles reveals kinetic intermediates predicted by theory.

    PubMed

    Castellanos, Milagros; Pérez, Rebeca; Carrillo, Pablo J P; de Pablo, Pedro J; Mateu, Mauricio G

    2012-06-06

    New experimental approaches are required to detect the elusive transient intermediates predicted by simulations of virus assembly or disassembly. Here, an atomic force microscope (AFM) was used to mechanically induce partial disassembly of single icosahedral T=1 capsids and virions of the minute virus of mice. The kinetic intermediates formed were imaged by AFM. The results revealed that induced disassembly of single minute-virus-of-mice particles is frequently initiated by loss of one of the 20 equivalent capsomers (trimers of capsid protein subunits) leading to a stable, nearly complete particle that does not readily lose further capsomers. With lower frequency, a fairly stable, three-fourths-complete capsid lacking one pentamer of capsomers and a free, stable pentamer were obtained. The intermediates most frequently identified (capsids missing one capsomer, capsids missing one pentamer of capsomers, and free pentamers of capsomers) had been predicted in theoretical studies of reversible capsid assembly based on thermodynamic-kinetic models, molecular dynamics, or oligomerization energies. We conclude that mechanical manipulation and imaging of simple virus particles by AFM can be used to experimentally identify kinetic intermediates predicted by simulations of assembly or disassembly. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Kinetic treatment of alpha-particle loss and energy deposition in ELMO Bumpy Torus

    SciTech Connect

    Fenstermacher, M.E.; Uckan, N.A.

    1982-12-01

    A formalism has been developed in terms of a drift kinetic equation with a Fokker-Planck collision operator to calculate alpha particle loss and energy deposition rate coefficients for one position in space and for steady-state operating conditions. A bounce-averaged drift kinetic equation for an ELMO Bumpy Torus (EBT) is expressed in invariant variables E = v/sup 2//2 and lambda = v/sub perpendicular//sup 2/B/sub MID//v/sup 2/B(l) and is used with energy scattering and pitch angle scattering terms in the collision operator. The alpha particle distribution function is expanded in terms of energy coefficients and pitch angle eigenfunctions. For the case of a square well magnetic field shape, the pitch angle eigenfunctions are the Legendre polynominals. With an expression for the distribution function the particle loss and energy deposition rates are calculated by taking the zeroth and first-order energy moments, respectively, of the kinetic equation.

  4. Mechanical Disassembly of Single Virus Particles Reveals Kinetic Intermediates Predicted by Theory

    PubMed Central

    Castellanos, Milagros; Pérez, Rebeca; Carrillo, Pablo J.P.; de Pablo, Pedro J.; Mateu, Mauricio G.

    2012-01-01

    New experimental approaches are required to detect the elusive transient intermediates predicted by simulations of virus assembly or disassembly. Here, an atomic force microscope (AFM) was used to mechanically induce partial disassembly of single icosahedral T = 1 capsids and virions of the minute virus of mice. The kinetic intermediates formed were imaged by AFM. The results revealed that induced disassembly of single minute-virus-of-mice particles is frequently initiated by loss of one of the 20 equivalent capsomers (trimers of capsid protein subunits) leading to a stable, nearly complete particle that does not readily lose further capsomers. With lower frequency, a fairly stable, three-fourths-complete capsid lacking one pentamer of capsomers and a free, stable pentamer were obtained. The intermediates most frequently identified (capsids missing one capsomer, capsids missing one pentamer of capsomers, and free pentamers of capsomers) had been predicted in theoretical studies of reversible capsid assembly based on thermodynamic-kinetic models, molecular dynamics, or oligomerization energies. We conclude that mechanical manipulation and imaging of simple virus particles by AFM can be used to experimentally identify kinetic intermediates predicted by simulations of assembly or disassembly. PMID:22713577

  5. Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres.

    PubMed

    Zhou, Limin; Wang, Yiping; Liu, Zhirong; Huang, Qunwu

    2009-01-30

    Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg(2+), Cu(2+), and Ni(2+) ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3mg/g for Hg(2+), Cu(2+), and Ni(2+) ions, respectively. TMCS displayed higher adsorption capacity for Hg(2+) in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88% using 0.01-0.1M ethylendiamine tetraacetic acid (EDTA).

  6. 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

  7. Kinetics of esterification of acidified oil with different alcohols by a cation ion-exchange resin/polyethersulfone hybrid catalytic membrane.

    PubMed

    Zhang, Honglei; Ding, Jincheng; Qiu, Yanli; Zhao, Zengdian

    2012-05-01

    Hybrid catalytic membranes consisting of cation ion-exchange resin particles (CERP) and polyethersulfone (PES) were prepared by immersion phase inversion and used as heterogeneous catalysts for the esterification of acidified oil with methanol, ethanol, propanol and butanol. The membranes were characterized by ion exchange capacity and swelling degree tests. The membranes were annealed at different temperatures to improve catalytic activity and membranes annealed at 393 K had the highest catalytic activity. Butanol allowed the highest free fatty acids (FFAs) conversion of 95.28% since it has better miscibility than the other alcohols which strengthened mass and heat transfer. Furthermore, pseudo-homogeneous kinetic models of the esterification of acidified oil with the four alcohols were established according to the experimental data. The kinetic models can well predict the FFA conversion. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Kinetics of ion admixture in a native gas in an external harmonic electric field

    NASA Astrophysics Data System (ADS)

    Ender, A. Ya.; Ender, I. A.; Gerasimenko, A. B.

    2016-11-01

    We have considered the spatially homogeneous problem of the behavior of an ion admixture in a background gas after applying a harmonic electric field with arbitrary parameters for various laws of interaction of particles. The Boltzmann equation has been solved using the modified method of moments. The ion distribution function and its first moments have been analyzed. It has been shown that the universal analytic expressions for the current density and the ion energy that we derived earlier for a small field amplitude-tofrequency ratio have a considerably wider range of applications.

  9. 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.

  10. Role of Ion Kinetic Physics in the Interaction of Magnetic Flux Ropes.

    PubMed

    Stanier, A; Daughton, W; Chacón, L; Karimabadi, H; Ng, J; Huang, Y-M; Hakim, A; Bhattacharjee, A

    2015-10-23

    To explain many natural magnetized plasma phenomena, it is crucial to understand how rates of collisionless magnetic reconnection scale in large magnetohydrodynamic (MHD) scale systems. Simulations of isolated current sheets conclude such rates are independent of system size and can be reproduced by the Hall-MHD model, but neglect sheet formation and coupling to MHD scales. Here, it is shown for the problem of flux-rope merging, which includes this formation and coupling, that the Hall-MHD model fails to reproduce the kinetic results. The minimum sufficient model must retain ion kinetic effects, which set the ion diffusion region geometry and give time-averaged rates that reduce significantly with system size, leading to different global evolution in large systems.

  11. Role of Ion Kinetic Physics in the Interaction of Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Stanier, A.; Daughton, W.; Chacón, L.; Karimabadi, H.; Ng, J.; Huang, Y.-M.; Hakim, A.; Bhattacharjee, A.

    2015-10-01

    To explain many natural magnetized plasma phenomena, it is crucial to understand how rates of collisionless magnetic reconnection scale in large magnetohydrodynamic (MHD) scale systems. Simulations of isolated current sheets conclude such rates are independent of system size and can be reproduced by the Hall-MHD model, but neglect sheet formation and coupling to MHD scales. Here, it is shown for the problem of flux-rope merging, which includes this formation and coupling, that the Hall-MHD model fails to reproduce the kinetic results. The minimum sufficient model must retain ion kinetic effects, which set the ion diffusion region geometry and give time-averaged rates that reduce significantly with system size, leading to different global evolution in large systems.

  12. Ion acoustic kinetic Alfvén rogue waves in two temperature electrons superthermal plasmas

    NASA Astrophysics Data System (ADS)

    Kaur, Nimardeep; Saini, N. S.

    2016-10-01

    The propagation properties of ion acoustic kinetic Alfvén (IAKA) solitary and rogue waves have been investigated in two temperature electrons magnetized superthermal plasma in the presence of dust impurity. A nonlinear analysis is carried out to derive the Korteweg-de Vries (KdV) equation using the reductive perturbation method (RPM) describing the evolution of solitary waves. The effect of various plasma parameters on the characteristics of the IAKA solitary waves is studied. The dynamics of ion acoustic kinetic Alfvén rogue waves (IAKARWs) are also studied by transforming the KdV equation into nonlinear Schrödinger (NLS) equation. The characteristics of rogue wave profile under the influence of various plasma parameters (κc, μc, σ , θ) are examined numerically by using the data of Saturn's magnetosphere (Schippers et al. 2008; Sakai et al. 2013).

