Weakly nonlinear electron plasma waves in collisional plasmas
DEFF Research Database (Denmark)
Pecseli, H. L.; Rasmussen, J. Juul; Tagare, S. G.
1986-01-01
The nonlinear evolution of a high frequency plasma wave in a weakly magnetized, collisional plasma is considered. In addition to the ponderomotive-force-nonlinearity the nonlinearity due to the heating of the electrons is taken into account. A set of nonlinear equations including the effect...... of a constantly maintained pump wave is derived and a general dispersion relation describing the modulation of the high frequency wave due to different low frequency responses is obtained. Particular attention is devoted to a purely growing modulation. The relative importance of the ponderomotive force...
Camporeale, E.; Pezzi, O.; Valentini, F.
2015-12-01
The longstanding problem of collisions in plasmas is a very fascinating and huge topic in plasma physics. The 'natural' operator that describes the Coulombian interactions between charged particles is the Landau (LAN) integral operator. The LAN operator is a nonlinear, integro-differential and Fokker-Planck type operator which satisfies the H theorem for the entropy growth. Due to its nonlinear nature and multi-dimensionality, any approach to the solution of the Landau integral is almost prohibitive. Therefore collisions are usually modeled by simplified collisional operators. Here collisional effects are modeled by i) the one-dimensional Lenard-Bernstein (LB) operator and ii) the three-dimensional Dougherty (DG) operator. In the first case i), by focusing on a 1D-1V phase space, we study recurrence effects in a weakly collisional plasma, being collisions modeled by the LB operator. By decomposing the linear Vlasov-Poisson system in the Fourier-Hermite space, the recurrence problem is investigated in the linear regime of the damping of a Langmuir wave and of the onset of the bump-on-tail instability. The analysis is then confirmed and extended to the nonlinear regime through a Eulerian collisional Vlasov-Poisson code. Despite being routinely used, an artificial collisionality is not in general a viable way of preventing recurrence in numerical simulations. Moreover, recursive phenomena affect both the linear exponential growth and the nonlinear saturation of a linear instability by producing a fake growth in the electric field, thus showing that, although the filamentation is usually associated with low amplitude fluctuations contexts, it can occur also in nonlinear phenomena. On the other hand ii), the effects of electron-electron collisions on the propagation of nonlinear electrostatic waves are shown by means of Eulerian simulations in a 1D-3V (one dimension in physical space, three dimensions in velocity space) phase space. The nonlinear regime of the symmetric
The Stability of Weakly Collisional Plasmas with Thermal and Composition Gradients
Pessah, Martin E; 10.1088/0004-637X/764/1/13
2013-01-01
Over the last decade, substantial efforts have been devoted to understanding the stability properties, transport phenomena, and long-term evolution of weakly-collisional, magnetized plasmas which are stratified in temperature. These studies have improved our understanding of the physics governing the intra-cluster medium (ICM), but assumed that ICM is a homogeneous. This, however, might not be a good approximation if heavy elements sediment in the inner region of the galaxy cluster. In this paper, we analyze the stability of a weakly-collisional, magnetized plane-parallel atmosphere which is stratified in both temperature and composition. This allows us to discuss for the first time the dynamics of weakly-collisional environments where heat conduction, momentum transport, and ion-diffusion are anisotropic with respect to the direction of the magnetic field. We show that, depending on the relative signs and magnitudes of the gradients in the temperature and the mean molecular weight, the plasma can be subject ...
Colloidal Plasmas : Dynamo transformation of the collisional R-T in a weakly ionized plasma
Indian Academy of Sciences (India)
C B Dwivedi
2000-11-01
Theoretical prediction of a new kind of normal mode behaviour of electro-mechanical nature was ﬁrst time reported by Dwivedi and Das in 1992 in the context of mesospheric modeling of observed neutral induced turbulence. Local dynamo action (due to relative neutral ﬂow) governs the basic physical principle for linear excitation of the neutral induced low frequency instability (NILF) in mesospheric plasma, which comprises of weakly ionized inhomogeneous gas conﬁned by the external gravity and ambient magnetic ﬁeld. The present contribution offers physical explanation in terms of dynamo transformation of neutral drag effect as a source to understand complete suppression of the usual collisional R-T and in turn linear driving of the NILF. It is therefore emphasized, worth calling it as the dynamo instability.
The stability of weakly collisional plasmas with thermal and composition gradients
DEFF Research Database (Denmark)
Pessah, M.E.; Chakraborty, S.
2013-01-01
Over the last decade, substantial efforts have been devoted to understanding the stability properties, transport phenomena, and long-term evolution of weakly collisional, magnetized plasmas which are stratified in temperature. The insights gained via these studies have led to a significant...... approximation if heavy elements are able to sediment in the inner region of the galaxy cluster. Motivated by the need to obtain a more complete picture of the dynamical properties of the ICM, we analyze the stability of a weakly collisional, magnetized plane-parallel atmosphere which is stratified in both...... in homogeneous media. We also find that there are new modes which are driven by heat conduction and particle diffusion. We discuss the astrophysical implications of our findings for a representative galaxy cluster where helium has sedimented. Our findings suggest that the core insulation that results from...
Energy Technology Data Exchange (ETDEWEB)
Schekochihin, A. A.; Cowley, S. C.; Dorland, W.; Hammett, G. W.; Howes, G. G.; Quataert, E.; Tatsuno, T.
2009-04-23
This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulentmotions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-fieldstrength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations
Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations
Hellinger, Petr
2014-01-01
Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the ...
A collisional-radiative model for low-pressure weakly magnetized Ar plasmas
Zhu, Xi-Ming; Tsankov, Tsanko; Czarnetzki, Uwe; Marchuk, Oleksandr
2016-09-01
Collisional-radiative (CR) models are widely investigated in plasma physics for describing the kinetics of reactive species and for optical emission spectroscopy. This work reports a new Ar CR model used in low-pressure (0.01-10 Pa) weakly magnetized (<0.1 Tesla) plasmas, including ECR, helicon, and NLD discharges. In this model 108 realistic levels are individually studied, i.e. 51 lowest levels of the Ar atom and 57 lowest levels of the Ar ion. We abandon the concept of an ``effective level'' usually adopted in previous models for glow discharges. Only in this way the model can correctly predict the non-equilibrium population distribution of close energy levels. In addition to studying atomic metastable and radiative levels, this model describes the kinetic processes of ionic metastable and radiative levels in detail for the first time. This is important for investigation of plasma-surface interaction and for optical diagnostics using atomic and ionic line-ratios. This model could also be used for studying Ar impurities in tokamaks and astrophysical plasmas.
Limitations of Hall MHD as a model for turbulence in weakly collisional plasmas
Directory of Open Access Journals (Sweden)
G. G. Howes
2009-03-01
Full Text Available The limitations of Hall MHD as a model for turbulence in weakly collisional plasmas are explored using quantitative comparisons to Vlasov-Maxwell kinetic theory over a wide range of parameter space. The validity of Hall MHD in the cold ion limit is shown, but spurious undamped wave modes exist in Hall MHD when the ion temperature is finite. It is argued that turbulence in the dissipation range of the solar wind must be one, or a mixture, of three electromagnetic wave modes: the parallel whistler, oblique whistler, or kinetic Alfvén waves. These modes are generally well described by Hall MHD. Determining the applicability of linear kinetic damping rates in turbulent plasmas requires a suite of fluid and kinetic nonlinear numerical simulations. Contrasting fluid and kinetic simulations will also shed light on whether the presence of spurious wave modes alters the nonlinear couplings inherent in turbulence and will illuminate the turbulent dynamics and energy transfer in the regime of the characteristic ion kinetic scales.
Sonnino, Giorgio; Peeters, Philippe; Sonnino, Alberto; Nardone, Pasquale; Steinbrecher, György
2015-01-01
In previous works, we derived stationary density distribution functions (DDF) where the local equilibrium is determined by imposing the maximum entropy (MaxEnt) principle, under the scale invariance restrictions, and the minimum entropy production theorem. In this paper we demonstrate that it is possible to reobtain these DDF solely from the MaxEnt principle subject to suitable scale invariant restrictions in all the variables. For the sake of concreteness, we analyse the example of ohmic, fully ionized, tokamak-plasmas, in the weak-collisional transport regime. In this case we show that it is possible to reinterpret the stationary distribution function in terms of the Prigogine distribution function where the logarithm of the DDF is directly linked to the entropy production of the plasma. This leads to the suggestive idea that also the stationary neoclassical distribution functions, for magnetically confined plasmas in the collisional transport regimes, may be derived solely by the MaxEnt principle.
Simulation of laser-driven plasma beat-wave propagation in collisional weakly relativistic plasmas
Kaur, Maninder; Nandan Gupta, Devki
2016-11-01
The process of interaction of lasers beating in a plasma has been explored by virtue of particle-in-cell (PIC) simulations in the presence of electron-ion collisions. A plasma beat wave is resonantly excited by ponderomotive force by two relatively long laser pulses of different frequencies. The amplitude of the plasma wave become maximum, when the difference in the frequencies is equal to the plasma frequency. We propose to demonstrate the energy transfer between the laser beat wave and the plasma wave in the presence of electron-ion collision in nearly relativistic regime with 2D-PIC simulations. The relativistic effect and electron-ion collision both affect the energy transfer between the interacting waves. The finding of simulation results shows that there is a considerable decay in the plasma wave and the field energy over time in the presence of electron-ion collisions.
Generation of Electrojets in Weakly Ionized Plasmas through a Collisional Dynamo
Dimant, Yakov S; Fletcher, Alex C
2016-01-01
Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earth's ionosphere near the magnetic equator where neutral winds drive the plasma across the geomagnetic field. Similar processes take place in the Solar chromosphere and MHD generators. This letter argues that not all convective neutral flows generate electrojets and it introduces the corresponding universal criterion for electrojet formation, $\
Dan, Li; Guo, Li-Xin; Li, Jiang-Ting; Chen, Wei; Yan, Xu; Huang, Qing-Qing
2017-09-01
The expression of complex dielectric permittivity for non-magnetized fully ionized dusty plasma is obtained based on the kinetic equation in the Fokker-Planck-Landau collision model and the charging equation of the statistical theory. The influences of density, average size of dust grains, and balanced charging of the charge number of dust particles on the attenuation properties of electromagnetic waves in fully ionized dusty plasma are investigated by calculating the attenuation constant. In addition, the attenuation characteristics of weakly ionized and fully ionized dusty plasmas are compared. Results enriched the physical mechanisms of microwave attenuation for fully ionized dusty plasma and provide a theoretical basis for future studies.
Rosin, M S; Rincon, F; Cowley, S C
2010-01-01
Plasmas have a natural tendency to develop pressure anisotropies with respect to the local direction of the magnetic field. These anisotropies trigger plasma instabilities at scales just above the ion Larmor radius with growth rates of a fraction of the ion cyclotron frequency - much faster than either the global dynamics or local turbulence. The instabilities can dramatically modify the macroscopic dynamics of the plasma. Nonlinear evolution of these instabilities is expected to drive pressure anisotropies towards marginal stability values, controlled by the plasma beta. This nonlinear evolution is worked out in an ab initio kinetic calculation for the simplest analytically tractable example - the parallel firehose instability in a high-beta plasma. A closed nonlinear equation for the firehose turbulence is derived and solved. In the nonlinear regime, the instability leads to secular (~t) growth of magnetic fluctuations. The fluctuations develop a k^{-3} spectrum, extending from scales somewhat larger than r...
Collisional properties of weakly bound heteronuclear dimers
Marcelis, B.; Kokkelmans, S.J.J.M.F.; Shlyapnikov, G.V.; Petrov, D.S.
2008-01-01
We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating
Fine velocity structures collisional dissipation in plasmas
Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi
2016-04-01
In a weakly collisional plasma, such as the solar wind, collisions are usually considered far too weak to produce any significant effect on the plasma dynamics [1]. However, the estimation of collisionality is often based on the restrictive assumption that the particle velocity distribution function (VDF) shape is close to Maxwellian [2]. On the other hand, in situ spacecraft measurements in the solar wind [3], as well as kinetic numerical experiments [4], indicate that marked non-Maxwellian features develop in the three-dimensional VDFs, (temperature anisotropies, generation of particle beams, ring-like modulations etc.) as a result of the kinetic turbulent cascade of energy towards short spatial scales. Therefore, since collisional effects are proportional to the velocity gradients of the VDF, the collisionless hypothesis may fail locally in velocity space. Here, the existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can increase locally due to the velocity space deformation of the particle velocity distribution. In particular, by means of Eulerian simulations of collisional relaxation of a spatially homogeneous force-free plasma, in which collisions among particles of the same species are modeled through the complete Landau operator, we show that the system entropy growth occurs over several time scales, inversely proportional to the steepness of the velocity gradients in the VDF. We report clear evidences that fine velocity structures are dissipated by collisions in a time much shorter than global non-Maxwellian features, like, for example, temperature anisotropies. Moreover we indicate that, if small-scale structures
Acceleration of weakly collisional solar-type winds
Zouganelis, I; Landi, S; Maksimovic, M; Pantellini, F
2005-01-01
One of the basic properties of the solar wind, that is the high speed of the fast wind, is still not satisfactorily explained. This is mainly due to the theoretical difficulty of treating weakly collisional plasmas. The fluid approach implies that the medium is collision dominated and that the particle velocity distributions are close to Maxwellians. However the electron velocity distributions observed in the solar wind depart significantly from Maxwellians. Recent kinetic collisionless models (called exospheric) using velocity distributions with a suprathermal tail have been able to reproduce the high speeds of the fast solar wind. In this letter we present new developments of these models by generalizing them over a large range of corona conditions. We also present new results obtained by numerical simulations that include collisions. Both approaches calculate the heat flux self-consistently without any assumption on the energy transport. We show that both approaches - the exospheric and the collisional one...
Buoyancy Instabilities in a Weakly Collisional Intracluster Medium
Kunz, Matthew W; Reynolds, Christopher S; Stone, James M
2012-01-01
The intracluster medium of galaxy clusters is a weakly collisional, high-beta plasma in which the transport of heat and momentum occurs primarily along magnetic-field lines. Anisotropic heat conduction allows convective instabilities to be driven by temperature gradients of either sign, the magnetothermal instability (MTI) in the outskirts of non-isothermal clusters and the heat-flux buoyancy-driven instability (HBI) in their cooling cores. We employ the Athena MHD code to investigate the nonlinear evolution of these instabilities, self-consistently including the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy), anisotropic conduction, and radiative cooling. We highlight the importance of the microscale instabilities that inevitably accompany and regulate the pressure anisotropies generated by the HBI and MTI. We find that, in all but the innermost regions of cool-core clusters, anisotropic viscosity significantly impairs the ability of the HBI to reorient magnetic-field lines orthogonal...
Collisional damping rates for plasma waves
Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.
2016-06-01
The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic ("Spitzer") formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.
Fe XVII Emission from Hot, Collisional Plasmas
Energy Technology Data Exchange (ETDEWEB)
Beiersdorfer, P; Bitter, M; von Goeler, S; Hill, K W
2004-12-03
The ratios of the Fe XVII 3s {yields} 2p transitions to that of the dominant 3d {yields} 2p transition measured in high-temperature tokamak plasmas are compared to solar and astrophysical observations. Good agreement is found, indicating that the collisional line formation processes active in opacity-free, low-density, high-temperature laboratory plasmas are a good description of those found in astrophysical plasmas.
Exact collisional moments for plasma fluid theories
Pfefferlé, D.; Hirvijoki, E.; Lingam, M.
2017-04-01
The velocity-space moments of the often troublesome nonlinear Landau collision operator are expressed exactly in terms of multi-index Hermite-polynomial moments of distribution functions. The collisional moments are shown to be generated by derivatives of two well-known functions, namely, the Rosenbluth-MacDonald-Judd-Trubnikov potentials for a Gaussian distribution. The resulting formula has a nonlinear dependency on the relative mean flow of the colliding species normalised to the root-mean-square of the corresponding thermal velocities and a bilinear dependency on densities and higher-order velocity moments of the distribution functions, with no restriction on temperature, flow, or mass ratio of the species. The result can be applied to both the classic transport theory of plasmas that relies on the Chapman-Enskog method, as well as to derive collisional fluid equations that follow Grad's moment approach. As an illustrative example, we provide the collisional ten-moment equations with exact conservation laws for momentum- and energy-transfer rates.
Collisional current drive in two interpenetrating plasma jets
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D.; Kugland, N. L.; Park, H.-S.; Pollaine, S. M.; Remington, B. A.; Ross, J. S. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
2011-10-15
The magnetic field generation in two interpenetrating, weakly collisional plasma streams produced by intense lasers is considered. The generation mechanism is very similar to the neutral beam injection current drive in toroidal fusion devices, with the differences related to the absence of the initial magnetic field, short interaction time, and different geometry. Spatial and temporal characteristics of the magnetic field produced in two counterstreaming jets are evaluated; it is shown that the magnetic field of order of 1 T can be generated for modest jet parameters. Conditions under which this mechanism dominates that of the ''Biermann battery'' are discussed. Other settings where the mechanism of the collisional current drive can be important for the generation of seed magnetic fields include astrophysics and interiors of hohlraums.
Collisional Drift Waves in Stellarator Plasmas
Energy Technology Data Exchange (ETDEWEB)
J.L.V. Lewandowski
2003-10-07
A computational study of resistive drift waves in the edge plasma of a stellarator with an helical magnetic axis is presented. Three coupled field equations, describing the collisional drift wave dynamics in the linear approximation, are solved as an initial-value problem along the magnetic field line. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally efficient systematic study of the impact of the magnetic field structure on drift wave stability.
Sydorenko, D; Kaganovich, I; Raitses, Y; Smolyakov, A
2009-10-02
A new regime of plasma-wall interaction is identified in particle-in-cell simulations of a hot plasma bounded by walls with secondary electron emission. Such a plasma has a strongly non-Maxwellian electron velocity distribution function and consists of bulk plasma electrons and beams of secondary electrons. In the new regime, the plasma sheath is not in a steady space charge limited state even though the secondary electron emission produced by the plasma bulk electrons is so intense that the corresponding partial emission coefficient exceeds unity. Instead, the plasma-sheath system performs relaxation oscillations by switching quasiperiodically between the space charge limited and non-space-charge limited states.
Nonlinear magnetic reconnection in low collisionality plasmas
Energy Technology Data Exchange (ETDEWEB)
Ottaviani, M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Porcelli, F. [Politecnico di Torino, Turin (Italy)
1994-07-01
The magnetic reconnection in collisionless regimes, where electron inertia is responsible for the decoupling of the plasma motion from that of the field lines, is discussed. Since the linear theory of m=1 modes breaks down for very small magnetic island widths, a non linear analysis is called for. Thus, the behaviour of a collisionless, 2-D fluid slab model in the limit {rho}/d -> 0, is analyzed. The main result is that, when the island size is larger than the linear layer but smaller than the equilibrium scale length, the reconnection rate exhibits a quasi-explosive time behaviour, during which a current density sub-layer narrower than the skin depth is formed. It is believed that the inclusion of the electron initial term in Ohm`s law opens the possibility to understand the rapidity of relaxation process observed in low collisionality plasmas. 7 refs., 6 figs.
Theory of sheath in a collisional multi-component plasma
Indian Academy of Sciences (India)
M K Mahanta; K S Goswami
2001-04-01
The aim of this brief report is to study the behaviour of sheath structure in a multicomponent plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-12-01
Laser-generated interpenetrating plasma jets are widely used in the studies of collisionless interaction of counter-streaming plasmas in conjunction with possible formation of collisionless shocks. In a number of experiments of this type the plasma is formed on plastic targets made of CH or CD. The study of the DD neutron production from the interaction between two CD jets on the one hand and between a CD jet and a CH jet could serve as a qualitative indicator of the collisionless shock formation. The purpose of this memo is a discussion of the effect of collisions on the neutron generation in the interpenetrating CH and CD jets. First, the kinematics of the large-deflection collisions of the deuterons and carbon are discussed. Then the scattering angles are related with the corresponding Rutherford cross-section. After that expression for the number of the backscattered deuterons is provided, and their contribution to the neutron yield is evaluated. The results may be of some significance to the kinetic codes benchmarking and developing the neutron diagnostic.
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-12-08
Part 1 of this note considered the kinematics of large-angle scattering (LAS) of the deuterons on the counter-streaming carbon ions, with both flows having the same velocity V. Due to a large mass ratio m_{C}/m_{D}, the backscattered deuterons have high velocity of up to (24/7)V. This significantly increases the cross-section for the neutron production in the collisions between the back-scattered and incoming deuterons and may provide significant contribution to the total neutron yield, despite the smallness of a large-angle Coulomb cross-section. This effect becomes particularly important when only one of the colliding streams is made of CD, whereas the other stream is made of CH. Part 1 evaluated the neutron yield produced by this mechanism and have found that its relative role increases for higher plasma densities and lower velocities. Part 2 discusses signatures of this effect which can be used to identify it experimentally and also discusses in some more detail its spatio-temporal characteristics. It goes without saying that a complete quantitative assessment should be based on numerical simulations accounting for the large-angle scattering.
Plasma ion stratification by weak planar shocks
Simakov, Andrei N.; Keenan, Brett D.; Taitano, William T.; Chacón, Luis
2017-09-01
We derive fluid equations for describing steady-state planar shocks of a moderate strength ( 0 shock Mach number) propagating through an unmagnetized quasineutral collisional plasma comprising two separate ion species. In addition to the standard fluid shock quantities, such as the total mass density, mass-flow velocity, and electron and average ion temperatures, the equations describe shock stratification in terms of variations in the relative concentrations and temperatures of the two ion species along the shock propagation direction. We have solved these equations analytically for weak shocks ( 0 shocks, and they have been used to verify kinetic simulations of shocks in multi-ion plasmas.
Eulerian simulations of collisional effects on electrostatic plasma waves
Pezzi, Oreste; Perrone, Denise; Veltri, Pierluigi
2013-01-01
The problem of collisions in a plasma is a wide subject with a huge historical literature. In fact, the description of realistic plasmas is a tough problem to attach, both from the theoretical and the numerical point of view, and which requires in general to approximate the original collisional Landau integral by simplified differential operators in reduced dimensionality. In this paper, a Eulerian time-splitting algorithm for the study of the propagation of electrostatic waves in collisional plasmas is presented. Collisions are modeled through one-dimensional operators of the Fokker-Planck type, both in linear and nonlinear form. The accuracy of the numerical code is discussed by comparing the numerical results to the analytical predictions obtained in some limit cases when trying to evaluate the effects of collisions in the phenomenon of wave plasma echo and collisional dissipation of Bernstein-Greene-Kruskal waves. Particular attention is devoted to the study of the nonlinear Dougherty collisional operator...
Langmuir probe in collisionless and collisional plasma including dusty plasma
Bose, Sayak; Kaur, Manjit; Chattopadhyay, P. K.; Ghosh, J.; Saxena, Y. C.; Pal, R.
2017-04-01
Measurements of local plasma parameters in dusty plasma are crucial for understanding the physics issues related to such systems. The Langmuir probe, a small electrode immersed in the plasma, provides such measurements. However, designing of a Langmuir probe system in a dusty plasma environment demands special consideration. First, the probe has to be miniaturized enough so that its perturbation on the ambient dust structure is minimal. At the same time, the probe dimensions must be such that a well-defined theory exists for interpretation of its characteristics. The associated instrumentation must also support the measurement of current collected by the probe with high signal to noise ratio. The most important consideration, of course, comes from the fact that the probes are prone to dust contamination, as the dust particles tend to stick to the probe surface and alter the current collecting area in unpredictable ways. This article describes the design and operation of a Langmuir probe system that resolves these challenging issues in dusty plasma. In doing so, first, different theories that are used to interpret the probe characteristics in collisionless as well as in collisional regimes are discussed, with special emphasis on application. The critical issues associated with the current-voltage characteristics of Langmuir probe obtained in different operating regimes are discussed. Then, an algorithm for processing these characteristics efficiently in presence of ion-neutral collisions in the probe sheath is presented.
Physics of Collisional Plasmas Introduction to High-Frequency Discharges
Moisan, Michel
2012-01-01
The Physics of Collisional Plasmas deals with the plasma physics of interest to laboratory research and industrial applications, such as lighting, fabrication of microelectronics, destruction of greenhouse gases. Its emphasis is on explaining the physical mechanisms, rather than the detailed mathematical description and theoretical analysis. At the introductory level, it is important to convey the characteristic physical phenomena of plasmas, before addressing the ultimate formalism of kinetic theory, with its microscopic, statistical mechanics approach. To this aim, this text translates the physical phenomena into more tractable equations, using the hydrodynamic model; this considers the plasma as a fluid, in which the macroscopic physical parameters are the statistical averages of the microscopic (individual) parameters. This book is an introduction to the physics of collisional plasmas, as opposed to plasmas in space. It is intended for graduate students in physics and engineering . The first chapter intr...
Validity of the Taylor Hypothesis for Linear Kinetic Waves in the Weakly Collisional Solar Wind
Howes, G G; TenBarge, J M
2014-01-01
The interpretation of single-point spacecraft measurements of solar wind turbulence is complicated by the fact that the measurements are made in a frame of reference in relative motion with respect to the turbulent plasma. The Taylor hypothesis---that temporal fluctuations measured by a stationary probe in a rapidly flowing fluid are dominated by the advection of spatial structures in the fluid rest frame---is often assumed to simplify the analysis. But measurements of turbulence in upcoming missions, such as Solar Probe Plus, threaten to violate the Taylor hypothesis, either due to slow flow of the plasma with respect to the spacecraft or to the dispersive nature of the plasma fluctuations at small scales. Assuming that the frequency of the turbulent fluctuations is characterized by the frequency of the linear waves supported by the plasma, we evaluate the validity of the Taylor hypothesis for the linear kinetic wave modes in the weakly collisional solar wind. The analysis predicts that a dissipation range o...
Validity of the Taylor hypothesis for linear kinetic waves in the weakly collisional solar wind
Energy Technology Data Exchange (ETDEWEB)
Howes, G. G.; Klein, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); TenBarge, J. M. [IREAP, University of Maryland, College Park, MD 20742 (United States)
2014-07-10
The interpretation of single-point spacecraft measurements of solar wind turbulence is complicated by the fact that the measurements are made in a frame of reference in relative motion with respect to the turbulent plasma. The Taylor hypothesis—that temporal fluctuations measured by a stationary probe in a rapidly flowing fluid are dominated by the advection of spatial structures in the fluid rest frame—is often assumed to simplify the analysis. But measurements of turbulence in upcoming missions, such as Solar Probe Plus, threaten to violate the Taylor hypothesis, either due to slow flow of the plasma with respect to the spacecraft or to the dispersive nature of the plasma fluctuations at small scales. Assuming that the frequency of the turbulent fluctuations is characterized by the frequency of the linear waves supported by the plasma, we evaluate the validity of the Taylor hypothesis for the linear kinetic wave modes in the weakly collisional solar wind. The analysis predicts that a dissipation range of solar wind turbulence supported by whistler waves is likely to violate the Taylor hypothesis, while one supported by kinetic Alfvén waves is not.
Latyshev, A. V.; Yushkanov, A. A.
2013-01-01
The formula for dielectric function of non-degenerate and maxwellian collisional plasmas is transformed to the form, convenient for research. Graphic comparison of longitudinal dielectric functions of quantum and classical non-degenerate collisional plasmas is made.
Latyshev, A V
2013-01-01
The formula for dielectric function of non-degenerate and maxwellian collisional plasmas is transformed to the form, convenient for research. Graphic comparison of longitudinal dielectric functions of quantum and classical non-degenerate collisional plasmas is made.
Surface waves in the magnetized, collisional dusty plasmas
Energy Technology Data Exchange (ETDEWEB)
Pandey, B. P. [Department of Physics, Astronomy and Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney NSW 2109 (Australia); Vladimirov, S. V. [School of Physics, The University of Sydney, Sydney NSW 2006 (Australia); Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan); Metamaterials Laboratory, National Research University of Information Technology, Mechanics, and Optics, St. Petersburg 199034 (Russian Federation); Ishihara, O. [Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan)
2013-10-15
The properties of the low frequency surface waves in inhomogeneous, magnetized collisional complex dusty plasma are investigated in this work. The inhomogeneity is modelled by the two distinct regions of the dusty medium with different dust densities. The external magnetic field is assumed to be oriented along the interface dividing the two medium. It is shown that the collisional momentum exchange that is responsible for the relative drift between the plasma particles affects the propagation of the surface waves in the complex plasma via the Hall drift of the magnetic fluctuations. The propagation properties of the sausage and kink waves depend not only on the grain charge and size distribution but also on the ambient plasma thermal conditions.
Complexity Reduction of Collisional-Radiative Kinetics for Atomic Plasma
2013-12-23
tioned (e.g., for non - Maxwellian kinetics), one must be able to correctly apportion the changes in energy, e.g., to Ee and Eh (for heavy particles) and (b...or disclose the work. 14. ABSTRACT Thermal non -equilibrium processes in partially ionized plasmas can be most accurately modeled by collisional...prohibitively large, making multidimensional and unsteady simulations of non -equilibrium radiating plasma particularly challenging. In this paper, we
Collisionality dependent transport in TCV SOL plasmas
DEFF Research Database (Denmark)
Garcia, Odd Erik; Pitts, R.A.; Horacek, J.
2007-01-01
Results are presented from probe measurements in the low field side scrape-off layer (SOL) region of TCV during plasma current scan experiments. It is shown that with decreasing plasma current the radial particle density profile becomes broader and the fluctuation levels and turbulence driven...... radial particle flux increase. In the far SOL the fluctuations exhibit a high degree of statistical similarity and the particle density and flux at the wall radius scale inversely with the plasma current. Together with previous TCV density scan experiments, this indicates that plasma fluctuations...
Renormalized dissipation in plasmas with finite collisionality
Energy Technology Data Exchange (ETDEWEB)
Parker, S.E. [Princeton Plasma Physics Lab., NJ (United States); Carati, D. [Universite Libre de Bruxelles (Belgium). Service de Physique Statistique
1995-05-01
A nonlinear truncation procedure for Fourier-Hermite expansion of Boltzmann-type plasma equations is presented which eliminates fine velocity scale, taking into account its effect on coarser scales. The truncated system is then transformed back to (x, v) space which results in a renormalized Boltzmann equation. The resulting equation may allow for coarser velocity space resolution in kinetic simulations while reducing to the original Boltzmann equation when fine velocity scales are resolved. To illustrate the procedure, renormalized equations are derived for one dimensional electrostatic plasmas in which collisions are modeled by the Lenard-Bernstein operator.
Longitudinal dielectric permettivity of quantum Maxwell collisional plasmas
Latyshev, A. V.; Yushkanov, A. A.
2010-01-01
The kinetic equation of Wigner -- Vlasov -- Boltzmann with collision integral in relaxation BGK (Bhatnagar, Gross and Krook) form in coordinate space for quantum non--degenerate (Maxwellian) collisional plasma is used. Exact expression (within the limits of considered model) is found. The analysis of longitudinal dielectric permeability is done. It is shown that in the limit when Planck's constant tends to zero of expression for dielectric permettivity transforms into the classical case of di...
Kinetic simulation study of one dimensional collisional bounded plasma
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
A self-consistent kinetic simulation study ofone dimensional collisional bounded plasma is presented.The formation of stable sheath potential is investigated.It is found that mass ratio of electron and ion not onlyaffects the level of sheath potential, but also affectsthe ion temperature of system. It is clarified that the effects of secondaryemission electron on both the total potential dropand the temperature are not important.
Construction of Larger Area Density-Uniform Plasma with Collisional Inductively Coupled Plasma Cells
Institute of Scientific and Technical Information of China (English)
OUYANG Liang; LIU Wandong; BAI Xiaoyan; CHEN Zhipeng; WANG Huihui; LI LUO Chen; JI Liangliang; HU Bei
2007-01-01
The plasma density and electron temperature of a multi-source plasma system composed of several collisional inductively coupled plasma (ICP) cells were measured by a double-probe. The discharges of the ICP cells were shown to be independent of each other. Furthermore, the total plasma density at simultaneous multi-cell discharge was observed to be approximately equal to the summation of the plasma density when the cells discharge separately. Based on the linear summation phenomenon, it was shown that a larger area plasma with a uniform density and temperature profile could be constructed with multi-collisional ICP cells.
Fully implicit kinetic modelling of collisional plasmas
Energy Technology Data Exchange (ETDEWEB)
Mousseau, V.A.
1996-05-01
This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. To this end, implementations of Chang-Cooper differencing and flux limited Quadratic Upstream Interpolation for Convective Kinematics (QUICK) are presented. Results are given for a fully kinetic ion-electron problem with a self consistent electric field calculated from the ion and electron distribution functions. This numerical method, including advanced differencing, provides accurate solutions, which quickly converge on workstation class machines. It is demonstrated that efficient steady-state solutions can be achieved to the non-linear integro-differential equation, obtaining quadratic convergence, without incurring the large memory requirements of an integral operator. Model problems are presented which simulate plasma impinging on a plate with both high and low neutral particle recycling typical of a divertor in a Tokamak device. These model problems demonstrate the performance of the new solution method.
The acoustic instabilities in magnetized collisional dusty plasmas
Energy Technology Data Exchange (ETDEWEB)
Pandey, B. P., E-mail: birendra.pandey@mq.edu.au [Department of Physics and Astrophysics, Macquarie University, Sydney, NSW 2109 (Australia); Vladimirov, S. V., E-mail: s.vladimirov@physics.usyd.edu.au [Metamaterials Laboratory, National Research University of Information Technology, Mechanics, and Optics, St. Petersburg 199034 (Russian Federation); Dwivedi, C. B., E-mail: jagatpurdwivedi@gmail.com [Ved–Vijnanam Pravartanam Samitihi, Pratapgarh (Awadh), Jagatpur, Bharat (India)
2014-09-15
The present work investigates the wave propagation in collisional dusty plasmas in the presence of electric and magnetic field. It is shown that the dust ion-acoustic waves may become unstable to the reactive instability whereas dust-acoustic waves may suffer from both reactive and dissipative instabilities. If the wave phase speed is smaller than the plasma drift speed, the instability is of reactive type whereas in the opposite case, the instability becomes dissipative in nature. Plasma in the vicinity of dust may also become unstable to reactive instability with the instability sensitive to the dust material: dielectric dust may considerably quench this instability. This has implications for the dust charging and the use of dust as a probe in the plasma sheath.
Modern methods in collisional-radiative modeling of plasmas
2016-01-01
This book provides a compact yet comprehensive overview of recent developments in collisional-radiative (CR) modeling of laboratory and astrophysical plasmas. It describes advances across the entire field, from basic considerations of model completeness to validation and verification of CR models to calculation of plasma kinetic characteristics and spectra in diverse plasmas. Various approaches to CR modeling are presented, together with numerous examples of applications. A number of important topics, such as atomic models for CR modeling, atomic data and its availability and quality, radiation transport, non-Maxwellian effects on plasma emission, ionization potential lowering, and verification and validation of CR models, are thoroughly addressed. Strong emphasis is placed on the most recent developments in the field, such as XFEL spectroscopy. Written by leading international research scientists from a number of key laboratories, the book offers a timely summary of the most recent progress in this area. It ...
Collisional-radiative model: a plasma spectroscopy theory for experimentalists
Energy Technology Data Exchange (ETDEWEB)
Fujimoto, Takashi [Kyoto Univ. (Japan); Sawada, Keiji
1997-01-01
The rate equation describing the population n(p) of an excited (and the ground state) level p of ions immersed in plasma is shown. In 1962, the method of quasi-steady state solution (collisional-radiative model) was proposed. Its idea is explained. The coupled differential equations reduce to a set of coupled linear equations for excited levels. The solution of these coupled equations is presented. The equations giving the ionization and recombination of this system of ions under consideration are described in terms of the effective rate coefficients. The collisional-radiative ionization and recombination rate coefficients are expressed in terms of the population coefficients for p > 1. As for ionizing plasma, the excited level populations, the populations, the population distribution among the excited levels, two regimes of the excited levels, the dominant flows of electrons among the levels and so on are shown. As for recombining plasma, the excited level populations, the population distribution among the excited levels, the dominant flows of electrons and so on are shown. Ionization balance plasma may be considered. (K.I.)