  13. Kinetics and thermodynamics studies of silver ions adsorption onto coconut shell activated carbon.

    PubMed

    Silva-Medeiros, Flávia V; Consolin-Filho, Nelson; Xavier de Lima, Mateus; Bazzo, Fernando Previato; Barros, Maria Angélica S D; Bergamasco, Rosângela; Tavares, Célia R G

    2016-12-01

    The presence of silver in the natural water environment has been of great concern because of its toxicity, especially when it is in the free ion form (Ag(+)). This paper aims to study the adsorption kinetics of silver ions from an aqueous solution onto coconut shell activated carbon using batch methods. Batch kinetic data were fitted to the first-order model and the pseudo-second-order model, and this last equation fits correctly the experimental data. Equilibrium experiments were carried out at 30°C, 40°C, and 50°C. The adsorption isotherms were reasonably fit using Langmuir model, and the adsorption process was slightly influenced by changes in temperature. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) were determined. The adsorption process seems to be non-favorable, exothermic, and have an increase in the orderness.

  14. Effects of ion dynamics on kinetic structures of the diffusion region during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Chen, L. J.; Shuster, J. R.; Bessho, N.; Li, G.; Torbert, R. B.; Daughton, W. S.

    2014-12-01

    Based on results from Particle-in-cell (PIC) simulations, we report how ion dynamics influencethe Hall electric field and electron velocity distributions in the diffusion region of magnetic reconnection.The Hall electric field is due to charge imbalance in the diffusion region. At early times, within a few ion cyclotron oscillations from the peak reconnection,electron orbit dynamics dominate, and the Hall electric field layer assumes the width of the electron current layer.As the pre-existing current sheet ions are accelerated and jetted away, inflowing ions form an ion phase space hole structure.The ion hole structure is self-consistently supported by the Hall electric field. The ion meandering orbit width increasesover the course of about 10 ion cyclotron oscillations from several to approximately 40 electron skin depths (two ion skin depths,where the skin depth is based on the initial current sheet density), and theHall electric field layer widens in the same manner to become much broader than the electron diffusion region.The electron velocity distributions upstream of the electron diffusion region and within the regionof counter streaming ions become fragmented as the ion hole establishes itself.The fragmentation is carried into the electron diffusion region, and through the electron outflow jet, leading to a multitude of arcs in the electron distributions at the end of the jet. The broadening of the Hall electric field layer resolves a longstanding discrepancy concerning whether the narrowest width of the layer is of the electron [Chen et al., 2008] or ion [Mozer et al., 2002] scale. The fragmentation of the electron distributions may be due to an electron-ion instability, and is underinvestigation.

  15. 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

  16. 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

  17. Application of the focused ion beam technique in aerosol science: detailed investigation of selected, airborne particles.

    PubMed

    Kaegi, R; Gasser, Ph

    2006-11-01

    The focused ion beam technique was used to fabricate transmission electron microscope lamellas of selected, micrometre-sized airborne particles. Particles were sampled from ambient air on Nuclepore polycarbonate filters and analysed with an environmental scanning electron microscope. A large number of particles between 0.6 and 10 microm in diameter (projected optical equivalent diameter) were detected and analysed using computer-controlled scanning electron microscopy. From the resulting dataset, where the chemistry, morphology and position of each individual particle are stored, two particles were selected for a more detailed investigation. For that purpose, the particle-loaded filter was transferred from the environmental scanning electron microscope to the focused ion beam, where lamellas of the selected particles were fabricated. The definition of a custom coordinate system enabled the relocation of the particles after the transfer. The lamellas were finally analysed with an analytical transmission electron microscope. Internal structure and elemental distribution maps of the interior of the particles provided additional information about the particles, which helped to assign the particles to their sources. The combination of computer-controlled scanning electron microscopy, focused ion beam and transmission electron microscopy offers new possibilities for characterizing airborne particles in great detail, eventually enabling a detailed source apportionment of specific particles. The particle of interest can be selected from a large dataset (e.g. based on chemistry and/or morphology) and then investigated in more detail in the transmission electron microscope.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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 anisotropic equations of state in the hybrid model provides a better match to the fully kinetic model. In agreement with fully 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. Implications for global modeling are discussed.

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

    DOE PAGES

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

    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

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

    SciTech Connect

    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 fully 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.

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

    SciTech Connect

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

    2016-03-15

    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 anisotropic equations of state in the hybrid model provides a better match to the fully kinetic model. In agreement with fully 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. Implications for global modeling are discussed.

  2. Ion kinetic dynamics in strongly-shocked plasmas relevant to ICF

    NASA Astrophysics Data System (ADS)

    Rinderknecht, H. G.; Amendt, P. A.; Rosenberg, M. J.; Li, C. K.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Séguin, F. H.; Petrasso, R. D.; Zylstra, A. B.; Kagan, G.; Hoffman, N. M.; Svyatsky, D.; Wilks, S. C.; Glebov, V. Yu.; Stoeckl, C.; Sangster, T. C.

    2017-06-01

    Implosions of thin-shell capsules produce strongly-shocked (M  >  10), low-density (ρ ˜ 1 mg cc-1), high-temperature ({{T}\\text{i}}˜ keV) plasmas, comparable to those produced in the strongly-shocked DT-vapor in inertial confinement fusion (ICF) experiments. A series of thin-glass targets filled with mixtures of deuterium and Helium-3 gas ranging from 7% to 100% deuterium was imploded to investigate the impact of multi-species ion kinetic mechanisms in ICF-relevant plasmas over a wide range of Knudsen numbers ({{N}\\text{K}}\\equiv {λ\\text{ii}}/R ). Slightly kinetic implosions ({{N}\\text{K}}˜ 0.01 -0.05) follow the expected yield trend with experimentally-inferred N K, suggesting effects associated with long mean-free-paths (such as energetic tail-ion loss) provide the dominant yield reduction mechanisms. In contrast, highly kinetic implosions (Rinderknecht et al 2015 Phys. Rev. Lett. 114 025001) with inferred {{N}\\text{K}}>0.5 produce the opposite yield trend from the Knudsen-number prediction, confirming the dominance of multi-species physics in these experiments. The impact of the observed kinetic physics mechanisms on the formation of the hotspot in ICF experiments is discussed.

  3. 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.

  4. 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.

  5. 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.

  6. In vitro analysis of human immunodeficiency virus particle dissociation: gag proteolytic processing influences dissociation kinetics.

    PubMed

    Müller, Barbara; Anders, Maria; Reinstein, Jochen

    2014-01-01

    Human immunodeficiency virus particles undergo a step of proteolytic maturation, in which the main structural polyprotein Gag is cleaved into its mature subunits matrix (MA), capsid (CA), nucleocapsid (NC) and p6. Gag proteolytic processing is accompanied by a dramatic structural rearrangement within the virion, which is necessary for virus infectivity and has been proposed to proceed through a sequence of dissociation and reformation of the capsid lattice. Morphological maturation appears to be tightly regulated, with sequential cleavage events and two small spacer peptides within Gag playing important roles by regulating the disassembly of the immature capsid layer and formation of the mature capsid lattice. In order to measure the influence of individual Gag domains on lattice stability, we established Förster's resonance energy transfer (FRET) reporter virions and employed rapid kinetic FRET and light scatter measurements. This approach allowed us to measure dissociation properties of HIV-1 particles assembled in eukaryotic cells containing Gag proteins in different states of proteolytic processing. While the complex dissociation behavior of the particles prevented an assignment of kinetic rate constants to individual dissociation steps, our analyses revealed characteristic differences in the dissociation properties of the MA layer dependent on the presence of additional domains. The most striking effect observed here was a pronounced stabilization of the MA-CA layer mediated by the presence of the 14 amino acid long spacer peptide SP1 at the CA C-terminus, underlining the crucial role of this peptide for the resolution of the immature particle architecture.

  7. Kinetic Modeling of Particle Acceleration in a Solar Null-point Reconnection Region

    NASA Astrophysics Data System (ADS)

    Baumann, G.; Haugbølle, T.; Nordlund, Å.

    2013-07-01

    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.

  8. Kinetics of formation of monodisperse colloidal silica particles through the hydrolysis and condensation of tetraethyorthosilicate

    SciTech Connect

    Chen, S.L.; Dong, P.; Yang, G.H.; Yang, J.J.

    1996-12-01

    Kinetic studies of the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) during the formation of uniform silica particles were performed through determining concentrations of TEOS and silicic acid by means of gas chromatography and a conductometer, respectively. It was shown that both hydrolysis of TEOS and condensation of Si(OH){sub 4} are first order with TEOS and Si(OH){sub 4}, respectively, and the relationships of the hydrolysis and condensation rate constants with reaction condition variables, such as temperature, NH{sub 3} concentration, and H{sub 2}O concentration, were determined. in addition, the particle growth rate was investigated with relation to the hydrolysis and condensation kinetics. Experiments showed that, during most of the reaction, the amount of formed particles is less than that of consumed TEOS, indicating that reaction intermediates exist during the process of silica formation. In the early stages of the Stoeber process, the reaction intermediates include silicic acid and subparticles, while in the case of seed growth experiments without the formation of new particles or after the early stages of Stoeber process, the reaction intermediates primarily consist of silicic acid and the growth rate of silica equals the rate of silicic acid condensation.

  9. 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.

  10. Ion acceleration and heating by kinetic Alfvén waves associated with magnetic reconnection

    DOE PAGES

    Liang, Ji; Lin, Yu; Johnson, Jay R.; ...