Longitudinal dielectric permettivity of quantum Maxwell collisional plasmas
Latyshev, A V
2010-01-01
The kinetic equation of Wigner -- Vlasov -- Boltzmann with collision integral in relaxation BGK (Bhatnagar, Gross and Krook) form in coordinate space for quantum non--degenerate (Maxwellian) collisional plasma is used. Exact expression (within the limits of considered model) is found. The analysis of longitudinal dielectric permeability is done. It is shown that in the limit when Planck's constant tends to zero of expression for dielectric permettivity transforms into the classical case of dielectric permettivity. At small values of wave number it has been received the solution of the dispersion equation. Damping of plasma oscillations has been analized. The analytical comparison with the dielectric Mermin' function received with the use of the kinetic equation in momentum space is done. Graphic comparison of the real and imaginary parts of dielectric permettivity of quantum and classical plasma is done also.
Electromagnetic drift waves dispersion for arbitrarily collisional plasmas
Energy Technology Data Exchange (ETDEWEB)
Lee, Wonjae, E-mail: wol023@ucsd.edu; Krasheninnikov, Sergei I., E-mail: skrash@mae.ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); Angus, J. R. [Naval Research Laboratory, 4555 Overlook Avenue, Washington, DC 20375 (United States)
2015-07-15
The impacts of the electromagnetic effects on resistive and collisionless drift waves are studied. A local linear analysis on an electromagnetic drift-kinetic equation with Bhatnagar-Gross-Krook-like collision operator demonstrates that the model is valid for describing linear growth rates of drift wave instabilities in a wide range of plasma parameters showing convergence to reference models for limiting cases. The wave-particle interactions drive collisionless drift-Alfvén wave instability in low collisionality and high beta plasma regime. The Landau resonance effects not only excite collisionless drift wave modes but also suppress high frequency electron inertia modes observed from an electromagnetic fluid model in collisionless and low beta regime. Considering ion temperature effects, it is found that the impact of finite Larmor radius effects significantly reduces the growth rate of the drift-Alfvén wave instability with synergistic effects of high beta stabilization and Landau resonance.
A Hybrid Model for Multiscale Laser Plasma Simulations with Detailed Collisional Physics
2017-06-23
account for all processes of the collisional cascade during the relaxation of a hot plasma. To this end, the focus was in the development of (a) a...Collisional Radiative operator was necessary to accurately account for all processes of the collisional cascade during the relaxation of a hot plasma. To this...important to note that this is a code-to- code comparison and the validation of these simulations is an area of active research in the non-local
Collisional-radiative modelling for the spectroscopic diagnostic of turbulent plasmas
Energy Technology Data Exchange (ETDEWEB)
Rosato, J.; Lefevre, T.; Escarguel, A.; Capes, H.; Catoire, F.; Marandet, Y.; Stamm, R. [PIIM, Universite de Provence, CNRS, Marseille (France); Rosmej, F.B. [Universite Pierre et Marie Curie, Paris (France)] [LULI, Palaiseau (France); Kadomtsev, M.B.; Levashova, M.G.; Lisitsa, V.S. [NFI, Russian Research Center, Kurchatov Institute, Moscow (Russian Federation); Bonhomme, G. [IJL, Universite de Nancy, CNRS, Vandoeuvre-les-Nancy (France)
2011-07-01
Spectroscopy is a diagnostic method widely used in plasma physics research, e.g. in laboratory experiments, in fusion devices or in astrophysics. Information on the plasma parameters (electron density, temperature etc.) can be obtained from the analysis of both line shapes and intensities through the use of suitable models. The aim of the present paper is to assess the role of turbulent fluctuations on line intensity ratios in the case of weakly radiating plasmas. This involves the use of collisional-radiative modelling. In the present work we address the radiation due to atomic lines in turbulent helium plasmas at low density/temperature. The statistical formalism previously used in line shape modelling is adapted in this way, and the atomic populations are calculated with a collisional-radiative code. Different regimes, according to the turbulence correlation time, have been considered. In the static case, which corresponds to low-frequency fluctuations, it has been shown that the turbulence can lead to an increase of the line intensities. An application to helium in realistic experimental conditions has revealed that line ratios are sensitive to the fluctuations, which offers a track to a diagnostic. In the dynamic case, the use of a reduced model in the case of an ideal two-level atom has revealed the possibility for a significant dependence of the atomic populations on the turbulence frequency
Energy Technology Data Exchange (ETDEWEB)
Mikkelsen, D. R., E-mail: dmikkelsen@pppl.gov; Bitter, M.; Delgado-Aparicio, L.; Hill, K. W. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Greenwald, M.; Howard, N. T.; Hughes, J. W.; Rice, J. E. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); Reinke, M. L. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Podpaly, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); AAAS S and T Fellow placed in the Directorate for Engineering, NSF, 4201 Wilson Blvd., Arlington, Virginia 22230 (United States); Ma, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Candy, J.; Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
2015-06-15
Peaked density profiles in low-collisionality AUG and JET H-mode plasmas are probably caused by a turbulently driven particle pinch, and Alcator C-Mod experiments confirmed that collisionality is a critical parameter. Density peaking in reactors could produce a number of important effects, some beneficial, such as enhanced fusion power and transport of fuel ions from the edge to the core, while others are undesirable, such as lower beta limits, reduced radiation from the plasma edge, and consequently higher divertor heat loads. Fundamental understanding of the pinch will enable planning to optimize these impacts. We show that density peaking is predicted by nonlinear gyrokinetic turbulence simulations based on measured profile data from low collisionality H-mode plasma in Alcator C-Mod. Multiple ion species are included to determine whether hydrogenic density peaking has an isotope dependence or is influenced by typical levels of low-Z impurities, and whether impurity density peaking depends on the species. We find that the deuterium density profile is slightly more peaked than that of hydrogen, and that experimentally relevant levels of boron have no appreciable effect on hydrogenic density peaking. The ratio of density at r/a = 0.44 to that at r/a = 0.74 is 1.2 for the majority D and minority H ions (and for electrons), and increases with impurity Z: 1.1 for helium, 1.15 for boron, 1.3 for neon, 1.4 for argon, and 1.5 for molybdenum. The ion temperature profile is varied to match better the predicted heat flux with the experimental transport analysis, but the resulting factor of two change in heat transport has only a weak effect on the predicted density peaking.
Amplitude limits and nonlinear damping of shear-Alfvén waves in high-beta low-collisionality plasmas
Squire, J.; Schekochihin, A. A.; Quataert, E.
2017-05-01
This work, which extends Squire et al (Astrophys. J. Lett. 2016 830 L25), explores the effect of self-generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality plasmas. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, ‘interrupting’ the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional ‘Braginskii’ regime, for both standing and traveling waves. The focus is on simplified models in one dimension, on scales much larger than the ion gyroradius. The effect has interesting implications for the physics of magnetized turbulence in the high-β conditions that are prevalent in many astrophysical plasmas.
Hsu, S. C.; Moser, A. L.; Merritt, E. C.; Adams, C. S.
2015-11-01
Over the past 4 years on the Plasma Liner Experiment (PLX) at LANL, we have studied obliquely and head-on-merging supersonic plasma jets of an argon/impurity or hydrogen/impurity mixture. The jets are formed/launched by pulsed-power-driven railguns. In successive experimental campaigns, we characterized the (a) evolution of plasma parameters of a single plasma jet as it propagated up to ~ 1 m away from the railgun nozzle, (b) density profiles and 2D morphology of the stagnation layer and oblique shocks that formed between obliquely merging jets, and (c) collisionless interpenetration transitioning to collisional stagnation between head-on-merging jets. Key plasma diagnostics included a fast-framing CCD camera, an 8-chord visible interferometer, a survey spectrometer, and a photodiode array. This talk summarizes the primary results mentioned above, and highlights analyses of inferred post-shock temperatures based on observations of density gradients that we attribute to shock-layer thickness. We also briefly describe more recent PLX experiments on Rayleigh-Taylor-instability evolution with magnetic and viscous effects, and potential future collisionless shock experiments enabled by low-impurity, higher-velocity plasma jets formed by contoured-gap coaxial guns. Supported by DOE Fusion Energy Sciences and LANL LDRD.
Plasma-statistical models of the atom in the theory of some collisional and radiative processes
Astapenko, VA
2002-01-01
A plasma-statistical model was used to describe collisional and radiative processes involving target ionization, namely, collisional ionization of atoms and incoherent polarization bremsstrahlung. The cross sections of these processes were expressed through the Compton profile of X-ray scattering, f
Laser plasma physics in shock ignition – transition from collisional to collisionless absorption
Directory of Open Access Journals (Sweden)
Klimo O.
2013-11-01
Full Text Available Shock Ignition is considered as a relatively robust and efficient approach to inertial confinement fusion. A strong converging shock, which is used to ignite the fuel, is launched by a high power laser pulse with intensity in the range of 1015 − 1016 W/cm2 (at the wavelength of 351 nm. In the lower end of this intensity range the interaction is dominated by collisions while the parametric instabilities are playing a secondary role. This is manifested in a relatively weak reflectivity and efficient electron heating. The interaction is dominated by collective effects at the upper edge of the intensity range. The stimulated Brillouin and Raman scattering (SBS and SRS respectively take place in a less dense plasma and cavitation provides an efficient collisionless absorption mechanism. The transition from collisional to collisionless absorption in laser plasma interactions at higher intensities is studied here with the help of large scale one-dimensional Particle-in-Cell (PIC simulations. The relation between the collisional and collisionless processes is manifested in the energy spectrum of electrons transporting the absorbed laser energy and in the spectrum of the reflected laser light.
Colloidal Plasmas : Electrostatic sheath at the boundary of a collisional dusty plasma
Indian Academy of Sciences (India)
S K Baishya; G C Das; Joyanti Chutia
2000-11-01
Considering the Boltzmann response of the ions and electrons in plasma dynamics and inertial dynamics of the dust charged grains in a highly collisional dusty plasma, the nature of the electrostatic potential near a boundary is investigated. Based on the ﬂuid approximation, the formation as well as the characteristic behaviours of the sheath is studied. It is expected that the presence of dust charged grains will lead to a very different behaviour of the sheath as compared to that of electron-ion plasma. Moreover, the collisions of the dust charged grains with the neutrals are expected to exhibit novel features.
First-principle description of collisional gyrokinetic turbulence in tokamak plasmas
Energy Technology Data Exchange (ETDEWEB)
Dif-Pradalier, G
2008-10-15
This dissertation starts in chapter 1 with a comprehensive introduction to nuclear fusion, its basic physics, goals and means. It especially defines the concept of a fusion plasma and some of its essential physical properties. The following chapter 2 discusses some fundamental concepts of statistical physics. It introduces the kinetic and the fluid frameworks, compares them and highlights their respective strengths and limitations. The end of the chapter is dedicated to the fluid theory. It presents two new sets of closure relations for fluid equations which retain important pieces of physics, relevant in the weakly collisional tokamak regimes: collective resonances which lead to Landau damping and entropy production. Nonetheless, since the evolution of the turbulence is intrinsically nonlinear and deeply influenced by velocity space effects, a kinetic collisional description is most relevant. First focusing on the kinetic aspect, chapter 3 introduces the so-called gyrokinetic framework along with the numerical solver - the GYSELA code - which will be used throughout this dissertation. Very generically, code solving is an initial value problem. The impact on turbulent nonlinear evolution of out of equilibrium initial conditions is discussed while studying transient flows, self-organizing dynamics and memory effects due to initial conditions. This dissertation introduces an operational definition, now of routine use in the GYSELA code, for the initial state and concludes on the special importance of the accurate calculation of the radial electric field. The GYSELA framework is further extended in chapter 4 to describe Coulomb collisions. The implementation of a collision operator acting on the full distribution function is presented. Its successful confrontation to collisional theory (neoclassical theory) is also shown. GYSELA is now part of the few gyrokinetic codes which can self-consistently address the interplay between turbulence and collisions. While
Terahertz generation by beating two Langmuir waves in a warm and collisional plasma
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiao-Bo; Qiao, Xin; Cheng, Li-Hong; Tang, Rong-An; Zhang, Ai-Xia; Xue, Ju-Kui, E-mail: xuejk@nwnu.edu.cn [Key Laboratory of Atomic & Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronics Engineering, Northwest Normal University, Lanzhou 730070 (China)
2015-09-15
Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length.
Drift waves in a weakly ionized plasma
DEFF Research Database (Denmark)
Popovic, M.; Melchior, H.
1968-01-01
A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....
Latyshev, A V
2013-01-01
The kinetic description of magnetic susceptibility and Landau diamagnetism of quantum collisional plasmas with any degeration of electronic gas is given. The correct expression of electric conductivity of quantum collisional plasmas with any degeration of electronic gas (see A. V. Latyshev and A. A. Yushkanov, Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach. - Theor. and Math. Phys., V. 175(1):559-569 (2013)) is used.
Collisional effects on the current-filamentation instability in a dense plasma
Institute of Scientific and Technical Information of China (English)
HAO Biao; SHENG Zheng-Ming; ZHANG Jie
2009-01-01
The collisional current-filamentation instability (CFI) is studied for a nonrelativistic electron beampenetrating an infinite uniform plasma.It is analytically shown that the CFI is driven by the drift-anisotropyrather than the classical anisotropy of the beam and the background plasma.Therefore,collisional effects can either attenuate or enhance the CFI depending on the drift-anisotropy of the beam-plasma system.Numerical results are given for some typical parameters,which show that collisional effects cannot stabilize but enhance the CFI in a dense plasma.Thus,the CFI may play a dominant role in the fast electron transport and deposition relevant to the fast ignition scenario(FIS).
Numerical study of drift-kinetic evolution of collisional plasmas in tori
Energy Technology Data Exchange (ETDEWEB)
Beasley, Jr., C. O.; Meier, H. K.; van Rij, W. I.; McCune, J. E.
1976-03-01
Preliminary numerical results for the dynamics of toroidally confined plasmas in the drift-kinetic, Fokker--Planck description are discussed. These solutions were obtained by using the techniques inherent to the collisional plasma model (CPM) described in detail elsewhere. An initial value problem is solved in the local approximation in which collisions and particle dynamics compete in a given magnetic field to set up a quasi-equilibrium. Both the plasma (guiding center) distribution function and many macroscopic quantities of interest are monitored. Good agreement with corresponding but more approximate theories is obtained over a wide range of collisionality, particularly with regard to the neoclassical particle flux. Encouraging confirmation of earlier results for the distribution function is achieved when due account is taken of the differing collisionality of particles with differing energies. These initial results indicate the potential importance of certain non-local effects as well as inclusion of self-consistency between fields and plasma currents and densities.
Energy Technology Data Exchange (ETDEWEB)
Venugopal, Chandu [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam-686 560, Kerala (India); Kurian, M J [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam-686 560, Kerala (India); Antony, S [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam-686 560, Kerala (India); Anilkumar, C P [Indian Institute of Geomagnetism, Tirunelveli-627 011, Tamil Nadu (India); Renuka, G [Department of Physics, University of Kerala, Kariavattom, Thiruvananthapuram-695 581, Kerala (India)
2007-05-15
We have investigated the stability of the lower hybrid wave in a collisional plasma containing hydrogen and positively and negatively charged oxygen ions. The collisions of all the species in the plasma have been considered. The electrons, streaming parallel to the magnetic field, can excite the instability if their drift velocity exceeds the parallel phase velocity of the wave. This is true for both the weakly as well as the strongly collisional cases. If the ion collisions are neglected, the growth/damping rate depends on the electron collision frequency and is modified by a factor dependent directly on the number densities and square of the charges on the oxygen ions and inversely on the masses of these ions. Ion collisions, however only damp the wave; this damping being dependent also on the ion collision frequencies, in addition to the above dependencies. We find that the dispersion relation in the low collisional limit can account for lower hybrid waves in the observed frequency range.
Self-Focusing/Defocusing of Chirped Gaussian Laser Beam in Collisional Plasma with Linear Absorption
Wani, Manzoor Ahmad; Kant, Niti
2016-09-01
This paper presents an investigation on the self-focusing/defocusing of chirped Gaussian laser beam in collisional plasma with linear absorption. We have derived the differential equation for the beam width parameter by using WKB and paraxial approximations and solved it numerically. The effect of chirp and other laser plasma parameters is seen on the behavior of beam width parameter with dimensionless distance of propagation. The results are discussed and presented graphically. Our simulation results show that the amplitude of oscillations decreases with the distance of propagation. Due to collisional frequency, the laser beam shows fast divergence which can be minimized by the introduction of chirp parameter. The chirp decreases the effect of defocusing and increases the ability of self-focusing of laser beam in collisional plasma. Supported by a financial grant from CSIR, New Delhi, India, under Project No. 03(1277)/13/EMR-II
Collisional Sheath in the Electronegative Radio-Frequency Plasma
Institute of Scientific and Technical Information of China (English)
GAN Baoxia; DENG Wenjuan; CHEN Yinhua
2007-01-01
A model of collisional RF sheath with negative ions is discussed in this paper.The influences of collision and negative ions on the parameters of the sheath are studied through numerical simulation.It is found that when the collision coefficient increases and the RF power is fixed,the electrode potential and sheath electric field potential increase,the electrode current and thickness of the sheath decrease.When the negative ion content changes,the same phenomenon occurs.
Stability of current-driven electrostatic waves in a magnetized and collisional negative ion plasma
Energy Technology Data Exchange (ETDEWEB)
Venugopal, Chandu; Varghese, Anu; S, Jyothi [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam 686 560, Kerala (India); Issac, Molly [Department of Physics, All Saints' College, Thiruvananthapuram 695 007, Kerala (India); Renuka, G [Department of Physics, University of Kerala, Kariavattom, Thiruvananthapuram 695 581, Kerala (India)], E-mail: cvgmgphys@yahoo.co.in
2008-10-15
The stability of electrostatic waves, propagating nearly parallel to a uniform external magnetic field, is studied in a fully ionized, collisional plasma of positive and negative ions and a field-aligned current of drifting electrons. Expressions have been derived for the dispersion relation and growth rate using fluid theory and retaining the collisional and conductivity terms for the electrons. The plasma can, in general, support two modes, which have frequencies that are a composite of the ion acoustic and ion gyro frequencies. The growth rate of the modes increases with increasing drift velocities of the electrons and decreases with increasing negative ion densities.
Shock Wave Dynamics in Weakly Ionized Plasmas
Johnson, Joseph A., III
1999-01-01
An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.