    2017-09-19

    In a previous study on the generation and signatures of kinetic Alfv en waves (KAWs) associated with magnetic reconnection in a current sheet revealed that KAWs are a common feature during reconnection [Liang et al. J. Geophys. Res.: Space Phys. 121, 6526 (2016)]. In this paper, ion acceleration and heating by the KAWs generated during magnetic reconnection are investigated with a three-dimensional (3-D) hybrid model. It is found that in the outflow region, a fraction of inflow ions are accelerated by the KAWs generated in the leading bulge region of reconnection, and their parallel velocities gradually increase up to slightly super-Alfv enic. As a result of waveparticle interactions, an accelerated ion beam forms in the direction of the anti-parallel magnetic field, in addition to the core ion population, leading to the development of non-Maxwellian velocity distributions, which include a trapped population with parallel velocities consistent with the wave speed. We then heat ions in both parallel and perpendicular directions. In the parallel direction, the heating results from nonlinear Landau resonance of trapped ions. In the perpendicular direction, however, evidence of stochastic heating by the KAWs is found during the acceleration stage, with an increase of magnetic moment μ. The coherence in the Tmore » $$\\perp$$ ion temperature and the perpendicular electric and magnetic fields of KAWs also provides evidence for perpendicular heating by KAWs. The parallel and perpendicular heating of the accelerated beam occur simultaneously, leading to the development of temperature anisotropy with the perpendicular temperature T$$\\perp$$>T$$\\parallel$$ temperature. The heating rate agrees with the damping rate of the KAWs, and the heating is dominated by the accelerated ion beam. In the later stage, with the increase of the fraction of the accelerated ions, interaction between the accelerated beam and the core population also contributes to the ion heating

  11. 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.

  12. Kinetic study on removal of heavy metal ions from aqueous solution by using soil.

    PubMed

    Lim, Soh-Fong; Lee, Agnes Yung Weng

    2015-07-01

    In the present study, the feasibility of soil used as a low-cost adsorbent for the removal of Cu(2+), Zn(2+), and Pb(2+) ions from aqueous solution was investigated. The kinetics for adsorption of the heavy metal ions from aqueous solution by soil was examined under batch mode. The influence of the contact time and initial concentration for the adsorption process at pH of 4.5, under a constant room temperature of 25 ± 1 °C were studied. The adsorption capacity of the three heavy metal ions from aqueous solution was decreased in order of Pb(2+) > Cu(2+) > Zn(2+). The soil was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopic-energy dispersive X-ray (SEM-EDX), and Brunauer, Emmett, and Teller (BET) surface area analyzer. From the FTIR analysis, the experimental data was corresponded to the peak changes of the spectra obtained before and after adsorption process. Studies on SEM-EDX showed distinct adsorption of the heavy metal ions and the mineral composition in the study areas were determined to be silica (SiO2), alumina (Al2O3), and iron(III) oxide (FeO3). A distinct decrease of the specific surface area and total pore volumes of the soil after adsorption was found from the BET analysis. The experimental results obtained were analyzed using four adsorption kinetic models, namely pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion. Evaluating the linear correlation coefficients, the kinetic studies showed that pseudo-second-order equation described the data appropriable than others. It was concluded that soil can be used as an effective adsorbent for removing Cu(2+), Zn(2+), and Pb(2+) ions from aqueous solution.

  13. 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.

  14. Kinetics of Particle Adsorption in Stagnation Point Flow Studied by Optical Reflectometry

    PubMed

    Böhmer; van der Zeeuw EA; Koper

    1998-01-15

    The kinetics of adsorption of nano-sized silica particles on a polymer pretreated surface were followed in situ by using optical reflectometry in a stagnation point flow setup. Conversion of the reflectometric signal to the surface coverage could be performed using a homogeneous slab model which was verified by determining the particle density on SEM pictures taken in the stagnation point and by comparison with a model which includes the particulate nature of the layer explicitly. The effects of salt concentration on the plateau adsorbed amounts for all particle sizes can be described with an effective hard sphere concept. Although initial slopes and plateau values are in reasonable agreement with a random sequential adsorption model, this model does not accurately describe the evolution of the surface coverage as a function of time in a stagnation point flow system. Copyright 1998 Academic Press. Copyright 1998Academic Press

  15. Kinetic analysis of competition between aerosol particle removal and generation by ionization air purifiers.

    PubMed

    Alshawa, Ahmad; Russell, Ashley R; Nizkorodov, Sergey A

    2007-04-01

    Ionization air purifiers are increasingly used to remove aerosol particles from indoor air. However, certain ionization air purifiers also emit ozone. Reactions between the emitted ozone and unsaturated volatile organic compounds (VOC) commonly found in indoor air produce additional respirable aerosol particles in the ultrafine (<0.1 microm) and fine (<2.5 microm) size domains. A simple kinetic model is used to analyze the competition between the removal and generation of particulate matter by ionization air purifiers under conditions of a typical residential building. This model predicts that certain widely used ionization air purifiers may actually increase the mass concentration of fine and ultrafine particulates in the presence of common unsaturated VOC, such as limonene contained in many household cleaning products. This prediction is supported by an explicit observation of ultrafine particle nucleation events caused by the addition of D-limonene to a ventilated office room equipped with a common ionization air purifier.

  16. Momentum transfer cross-section for ion scattering on dust particles

    NASA Astrophysics Data System (ADS)

    Semenov, I. L.; Khrapak, S. A.; Thomas, H. M.

    2017-03-01

    The momentum transfer cross-section for ion scattering on charged dust particles is calculated using different models of the interaction potential. The results are applied to estimate the ion drag force for typical conditions used in the experiments with complex (dusty) plasmas. The influence of two factors on the ion-dust collision cross section is discussed. The first is related to the nonlinear screening effects associated with the strong coupling between ions and dust particles. The second factor is the plasma absorption by dust particles. It is shown that the nonlinear screening effects are of importance and affect both the momentum transfer cross-section and the ion drag force. On the other hand, the absorption process affects the scattering momentum transfer cross-section only at low collision energies and thus can be neglected in estimating the ion drag force.

  17. Numerical investigation of non-perturbative kinetic effects of energetic particles on toroidicity-induced Alfvén eigenmodes in tokamaks and stellarators

    SciTech Connect

    Slaby, Christoph; Könies, Axel; Kleiber, Ralf

    2016-09-15

    The resonant interaction of shear Alfvén waves with energetic particles is investigated numerically in tokamak and stellarator geometry using a non-perturbative MHD-kinetic hybrid approach. The focus lies on toroidicity-induced Alfvén eigenmodes (TAEs), which are most easily destabilized by a fast-particle population in fusion plasmas. While the background plasma is treated within the framework of an ideal-MHD theory, the drive of the fast particles, as well as Landau damping of the background plasma, is modelled using the drift-kinetic Vlasov equation without collisions. Building on analytical theory, a fast numerical tool, STAE-K, has been developed to solve the resulting eigenvalue problem using a Riccati shooting method. The code, which can be used for parameter scans, is applied to tokamaks and the stellarator Wendelstein 7-X. High energetic-ion pressure leads to large growth rates of the TAEs and to their conversion into kinetically modified TAEs and kinetic Alfvén waves via continuum interaction. To better understand the physics of this conversion mechanism, the connections between TAEs and the shear Alfvén wave continuum are examined. It is shown that, when energetic particles are present, the continuum deforms substantially and the TAE frequency can leave the continuum gap. The interaction of the TAE with the continuum leads to singularities in the eigenfunctions. To further advance the physical model and also to eliminate the MHD continuum together with the singularities in the eigenfunctions, a fourth-order term connected to radiative damping has been included. The radiative damping term is connected to non-ideal effects of the bulk plasma and introduces higher-order derivatives to the model. Thus, it has the potential to substantially change the nature of the solution. For the first time, the fast-particle drive, Landau damping, continuum damping, and radiative damping have been modelled together in tokamak- as well as in stellarator geometry.

  18. Kinetics and mechanism of the oxidation of pentathionate ion by chlorine dioxide in a slightly acidic medium.

    PubMed

    Xu, Li; Csekő, György; Petz, Andrea; Horváth, Attila K

    2014-02-27

    The chlorine dioxide-pentathionate reaction has been studied at a slightly acidic medium by conventional UV-vis spectroscopy monitoring the absorbance at 430 nm. We have shown that pentathionate was oxidized to sulfate, but chlorate is also a marginal product of the reaction besides the chloride ion. The stoichiometry of the reaction can be established as a linear combination of two limiting stoichiometries under our experimental conditions. Kinetics of the reaction was found to be also complex because initial rate studies revealed that formal kinetic orders of both the hydrogen ion and chlorine dioxide is far from unity. Moreover, log-log plot of the initial rate against pentathionate concentration indicated a nonconstant formal kinetic order. We also observed a significant catalytic effect of chloride ion. Based on our observations and simultaneous evaluation of the kinetic curves, an 11-step kinetic model is obtained with 6 fitted rate coefficients. A relatively simple rate equation has also been derived and discussed.

  19. Global particle-in-cell simulations of microturbulence with kinetic electrons

    SciTech Connect

    Lewandowski, J. L. V.; Rewoldt, G.; Ethier, S.; Lee, W. W.; Lin, Z.