Nonlinear wave structures in collisional plasma of auroral E-region ionosphere
Directory of Open Access Journals (Sweden)
A. V. Volosevich
Full Text Available Studies of the auroral plasma with small-scale inhomogenieties producing the VHF-radar reflections (radar aurora when observed in conditions of the saturated Farley-Buneman instability within the auroral E region, show strong nonlinear interactions and density fluctuations of 5–15%. Such nonlinearity and high fluctation amplitudes are inconsistent with the limitations of the weak turbulence theory, and thus a theory for arbitrary amplitudes is needed. To this end, a nonlinear theory is described for electrostatic MHD moving plasma structures of arbitrary amplitude for conditions throughout the altitude range of the collisional auroral E region. The equations are derived, from electron and ion motion self-consistent with the electric field, for the general case of the one-dimensional problem. They take into account nonlinearity, electron and ion inertia, diffusion, deviation from quasi-neutrality, and dynamical ion viscosity. The importance of the ion viscosity for dispersion is stressed, while deviation from the quasi-neutrality can be important only at rather low plasma densities, not typical for the auroral E region. In a small amplitude limit these equations have classical nonlinear solutions of the type of "electrostatic shock wave" or of knoidal waves. In a particular case these knoidal waves degrade to a dissipative soliton. A two-dimensional case of a quasi-neutral plasma is considered in the plane perpendicular to the magnetic field by way of the Poisson brackets, but neglecting the nonlinearity and ion inertia. It is shown that in these conditions an effective saturation can be achieved at the stationary turbulence level of order of 10%.
Collisional Energy Loss of a Heavy Quark in an Anisotropic Quark-Gluon Plasma
Romatschke, P; Romatschke, Paul; Strickland, Michael
2004-01-01
We compute the leading-order collisional energy loss of a heavy quark propagating through a quark-gluon plasma in which the quark and gluon distributions are anisotropic in momentum space. Following the calculation outlined for QED in an earlier work we indicate the differences encountered in QCD and their effect on the collisional energy loss results. For a 20 GeV bottom quark we show that momentum space anisotropies can result in the collisional heavy quark energy loss varying with the angle of propagation by up to 50%. For low velocity quarks we show that anisotropies result in energy gain instead of energy loss with the energy gain focused in such a way as to accelerate particles along the anisotropy direction thereby reducing the momentum-space anisotropy. The origin of this negative energy loss is explicitly identified as being related to the presence of plasma instabilities in the system.
Solitons and Weakly Nonlinear Waves in Plasmas
DEFF Research Database (Denmark)
Pécseli, Hans
1985-01-01
Theoretical descriptions of solitons and weakly nonlinear waves propagating in plasma media are reviewed, with particular attention to the Korteweg-de Vries (KDV) equation and the Nonlinear Schrödinger equation (NLS). The modifications of these basic equations due to the effects of resonant...
Nonlinear acoustic waves in a collisional self-gravitating dusty plasma
Institute of Scientific and Technical Information of China (English)
Guo Zhi-Rong; Yang Zeng-Qiang; Yin Bao-Xiang; Sun Mao-Zhu
2010-01-01
Using the reductive perturbation method,we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma.The result shows that the small amplitude dust acoustic wave can be expressed by a modified Korteweg-de Vries equation,and the nonlinear wave is instable because of the collisions between the neutral gas molecules and the charged particles.
Latyshev, A V
2015-01-01
From kinetic Vlasov equation for collisional plasmas distribution function is received in square-law approximation on size of electromagnetic field. The formula for calculation electric current is deduced at any temperature (any degree of degeneration electronic gas). This formula contains one-dimension quadrature. It is shown, that the nonlinearity account leads to occurrence the longitudinal electric current directed along a wave vector. This longitudinal current is perpendicular to the known transversal classical current, received at the linear analysis. When frequency of collisions tends to zero, all received results for collisional plasma pass in known corresponding formulas for collisionless plasma. The case of small values of wave number is considered. It is shown, that the received quantity of longitudinal current at tendency of frequency of collisions to zero also passes in known corresponding expression of current for collisionless plasmas. Graphic comparison of dimensionless size of current is spen...
Sugama, H.; Nunami, M.; Nakata, M.; Watanabe, T.-H.
2017-02-01
A novel gyrokinetic formulation is presented by including collisional effects into the Lagrangian variational principle to yield the governing equations for background and turbulent electromagnetic fields and gyrocenter distribution functions, which can simultaneously describe classical, neoclassical, and turbulent transport processes in toroidal plasmas with large toroidal flows on the order of the ion thermal velocity. Noether's theorem modified for collisional systems and the collision operator given in terms of Poisson brackets are applied to derivation of the particle, energy, and toroidal momentum balance equations in the conservative forms, which are desirable properties for long-time global transport simulation.
Collisional effects on the oblique instability in relativistic beam-plasma interactions
Hao, B.; Ding, W. J.; Sheng, Z. M.; Ren, C.; Kong, X.; Mu, J.; Zhang, J.
2012-07-01
The general oblique instability for a relativistic electron beam propagating through a warm and resistive plasma is investigated fully kinetically by a variable rotation method. Analysis shows that the electrostatic part of the oblique instability is attenuated and eventually stabilized by collisional effects. However, the electromagnetic part of the oblique instability (EMOI) is enhanced. Since the current-filamentation instability as a special case of the EMOI has a larger growth rate, it becomes dominant in the collisional case as shown in our two-dimensional particle-in-cell simulations. While the beam diverges in the collisionless case, it can become magnetically collimated in the collisional case due to stabilization of the electrostatic instabilities when the initial beam spreading angle is less than certain magnitude such as a dozen degrees.
Collisional Thermalization in Strongly Coupled Ultracold Neutral Plasmas
2017-01-25
ultracold neutral plasmas, which are formed by photoionizing laser cooled atoms. These are the coldest neutral plasmas every created, and they allow...and received the “Editors’ Suggestion” distinction. We also completed numerical modeling of laser cooling a neutral plasma and construction of the...We also had to install several laser systems for driving the laser - cooling transitions in the ions and for repumping atoms out of dark states
Hedin, G.; Brzozowski, J. H.; Hörling, P.; Mazur, S.; Nordlund, P.; Drake, J. R.
1996-05-01
The effects of plasma collisionality on power balance and magnetic fluctuations have been studied on the Extrap T1 reversed-field pinch. A characteristic minimum in loop voltage is observed as the plasma collisionality decreases. The minimum is caused by an increase in the anomalous input power and coincides with a change of scaling of the magnetic fluctuations and a rapid increase of the electron mean free path. However, the increase of anomalous input power in the low collisional regime appears to have little influence on the total amount of energy stored in the plasma.
Collisional transport in a plasma with steep gradients
Energy Technology Data Exchange (ETDEWEB)
Wang, W.; Okamoto, M.; Nakajima, N.; Murakami, S. [National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-06-01
The validity is given to the newly proposed two {delta}f method for neoclassical transport calculation, which can be solve the drift kinetic equation considering effects of steep plasma gradients, large radial electric field, finite banana width, and an orbit topology near the axis. The new method is applied to the study of ion transport with steep plasma gradients. It is found that the ion thermal diffusivity decreases as the scale length of density gradient decreases, while the ion particle flux due to ion-ion self collisions increases with increasing gradient. (author)
Propagation of surface waves on a semi-bounded quantum magnetized collisional plasma
Energy Technology Data Exchange (ETDEWEB)
Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Taheri Boroujeni, S.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)
2013-12-15
The propagation of surface waves on a semi-bounded quantum plasma in the presence of the external magnetic field and collisional effects is investigated by using quantum magnetohydrodynamics model. A general analytical expression for the dispersion relation of surface waves is obtained by considering the boundary conditions. It is shown that, in some special cases, the obtained dispersion relation reduces to the results reported in previous works. It is also indicated that the quantum, external magnetic field and collisional effects can facilitate the propagation of surface waves on a semi-bounded plasma. In addition, it is found that the growth rate of the surface wave instability is enhanced by increasing the collision frequency and plasmonic parameter.
Kolmogorov Dissipation scales in Weakly Ionized Plasmas
Krishan, V
2009-01-01
In a weakly ionized plasma, the evolution of the magnetic field is described by a "generalized Ohm's law" that includes the Hall effect and the ambipolar diffusion terms. These terms introduce additional spatial and time scales which play a decisive role in the cascading and the dissipation mechanisms in magnetohydrodynamic turbulence. We determine the Kolmogorov dissipation scales for the viscous, the resistive and the ambipolar dissipation mechanisms. The plasma, depending on its properties and the energy injection rate, may preferentially select one of the these dissipation scales. thus determining the shortest spatial scale of the supposedly self-similar spectral distribution of the magnetic field. The results are illustrated taking the partially ionized part of the solar atmosphere as an example. Thus the shortest spatial scale of the supposedly self-similar spectral distribution of the solar magnetic field is determined by any of the four dissipation scales given by the viscosity, the Spizer resistivity...
Dielectric function of a collisional plasma for arbitrary ionic charge
Nersisyan, H B; Andreev, N E; Matevosyan, H H
2013-01-01
Simple model for the dielectric function of a completely ionized plasma with an arbitrary ionic charge, that is valid for the long-wavelength, high-frequency perturbations is derived using approximate solution of a linearized Fokker-Planck kinetic equation for electrons with a Landau collision integral. The model accounts for both the electron-ion collisions and the collisions of the subthermal (cold) electrons with thermal ones. The relative contribution of the latter collisions into dielectric function is treated phenomenologically introducing some parameter $\\varkappa $ which is chosen in such a way to get well-known expression for stationary electric conductivity in low-frequency region and fulfill requirement of vanishing contribution of electron-electron collisions at high frequency region. This procedure ensures the applicability of our model in the wide ranges of plasma parameters as well as the frequency of the electromagnetic radiation. Unlike interpolation formula proposed earlier by Brantov \\emph{...
An experimentally constrained MHD model for a collisional, rotating plasma column
Wright, A. M.; Qu, Z. S.; Caneses, J. F.; Hole, M. J.
2017-02-01
A steady-state single fluid MHD model which describes the equilibrium of plasma parameters in a collisional, rotating plasma column with temperature gradients and a non-uniform externally applied magnetic field is developed. Two novel methods of simplifying the governing equations are introduced. Specifically, a ‘radial transport constraint’ and an ordering argument are applied. The reduced system is subsequently solved to yield the equilibrium of macroscopic plasma parameters in the bulk region of the plasma. The model is benchmarked by comparing these solutions to experimental measurements of axial velocity and density for a hydrogen plasma in the converging-field experiment MAGPIE and overall a good agreement is observed. The plasma equilibrium is determined by the interaction of a density gradient, due to a temperature gradient, with an electric field. The magnetic field and temperature gradient are identified as key parameters in determining the flow profile, which may be important considerations in other applications.
Particle in cell calculation of plasma force on a small grain in a non-uniform collisional sheath
Hutchinson, I H
2013-01-01
The plasma force on grains of specified charge and height in a collisional plasma sheath are calculated using the multidimensional particle in cell code COPTIC. The background ion velocity distribution functions for the unperturbed sheath vary substantially with collisionality. The grain force is found to agree quite well with a combination of background electric field force plus ion drag force. However, the drag force must take account of the non-Maxwellian (and spatially varying) ion distribution function, and the collisional drag enhancement. It is shown how to translate the dimensionless results into practical equilibrium including other forces such as gravity.
Collisional processes of interest in MFE plasma research
Energy Technology Data Exchange (ETDEWEB)
Olson, R.E.
1990-05-24
Research on this grant is devoted to the calculation of heavy particle collision cross sections needed for diagnostic studies of magnetic fusion plasmas. This work requires the development and testing of new theoretical methods, with the implementation of benchmarked techniques to collisions pertinent to fusion reactors. Within the last context, we have provided charge-exchange-recombination cross sections to specific n,1-levels for diagnostic studies on TFTR and for a major compilation for IAEA. We have also completed a cross section study related to the planned neutral beam current drive for ITER. In addition, calculations were completed to assess the use of He neutral atom angular scattering measurements for JT-60. Also, new theoretical methods have been developed to more accurately calculate cross sections involving either He or H{sub 2} targets and partially stripped multiply-charged ions.
Energy Technology Data Exchange (ETDEWEB)
Borovsky, J.E.
1987-02-01
The propagation of ultralow-frequency (ulf) electromagnetic signals (Alfven and magnetosonic waves) in collisional, inhomogeneous, magnetized plasmas is analyzed by numerical simulation. The problem is formulated from a Maxwell-equation orbit-theory approach rather than from a magnetohydrodynamic point of view, and the problem is numerically treated in a fully time-dependent manner. Boundary-value-problem behavior is distinguished from initial-value-problem behavior. The propagation of two-dimensional small-amplitude electromagnetic disturbances in plasmas with spatially dependent densities and in plasmas with spatially dependent conductivities is numerically simulated, and when possible, the simulations are compared with theory. Changes in the plasma density lead to changes in the signal speed and to reflections; collisions lead to changes in the signal speed, to reflections, and to attenuations. Theoretical descriptions based upon discontinuities in the media are generally incorrect in predicting the amplitudes of signals reflected from plasma inhomogeneities. 19 refs., 16 figs.
Moradi, Afshin
2016-04-01
In a recent article [Niknam et al., Phys. Plasmas 20, 122106 (2013)], Niknam et al. investigated the propagation of TM surface waves on a semi-bounded quantum magnetized collisional plasma in the Faraday configuration (in this case, the magnetic field is parallel to the both of the plasma surface and direction of propagation). Here, we present a fresh look at the problem and show that TM surface waves cannot propagate on surface of the present system. We find in the Faraday configuration the surface waves acquire both TM and TE components due to the cyclotron motion of electrons. Therefore, the main result of the work by Niknam et al. is incorrect.
Formation and evolution of vortices in a collisional strongly coupled dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Jana, Sayanee [Saha Institute of Nuclear Physics, a/AF Bidhannagar, Kolkata 700 064 (India); Banerjee, Debabrata, E-mail: debu@ustc.edu.cn [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, a/AF Bidhannagar, Kolkata 700 064 (India)
2016-07-29
Formation and evolution of vortices are studied in a collisional strongly coupled dusty plasma in the framework of a Generalized Hydrodynamic model (GH). Here we mainly present the nonlinear dynamical response of this strongly coupled system in presence of dust-neutral collisional drag. It is shown that the interplay between the nonlinear elastic stress and the dust-neutral collisional drag results in the generation of non-propagating monopole vortex for some duration before it starts to propagate like transverse shear wave. It is also found that the interaction between two unshielded monopole vortices having both same (co-rotating) and opposite (counter rotating) rotations result in the formation of two propagating dipole vortices of equal and unequal strength respectively. These results will provide some new understanding on the transport properties in such a strongly coupled system. The numerical simulation is carried out using a de-aliased doubly periodic pseudo-spectral code with Runge–Kutta–Gill time integrator. - Highlights: • A numerical study of vortex evolution in strongly coupled dusty plasma is presented. • Dust-neutral drag is first time considered with the Generalized Hydrodynamic model (GH). • Dust-neutral drag force balances the nonlinear effect of elastic stress. • Localized non-propagating monopole structure is generated for some duration. • Dipole vortices are produced after interaction between two monopole vortices.
Collisional Thermalization of Hydrogen and Helium in Solar Wind Plasma
Maruca, Bennett A; Sorriso-Valvo, Luca; Kasper, Justin C; Stevens, Michael L
2013-01-01
In situ observations of the solar wind frequently show the temperature of $\\alpha$-particles (fully ionized helium), $T_\\alpha$, to significantly differ from that of protons (ionized hydrogen), $T_p$. Many heating processes in the plasma act preferentially on $\\alpha$-particles, even as collisions among ions act to gradually establish thermal equilibrium. Measurements from the $\\textit{Wind}$ spacecraft's Faraday cups reveal that, at $r=1.0\\ \\textrm{AU}$ from the Sun, the observed values of the $\\alpha$-proton temperature ratio, $\\theta_{\\alpha p} \\equiv T_\\alpha\\,/\\,T_p$ has a complex, bimodal distribution. This study applied a simple model for the radial evolution of $\\theta_{\\alpha p}$ to these data to compute expected values of $\\theta_{\\alpha p}$ at $r=0.1\\ \\textrm{AU}$. These inferred $\\theta_{\\alpha p}$-values have no trace of the bimodality seen in the $\\theta_{\\alpha p}$-values measured at $r=1.0\\ \\textrm{AU}$ but are instead consistent with the actions of the known mechanisms for $\\alpha$-particle p...
Singh, Navpreet; Gupta, Naveen; Singh, Arvinder
2016-12-01
This paper investigates second harmonic generation (SHG) of an intense Cosh-Gaussian (ChG) laser beam propagating through a preformed underdense collisional plasma with nonlinear absorption. Nonuniform heating of plasma electrons takes place due to the nonuniform irradiance of intensity along the wavefront of laser beam. This nonuniform heating of plasma leads to the self-focusing of the laser beam and thus produces strong density gradients in the transverse direction. The density gradients so generated excite an electron plasma wave (EPW) at pump frequency that interacts with the pump beam to produce its second harmonics. To envision the propagation dynamics of the ChG laser beam, moment theory in Wentzel-Kramers-Brillouin (W.K.B) approximation has been invoked. The effects of nonlinear absorption on self-focusing of the laser beam as well as on the conversion efficiency of its second harmonics have been theoretically investigated.
Moser, A L
2014-01-01
We present results from experiments on the head-on merging of two supersonic plasma jets in an initially collisionless regime for the counter-streaming ions [A. L. Moser & S. C. Hsu, Phys. Plasmas, submitted (2014)]. The plasma jets are of either an argon/impurity or hydrogen/impurity mixture and are produced by pulsed-power-driven railguns. Based on time- and space-resolved fast-imaging, multi-chord interferometry, and survey-spectroscopy measurements of the overlapping region between the merging jets, we observe that the jets initially interpenetrate, consistent with calculated inter-jet ion collision lengths, which are long. As the jets interpenetrate, a rising mean-charge state causes a rapid decrease in the inter-jet ion collision length. Finally, the interaction becomes collisional and the jets stagnate, eventually producing structures consistent with collisional shocks. These experimental observations can aid in the validation of plasma collisionality and ionization models for plasmas with complex ...
Collisional damping of helicon waves in a high density hydrogen linear plasma device
Caneses, Juan F.; Blackwell, Boyd D.