    2006-07-15

    The effects of nonadiabatic electrons on ion temperature gradient drift instabilities have been studied in global toroidal geometry using the gyrokinetic particle simulation approach. Compared to the nonlinear global simulations based on only the adiabatic response of the electrons, we have found that the cross-field ion heat transport is two to three times larger in the presence of trapped electrons as compared to the purely adiabatic electron case, and that the zonal component of the electrostatic potential has a shorter wavelength. The numerical methods for calculating both the adiabatic and the nonadiabatic responses for the electrons are presented.

  20. 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

  1. Activating molecules, ions, and solid particles with acoustic cavitation.

    PubMed

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

    2014-04-11

    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.

  2. 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.

  3. Angular Momentum Transport and Particle Acceleration During Magnetorotational Instability in a Kinetic Accretion Disk

    NASA Astrophysics Data System (ADS)

    Hoshino, Masahiro

    2015-02-01

    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.

  4. 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.

  5. Particle reflection and ion-induced desorption from tungsten surfaces with chemisorbed nitrogen

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.; Kimura, H.

    1987-06-01

    Using the Monte Carlo simulation program ACAT, ion-induced desorption yields of nitrogen chemisorbed on tungsten surfaces and the associated particle reflection coefficients have been calculated for low-energy helium-ions. It is found that both the particle reflection coefficients and the energy distributions of the reflected particles depend strongly on the thickness of the adsorbate layer on the surface if the ion energy is in the threshold regime and that the collision sequence of the near-threshold mechanism includes at least two adsorbate atoms. The ACAT desorption yields are found to be in good agreement with experimental yields.

  6. Particle reflection and ion-induced desorption from tungsten surfaces with chemisorbed nitrogen

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.; Kimura, H.

    Using the Monte Carlo simulation program ACAT, ion-induced desorption yields of nitrogen chemisorbed on tungsten surfaces and the associated particle reflection coefficients have been calculated for low-energy helium-ions. It is found that both the particle reflection coefficients and the energy distributions of the reflected particles depend strongly on the thickness of the adsorbate layer on the surface if the ion energy is in the threshold regime and that the collision sequence of the near-threshold mechanism includes at least two adsorbate atoms. The ACAT desorption yields are found to be in good agreement with experimental yields.

  7. Efficient production of high-energy nonthermal particles during magnetic reconnection in a magnetically dominated ion-electron plasma

    DOE PAGES

    Guo, Fan; Li, Xiaocan; Li, Hui; ...

    2016-02-03

    Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. 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 ofmore » $${\\sigma }_{0}={B}^{2}/(4\\pi n({m}_{i}+{m}_{e}){c}^{2})$$, the magnetization for each species is $${\\sigma }_{i}\\sim {\\sigma }_{0}$$ and $${\\sigma }_{e}\\sim ({m}_{i}/{m}_{e}){\\sigma }_{0}$$, 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 $${m}_{i}/{m}_{e}=1-1836$$. Our 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 $${\\gamma }_{{be}}\\sim {\\sigma }_{e}$$ and $${\\gamma }_{{bi}}\\sim {\\sigma }_{i}$$, 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. Finally, 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.« less

  8. Efficient production of high-energy nonthermal particles during magnetic reconnection in a magnetically dominated ion-electron plasma

    SciTech Connect

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

    2016-02-03

    Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. 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 ${\\sigma }_{0}={B}^{2}/(4\\pi n({m}_{i}+{m}_{e}){c}^{2})$, the magnetization for each species is ${\\sigma }_{i}\\sim {\\sigma }_{0}$ and ${\\sigma }_{e}\\sim ({m}_{i}/{m}_{e}){\\sigma }_{0}$, 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 ${m}_{i}/{m}_{e}=1-1836$. Our 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 ${\\gamma }_{{be}}\\sim {\\sigma }_{e}$ and ${\\gamma }_{{bi}}\\sim {\\sigma }_{i}$, 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. Finally, 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.

  9. Laboratory investigation of electric charging of dust particles by electrons, ions, and UV radiation

    NASA Technical Reports Server (NTRS)

    Svestka, Jiri; Pinter, S.; Gruen, E.

    1989-01-01

    In many cosmic environments electric charging of dust particles occurs by electrons, ions, and UV radiation. In case of interstellar dust particles the value of their electric charge can have, for instance, very important consequences for their destruction rate in supernova remnant's shock waves and can globally influence the overall life cycle of dust particles in galaxies. For experimental simulation of charging processes a vacuum chamber was used in which the particles fall through an electron or ion beam of energies up to 10 KeV. The aim of the experiments was to attain maximum charge of dust particles. Furthermore the influence of the rest gas was also determined because electrons and ions produced by collisional ionization of the rest gas can result in significant effects. For measurement particles from 1 to 100 microns from glass, carbon, Al, Fe, MgO, and very loosely bound conglomerates of Al2O3 were used.

  10. 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.

  11. 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.

  12. Potential and kinetic sputtering of alkanethiol self-assembled monolayers by impact of highly charged ions

    NASA Astrophysics Data System (ADS)

    Flores, M.; O'Rourke, B. E.; Yamazaki, Y.; Esaulov, V. A.

    2009-02-01

    Highly charged ions have been used to study the sputtering of positive molecular fragments from mercaptoundecanoic acid and dodecanethiol self-assembled monolayers on gold surfaces. The samples were bombarded with Arq+ (4⩽q⩽10) ions with kinetic energies from 2to18keV . The main fragments detected were H+ , CnH2n+ , and Cn+1O2H2n+1+ from mercaptoundecanoic and H+ , CnH2n+ , and Cn+1H2n+3+ from dodecanethiol. The proton yields were increased with larger charge state q of the highly charged ion (HCI) in both samples, scaling as qγ , with γ˜5 . The charge state dependence is discussed in terms of electron transfer to the HCI. The final yield of protons depends on molecular functional group characteristics, orientation on the surface, and reneutralization phenomena.

  13. Sulfate radical-based degradation of polychlorinated biphenyls: effects of chloride ion and reaction kinetics.

    PubMed

    Fang, Guo-Dong; Dionysiou, Dionysios D; Wang, Yu; Al-Abed, Souhail R; Zhou, Dong-Mei

    2012-08-15

    Advanced oxidation processes (AOPs) based on sulfate radical (SO(4)(·-)) have been recently used for soil and groundwater remediation. The presence of chloride ion in natural or wastewater decreases the reactivity of sulfate radical system, but explanations for this behavior were inconsistent, and the mechanisms are poorly understood. Therefore, in this paper we investigated the effect of chloride ion on the degradation of 2,4,4'-CB (PCB28) and biphenyl (BP) by persulfate, based on the produced SO(4)(·-). The results showed that the presence of chloride ion greatly inhibited the transformation of PCB28 and BP. Transformation intermediates of BP were monitored, suggesting that the chloride ion can react with SO(4)(·-) to produce chlorine radical, which reacts with BP to generate chlorinated compounds. To better understand the underlying mechanisms of these processes, a kinetic model was developed for predicting the effect of chloride ion on the types of radical species and their distributions. The results showed that chloride ion could influence the selectivity of radical species and their distribution, and increase the concentration of the sum of radical species. In addition, the second-order rate constants of sulfate radical with PCBs were determined, and quantum-chemical descriptors were introduced to predict the rate constants of other PCBs based on our experimental data.

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

    PubMed

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

    2012-02-01

    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(+), H(2)(+), H(3)(+), C(4+), and C(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.

  15. 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

  16. 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

  17. Chemical reduction kinetics of nitrate in aqueous solution by Mg/Cu bimetallic particles.

    PubMed

    Mortazavi, S B; Ramavandi, B; Moussavi, G

    2011-01-01

    Synthesized magnesium/copper (Mg/Cu) bimetallic particles have shown good potential for use in the reduction of nitrate from aqueous solutions. This study was conducted to investigate the main factors affecting the kinetics of nitrate reduction by Mg/Cu particles (<100 microm) in uncontrolled reaction conditions. The Mg/Cu bimetallic particles removed the majority of the various nitrate concentrations tested (50, 100, 150, 200 and 300 mg L(-1)) within a short period. The time required for the removal of 90.6% of the NO3(-) from a 100 mg L(-1) solution was about 20 min using 2 gL(-1) bimetallic Mg/Cu at an initial solution pH of 6. The activation energy (Ea) for nitrate reduction by Mg/Cu over the temperature range of 5 to 60 degrees C was 14.21 kJ mol(-1). The experimental results of the kinetic analysis from batch studies indicated that a higher initial nitrate concentration yielded a greater reaction-rate constant and the denitrification rate increased with increase Mg/Cu dosage.