2016-10-01
In this paper, we investigate the propagation and damping of helicon waves along the length (50 cm) of a helicon-produced 20 kW hydrogen plasma ({{n}\\text{e}}∼ 1–2 × 1019 m‑3, {{T}\\text{e}}∼ 1–6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50–200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (4–8 G and {λz}∼ 10–15 cm) propagating away from the antenna region which become collisionally absorbed within 40–50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based on experimental measurements. Theoretical calculations are consistent with experiment and indicate that for conditions where Coulomb collisions are dominant classical collisionality is sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in helicon based linear plasma devices.
Rosenberg, M J; Li, C K; Fox, W; Zylstra, A B; Stoeckl, C; Séguin, F H; Frenje, J A; Petrasso, R D
2015-05-22
An evolution of magnetic reconnection behavior, from fast jets to the slowing of reconnection and the establishment of a stable current sheet, has been observed in strongly driven, β≲20 laser-produced plasma experiments. This process has been inferred to occur alongside a slowing of plasma inflows carrying the oppositely directed magnetic fields as well as the evolution of plasma conditions from collisionless to collisional. High-resolution proton radiography has revealed unprecedented detail of the forced interaction of magnetic fields and super-Alfvénic electron jets (V_{jet}∼20V_{A}) ejected from the reconnection region, indicating that two-fluid or collisionless magnetic reconnection occurs early in time. The absence of jets and the persistence of strong, stable magnetic fields at late times indicates that the reconnection process slows down, while plasma flows stagnate and plasma conditions evolve to a cooler, denser, more collisional state. These results demonstrate that powerful initial plasma flows are not sufficient to force a complete reconnection of magnetic fields, even in the strongly driven regime.
Tungsten Ions in Plasmas: Statistical Theory of Radiative-Collisional Processes
Directory of Open Access Journals (Sweden)
Alexander V. Demura
2015-05-01
Full Text Available The statistical model for calculations of the collisional-radiative processes in plasmas with tungsten impurity was developed. The electron structure of tungsten multielectron ions is considered in terms of both the Thomas-Fermi model and the Brandt-Lundquist model of collective oscillations of atomic electron density. The excitation or ionization of atomic electrons by plasma electron impacts are represented as photo-processes under the action of flux of equivalent photons introduced by E. Fermi. The total electron impact single ionization cross-sections of ions Wk+ with respective rates have been calculated and compared with the available experimental and modeling data (e.g., CADW. Plasma radiative losses on tungsten impurity were also calculated in a wide range of electron temperatures 1 eV–20 keV. The numerical code TFATOM was developed for calculations of radiative-collisional processes involving tungsten ions. The needed computational resources for TFATOM code are orders of magnitudes less than for the other conventional numerical codes. The transition from corona to Boltzmann limit was investigated in detail. The results of statistical approach have been tested by comparison with the vast experimental and conventional code data for a set of ions Wk+. It is shown that the universal statistical model accuracy for the ionization cross-sections and radiation losses is within the data scattering of significantly more complex quantum numerical codes, using different approximations for the calculation of atomic structure and the electronic cross-sections.
Ponderomotive self-focusing of Gaussian laser beam in warm collisional plasma
Energy Technology Data Exchange (ETDEWEB)
Jafari Milani, M. R., E-mail: mrj.milani@gmail.com [Plasma Physics Research School, Tehran (Iran, Islamic Republic of); Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Niknam, A. R., E-mail: a-niknam@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Farahbod, A. H. [Plasma Physics Research School, Tehran (Iran, Islamic Republic of)
2014-06-15
The propagation characteristics of a Gaussian laser beam through warm collisional plasma are investigated by considering the ponderomotive force nonlinearity and the complex eikonal function. By introducing the dielectric permittivity of warm unmagnetized plasma and using the WKB and paraxial ray approximations, the coupled differential equations defining the variations of laser beam parameters are obtained and solved numerically. Effects of laser and plasma parameters such as the collision frequency, the initial laser intensity and its spot size on the beam width parameter and the axis laser intensity distribution are analyzed. It is shown that, self-focusing of the laser beam takes place faster by increasing the collision frequency and initial laser spot size and then after some distance propagation the laser beam abruptly loses its initial diameter and vastly diverges. Furthermore, the modified electron density distribution is obtained and the collision frequency effect on this distribution is studied.
A Numerical Model for Ion Charge Distribution of Plasmas in Collisional Radiative Steady State
Institute of Scientific and Technical Information of China (English)
DUAN Yaoyong; GUO Yonghui; QIU Aici; KUAI Bin
2009-01-01
A numerical model for the charge state distribution of plasmas in a collisional ra-diative steady state (CRSS) is established by averaging over the atomic process rate coefficients in universal kinetic equations.It is used to calculate the mean ion charge and ion population for a given temperature and density of the plasmas,ranging from low Z to high Z elements.The comparisons of the calculated results with those of other non-local thermodynamic equilibrium kinetics codes show that this model possesses acceptable precision.Furthermore,the NLTE effects are investigated by virtue of the model,and the differences between CRSS and LTE models for low density plasmas are quite evident.
Linear Instabilities Driven by Differential Rotation in Very Weakly Magnetized Plasmas
Quataert, Eliot; Spitkovsky, Anatoly
2014-01-01
We study the linear stability of weakly magnetized differentially rotating plasmas in both collisionless kinetic theory and Braginskii's theory of collisional, magnetized plasmas. We focus on the very weakly magnetized limit that is important for understanding how astrophysical magnetic fields originate and are amplified at high redshift. We show that the single instability of fluid theory - the magnetorotational instability mediated by magnetic tension - is replaced by two distinct instabilities, one associated with ions and one with electrons. Each of these has a different way of tapping into the free energy of differential rotation. The ion instability is driven by viscous transport of momentum across magnetic field lines due to a finite ion cyclotron frequency (gyroviscosity); the fastest growing modes have wavelengths significantly longer than MHD and Hall MHD predictions. The electron instability is a whistler mode driven unstable by the temperature anisotropy generated by differential rotation; the gro...
Liang, G Y; Wang, F L; Wu, Y; Zhong, J Y; Zhao, G
2014-01-01
Several laboratory facilities were used to benchmark theoretical spectral models those extensively used by astronomical communities. However there are still many differences between astrophysical environments and laboratory miniatures that can be archived. Here we setup a spectral analysis system for astrophysical and laboratory (SASAL) plasmas to make a bridge between them, and investigate the effects from non-thermal electrons, contribution from metastable level-population on level populations and charge stage distribution for coronal-like, photoionized, and geocoronal plasmas. Test applications to laboratory measurement (i.e. EBIT plasma) and astrophysical observation (i.e. Comet, Cygnus X-3) are presented. Time evolution of charge stage and level population are also explored for collisional and photoionized plasmas.
Dust charging and charge fluctuations in a weakly collisional radio-frequency sheath at low pressure
Energy Technology Data Exchange (ETDEWEB)
Piel, Alexander, E-mail: piel@physik.uni-kiel.de; Schmidt, Christian [IEAP, Christian-Albrechts-Universität, Kiel (Germany)
2015-05-15
Models for the charging of dust particles in the bulk plasma and in the sheath region are discussed. A new model is proposed that describes collision-enhanced ion currents in the sheath. The collisions result in a substantial reduction of the negative charge of the dust. Experimental data for the dust charge in the sheath can be described by this model when a Bi-Maxwellian electron distribution is taken into account. Expressions for the dust charging rate for all considered models are presented and their influence on the rise of the kinetic dust temperature is discussed.
Collisional effects in the ion Weibel instability for two counter-propagating plasma streams
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D.; Fiuza, F.; Huntington, C. M.; Ross, J. S.; Park, H.-S. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2014-03-15
Experiments directed towards the study of the collisionless interaction between two counter-streaming plasma flows generated by high-power lasers are designed in such a way as to make collisions between the ions of the two flows negligibly rare. This is reached by making flow velocities v as high as possible and thereby exploiting the 1/v{sup 4} dependence of the Rutherford cross-section. At the same time, the plasma temperature of each flow may be relatively low so that collisional mean-free paths for the intra-stream particle collisions may be much smaller than the characteristic spatial scale of the unstable modes required for the shock formation. The corresponding effects are studied in this paper for the case of the ion Weibel (filamentation) instability. Dispersion relations for the case of strong intra-stream collisions are derived. It is shown that the growth-rates become significantly smaller than those stemming from a collisionless model. The underlying physics is mostly related to the increase of the electron stabilizing term. Additional effects are an increased “stiffness” of the collisional ion gas and the ion viscous dissipation. A parameter domain where collisions are important is identified.
Stults, Joshua
This research presents a numerical framework for diagnosing electron properties in collisional plasmas. Microwave diagnostics achieved a significant level of development during the middle part of the last century due to work in nuclear weapons and fusion plasma research. With the growing use of plasma-based devices in fields as diverse as space propulsion, materials processing and fluid flow control, there is a need for improved, flexible diagnostic techniques suitable for use under the practical constraints imposed by plasma fields generated in a wide variety of aerospace devices. Much of the current diagnostic methodology in the engineering literature is based on analytical diagnostic, or forward, models. The Appleton-Hartree formula is an oft-used analytical relation for the refractive index of a cold, collisional plasma. Most of the assumptions underlying the model are applicable to diagnostics for plasma fields such as those found in Hall Thrusters and dielectric barrier discharge (DBD) plasma actuators. Among the assumptions is uniform material properties, this assumption is relaxed in the present research by introducing a flexible, numerical model of diagnostic wave propagation that can capture the effects of spatial gradients in the plasma state. The numerical approach is chosen for its flexibility in handling future extensions such as multiple spatial dimensions to account for scattering effects when the spatial extent of the plasma is small relative to the probing beam's width, and velocity dependent collision frequency for situations where the constant collision frequency assumption is not justified. The numerical wave propagation model (forward model) is incorporated into a general tomographic reconstruction framework that enables the combination of multiple interferometry measurements. The combined measurements provide a quantitative picture of the spatial variation in the plasma properties. The benefit of combining multiple measurements in a coherent
X-ray spectra of high temperature tungsten plasma calculated with collisional radiative model
Institute of Scientific and Technical Information of China (English)
Wang Jun; Zhang Hong; Cheng Xin-Lu
2013-01-01
Tungsten is regarded as an important candidate of plasma facing material in international thermonuclear experimental reactor (ITER),so the determination and modeling of spectra of tungsten plasma,especially the spectra at high temperature were intensely focused on recently.In this work,using the atomic structure code of Cowan,a collisional radiative model (CRM) based on the spin-orbit-split-arrays is developed.Based on this model,the charge state distribution of tungsten ions is determined and the soft X-ray spectra from high charged ions of tungsten at different temperatures are calculated.The results show that both the average ionization charge and line positions are well agreed with others calculations and measurements with discrepancies of less than 0.63％ and 1.26％,respectively.The spectra at higher temperatures are also reported and the relationship between ion abundance and temperature is predicted in this work.
Nonlinear Transport Processes in Tokamak Plasmas. Part I: The Collisional Regimes
Sonnino, Giorgio
2008-01-01
An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear (Onsager) transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for JET plasmas are also reported. We found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor, which may be of the order 100. The nonlinear classical coefficients exceed the neoclassical ones by a factor, which may be of order 2. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain...
The frequency and damping of ion acoustic waves in collisional and collisionless two-species plasma
Energy Technology Data Exchange (ETDEWEB)
Berger, R L; Valeo, E J
2004-07-15
The dispersion properties of ion acoustic waves (IAW) are sensitive to the strength of ion-ion collisions in multi-species plasma in which the different species usually have differing charge-to-mass ratios. The modification of the frequency and damping of the fast and slow acoustic modes in a plasma composed of light (low Z) and heavy (high Z) ions is considered. In the fluid limit where the light ion scattering mean free path, {lambda}{sub th} is smaller than the acoustic wavelength, {lambda} = 2{pi}/k, the interspecies friction and heat flow carried by the light ions scattering from the heavy ions causes the damping. In the collisionless limit, k{lambda}{sub lh} >> 1, Landau damping by the light ions provides the dissipation. In the intermediate regime when k{lambda}{sub lh} {approx} 1, the damping is at least as large as the sum of the collisional and Landau damping.
The Frequency and Damping of Ion Acoustic Waves in Collisional and Collisionless Two-species Plasma
Energy Technology Data Exchange (ETDEWEB)
R.L. Berger; E.J. Valeo
2004-08-18
The dispersion properties of ion acoustic waves (IAW) are sensitive to the strength of ion-ion collisions in multi-species plasma in which the different species usually have differing charge-to-mass ratios. The modification of the frequency and damping of the fast and slow acoustic modes in a plasma composed of light (low Z) and heavy (high Z) ions is considered. In the fluid limit where the light ion scattering mean free path, {lambda}{sub th} is smaller than the acoustic wavelength, {lambda} = 2{pi}/k, the interspecies friction and heat flow carried by the light ions scattering from the heavy ions causes the damping. In the collisionless limit, k{lambda}{sub th} >> 1, Landau damping by the light ions provides the dissipation. In the intermediate regime when k{lambda}{sub th} {approx} 1, the damping is at least as large as the sum of the collisional and Landau damping.
Coupled dust drift acoustic shock and soliton in collisional four component magnetized dusty plasmas
Farooq, M.; Ahmad, Mushtaq; Jan, Qasim
2017-09-01
Low frequency electrostatic coupled dust drift dust acoustic waves are studied in an inhomogeneous, collisional four component dust magnetoplasma composed of dust components of opposite polarity, along with Boltzmannian ions and electrons. The nonlinear evolution equation in the form of an ordinary differential equation and its limiting cases are derived and solved using the Tanh-method. The numerical analysis of the obtained solutions is studied for both laboratory and cosmic plasma systems. It is observed that, depending on the values of the plasma parameters like ion and electron temperatures, and charge number, both rarefactive and compressive shock and solitary waves may exist. It is shown that the concepts of a critical ion and electron temperatures/density in the nonlinear equations treatment, and of a changeover from compressive to rarefactive shock and soliton characters, correspond to the formation of rarefactive regimes, at which the electric stresses maximize and density minimizes.
Theory of Collisional Two-Stream Plasma Instabilities in the Solar Chromosphere
Madsen, Chad Allen; Dimant, Yakov; Oppenheim, Meers; Fontenla, Juan
2014-06-01
The solar chromosphere experiences intense heating just above its temperature minimum. The heating increases the electron temperature in this region by over 2000 K. Furthermore, it exhibits little time variation and appears widespread across the solar disk. Although semi-empirical models, UV continuum observations, and line emission measurements confirm the existence of the heating, its source remains unexplained. Potential heating sources such as acoustic shocks, resistive dissipation, and magnetic reconnection via nanoflares fail to account for the intensity, persistence, and ubiquity of the heating. Fontenla (2005) suggested turbulence from a collisional two-stream plasma instability known as the Farley-Buneman instability (FBI) could contribute significantly to the heating. This instability is known to heat the plasma of the E-region ionosphere which bears many similarities to the chromospheric plasma. However, the ionospheric theory of the FBI does not account for the diverse ion species found in the solar chromosphere. This work develops a new collisional, two-stream instability theory appropriate for the chromospheric plasma environment using a linear fluid analysis to derive a new dispersion relationship and critical E x B drift velocity required to trigger the instability. Using a 1D, non-local thermodynamic equilibrium, radiative transfer model and careful estimates of collision rates and magnetic field strengths, we calculate the trigger velocities necessary to induce the instability throughout the chromosphere. Trigger velocities as low as 4 km s^-1 are found near the temperature minimum, well below the local neutral acoustic speed in that region. From this, we expect the instability to occur frequently, converting kinetic energy contained in neutral convective flows from the photosphere into thermal energy via turbulence. This could contribute significantly to chromospheric heating and explain its persistent and ubiquitous nature.
Institute of Scientific and Technical Information of China (English)
夏雄平; 易林
2012-01-01
Effect of higher order axial electron temperature on self-focusing of electromagnetic pulsed beam in collisional plasma is investigated.It is shown that higher order axial electron temperature T p4 is not trivial than T p0 and T p2,which can modify slightly radial redistribution of electron density and increases effective dielectric constant.As a result,on one hand,slightly reduce electromagnetic beam self-focusing in the course of oscillatory convergence,on the other hand,quicken beam divergence in the course of steady divergence,i.e.,higher order axial electron temperature T p4 can decrease the influence of collisional nonlinearity in collisional plasma.
Impact of the Collisional Plasma on the Propagation of Millimeter Waves
Institute of Scientific and Technical Information of China (English)
袁忠才; 时家明; 汪家春; 许波
2004-01-01
The plasma generated in the low-altitude atmosphere is of high collision frequencies.In this paper, the transmission coefficients of millimeter(MM) waves normally incident upon the plasma with high collision frequencies are calculated and analyzed. The experimental results of reflection and attenuation are presented for the eight-millimeter waves propagating through the plasma. Both the calculated experimental results indicate that the MM-waves concerned are attenuated significantly and reflected weakly, when propagating through the plasma of high collision frequencies.
Sheath Criterion for a Collisional Electronegative Plasma Sheath in an Applied Magnetic Field
Institute of Scientific and Technical Information of China (English)
邹秀; 刘惠平; 邱明辉; 孙骁航
2011-01-01
The sheath criterion for a collisional electronegative plasma sheath in an applied magnetic field is investigated.It is assumed that the system consists of hot electrons,hot negative ions and cold positive ions.The effect of an applied magnetic field on the sheath criterion is discussed.The results reveal that the magnetic field has effects on both the upper and lower limits,which cause the range of the ion Mach number to increase.In addition,the numerical calculations of the electronegative plasma sheath are carried out to demonstrate the effects of sheath criterion on the characteristics of the sheath.%The sheath criterion for a collisioned electronegative plasma sheath in an applied magnetic Geld is investigated. It is assumed that the system consists of hot electrons, hot negative ions and cold positive ions. The effect of an applied magnetic Reid on the sheath criterion is discussed. The results reveal that the magnetic field has effects on both the upper and lower limits, which cause the range of the ion Mach number to increase. In addition, the numerical calculations of the electronegative plasma sheath are carried out to demonstrate the effects of sheath criterion on the characteristics of the sheath.