  18. Modelling the kinetics of antigen-antibody reactions at particle enhanced optical immunoassays.

    PubMed

    Quesada, M; Puig, J; Delgado, J M; Hidalgo-Alvarez, R

    1998-01-01

    Functionalized latexes coated by antibodies are used in diagnostic tests for the detection of antigens in biological fluids. A simple kinetic model is presented which is related to the optical monitoring of the formation of specific complexes between antigen and antibody amplified by latex beads. The antibodies are chemically coupled onto chloromethylstyrene (CMST) particles. The kinetic model is able to describe the immunoprecipitin curves of immunolatex beads. The number of fitting parameters is relatively reduced (only three), and the meaning of these parameters can be interpreted in terms of the chemical equilibrium constant, the percentage of active IgG on the latex beads, and optical response. The model explains very well the optical response of immunolatex prepared by covalent coupling of antibodies on polymer carriers.

  19. Fast electron energy deposition in a magnetized plasma: Kinetic theory and particle-in-cell simulation

    SciTech Connect

    Robiche, J.; Rax, J.-M.; Bonnaud, G.; Gremillet, L.

    2010-03-15

    The collisional dynamics of a relativistic electron jet in a magnetized plasma are investigated within the framework of kinetic theory. The relativistic Fokker-Planck equation describing slowing down, pitch angle scattering, and cyclotron rotation is derived and solved. Based on the solution of this Fokker-Planck equation, an analytical formula for the root mean square spot size transverse to the magnetic field is derived and this result predicts a reduction in radial transport. Some comparisons with particle-in-cell simulation are made and confirm striking agreement between the theory and the simulation. For fast electron with 1 MeV typical kinetic energy interacting with a solid density hydrogen plasma, the energy deposition density in the transverse direction increases by a factor 2 for magnetic field of the order of 1 T. Along the magnetic field, the energy deposition profile is unaltered compared with the field-free case.

  20. Shear-induced reaction-limited aggregation kinetics of brownian particles at arbitrary concentrations.

    PubMed

    Zaccone, Alessio; Gentili, Daniele; Wu, Hua; Morbidelli, Massimo

    2010-04-07

    The aggregation of interacting brownian particles in sheared concentrated suspensions is an important issue in colloid and soft matter science per se. Also, it serves as a model to understand biochemical reactions occurring in vivo where both crowding and shear play an important role. We present an effective medium approach within the Smoluchowski equation with shear which allows one to calculate the encounter kinetics through a potential barrier under shear at arbitrary colloid concentrations. Experiments on a model colloidal system in simple shear flow support the validity of the model in the concentration range considered. By generalizing Kramers' rate theory to the presence of shear and collective hydrodynamics, our model explains the significant increase in the shear-induced reaction-limited aggregation kinetics upon increasing the colloid concentration.

  1. Particle formation by ion nucleation in the upper troposphere and lower stratosphere.

    PubMed

    Lee, S-H; Reeves, J M; Wilson, J C; Hunton, D E; Viggiano, A A; Miller, T M; Ballenthin, J O; Lait, L R

    2003-09-26

    Unexpectedly high concentrations of ultrafine particles were observed over a wide range of latitudes in the upper troposphere and lower stratosphere. Particle number concentrations and size distributions simulated by a numerical model of ion-induced nucleation, constrained by measured thermodynamic data and observed atmospheric key species, were consistent with the observations. These findings indicate that, at typical upper troposphere and lower stratosphere conditions, particles are formed by this nucleation process and grow to measurable sizes with sufficient sun exposure and low preexisting aerosol surface area. Ion-induced nucleation is thus a globally important source of aerosol particles, potentially affecting cloud formation and radiative transfer.

  2. [Heavy charged particles radiotherapy--mainly carbon ion beams].

    PubMed

    Yanagi, Takeshi; Tsuji, Hiroshi; Tsujii, Hirohiko

    2003-12-01

    Carbon ion beams have superior dose distribution allowing selective irradiation to the tumor while minimizing irradiation to the surrounding normal tissues. Furthermore, carbon ions produce an increased density of local energy deposition with high-energy transfer (LET) components, resulting in radiobiological advantages. Stimulated by the favorable results in fast neutrons, helium ions, and neon ions, a clinical trial of carbon ion therapy was begun at the National Institute of Radiological Sciences in 1994. Carbon ions were generated by a medically dedicated accelerator (HIMAC, Heavy Ion Medical Accelerator in Chiba, Japan), which was the world's first heavy ion accelerator complex dedicated to medical use in a hospital environment. In general, patients were selected for treatment when their tumors could not be expected to respond favorably to conventional forms of therapy. A total of 1601 patients were registered in this clinical trial so far. The normal tissue reactions were acceptable, and there were no carbon related deaths. Carbon ion radiotherapy seemed to be a clinically feasible curative treatment modality, and appears to offer improved results not only over conventional X-rays but also even over surgery in some selected carcinomas.

  3. Ion Beam Collimation For Improved Resolution In Associated Particle Imaging

    NASA Astrophysics Data System (ADS)

    Sy, Amy; Ji, Qing

    2011-06-01

    Beam spot size on target for a Penning ion source has been measured under different source operating pressures as a function of the extraction channel length and beam energy. A beam halo/core structure was observed for ion extraction at low extraction voltages, and was greatly reduced at higher beam energy. Collimation through use of longer extraction channels results in reduced ion current on target; the resultant reduction in neutron yield for an API system driven by such an ion source can be compensated for by use of even higher beam energies.

  4. 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).

  5. 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.

  6. 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.

  7. Active matter beyond mean-field: ring-kinetic theory for self-propelled particles.

    PubMed

    Chou, Yen-Liang; Ihle, Thomas

    2015-02-01

    Recently, Hanke et al. [Phys. Rev. E 88, 052309 (2013)] 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.

  8. 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.

  9. Relativistic kinetic equation for spin-1/2 particles in the long-scale-length approximation

    NASA Astrophysics Data System (ADS)

    Ekman, R.; Asenjo, F. A.; Zamanian, J.

    2017-08-01

    In this paper, we derive a fully relativistic kinetic theory for spin-1/2 particles and its coupling to Maxwell's equations, valid in the long-scale-length limit, where the fields vary on a scale much longer than the localization of the particles; we work to first order in ℏ . Our starting point is a Foldy-Wouthuysen (FW) transformation, applicable to this regime, of the Dirac Hamiltonian. We derive the corresponding evolution equation for the Wigner quasidistribution in an external electromagnetic field. Using a Lagrangian method we find expressions for the charge and current densities, expressed as free and bound parts. It is furthermore found that the velocity is nontrivially related to the momentum variable, with the difference depending on the spin and the external electromagnetic fields. This fact that has previously been discussed as "hidden momentum" and is due to that the FW transformation maps pointlike particles to particle clouds for which the prescription of minimal coupling is incorrect, as they have multipole moments. We express energy and momentum conservation for the system of particles and the electromagnetic field, and discuss our results in the context of the Abraham-Minkowski dilemma.

  10. Impact of the rippling of a 2D perpendicular shock front on ion acceleration mechanisms: PIC and test particles simulations

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Lembege, B.; Lu, Q.

    2012-04-01

    Both hybrid/full particle simulations and recent experimental results have clearly evidenced that the front of a supercritical quasi-perpendicular shock can be rippled. Recent two-dimensional simulations have focussed on two different types of shock front rippling: (1) one characterized by a small spatial scale along the front is supported by lower hybrid wave activity, (2) the other characterized by a large spatial scale along the front is supported by the emission of large amplitude nonlinear whistler waves. These two rippled shock fronts are observed self-consistently respectively when the static magnetic field is perpendicular to (so called "B0-OUT" case) or within (so called "B0-IN" case) the simulation plane. "B0-OUT" and "B0-IN" cases are respectively characterized by a small and large rippling scale along the shock front. On the other hand, several studies have been made on the reflection and energization of incoming ions with a shock but most have been restricted to a one dimensional shock profile only (no rippling effects). Herein, two-dimensional test particle simulations based on strictly perpendicular shock profiles produced in two-dimensional PIC simulations are performed in order to investigate the impact of the shock front ripples on incident ion (H+) dynamics. The acceleration mechanisms and energy spectra of the test-ions (described by shell distributions with different initial kinetic energy) interacting with a rippled shock front are analyzed in detail. Both "B0-OUT" and "B0-IN" cases are considered separately; in each case, y-averaged (front rippling excluded) and non-averaged (front rippling included) profiles will be analyzed. Present results show that: (1) the incident ions suffer both shock drift acceleration (SDA) and shock surfing acceleration (SSA) mechanisms. Moreover, a striking feature is that SSA ions not only are identified at the ramp but also within the foot which confirms previous 1-D simulation results; (2) the percentage of SSA

  11. The influence of a cerium additive on ultrafine diesel particle emissions and kinetics of oxidation

    SciTech Connect

    Jung, Heejung; Kittelson, David B.; Zachariah, Michael R.

    2005-08-01

    The influence of a cerium additive on the kinetics of oxidation and size distribution of ultrafine diesel particles was studied using a high-temperature oxidation-tandem differential mobility analysis method over the temperature range 300-700|{sup o}C. The addition of cerium to the diesel fuel was observed to cause significant changes in number-weighted size distributions, light-off temperature, and kinetics of oxidation. The peak number concentration in the accumulation mode decreased 50 and 65%, respectively, for 25 and 100 ppm dosing levels under 1400 rpm and 75% engine load. The light-off temperature was reduced by 250 and 300|{sup o}C, respectively, for 25 and 100 ppm dosing levels. The oxidation rate increased significantly (x20) with the addition of cerium to the fuel; however, the rate was relatively insensitive to dosing level. The activation energy for cerium-dosed oxidation was, within experimental error, equivalent to that for undosed fuel (E{sub a}=100-110 kJmol{sup -1}). From a phenomenological kinetic rate perspective, the increase in oxidation rate was attributed solely to an increase in the preexponential factor. These results suggested that diesel particles using regular, undosed diesel fuels were already metal-catalyzed to some extent, most likely from metals in the lube oil. The addition of cerium likely increased the number of catalytic sites but had no effect on the overall activation energy due to the presence of other metals in the diesel particulate matter coming from lube oil. The characteristics of cerium-laden diesel particles were also investigated. Two principal types of aggregates were found using transmission electron microscopy and energy-dispersive spectrometry analysis. The first was composed mainly of agglomerates of carbonaceous spherules and a few, considerably smaller cerium oxide nanoparticles. The second consisted of metallic aggregates composed mainly of cerium oxide nanoparticles and some carbon.

  12. Fully kinetic simulation study of ion-acoustic solitons in the presence of trapped electrons.

    PubMed

    Hosseini Jenab, S M; Spanier, F

    2017-05-01

    The nonlinear fluid theory developed by Schamel suggests a modified KdV equation to describe the temporal evolution of ion acoustic (IA) solitons in the presence of trapped electrons. The validity of this theory is studied here by verifying solitons' main characteristic, i.e., stability against successive mutual collisions. We have employed a kinetic model as a more comprehensive theory than the fluid one, and utilized a fully kinetic simulation approach (both ions and electrons are treated based on the Vlasov equation). In the simulation approach, these solitons are excited self-consistently by employing the nonlinear process of IA solitons formation from an initial density perturbation (IDP). The effect of the size of IDPs on the chain formation is proved by the simulation code as a benchmark test. It is shown that the IA solitons, in the presence of trapped electrons, can retain their features (both in spatial and velocity direction) after successive mutual collisions. The collisions here include encounters of IA solitons with the same trapping parameter, while differing in size. Kinetic simulation results reveal a complicated behavior during a collision between IA solitons in contrast to the fluid theory predictions and simulations. In the range of parameters considered here, two oppositely propagating solitons rotate around their collective center in the phase space during a collision, independent of their trapping parameters. Furthermore, they exchange some portions of their trapped populations.

  13. Fully kinetic simulation study of ion-acoustic solitons in the presence of trapped electrons

    NASA Astrophysics Data System (ADS)

    Hosseini Jenab, S. M.; Spanier, F.

    2017-05-01

    The nonlinear fluid theory developed by Schamel suggests a modified KdV equation to describe the temporal evolution of ion acoustic (IA) solitons in the presence of trapped electrons. The validity of this theory is studied here by verifying solitons' main characteristic, i.e., stability against successive mutual collisions. We have employed a kinetic model as a more comprehensive theory than the fluid one, and utilized a fully kinetic simulation approach (both ions and electrons are treated based on the Vlasov equation). In the simulation approach, these solitons are excited self-consistently by employing the nonlinear process of IA solitons formation from an initial density perturbation (IDP). The effect of the size of IDPs on the chain formation is proved by the simulation code as a benchmark test. It is shown that the IA solitons, in the presence of trapped electrons, can retain their features (both in spatial and velocity direction) after successive mutual collisions. The collisions here include encounters of IA solitons with the same trapping parameter, while differing in size. Kinetic simulation results reveal a complicated behavior during a collision between IA solitons in contrast to the fluid theory predictions and simulations. In the range of parameters considered here, two oppositely propagating solitons rotate around their collective center in the phase space during a collision, independent of their trapping parameters. Furthermore, they exchange some portions of their trapped populations.

  14. Kinetic Modeling of Radiative Turbulence in Relativistic Astrophysical Plasmas: Particle Acceleration and High-Energy Flares

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri

    Relativistic astrophysical plasma environments routinely produce intense high-energy emission, which is often observed to be nonthermal and rapidly flaring. The recently discovered gamma-ray (> 100 MeV) flares in Crab Pulsar Wind Nebula (PWN) provide a quintessential illustration of this, but other notable examples include relativistic active galactic nuclei (AGN) jets, including blazars, and Gamma-ray Bursts (GRBs). Understanding the processes responsible for the very efficient and rapid relativistic particle acceleration and subsequent emission that occurs in these sources poses a strong challenge to modern high-energy astrophysics, especially in light of the necessity to overcome radiation reaction during the acceleration process. Magnetic reconnection and collisionless shocks have been invoked as possible mechanisms. However, the inferred extreme particle acceleration requires the presence of coherent electric-field structures. How such large-scale accelerating structures (such as reconnecting current sheets) can spontaneously arise in turbulent astrophysical environments still remains a mystery. The proposed project will conduct a first-principles computational and theoretical study of kinetic turbulence in relativistic collisionless plasmas with a special focus on nonthermal particle acceleration and radiation emission. The main computational tool employed in this study will be the relativistic radiative particle-in-cell (PIC) code Zeltron, developed by the team members at the Univ. of Colorado. This code has a unique capability to self-consistently include the synchrotron and inverse-Compton radiation reaction force on the relativistic particles, while simultaneously computing the resulting observable radiative signatures. This proposal envisions performing massively parallel, large-scale three-dimensional simulations of driven and decaying kinetic turbulence in physical regimes relevant to real astrophysical systems (such as the Crab PWN), including the

  15. Kinetic, equilibrium and thermodynamic studies for the removal of lead (II) and copper (II) ions from aqueous solutions by nanocrystalline TiO

    NASA Astrophysics Data System (ADS)

    Rashidi, Fatemeh; Sarabi, Reza Sadeghi; Ghasemi, Zinab; Seif, Ahmad

    2010-12-01

    Titanium dioxide nanocrystallites were synthesized as adsorbents through the hydrolysis of titanium tetrachloride as the precursor in hydrochloric acid. The product was analyzed by XRD, BET and SEM-EDX; analysis indicated that the particles were a mixture of 86.8% rutile and 13.2% anatase TiO 2 with spherical shapes. The adsorption of Pb (II) and Cu (II) metal ions from aqueous solution onto nano- TiO 2 were investigated with variations in pH, contact time, initial metal ion concentration and temperature. The kinetics, adsorption isotherm and adsorption thermodynamics of the heavy metals were studied. The kinetics data were analyzed by the pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models; the best correlation coefficients were obtained for the pseudo-second order kinetic model. The adsorption results obtained from equilibrium experiments were analyzed by Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms with the Freundlich isotherm giving the best fitting isotherm to the equilibrium data. The thermodynamic parameters ( ΔG°, ΔH° and ΔS°) were calculated and it was found that the adsorption process is spontaneous and endothermic and is favored at higher temperature.

  16. Channeling of fusion alpha-particle power using minority ion catalysis.

    PubMed

    Zhmoginov, A I; Fisch, N J

    2011-10-21

    Maintaining fuel ions hotter than electrons would greatly facilitate controlled nuclear fusion. The parameter range for achieving this temperature disparity is shown here to be enhanced by catalyzing the α-channeling effect (wave-induced simultaneous expulsion and cooling of α particles) through minority-ion heating. Specifically, a wave can extract energy from hot α particles and transfer it to colder minority ions, which act as a catalyst, eventually forwarding the energy to still colder fuel ions through collisions. In comparison with the traditional α-channeling mechanism, the requirements are thereby relaxed on the waves that accomplish the α channeling, which no longer have to interact simultaneously with α particles and fuel ions. Numerical simulations illustrate how the new scheme may increase, for example, the effective fusion reactivity of mirror-confined plasmas. © 2011 American Physical Society

  17. Channeling of Fusion Alpha-Particle Power Using Minority Ion Catalysis

    NASA Astrophysics Data System (ADS)

    Zhmoginov, A. I.; Fisch, N. J.

    2011-10-01

    Maintaining fuel ions hotter than electrons would greatly facilitate controlled nuclear fusion. The parameter range for achieving this temperature disparity is shown here to be enhanced by catalyzing the α-channeling effect (wave-induced simultaneous expulsion and cooling of α particles) through minority-ion heating. Specifically, a wave can extract energy from hot α particles and transfer it to colder minority ions, which act as a catalyst, eventually forwarding the energy to still colder fuel ions through collisions. In comparison with the traditional α-channeling mechanism, the requirements are thereby relaxed on the waves that accomplish the α channeling, which no longer have to interact simultaneously with α particles and fuel ions. Numerical simulations illustrate how the new scheme may increase, for example, the effective fusion reactivity of mirror-confined plasmas.

  18. 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.

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

    SciTech Connect

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

    2016-02-15

    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.

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

    DOE PAGES

    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

  1. 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.

  2. 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.

  3. 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.