Fluid Simulation of the Ion Temperature Effects on a Collisional Magnetized Sheath of a Dusty Plasma
Directory of Open Access Journals (Sweden)
I Driouch
2013-01-01
Full Text Available The properties of magnetized dusty plasma sheath with finite ion temperature are studied using a fluid model. Hot electrons, fluid ions, neutral particles and cold fluid dust grains are taken into account in this system. Considering the cross section for collisions between the dust and neutrals has a power law dependence on the dust flow velocity, the fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures. A significant change is observed in the quantities characterizing the sheath with respect to the cold ion assumption. In addition, the result reveals that the effect of ion temperature is more obvious on the dust dynamics in collisional sheath with constant cross section.
Merritt, Elizabeth C; Hsu, Scott C; Adams, Colin S; Gilmore, Mark A
2013-01-01
We report spatially resolved experimental measurements of the oblique merging of two supersonic laboratory plasma jets. The jets are formed and launched by pulsed-power-driven railguns using injected argon, and have electron density $\\sim 10^{14}$ cm$^{-3}$, electron temperature $\\approx 1.4$ eV, ionization fraction near unity, and velocity $\\approx 40$ km/s just prior to merging. The jet merging produces a few-cm-thick stagnation layer, as observed in both fast-framing camera images and multi-chord interferometer data, consistent with collisional shock formation [E. C. Merritt et al., Phys. Rev. Lett. 111, 085003 (2013)]. The observed stagnation layer emission morphology is consistent with hydrodynamic oblique shock theory at early times, and then undergoes an evolution at later times that is coincident with the theoretically predicted transition to detached shock formation.
Energy Technology Data Exchange (ETDEWEB)
Khorashadizadeh, S. M., E-mail: smkhorashadi@birjand.ac.ir; Taheri Boroujeni, S. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of); Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)
2015-11-15
In this paper, we have investigated the nonlinear interaction between high-frequency surface plasmons and low-frequency ion oscillations in a semi-bounded collisional quantum plasma. By coupling the nonlinear Schrodinger equation and quantum hydrodynamic model, and taking into account the ponderomotive force, the dispersion equation is obtained. By solving this equation, it is shown that there is a modulational instability in the system, and collisions and quantum forces play significant roles on this instability. The quantum tunneling increases the phase and group velocities of the modulated waves and collisions increase the growth rate of the modulational instability. It is also shown that the effect of quantum forces and collisions is more significant in high modulated wavenumber regions.
Uttamsing Rajput, Rajendrasing; Alona, Khaustova; Loyan, Andriy V.
2017-03-01
Electric propulsion offers higher specific impulse compared to the chemical propulsion systems. It reduces the overall propellant mass and enables high operational lifetimes. Scientific Technological Center of Space Power and Energy (STC SPE), KhAI is involved in designing, manufacturing and testing of stationary plasma thrusters (SPT). Efforts are made to perform plasma diagnostics with corona and collisional radiative models (C-R model), as expected corona model falls short below 4 eV because of the heavy particle collisions elimination, whereas the C-R model's applicability is confirmed. Several tests are performed to analyze the electron temperature at various operational parameters of thruster like discharge voltage and mass flow rate. SPT-20M8 far and near-field plumes diagnostics are performed. Feasibility of C-R model by comparing its result to optical emission spectroscopy (OES) to investigate the electron temperature is validated with the probe measurements within the 10% of discrepancy.
SPEX (Plasma Code Spectral Fitting Tool). Collisional ionization for atoms and ions of H to Zn.
Urdampilleta, I.; Kaastra, J. S.
2017-03-01
Every observation of astrophysical objects involving a spectrum requires atomic data for the interpretation of line fluxes, ratios and ionization state of the emitting plasma. One of processes which determines it is collisional ionization. In this study an update of the direct ionization (DI) and excitation-autoionization (EA) processes is discussed for the H to Zn-like isoelectronic sequences. The previous assessments were performed by Dere (2007, A&A 466, 771) for H to Zn isoelectronc sequences, Arnaud & Raymond (1992, ApJ. 398, 394) for Fe and Arnaud & Rothenflug (1985, A&AS, 60, 425). However, in the last years new laboratory measurements and theoretical calculations of ionization cross sections have become accessible. We provide a review, extension and update of this previous work and fit the cross sections of all individuals shells of all ions from H to Zn. These data are described using an extension of Younger's formula, suitable for integration over a Maxwellian velocity distribution to derive the subshell ionization rate coefficients. These ionization rate coefficients are included together with the radiative recombination rates data (Mao et al. 2016, A&AS, 27568) and a change-exchange model (Gu et al. 2016, A&A 588, A52, 11) into the high-resolution plasma code and spectral fit tool SPEX V3.0 (Kaastra et al. 1996, UV and X-ray Spectroscopy of Astrophysical and Laboratory Plasmas).
Collisional relaxation of a strongly magnetized two-species pure ion plasma
Energy Technology Data Exchange (ETDEWEB)
Chim, Chi Yung; O’Neil, Thomas M.; Dubin, Daniel H. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States)
2014-04-15
The collisional relaxation of a strongly magnetized pure ion plasma that is composed of two species with slightly different masses is discussed. We have in mind two isotopes of the same singly ionized atom. Parameters are assumed to be ordered as Ω{sub 1},Ω{sub 2}≫|Ω{sub 1}−Ω{sub 2}|≫v{sup ¯}{sub ij}/b{sup ¯} and v{sup ¯}{sub ⊥j}/Ω{sub j}≪b{sup ¯}, where Ω{sub 1} and Ω{sub 2} are two cyclotron frequencies, v{sup ¯}{sub ij}=√(T{sub ∥}/μ{sub ij}) is the relative parallel thermal velocity characterizing collisions between particles of species i and j, and b{sup ¯}=2e{sup 2}/T{sub ∥} is the classical distance of closest approach for such collisions, and v{sup ¯}{sub ⊥j}/Ω{sub j}=√(2T{sub ⊥j}/m{sub j})/Ω{sub j} is the characteristic cyclotron radius for particles of species j. Here, μ{sub ij} is the reduced mass for the two particles, and T{sub ∥} and T{sub ⊥j} are temperatures that characterize velocity components parallel and perpendicular to the magnetic field. For this ordering, the total cyclotron action for the two species, I{sub 1}=∑{sub i∈1}m{sub 1}v{sub ⊥i}{sup 2}/(2Ω{sub 1}) and I{sub 2}=∑{sub i∈2}m{sub 2}v{sub ⊥i}{sup 2}/(2Ω{sub 2}) are adiabatic invariants that constrain the collisional dynamics. On the timescale of a few collisions, entropy is maximized subject to the constancy of the total Hamiltonian H and the two actions I{sub 1} and I{sub 2}, yielding a modified Gibbs distribution of the form exp[−H/T{sub ∥}−α{sub 1}I{sub 1}−α{sub 2}I{sub 2}]. Here, the α{sub j}’s are related to T{sub ∥} and T{sub ⊥j} through T{sub ⊥j}=(1/T{sub ∥}+α{sub j}/Ω{sub j}){sup −1}. Collisional relaxation to the usual Gibbs distribution, exp[−H/T{sub ∥}], takes place on two timescales. On a timescale longer than the collisional timescale by a factor of (b{sup ¯2}Ω{sub 1}{sup 2}/v{sup ¯}{sub 11}{sup 2})exp(5[3π(b{sup ¯}|Ω{sub 1}−Ω{sub 2}|/v{sup ¯}{sub 12})]{sup 2/5}/6), the two
Institute of Scientific and Technical Information of China (English)
刘秋艳; 李弘; 陈志鹏; 谢锦林; 刘万东
2011-01-01
Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron tem- perature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method.
Baalrud, S. D.; Hegna, C. C.; Callen, J. D.
2009-11-01
Ion-ion streaming instabilities are excited in the presheath region of plasmas with multiple ion species if the ions are much colder than the electrons. Streaming instabilities onset when the relative fluid flow between ion species exceeds a critical speed, δVc, of order the ion thermal speeds. Using a generalized Lenard-Balescu theory that accounts for instability-enhanced collective responses [1], one is able to show the instabilities rapidly enhance the collisional friction between ion species far beyond the contribution from Coulomb collisions alone. This strong frictional force determines the relative fluid speed between species. When this condition is combined with the Bohm criterion generalized for multiple ion species, the fluid speed of each ion species is determined at the sheath edge. For each species, this speed differs from the common ``system'' sound speed by a factor that depends on the species concentrations, masses and δVc.[4pt] [1] S.D. Baalrud, J.D. Callen, and C.C. Hegna, Phys. Plasmas 15, 092111 (2008).
The exact form of the Bohm criterion for a collisional plasma
Tsankov, Tsanko Vaskov
2016-01-01
A long-standing debate in the literature about the kinetic form of the Bohm criterion is resolved for plasmas with single positive ion species when transport is dominated by charge exchange collisions. The solution of the Boltzmann equation for the ions gives the exact form free of any divergence and contains an additional term that is not included in the classical result. This term includes collisional and geometric effects and leads to a noticeable correction. Further, the question is addressed whether the space charge argument at the bottom of the Bohm criterion can actually lead to a meaningful definition of the transition point between bulk and sheath. The analysis is supported by a numerical model and experiments, showing excellent agreement throughout. As a novelty in diagnostics, the theoretical results allow from the ion velocity distribution function (IVDF), measured at the wall, a reconstruction of the IVDF and the electric field at any point in the plasma. This property is used to reconstruct non-...
Sheared velocity flows as a source of pressure anisotropy in low collisionality plasmas
Del Sarto, Daniele; Pegoraro, Francesco; Cerri, Silvio Sergio; Califano, Francesco; Tenerani, Anna
2015-04-01
Non-Maxwellian metaequilibrium states may exist in low-collisionality plasmas as evidenced by direct (particle distributions) and indirect (e.g., instabilities driven by pressure anisotropy) satellite and laboratory measurements. These are directly observed in the solar wind (e.g. [1]), in magnetospheric reconnection events [2], in magnetically confined plasmas [3] or in simulations of Vlasov turbulence [4]. By including the full pressure tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes an initial isotropic state anisotropic. We discuss how the propagation of "magneto-elastic" waves can affect the pressure tensor anisotropization and the small scale formation that arise from the interplay between the gyrotropic terms due to the magnetic field and flow vorticity, and the non-gyropropic effect of the flow strain tensor. We support this analysis by a numerical integration of the nonlinear equations describing the pressure tensor evolution. This anisotropization mechanism might provide a good candidate for the understanding of the observed correlation between the presence of a sheared velocity flow and the signature of pressure anisotropies which are not yet explained within the standard models based e.g. on the CGL paradigm (see also [5]). Examples of these signatures are provided by the threshold lowering of ion-Weibel instabilities in the geomagnetic tail, observed in concomitance to the presence of a velocity shear in the near-earth plasma profile [6], or by the relatively stronger anisotropization measured for core protons in the fast solar wind [4,7] or in "space simulation" laboratory plasma experiments [3]. 1] E. Marsch et al., Journ. Geophys. Res. 109, A04120 (2004); Yu. V. Khotyainstev at el., Phys. Rev. Lett. 106, 165001 (2011). [2] N. Aunai et al., Ann. Geophys. 29, 1571 (2011); N. Aunai et al., Journ. Geophys. Res. 116, A09232 (2011). [3] E.E. Scime et al., Phys. Plasmas 7, 2157
Resonant scattering as a sensitive diagnostic of current collisional plasma models
Ogorzalek, Anna; Zhuravleva, Irina; Allen, Steven W.; Pinto, Ciro; Werner, Norbert; Mantz, Adam; Canning, Rebecca; Fabian, Andrew C.; Kaastra, Jelle S.; de Plaa, Jelle
2017-08-01
Resonant scattering is a subtle process that suppresses fluxes of some of the brightest optically thick X-ray emission lines produced by collisional plasmas in galaxy clusters and massive early-type galaxies. The amplitude of the effect depends on the turbulent structure of the hot gas, making it a sensitive velocity probe. It is therefore crucial to properly model this effect in order to correctly interpret high resolution X-ray spectra. Our measurements of resonant scattering with XMM-Newton Reflection Grating Spectrometer in giant elliptical galaxies and with Hitomi in the center of Perseus Cluster show that the potentially rich inference from this effect is limited by the uncertainties in the atomic data underlying plasma codes such as APEC and SPEX. Typically, the effect is of the order of 10-20%, while the discrepancy between the two codes is of similar order or even higher. Precise knowledge of the emissivity and oscillator strengths of lines emitted by Fe XVII and Fe XXV, as well as their respective uncertainties propagated through plasma codes are key to understanding gas dynamics and microphysics in giant galaxies and cluster ICM, respectively. This is especially crucial for massive ellipticals, where sub-eV resolution would be needed to measure line broadening precisely, making resonant scattering an important velocity diagnostic in these systems for the foreseeable future. In this poster, I will summarize current status of resonant scattering measurements and show how they depend on the assumed atomic data. I will also discuss which improvements are essential to maximize scientific inference from future high resolution X-ray spectra.
Anomalous collisional absorption of laser pulses in underdense plasma at low temperature
Kundu, M.
2015-04-01
In a previous paper [M. Kundu, Phys. Plasmas 21, 013302 (2014), 10.1063/1.4862038], fractional collisional absorption (α ) of laser light in underdense plasma was studied by using a classical scattering model of electron-ion collision frequency νei, where total velocity v =√{vth2+v02 } (with vth and v0 as the thermal and the ponderomotive velocity of an electron) dependent Coulomb logarithm lnΛ (v ) was shown to be responsible for the anomalous (unconventional) increase of νei and α (∝νei ) with the laser intensity I0 up to a maximum value about an intensity Ic in the low temperature (TeIc . One may object that the anomalous increase in νei and α were partly due to the artifact introduced in lnΛ through the maximum cutoff distance bmax∝v . In this work, we show similar anomalous increase in νei and α versus I0 (in the low temperature and underdense density regime) with more accurate quantum and classical kinetic models of νei without using lnΛ , but with a proper choice of the total velocity dependent inverse cutoff length kmax∝v2 (classical) or kmax∝v (quantum). For a given I0<5 ×1014Wcm -2 , νei versus Te also exhibits so far unnoticed identical anomalous increase as νei versus I0, even if the conventional kmax∝vth2 or kmax∝vth (without v0) is chosen. The total velocity dependent kmax in the kinetic models, as proposed here, is found to explain the anomalous increase of α with I0 measured in some earlier laser-plasma experiments.
Collisional thermalization of hydrogen and helium in solar-wind plasma.
Maruca, B A; Bale, S D; Sorriso-Valvo, L; Kasper, J C; Stevens, M L
2013-12-13
In situ observations of the solar wind frequently show the temperature of α particles (fully ionized helium) Tα to significantly differ from that of protons (ionized hydrogen) Tp. Many heating processes in the plasma act preferentially on α particles, even as collisions among ions act to gradually establish thermal equilibrium. Measurements from the Wind spacecraft's Faraday cups reveal that, at r=1.0 AU from the Sun, the observed values of the α-proton temperature ratio, θαp≡Tα/Tp, has a complex, bimodal distribution. This study applied a simple model for the radial evolution of θαp to these data to compute expected values of θαp at r=0.1 AU. These inferred θαp values have no trace of the bimodality seen in the θαp values measured at r=1.0 AU but are instead consistent with the actions of the known mechanisms for α-particle preferential heating. This result underscores the importance of collisional processes in the dynamics of the solar wind and suggests that similar mechanisms may lead to preferential α-particle heating in both slow and fast wind.
An advanced time-dependent collisional-radiative model of helium plasma discharges
Claustre, J.; Boukandou-Mombo, C.; Margot, J.; Matte, J.-P.; Vidal, F.
2017-10-01
A new spatially averaged time-dependent collisional-radiative model for helium plasmas, coupled to the electron Boltzmann equation (EBE), has been developed. Its main novelties are: (1) full time dependence for both the multi-species kinetics and the EBE. It is shown that this is necessary to correctly simulate discharges where the parameters vary on nanoseconds-microsecond timescales. (2) All electron processes are accounted for accurately. In particular, for the various ionization and recombination processes, free electrons are added or removed at the appropriate energy, with the appropriate interpolation on the energy grid. (3) The energy dependence of the electron loss by ambipolar diffusion is taken into account approximately. (4) All of the processes which are known to be important in helium discharges for pressure P≤slant 760 Torr are included, and 42 energy levels up to n = 6, where n is the main quantum number, are taken into account. Atomic and molecular ions, as well as excimers, are also included. (5) The gas temperature is calculated self-consistently. The model is validated through comparisons with known numerical steady-state results of Santos et al (2014 J. Phys. D. 47 265201) which they compared to their experimental results, and good agreement is obtained for their measured quantities. It is then applied to post-discharge decay cases with very short power decay times. The time evolution of the population densities and reaction rates are analyzed in detail with emphasis on the observed large increase of the metastable density.
Directory of Open Access Journals (Sweden)
Nersisyan Hrachya B.
2013-11-01
Full Text Available The low-velocity stopping power of ions in a magnetized collisional plasma is studied through the linear response theory. The collisions are taken into account through a number-conserving relaxation time approximation. One of the major objectives of this study is to compare and contrast our theoretical results with those obtained through a diffusion coefficient formulation based on Dufty-Berkovsky relation.
Resonance broadening modification of weak plasma turbulence theory
Energy Technology Data Exchange (ETDEWEB)
Hanssen, A. (Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau (West Germany))
1991-02-01
The author examines the effects on energy spectra of weak Langmuir turbulence when he includes a nonlinear damping due to the perturbation of electron orbits. The physical mechanism under consideration is usually known as a resonance broadening effect. The calculations show that the inclusion of this additional damping reduces the number of cascades predicted from weak turbulence theory for waves detectable with the EISCAT UHF (933 MHz) radar in Tromso, Norway, during RF modification of the ionospheric plasma.
A comparison of weak-turbulence and PIC simulations of weak electron-beam plasma interaction
Ratcliffe, Heather; Rozenan, Mohammed B Che; Nakariakov, Valery
2014-01-01
Quasilinear theory has long been used to treat the problem of a weak electron beam interacting with plasma and generating Langmuir waves. Its extension to weak-turbulence theory treats resonant interactions of these Langmuir waves with other plasma wave modes, in particular ion-sound waves. These are strongly damped in plasma of equal ion and electron temperatures, as sometimes seen in, for example, the solar corona and wind. Weak turbulence theory is derived in the weak damping limit, with a term describing ion-sound wave damping then added. In this paper we use the EPOCH particle-in-cell code to numerically test weak turbulence theory for a range of electron-ion temperature ratios. We find that in the cold ion limit the results agree well, but increasing ion temperature the three-wave resonance becomes broadened in proportion to the ion-sound wave damping rate. This may be important in, for example, the theory of solar radio bursts, where the spectrum of Langmuir waves is critical. Additionally we establish...