  4. Anaerobic biohydrogen production from wheat stalk by mixed microflora: kinetic model and particle size influence.

    PubMed

    Yuan, Xianzheng; Shi, Xiaoshuang; Zhang, Peidong; Wei, Yueli; Guo, Rongbo; Wang, Lisheng

    2011-10-01

    This study investigated the influence of particle size on anaerobic biohydrogen production from wheat stalk by mixed microflora. In addition, the kinetic model for the formation of main products was also mentioned. The results demonstrated that all the cumulative productions of hydrogen, acetate and butyrate decreased as the particle size increasing from 1 to 10mm at a constant TS value of 2%, 5% and 8%, respectively. However, this difference for aqueous products was not very obvious compared with hydrogen. A modified Gompertz equation was able to adequately describe the cumulative production of hydrogen, acetate and butyrate (R² higher than 0.989). The results also indicated that the formation of the main products were all associated with the degradation of cellulose and hemicellulose (R² higher than 0.855).

  5. 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).

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

    PubMed

    Veltri, P; Cavenago, M; Serianni, G

    2014-02-01

    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 λD. 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.

  7. 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.

  8. Statistical rate theory and kinetic energy-resolved ion chemistry: theory and applications.

    PubMed

    Armentrout, P B; Ervin, Kent M; Rodgers, M T

    2008-10-16

    Ion chemistry, first discovered 100 years ago, has profitably been coupled with statistical rate theories, developed about 80 years ago and refined since. In this overview, the application of statistical rate theory to the analysis of kinetic-energy-dependent collision-induced dissociation (CID) reactions is reviewed. This procedure accounts for and quantifies the kinetic shifts that are observed as systems increase in size. The statistical approach developed allows straightforward extension to systems undergoing competitive or sequential dissociations. Such methods can also be applied to the reverse of the CID process, association reactions, as well as to quantitative analysis of ligand exchange processes. Examples of each of these types of reactions are provided and the literature surveyed for successful applications of this statistical approach to provide quantitative thermochemical information. Such applications include metal-ligand complexes, metal clusters, proton-bound complexes, organic intermediates, biological systems, saturated organometallic complexes, and hydrated and solvated species.

  9. Small amplitude Kinetic Alfven waves in a superthermal electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Adnan, Muhammad; Mahmood, Sahahzad; Qamar, Anisa; Tribeche, Mouloud

    2016-11-01

    We are investigating the propagating properties of coupled Kinetic Alfven-acoustic waves in a low beta plasma having superthermal electrons and positrons. Using the standard reductive perturbation method, a nonlinear Korteweg-de Vries (KdV) type equation is derived which describes the evolution of Kinetic Alfven waves. It is found that nonlinearity and Larmor radius effects can compromise and give rise to solitary structures. The parametric role of superthermality and positron content on the characteristics of solitary wave structures is also investigated. It is found that only sub-Alfvenic and compressive solitons are supported in the present model. The present study may find applications in a low β electron-positron-ion plasma having superthermal electrons and positrons.

  10. Permeant ion effects on the gating kinetics of the type L potassium channel in mouse lymphocytes

    PubMed Central

    1991-01-01

    Permeant ion species was found to profoundly affect the gating kinetics of type l K+ currents in mouse T lymphocytes studied with the whole- cell or on-cell patch gigaohm-seal techniques. Replacing external K+ with Rb+ (as the sole monovalent cation, at 160 mM) shifted the peak conductance voltage (g-V) relation by approximately 20 mV to more negative potentials, while NH4+ shifted the g-V curve by 15 mV to more positive potentials. Deactivation (the tail current time constant, tau tail) was slowed by an average of 14-fold at -70 mV in external Rb+, by approximately 8-fold in Cs+, and by a factor of two to three in NH4+. Changing the external K+ concentration, [K+]o, from 4.5 to 160 mM or [Rb+]o from 10 to 160 mM had no effect on tau tail. With all the internal K+ replaced by Rb+ or Cs+ and either isotonic Rb+ or K+ in the bath, tau tail was indistinguishable from that with K+ in the cell. With the exception of NH4+, activation time constants were insensitive to permeant ion species. These results indicate that external permeant ions have stronger effects than internal permeant ions, suggesting an external modulatory site that influences K+ channel gating. However, in bi-ionic experiments with reduced external permeant ion concentrations, tau tail was sensitive to the direction of current flow, indicating that the modulatory site is either within the permeation pathway or in the outer vestibule of the channel. The latter interpretation implies that outward current through an open type l K+ channel significantly alters local ion concentrations at the modulatory site in the outer vestibule, and consequently at the mouth of the channel. Experiments with mixtures of K+ and Rb+ in the external solution reveal that deactivation kinetics are minimally affected by addition of Rb+ until the Rb+ mole fraction approaches unity. This relationship between mole fraction and tau tail, together with the concentration independence of tau tail, was hard to reconcile with simple

  11. Nano- and microcrystalline particles of palladium formed on hydrogen-bombarded palladium surfaces; their structure and formation kinetics

    NASA Astrophysics Data System (ADS)

    Senda, S.; Muto, H.; Takamori, H.; Okuyama, F.

    2003-03-01

    Crystalline particles of palladium are known to form on polycrystalline Pd interacting with low-energy hydrogen ions. These particles disperse on the glassy medium called the “matrix". The particles were recently confirmed by transmission electron microscopy to be classified into two groups: the particles emerging from the projectile-implanted subsurface together with the outflowing matrix and those newly produced on the hydrogen-bombarded matrix. The latter type of particles was nucleated as a crystalline cluster on the disordered substrate, and then underwent three-dimensional growth into a nanocrystal under the bombard- ment of showering hydrogen ions. Some particles presented a bubble-like TEM contrast, independently of their growth history. Such particles were chestnut-like in structure, with a hard shell wrapping the less-dense interior, and their formation may be attributed to a chemical process occurring within the particles.

  12. IONEX: A meshfree ion extraction code based on ''particle in cloud of points'' concept

    SciTech Connect

    Galkin, S. A.; Grubert, J. E.; Cluggish, B. P.; Barov, N.; Kim, J. S.

    2010-02-15

    Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson's equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.

  13. IONEX: a meshfree ion extraction code based on "particle in cloud of points" concept.

    PubMed

    Galkin, S A; Grubert, J E; Cluggish, B P; Barov, N; Kim, J S

    2010-02-01

    Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson's equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.

  14. Yields of clustered DNA damage induced by charged-particle radiations of similar kinetic energy per nucleon: LET dependence in different DNA microenvironments

    SciTech Connect

    Keszenman, D.J.; Sutherland, B. M.

    2010-08-01

    To determine the linear energy transfer (LET) dependence of the biological effects of densely ionizing radiation in relation to changes in the ionization density along the track, we measured the yields and spectrum of clustered DNA damages induced by charged particles of different atomic number but similar kinetic energy per nucleon in different DNA microenvironments. Yeast DNA embedded in agarose in solutions of different free radical scavenging capacity was irradiated with 1 GeV protons, 1 GeV/nucleon oxygen ions, 980 MeV/nucleon titanium ions or 968 MeV/nucleon iron ions. The frequencies of double-strand breaks (DSBs), abasic sites and oxypurine clusters were quantified. The total DNA damage yields per absorbed dose induced in non-radioquenching solution decreased with LET, with minor variations in radioquenching conditions being detected. However, the total damage yields per particle fluence increased with LET in both conditions, indicating a higher efficiency per particle to induce clustered DNA damages. The yields of DSBs and non-DSB clusters as well as the damage spectra varied with LET and DNA milieu, suggesting the involvement of more than one mechanism in the formation of the different types of clustered damages.

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

    PubMed

    Dang, Liem X; Chang, Tsun-Mei

    2016-09-07

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. 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.

  18. EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events

    NASA Astrophysics Data System (ADS)

    Manninen, H. E.; Nieminen, T.; Asmi, E.; Gagné, S.; Häkkinen, S.; Lehtipalo, K.; Aalto, P.; Vana, M.; Mirme, A.; Mirme, S.; Hõrrak, U.; Plass-Dülmer, C.; Stange, G.; Kiss, G.; Hoffer, A.; Törő, N.; Moerman, M.; Henzing, B.; de Leeuw, G.; Brinkenberg, M.; Kouvarakis, G. N.; Bougiatioti, A.; Mihalopoulos, N.; O'Dowd, C.; Ceburnis, D.; Arneth, A.; Svenningsson, B.; Swietlicki, E.; Tarozzi, L.; Decesari, S.; Facchini, M. C.; Birmili, W.; Sonntag, A.; Wiedensohler, A.; Boulon, J.; Sellegri, K.; Laj, P.; Gysel, M.; Bukowiecki, N.; Weingartner, E.; Wehrle, G.; Laaksonen, A.; Hamed, A.; Joutsensaari, J.; Petäjä, T.; Kerminen, V.-M.; Kulmala, M.

    2010-08-01

    We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ~1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.

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

    SciTech Connect

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

    2015-06-15

    The significance and nature of ion kinetic effects in D{sup 3}He-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, N{sub K}) 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 (N{sub K} ∼ 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.

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

    DOE PAGES

    Rosenberg, M. J.; Séguin, F. H.; Amendt, P. 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 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

  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. 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.

  3. 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

  4. Kinetic Monte Carlo (KMC) simulation of fission product silver transport through TRISO fuel particle

    NASA Astrophysics Data System (ADS)

    de Bellefon, G. M.; Wirth, B. D.

    2011-06-01

    A mesoscale kinetic Monte Carlo (KMC) model developed to investigate the diffusion of silver through the pyrolytic carbon and silicon carbide containment layers of a TRISO fuel particle is described. The release of radioactive silver from TRISO particles has been studied for nearly three decades, yet the mechanisms governing silver transport are not fully understood. This model atomically resolves Ag, but provides a mesoscale medium of carbon and silicon carbide, which can include a variety of defects including grain boundaries, reflective interfaces, cracks, and radiation-induced cavities that can either accelerate silver diffusion or slow diffusion by acting as traps for silver. The key input parameters to the model (diffusion coefficients, trap binding energies, interface characteristics) are determined from available experimental data, or parametrically varied, until more precise values become available from lower length scale modeling or experiment. The predicted results, in terms of the time/temperature dependence of silver release during post-irradiation annealing and the variability of silver release from particle to particle have been compared to available experimental data from the German HTR Fuel Program ( Gontard and Nabielek [1]) and Minato and co-workers ( Minato et al. [2]).

  5. 2D Kinetic Particle in Cell Simulations of a Shear-Flow Stabilized Z-Pinch

    NASA Astrophysics Data System (ADS)

    Tummel, Kurt; Higginson, Drew; Schmidt, Andrea; Link, Anthony; McLean, Harry; Shumlak, Uri; Nelson, Brian; Golingo, Raymond; Claveau, Elliot; Lawrence Livermore National Lab Team; University of Washington Team

    2016-10-01

    The Z-pinch is a relatively simple and attractive potential fusion reactor design, but attempts to develop such a reactor have consistently struggled to overcome Z-pinch instabilities. The ``sausage'' and ``kink'' modes are among the most robust and prevalent Z-pinch instabilities, but theory and simulations suggest that axial flow-shear, dvz / dr ≠ 0 , can suppress these modes. Experiments have confirmed that Z-pinch plasmas with embedded axial flow-shear display a significantly enhanced resilience to the sausage and kink modes at a demonstration current of 50kAmps. A new experiment is under way to test the concept at higher current, and efforts to model these plasmas are being expanded. The performance and stability of these devices will depend on features like the plasma viscosity, anomalous resistivity, and finite Larmor radius effects, which are most accurately characterized in kinetic models. To predict these features, kinetic simulations using the particle in cell code LSP are now in development, and initial benchmarking and 2D stability analyses of the sausage mode are presented here. These results represent the first kinetic modeling of the flow-shear stabilized Z-pinch. This work is funded by the USDOE/ARPAe Alpha Program. Prepared by LLNL under Contract DE-AC52-07NA27344.

  6. 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.

  7. Electron beam ion sources for use in second generation synchrotrons for medical particle therapy

    NASA Astrophysics Data System (ADS)

    Zschornack, G.; Ritter, E.; Schmidt, M.; Schwan, A.

    2014-02-01

    Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C4 + and C6 + ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, "A survey of Hadron therapy accelerator technology," in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., "Cyclinac medical accelerators using pulsed C6 +/H+_2 ion sources," in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 109 protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA.

  8. Electron beam ion sources for use in second generation synchrotrons for medical particle therapy.

    PubMed

    Zschornack, G; Ritter, E; Schmidt, M; Schwan, A

    2014-02-01

    Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C(4 +) and C(6 +) ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, "A survey of Hadron therapy accelerator technology," in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., "Cyclinac medical accelerators using pulsed C(6 +)/H2(+) ion sources," in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 10(9) protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA.

  9. 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.

  10. Kinetic theory for systems of self-propelled particles with metric-free interactions.

    PubMed

    Chou, Yen-Liang; Wolfe, Rylan; Ihle, Thomas

    2012-08-01

    A model of self-driven particles similar to the Vicsek model [Phys. Rev. Lett. 75, 1226 (1995)] but with metric-free interactions is studied by means of a novel Enskog-type kinetic theory. In this model, N particles of constant speed v(0) try to align their travel directions with the average direction of a fixed number of closest neighbors. At strong alignment a global flocking state forms. The alignment is defined by a stochastic rule, not by a Hamiltonian. The corresponding interactions are of genuine multibody nature. The theory is based on a Master equation in 3N-dimensional phase space, which is made tractable by means of the molecular chaos approximation. The phase diagram for the transition to collective motion is calculated and compared to direct numerical simulations. A linear stability analysis of a homogeneous ordered state is performed using the kinetic but not the hydrodynamic equations in order to achieve high accuracy. In contrast to the regular metric Vicsek-model no instabilities occur. This confirms previous direct simulations that, for Vicsek-like models with metric-free interactions, there is no formation of density bands and that the flocking transition is continuous.

  11. 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.

  12. 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

  13. Novel kinetic model of the removal of divalent heavy metal ions from aqueous solutions by natural clinoptilolite.

    PubMed

    Jovanovic, Mina; Rajic, Nevenka; Obradovic, Bojana

    2012-09-30

    Removal of heavy metal ions from aqueous solutions using zeolites is widely described by pseudo-second order kinetics although this model may not be valid under all conditions. In this work, we have extended approaches used for derivation of this model in order to develop a novel kinetic model that is related to the ion exchange mechanism underlying sorption of metal ions in zeolites. The novel model assumed two reversible steps, i.e. release of sodium ions from the zeolite lattice followed by bonding of the metal ion. The model was applied to experimental results of Cu(II) sorption by natural clinoptilolite-rich zeolitic tuff at different initial concentrations and temperatures and then validated by predictions of ion exchange kinetics of other divalent heavy metal ions (i.e. Mn(II), Zn(II) and Pb(II)). Model predictions were in excellent agreements with experimental data for all investigated systems. In regard to the proposed mechanism, modeling results implied that the sodium ion release rate was constant for all investigated metals while the overall rate was mainly determined by the rate of heavy metal ion bonding to the lattice. In addition, prediction capabilities of the novel model were demonstrated requiring one experimentally determined parameter, only. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. 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

  15. Kinetic energy distribution of multiply charged ions in Coulomb explosion of Xe clusters.

    PubMed

    Heidenreich, Andreas; Jortner, Joshua

    2011-02-21

    We report on the calculations of kinetic energy distribution (KED) functions of multiply charged, high-energy ions in Coulomb explosion (CE) of an assembly of elemental Xe(n) clusters (average size (n) = 200-2171) driven by ultra-intense, near-infrared, Gaussian laser fields (peak intensities 10(15) - 4 × 10(16) W cm(-2), pulse lengths 65-230 fs). In this cluster size and pulse parameter domain, outer ionization is incomplete∕vertical, incomplete∕nonvertical, or complete∕nonvertical, with CE occurring in the presence of nanoplasma electrons. The KEDs were obtained from double averaging of single-trajectory molecular dynamics simulation ion kinetic energies. The KEDs were doubly averaged over a log-normal cluster size distribution and over the laser intensity distribution of a spatial Gaussian beam, which constitutes either a two-dimensional (2D) or a three-dimensional (3D) profile, with the 3D profile (when the cluster beam radius is larger than the Rayleigh length) usually being experimentally realized. The general features of the doubly averaged KEDs manifest the smearing out of the structure corresponding to the distribution of ion charges, a marked increase of the KEDs at very low energies due to the contribution from the persistent nanoplasma, a distortion of the KEDs and of the average energies toward lower energy values, and the appearance of long low-intensity high-energy tails caused by the admixture of contributions from large clusters by size averaging. The doubly averaged simulation results account reasonably well (within 30%) for the experimental data for the cluster-size dependence of the CE energetics and for its dependence on the laser pulse parameters, as well as for the anisotropy in the angular distribution of the energies of the Xe(q+) ions. Possible applications of this computational study include a control of the ion kinetic energies by the choice of the laser intensity profile (2D∕3D) in the laser-cluster interaction volume.

  16. A novel approach to ion-ion Langevin self-collisions in particle-in-cell modules applied to hybrid MHD codes

    NASA Astrophysics Data System (ADS)

    Nicolas, T.; Luciani, J.-F.; Lütjens, H.; Garbet, X.; Graves, J.

    2017-05-01

    In order to have a better closure for magnetohydrodynamic (MHD) equations, a common approach is to obtain the ion fluid pressure tensor by directly computing the moments of an ion distribution function, obtained by a particle-in-cell solver of the Vlasov or Boltzmann equation. This is the so-called hybrid approach. Long MHD simulations are required for problems such as investigating the properties of the sawtooth cycle. In such long hybrid simulations, collisions are required to relax the distribution function after violent MHD events, and to obtain the self-consistent neoclassical transport. In this paper, we present a new approach to ion self-collisions, based on temperature- and velocity-shifted Maxwellian distributions. It is shown that the approach emulates the effect of the background reaction, without the need to explicitly implement it. Arbitrariness in the choice of the closest Maxwellian is removed. The model compares very well with binary collision Monte-Carlo simulations. The practical implementation as a Fokker-Planck module in a hybrid kinetic/MHD simulation code is discussed. This requires an additional manipulation in order to conserve energy and momentum.

  17. 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,