Weak Interaction Neutron Production Rates in Fully Ionized Plasmas
Widom, A.; Swain, J.; Srivastava, Y. N.
2013-01-01
Employing the weak interaction reaction wherein a heavy electron is captured by a proton to produce a neutron and a neutrino, the neutron production rate for neutral hydrogen gases and for fully ionized plasmas is computed. Using the Coulomb atomic bound state wave functions of a neutral hydrogen gas, our production rate results are in agreement with recent estimates by Maiani {\\it et al}. Using Coulomb scattering state wave functions for the fully ionized plasma, we find a substantially enha...
Weak Interaction Neutron Production Rates in Fully Ionized Plasmas
Widom, A; Srivastava, Y N
2013-01-01
Employing the weak interaction reaction wherein a heavy electron is captured by a proton to produce a neutron and a neutrino, the neutron production rate for neutral hydrogen gases and for fully ionized plasmas is computed. Using the Coulomb atomic bound state wave functions of a neutral hydrogen gas, our production rate results are in agreement with recent estimates by Maiani {\\it et al}. Using Coulomb scattering state wave functions for the fully ionized plasma, we find a substantially enhanced neutron production rate. The scattering wave function should replace the bound state wave function for estimates of the enhanced neutron production rate on water plasma drenched cathodes of chemical cells.
Energy Technology Data Exchange (ETDEWEB)
Khorashadizadeh, S. M., E-mail: smkhorashadi@birjand.ac.ir; Rastbood, E. [Physics Department, University of Birjand, Birjand 97179-63384 (Iran, Islamic Republic of); Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 19839-63113 (Iran, Islamic Republic of)
2015-07-15
The evolution of filamentation instability in a weakly ionized current-carrying plasma with nonextensive distribution was studied in the diffusion frequency region, taking into account the effects of electron-neutral collisions. Using the kinetic theory, Lorentz transformation formulas, and Bhatnagar-Gross-Krook collision model, the generalized dielectric permittivity functions of this plasma system were achieved. By obtaining the dispersion relation of low-frequency waves, the possibility of filamentation instability and its growth rate were investigated. It was shown that collisions can increase the maximum growth rate of instability. The analysis of temporal evolution of filamentation instability revealed that the growth rate of instability increased by increasing the q-parameter and electron drift velocity. Finally, the results of Maxwellian and q-nonextensive velocity distributions were compared and discussed.
Energy Technology Data Exchange (ETDEWEB)
Sosenko, P.; Pierre, Th. [Universite Marseille, Lab. PIIM - UMR6633 CNRS, Centre Saint Jerome, 13 - Marseille (France); Zagorodny, A. [Nancy-1 Univ. Henri Poincare, Lab. de Physique des Milieux Ionises (LPMIA, UPRES-A), Nancy 54 (France); International Centre of Physics, Kyiv (Ukraine)
2004-07-01
The linear and non-linear properties of global low-frequency oscillations in cylindrical weakly ionized magnetized plasmas are investigated analytically for the conditions of equilibrium plasma rotation. The theoretical results are compared with the experimental observations of rotating plasmas in laboratory devices, such as Mistral and Mirabelle in France, and KIWI in Germany. (authors)
Keenan, Brett D; Medvedev, Mikhail V
2015-01-01
High-amplitude, chaotic/turbulent electromagnetic fluctuations are ubiquitous in high-energy-density laboratory and astrophysical plasmas, where they can be excited by various kinetic-streaming and/or anisotropy-driven instabilities, such as the Weibel instability. These fields typically exist on "sub-Larmor scales" -- scales smaller than the electron Larmor radius. Electrons moving through such magnetic fields undergo small-angle stochastic deflections of their pitch-angles, thus establishing diffusive transport on long time-scales. We show that this behavior, under certain conditions, is equivalent to Coulomb collisions in collisional plasmas. The magnetic pitch-angle diffusion coefficient, which acts as an effective "collision" frequency, may be substantial in these, otherwise, collisionless environments. We show that this effect, colloquially referred to as the plasma "quasicollisionality", may radically alter the expected radiative transport properties of candidate plasmas. We argue that the modified mag...
Emission of strong Terahertz pulses from laser wakefields in weakly coupled plasma
Singh, Divya; Malik, Hitendra K.
2016-09-01
The present paper discusses the laser plasma interaction for the wakefield excitation and the role of external magnetic field for the emission of Terahertz radiation in a collisional plasma. Flat top lasers are shown to be more appropriate than the conventional Gaussian lasers for the effective excitation of wakefields and hence, the generation of strong Terahertz radiation through the transverse component of wakefield.
Directory of Open Access Journals (Sweden)
Keiji Sawada
2016-12-01
Full Text Available A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below six is developed. The rovibrational X 1 Σ g + population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.
Energy Technology Data Exchange (ETDEWEB)
Krychowiak, M; Koenig, R; Wolf, R; Klinger, T [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Greifswald (Germany); Mertens, Ph; Schweer, B; Brezinsek, S; Schmitz, O; Samm, U [Institut fuer Energieforschung (Plasmaphysik), FZ Juelich, EURATOM Association, TEC, Juelich (Germany); Brix, M, E-mail: maciej.krychowiak@ipp.mpg.d [UKAEA, JET-Experimental Department, EURATOM Association, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom)
2010-05-01
Local values of the electron density and temperature in the edge of a fusion plasma can be derived with high space and time resolution by the use of line radiation of atomic helium beams. The accuracy of this method is mainly limited by the uncertainties in the collisional-radiative (CR) model which is needed in order to obtain both plasma parameters from the measured relative intensities of atomic helium lines. Laser-induced fluorescence spectroscopy on a thermal helium beam in the edge plasma of the tokamak TEXTOR in Juelich was applied to validate the CR model of helium. By use of a high-power, pulsed laser system (a dye laser pumped by an excimer laser) several laser excitation schemes starting from the n=2 levels have been tried. The fluorescence light was observed at the laser wavelength and elsewhere in the spectrum providing information on population densities of initial levels as well as on collisional population transfer between excited levels. This paper summarises the results of the measurements, showing principal limits and possible improvements of this experimental validation method of the CR model of the diagnostic helium beam.
Krychowiak, M.; Mertens, Ph; König, R.; Schweer, B.; Brezinsek, S.; Schmitz, O.; Brix, M.; Samm, U.; Wolf, R.; Klinger, T.
2010-05-01
Local values of the electron density and temperature in the edge of a fusion plasma can be derived with high space and time resolution by the use of line radiation of atomic helium beams. The accuracy of this method is mainly limited by the uncertainties in the collisional-radiative (CR) model which is needed in order to obtain both plasma parameters from the measured relative intensities of atomic helium lines. Laser-induced fluorescence spectroscopy on a thermal helium beam in the edge plasma of the tokamak TEXTOR in Jülich was applied to validate the CR model of helium. By use of a high-power, pulsed laser system (a dye laser pumped by an excimer laser) several laser excitation schemes starting from the n=2 levels have been tried. The fluorescence light was observed at the laser wavelength and elsewhere in the spectrum providing information on population densities of initial levels as well as on collisional population transfer between excited levels. This paper summarises the results of the measurements, showing principal limits and possible improvements of this experimental validation method of the CR model of the diagnostic helium beam.
Collisional excitation and emission of H-alpha Stark multiplet in fusion plasmas
Marchuk, O.; Ralchenko, Y.; Janev, R. K.; Biel, W.; Delabie, E.; Urnov, A. M.
2010-01-01
We study the excitation of parabolic Stark states in hydrogen atoms by collisions with fast ions. It is shown that excitation cross sections are very sensitive to the angle between the electric field and the projectile velocity. The calculated collisional data are implemented in a newly developed co
Frassinetti, L.; Beurskens, M. N. A.; Saarelma, S.; Boom, J. E.; Delabie, E.; Flanagan, J.; Kempenaars, M.; Giroud, C.; Lomas, P.; Meneses, L.; Maggi, C. S.; Menmuir, S.; Nunes, I.; Rimini, F.; Stefanikova, E.; Urano, H.; Verdoolaege, G.; Contributors, JET
2017-01-01
A dimensionless collisionality scan in low-triangularity plasmas in the Joint European Torus with the ITER-like wall (JET-ILW) has been performed. The increase of the normalized energy confinement (defined as the ratio between thermal energy confinement and Bohm confinement time) with decreasing collisionality is observed. Moreover, at low collisionality, a confinement factor H98, comparable to JET-C, is achieved. At high collisionality, the low normalized confinement is related to a degraded pedestal stability and a reduction in the density-profile peaking. The increase of normalized energy confinement is due to both an increase in the pedestal and in the core regions. The improvement in the pedestal is related to the increase of the stability. The improvement in the core is driven by (i) the core temperature increase via the temperature-profile stiffness and by (ii) the density-peaking increase driven by the low collisionality. Pedestal stability analysis performed with the ELITE (edge-localized instabilities in tokamak equilibria) code has a reasonable qualitative agreement with the experimental results. An improvement of the pedestal stability with decreasing collisionality is observed. The improvement is ascribed to the reduction of the pedestal width, the increase of the bootstrap current and the reduction of the relative shift between the positions of the pedestal density and pedestal temperature. The EPED1 model predictions for the pedestal pressure height are qualitatively well correlated with the experimental results. Quantitatively, EPED1 overestimates the experimental pressure by 15-35%. In terms of the pedestal width, a correct agreement (within 10-15%) between the EPED1 and the experimental width is found at low collisionality. The experimental pedestal width increases with collisionality. Nonetheless, an extrapolation to low-collisionality values suggests that the width predictions from the KBM constraint are reasonable for ITER.
Institute of Scientific and Technical Information of China (English)
Yu Yi-Qing; Xin Yu; Ning Zhao-Yuan
2011-01-01
This paper proposes a simple collisional-radiative model to characterise capacitively coupled argon plasmas driven by conventional radio frequency in combination with optical emission spectroscopy and Langmuir probe measurements.Two major processes are considered in this model, electron-impact excitation and the spontaneous radiative decay.taken into account. Behaviours of representative metastable and radiative states are discussed. Two emission lines (located at 696.5 nm and 750.4 nm) are selected and intensities are measured to obtain populated densities of the corresponding radiative states in the argon plasma. The calculated results agree well with that measured by Langmuir probe, indicating that the current model combined with optical emission spectroscopy is a candidate tool for electron density and temperature measurement in radio frequency capacitively coupled discharges.
Energy Technology Data Exchange (ETDEWEB)
Tracy, M.D.
1993-01-08
Collective Thomson scattering from ion-acoustic waves at 266nm is used to obtain spatially resolved, two-dimensional electron density, sound speed, and radial drift profiles of a collisional laser plasma. An ultraviolet diagnostic wavelength minimizes the complicating effects of inverse bremsstrahlung and refractive turning in the coronal region of interest, where the electron densities approach n{sub c}/10. Laser plasmas of this type are important because they model some of the aspects of the plasmas found in high-gain laser-fusion pellets irradiated by long pulse widths where the laser light is absorbed mostly in the corona. The experimental results and LASNEX simulations agree within a percent standard deviation of 40% for the electron density and 50% for the sound speed and radial drift velocity. Thus it is shown that the hydrodynamics equations with classical coefficients and the numerical approximations in LASNEX are valid models of laser-heated, highly collisional plasmas. The versatility of Thomson scattering is expanded upon by extending existing theory with a Fokker-Planck based model to include plasmas that are characterized by (0 {le} k{sub ia}{lambda}{sub ii} {le} {infinity}) and ZT{sub e}/T{sub i}, where k{sub ia} is the ion- acoustic wave number, {lambda}{sub ii} is the ion-ion mean free path, Z is the ionization state of the plasma, and T{sub e}, T{sub i} are the electron and ion temperatures in electron volts respectively. The model is valid for plasmas in which the electrons are approximately collisionless, (k{sub ia}{lambda}{sub ei}, k{sub ia}{lambda}{sub ee} {ge} 1), and quasineutrality holds, ({alpha} {much_gt}1), where {alpha} = 1/k{lambda}{sub DE} and {lambda}{sub DE} is the electron Debye length. This newly developed model predicts the lineshape of the ion-acoustic Thomson spectra and when fit to experimental data provides a direct measurement of the relative thermal flow velocity between the electrons and ions.
Energy Technology Data Exchange (ETDEWEB)
Gupta, Naveen, E-mail: naveens222@rediffmail.com; Singh, Arvinder, E-mail: arvinder6@lycos.com [Department of Physics, National Institute of Technology Jalandhar (India); Singh, Navpreet, E-mail: navpreet.nit@gmail.com [Guru Nanak Dev University College, Kapurthala, Punjab (India)
2015-11-15
This paper presents a scheme for second harmonic generation of an intense q-Gaussian laser beam in a preformed parabolic plasma channel, where collisional nonlinearity is operative with nonlinear absorption. Due to nonuniform irradiance of intensity along the wavefront of the laser beam, nonuniform Ohmic heating of plasma electrons takes place. Due to this nonuniform heating of plasma, the laser beam gets self-focused and produces strong density gradients in the transverse direction. The generated density gradients excite an electron plasma wave at pump frequency that interacts with the pump beam to produce its second harmonics. The formulation is based on a numerical solution of the nonlinear Schrodinger wave equation in WKB approximation followed by moment theory approach. A second order nonlinear differential equation governing the propagation dynamics of the laser beam with distance of propagation has been obtained and is solved numerically by Runge Kutta fourth order technique. The effect of nonlinear absorption on self-focusing of the laser beam and conversion efficiency of its second harmonics has been investigated.
Jiang, Bing-feng; Hou, De-fu; Li, Jia-rong
2016-10-01
We derive the electric permittivity ɛ and magnetic permeability μM of the quark-gluon plasma (QGP) with the kinetic theory associated with a Bhatnagar-Gross-Krook (BGK) collisional kernel. Based on them, we study the effect of collisions on the refractive index of QGP. Compared to the collisionless case, collisions change the ω -behavior of ɛ and μM dramatically, which is responsible for the fact that the real and imaginary parts of n2 and the Depine-Lakhtakia index nDL are smooth functions of ω . For a small collision rate ν , the Depine-Lakhtakia index nDL is negative in some frequency range. When the collision rate increases, the frequency range for nDLindex nDL is positive for all frequency regions, which indicates a normal refractive index. In contrast to the collisionless case, there exists some frequency range in which nDLnegative refractive index.
Quantum ion-acoustic solitary waves in weak relativistic plasma
Indian Academy of Sciences (India)
Biswajit Sahu
2011-06-01
Small amplitude quantum ion-acoustic solitary waves are studied in an unmagnetized twospecies relativistic quantum plasma system, comprised of electrons and ions. The one-dimensional quantum hydrodynamic model (QHD) is used to obtain a deformed Korteweg–de Vries (dKdV) equation by reductive perturbation method. A linear dispersion relation is also obtained taking into account the relativistic effect. The properties of quantum ion-acoustic solitary waves, obtained from the deformed KdV equation, are studied taking into account the quantum mechanical effects in the weak relativistic limit. It is found that relativistic effects signiﬁcantly modify the properties of quantum ion-acoustic waves. Also the effect of the quantum parameter on the nature of solitary wave solutions is studied in some detail.
Wakefields generated by collisional neutrinos in neutral-electron-positron-ion plasma
Energy Technology Data Exchange (ETDEWEB)
Tinakiche, Nouara [Faculty of Sciences, Department of Physics, University of Boumeredes U.M.B.B., Boumerdes 35000 (Algeria)
2015-12-15
A classical fluid description is adopted to investigate nonlinear interaction between an electron-type neutrino beam and a relativistic collisionless unmagnetized neutral-electron-positron-ion plasma. In this work, we consider the collisions of the neutrinos with neutrals in the plasma and study their effect on the generation of wakefields in presence of a fraction of ions in a neutral-electron-positron plasma. The results obtained in the present work are interpreted and compared with previous studies.
Long-Lived Vortex Structures in Collisional Pure and Gas-Discharge Nonneutral Electron Plasmas
Kervalishvili, N. A.
2013-01-01
The analysis of experimental investigations of equilibrium, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas during the time much more than the electron-neutral collision time has been carried out. The problem of long confinement of the column of pure electron plasma in Penning-Malmberg trap is considered. The mechanism of stability of long-lived vortex structure in gas-discharge nonneutral electron plasma is investigated. The collap...
Energy Technology Data Exchange (ETDEWEB)
Song, Mi-Young; Yoon, Jung-Sik [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Osikdo-Dong, Gunsan-City, Jeollabuk-Do 573-540 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States); Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)
2015-03-15
The electron-neutral collision effects on the Compton scattering process are investigated in warm collisional plasmas. The Compton scattering cross section in warm collisional plasmas is obtained by the Salpeter structure factor with the fluctuation-dissipation theorem and the plasma dielectric function as a function of the electron-neutral collision frequency, Debye length, and wave number. It is shown that the influence of electron-neutral collision strongly suppresses the Compton scattering cross section in warm collisional plasmas. It is also found that the electron-neutral collision effect on the differential Compton scattering cross section is more significant in forward scattering directions. We show that the differential Compton scattering cross section has a maximum at the scattering angle φ=π/2. In addition, we find that the electron-neutral collision effect on the total Compton scattering cross section increases with increasing Debye length and wave number. The variation of the Compton scattering cross section due to the change of collision frequency and plasma parameters is also discussed.
Bryans, P; Gorczyca, T W; Laming, J M; Mitthumsiri, W; Savin, D W
2006-01-01
Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and are often highly suspect. This translates directly into the reliability of the collisional ionization equilibrium (CIE) calculations. We make use of state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He up to and including Zn. We also make use of state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H through to Zn. Here we present improved CIE calculations for temperatures from $10^4$ to $10^9$ K using our data and the recommended electron impact ionization data of \\citet{Mazz98a} for elements up to and including Ni and Mazzotta (private communication) for Cu and Zn. DR and RR ...
Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles
Institute of Scientific and Technical Information of China (English)
LIN Mai-Mai; DUAN Wen-Shan
2005-01-01
The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma.It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field E0 has also been studied in this paper.
Spectroscopic modeling and characterization of a collisionally confined laser-ablated plasma plume.
Sherrill, M E; Mancini, R C; Bailey, J; Filuk, A; Clark, B; Lake, P; Abdallah, J
2007-11-01
Plasma plumes produced by laser ablation are an established method for manufacturing the high quality stoichiometrically complex thin films used for a variety of optical, photoelectric, and superconducting applications. The state and reproducibility of the plasma close to the surface of the irradiated target plays a critical role in producing high quality thin films. Unfortunately, this dense plasma has historically eluded quantifiable characterization. The difficulty in modeling the plume formation arises in the accounting for the small amount of energy deposited into the target when physical properties of these exotic target materials are not known. In this work we obtain the high density state of the plasma plume through the use of an experimental spectroscopic technique and a custom spectroscopic model. In addition to obtaining detailed temperature and density profiles, issues regarding line broadening and opacity for spectroscopic characterization will be addressed for this unique environment.
Long-Lived Vortex Structures in Collisional Pure and Gas-Discharge Nonneutral Electron Plasmas
Kervalishvili, N A
2013-01-01
The analysis of experimental investigations of equilibrium, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas during the time much more than the electron-neutral collision time has been carried out. The problem of long confinement of the column of pure electron plasma in Penning-Malmberg trap is considered. The mechanism of stability of long-lived vortex structure in gas-discharge nonneutral electron plasma is investigated. The collapse of electron sheath in gas-discharge nonneutral electron plasma in Penning cell at high pressures of neutral gas is described. The interaction between the stable vortex structure and the annular electron sheath, and the action of vortex structures on the transport of electrons along and across the magnetic field are discussed.
Continuum Kinetic Model for Simulating Low-Collisionality Regimes in Plasmas
2013-06-01
properties for non -linear plasma phenomena require further investigation. VII. CONCLUSIONS A fourth order accurate algorithm in space and time has been...theory, each particle species is treated as a distribution function evolving in position-velocity phase space . For a collisionless plasma , the evolution... Maxwellian distribution in velocity space with a small position-dependent perturbation: f(x, v)|t=0 = 1√ 2π exp ( −v 2 2 ) (1 + a cos(kx)) , (16) with
Moment fluid equations for ions in weakly-ionized plasma
Semenov, I L
2016-01-01
A new one-dimensional fluid model for ions in weakly-ionized plasma is proposed. The model differs from the existing ones in two aspects. First, a more accurate approximation of the collision terms in the fluid equations is suggested. For this purpose, the results obtained using the Monte-Carlo kinetic model of the ion swarm experiments are considered. Second, the ion energy equation is taken into account. The fluid equations are closed using a simple model of the ion velocity distribution function. The accuracy of the fluid model is examined by comparing with the results of particle-in-cell/Monte Carlo simulations. In particular, several test problems are considered using a parallel plate model of the capacitively coupled radio-frequency discharge. It is shown that the results obtained using the proposed fluid model are in good agreement with those obtained from the simulations over a wide range of discharge conditions. An approximation of the ion velocity distribution function for the problem under consider...
On RF heating of inhomogeneous collisional plasma under ion-cyclotron resonance conditions
Energy Technology Data Exchange (ETDEWEB)
Timofeev, A. V., E-mail: Timofeev-AV@nrcki.ru [Kurchatov Institute (Russian Federation)
2015-11-15
During ion-cyclotron resonance (ICR) heating of plasma by the magnetic beach method, as well as in some other versions of ICR heating, it is necessary to excite Alfvén oscillations. In this case, it is difficult to avoid the phenomenon of the Alfvén resonance, in which Alfvén oscillations transform into lower hybrid oscillations. The latter efficiently interact with electrons, due to which most of the deposited RF energy is spent on electron (rather than ion) heating. The Alfvén resonance takes place due to plasma inhomogeneity across the external magnetic field. Therefore, it could be expected that variations in the plasma density profile would substantially affect the efficiency of the interaction of RF fields with charged particles. However, the results obtained for different plasma density profiles proved to be nearly the same. In the present work, a plasma is considered the parameters of which correspond to those planned in future ICR plasma heating experiments on the PS-1 facility at the Kurchatov Institute. When analyzing the interaction of RF fields with charged particles, both the collisionless resonance interaction and the interaction caused by Coulomb collisions are taken into account, because, in those experiments, the Coulomb collision frequency will be comparable with the frequency of the heating field. Antennas used for ICR heating excite RF oscillations with a wide spectrum of wavenumbers along the magnetic field. After averaging over the spectrum, the absorbed RF energy calculated with allowance for collisions turns out to be close to that absorbed in collisionless plasma, the energy fraction absorbed by electrons being substantially larger than that absorbed by ions.
On RF heating of inhomogeneous collisional plasma under ion-cyclotron resonance conditions
Timofeev, A. V.
2015-11-01
During ion-cyclotron resonance (ICR) heating of plasma by the magnetic beach method, as well as in some other versions of ICR heating, it is necessary to excite Alfvén oscillations. In this case, it is difficult to avoid the phenomenon of the Alfvén resonance, in which Alfvén oscillations transform into lower hybrid oscillations. The latter efficiently interact with electrons, due to which most of the deposited RF energy is spent on electron (rather than ion) heating. The Alfvén resonance takes place due to plasma inhomogeneity across the external magnetic field. Therefore, it could be expected that variations in the plasma density profile would substantially affect the efficiency of the interaction of RF fields with charged particles. However, the results obtained for different plasma density profiles proved to be nearly the same. In the present work, a plasma is considered the parameters of which correspond to those planned in future ICR plasma heating experiments on the PS-1 facility at the Kurchatov Institute. When analyzing the interaction of RF fields with charged particles, both the collisionless resonance interaction and the interaction caused by Coulomb collisions are taken into account, because, in those experiments, the Coulomb collision frequency will be comparable with the frequency of the heating field. Antennas used for ICR heating excite RF oscillations with a wide spectrum of wavenumbers along the magnetic field. After averaging over the spectrum, the absorbed RF energy calculated with allowance for collisions turns out to be close to that absorbed in collisionless plasma, the energy fraction absorbed by electrons being substantially larger than that absorbed by ions.
Energy Technology Data Exchange (ETDEWEB)
May, M J; Schneider, M B; Hansen, S B; Chung, H; Hinkel, D E; Baldis, H A; Constantin, C
2008-02-20
M-Band and L-Band Gold spectra between 3 to 5 keV and 8 to 13 keV, respectively, have been recorded by a photometrically calibrated crystal spectrometer. The spectra were emitted from the plasma in the laser deposition region of a 'hot hohlraum'. This is a reduced-scale hohlraum heated with {approx} 9 kJ of 351 nm light in a 1 ns square pulse at the Omega laser. The space- and time-integrated spectra included L-Band line emission from Co-like to Ne-like gold. The three L-Band line features were identified to be the 3s {yields} 2p, 3d{sub 5/2} {yields} 2p{sub 3/2} and 3d{sub 3/2} {yields} 2p{sub 1/2} transitions at {approx}9 keV, {approx}10 keV and {approx}13 keV, respectively. M-Band 5f {yields} 3d, 4d {yields} 3p, and 4p {yields} 3s transition features from Fe-like to P-like gold were also recorded between 3 to 5 keV. Modeling from the radiation-hydrodynamics code LASNEX, the collisional-radiative codes FLYCHK and SCRAM, and the atomic structure code FAC were used to model the plasma and generate simulated spectra for comparison with the recorded spectra. Through these comparisons, we have determined the average electron temperature of the emitting plasma to be {approx} 6.5 keV. The electron temperatures predicted by LASNEX appear to be too large by a factor of about 1.5.
Energy Technology Data Exchange (ETDEWEB)
May, M J; Schneider, M B; Hansen, S B; Chung, H; Hinkel, D E; Baldis, H A; Constantin, C
2008-07-02
M-Band and L-Band Gold spectra between 3 to 5 keV and 8 to 13 keV, respectively, have been recorded by a photometrically calibrated crystal spectrometer. The spectra were emitted from the plasma in the laser deposition region of a 'hot hohlraum'. This is a reduced-scale hohlraum heated with {approx} 9 kJ of 351 nm light in a 1 ns square pulse at the OMEGA laser. The space- and time-integrated spectra included L-Band line emission from Co-like to Ne-like gold. The three L-Band line features were identified to be the 3s {yields} 2p, 3d{sub 5/2} {yields} 2p{sub 3/2} and 3d{sub 3/2} {yields} 2p{sub 1/2} transitions at {approx}9 keV, {approx}10 keV and {approx}13 keV, respectively. M-Band 5f {yields} 3d, 4d {yields} 3p, and 4p {yields} 3s transition features from Fe-like to P-like gold were also recorded between 3 to 5 keV. Modeling from the radiation-hydrodynamics code LASNEX, the collisional-radiative codes FLYCHK and SCRAM, and the atomic structure code FAC were used to model the plasma and generate simulated spectra for comparison with the recorded spectra. Through these comparisons, we have determined the average electron temperature of the emitting plasma to be between 6.0 and 6.5 keV. The electron temperatures predicted by LASNEX appear to be too large by a factor of about 1.5.
Advanced Multifluid and Collisional-Radiative Models for Laser-Plasma Interaction (Briefing Charts)
2014-12-01
direct control of computational cost in particle methods • Future Work: Test merge in non - Maxwellian laser plasma test case Control Merge & Split...shocks Current focus: Develop advanced multiscale algorithms for plasma M&S in highly non ‐equilibrium condition and with collisional‐radiative kinetics...Radiative (CR) model • Non -equilibrium modeling of the atomic state distribution function (ASDF) – Detailed state-to-state model of atomic
Spatial mode structures of electrostatic drift waves in a collisional cylindrical helicon plasma
DEFF Research Database (Denmark)
Schröder, C.; Grulke, O.; Klinger, T.;
2004-01-01
In a cylindrical helicon plasma, mode structures of coherent drift waves are studied in the poloidal plane, the plane perpendicular to the ambient magnetic field. The mode structures rotate with a constant angular velocity in the direction of the electron diamagnetic drift and show significant...
Latyshev, A V
2013-01-01
Formulas for transverse conductance and dielectric permeability in quantum non-degenerate and Maxwellian collisional plasma with arbitrary variable collision frequency in Mermin's approach are deduced. Frequency of collisions of particles depends arbitrarily on a wave vector. The special case of frequency of collisions proportional to the module of a wave vector is considered. The graphic analysis of the real and imaginary parts of dielectric function is made.
Modulational Instability of Dust Ion Acoustic Waves in a Collisional Dusty Plasma
Institute of Scientific and Technical Information of China (English)
XUEJu-Kui
2003-01-01
The modulational instability of dust ion accoustic waves in a dust plasma with ion-dust collision effects is studied.Using the perturbation method,a modified nonlinear Schroedinger equation contains a damping term that comes from the effect of the ion-dust collision is derived.It is found that the inclusion of the ion-dust collision would modify the modulational instability of the wave packet and could not admit any stationary envelope solitary waves.
Filamentation instability of current-driven dust ion-acoustic waves in a collisional dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 19839-63113 (Iran, Islamic Republic of); Haghtalab, T.; Khorashadizadeh, S. M. [Physics Department, Birjand University, Birjand 97179-63384 (Iran, Islamic Republic of)
2011-11-15
A theoretical investigation has been made of the dust ion-acoustic filamentation instability in an unmagnetized current-driven dusty plasma by using the Lorentz transformation formulas. The effect of collision between the charged particles with neutrals and their thermal motion on this instability is considered. Developing the filamentation instability of the current-driven dust ion-acoustic wave allows us to determine the period and the establishment time of the filamentation structure and threshold for instability development.
Nonlinear penetration of whistler pulses into collisional plasmas via conductivity modifications
Urrutia, J. M.; Stenzel, R. L.
1991-01-01
A strong electromagnetic impulse (about 0.2 microsec) with central frequency in the whistler-wave regime is applied to a large laboratory plasma dominated by Coulomb collisions. Local electron heating at the antenna and transport along B0 create a channel of high conductivity along which the whistler pulse penetrates with little damping. Because of its rapid temporal evolution, this new form of modulational instability does not involve ducting by density gradients which require ion time scales to develop.
A Hybrid Model for Multiscale Laser Plasma Simulations with Detailed Collisional Physics
2016-11-29
other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a ...Briefing Charts 3. DATES COVERED (From - To) 02 November 2016 – 30 November 2016 4. TITLE AND SUBTITLE A Hybrid Model for Multiscale Laser Plasma...Briefing Charts 15. SUBJECT TERMS N/ A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE
2014-07-01
Magnetized plasmas are often modeled with MHD with a hierarchy of descriptions: Ideal, resistive, Hall MHD . – Generalized model : multi-fluid (Braginskii... modeling of the atomic state distribution function (ASDF) – Detailed state-to-state model of atomic transition, i.e., excitation and ionization...moment of the kinetic equations with fluid closure – 5-moment model yields Euler/NS systems: multi-species, multi- temperature CR models
Electron-ion collisional effect on Weibel instability in a Kappa distributed unmagnetized plasma
Energy Technology Data Exchange (ETDEWEB)
Kumar Kuri, Deep, E-mail: deepkuri303@gmail.com; Das, Nilakshi, E-mail: ndas@tezu.ernet.in [Department of Physics, Tezpur University, Tezpur, Assam 784 028 (India)
2014-04-15
Weibel instability has been investigated in the presence of electron-ion collisions by using standard Vlasov-Maxwell equations. The presence of suprathermal electrons has been included here by using Kappa distribution for the particles. The growth rate γ of Weibel instability has been calculated for different values of spectral index κ, collision frequency ν{sub ei}, and temperature anisotropy parameter β. A comparative study between plasma obeying Kappa distribution and that obeying Maxwellian distribution shows that the growth of instability is higher for the Maxwellian particles. However, in the presence of collisions, the suprathermal particles result in lower damping of Weibel mode.
Transition from Collisionless to Collisional MRI
Energy Technology Data Exchange (ETDEWEB)
Prateek Sharma; Gregory W. Hammett; Eliot Quataert
2003-07-24
Recent calculations by Quataert et al. (2002) found that the growth rates of the magnetorotational instability (MRI) in a collisionless plasma can differ significantly from those calculated using MHD. This can be important in hot accretion flows around compact objects. In this paper, we study the transition from the collisionless kinetic regime to the collisional MHD regime, mapping out the dependence of the MRI growth rate on collisionality. A kinetic closure scheme for a magnetized plasma is used that includes the effect of collisions via a BGK operator. The transition to MHD occurs as the mean free path becomes short compared to the parallel wavelength 2*/k(sub)||. In the weak magnetic field regime where the Alfven and MRI frequencies w are small compared to the sound wave frequency k(sub)||c(sub)0, the dynamics are still effectively collisionless even if omega << v, so long as the collision frequency v << k(sub)||c(sub)0; for an accretion flow this requires n less than or approximately equal to *(square root of b). The low collisionality regime not only modifies the MRI growth rate, but also introduces collisionless Landau or Barnes damping of long wavelength modes, which may be important for the nonlinear saturation of the MRI.
Energy Technology Data Exchange (ETDEWEB)
Olson, R.E.
1981-10-15
Research on this contract can be divided into two general topics: (1) D/sup -/ formation collision processes, and (2) the determination of scattering cross sections used to diagnose properties of magnetically-confined plasmas. For topic (1) during last year, we completed theoretical calculations on the differential (angular) scattering of H/sup 0/ and D/sup 0/ on Cs, and determined the mechanisms and trends in the electron detachment cross sections for collisions of H/sup -/ and D/sup -/ on He, Ne, and the alkali and heavy alkaline earth atom systems. On topic (2) a major accomplishment was the determination of the electron capture and ionization cross sections for the C/sup 5 +/, N/sup 5 +/, and O/sup 6 +/ + H systems in the energy range from 13 eV/amu to 2.1 MeV/amu.
Energy Technology Data Exchange (ETDEWEB)
Rocca, J.J.; Cortazar, O.D.; Tomasel, F.G.; Szapiro, B.T. (Department of Electrical Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States))
1993-10-01
Fast discharges through 1.5-mm-diam capillaries have produced dense Ca and Ti plasma columns with an abundance of Ne-like ions, which are of interest for the development of small-scale, collisionally excited soft-x-ray lasers. Current pulses of 30 ns full width at half maximum and peak currents of less than 70 kA produced plasmas with line emission from ions with charge up to the F-like state. Line emission at the wavelengths of the 3[ital p]-3[ital s] and 3[ital d]-3[ital p] transitions of the Ne-like ions has been observed.
A New Hybrid Scheme for Simulations of Highly Collisional RF-Driven Plasmas
Eremin, Denis; Mussenbrock, Thomas
2015-01-01
This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using Particle-In-Cell/Monte-Carlo (PIC/MCC) scheme, whereas the heavy species are modeled within a fluid description. Validity of the popular drift-diffusion approximation is verified against a "full" fluid model accounting for the ion inertia and a fully kinetic PIC/MCC code for ions as well as electrons. The fluid models require knowledge of the momentum exchange frequency and dependence of the ion mobilities on the electric field when the ions are in equilibrium with the latter. To this end an auxiliary Monte-Carlo scheme is constructed. It is demonstrated that the drift-diffusion approximation can overestimate ion transport in simulations of RF-driven discharges with heavy ion species operated in the $\\gamma$ mode at the atmospheric pressure or in all discharge simulations for lower pressures. This can lead to exaggerated plasma ...
Energy Technology Data Exchange (ETDEWEB)
Prajapati, R. P., E-mail: prajapati-iter@yahoo.co.in; Bhakta, S. [Department of Pure and Applied Physics, Guru Ghasidas Central University, Bilaspur-495009 (C.G.) (India); Chhajlani, R. K. [Retired from School of Studies in Physics, Vikram University, Ujjain-456010 (M.P.) (India)
2016-05-15
The influence of dust-neutral collisions, polarization force, and electron radiative condensation is analysed on the Jeans (gravitational) instability of partially ionized strongly coupled dusty plasma (SCDP) using linear perturbation (normal mode) analysis. The Boltzmann distributed ions, dynamics of inertialess electrons, charged dust and neutral particles are considered. Using the plane wave solutions, a general dispersion relation is derived which is modified due to the presence of dust-neutral collisions, strong coupling effect, polarization force, electron radiative condensation, and Jeans dust/neutral frequencies. In the long wavelength perturbations, the Jeans instability criterion depends upon strong coupling effect, polarization interaction parameter, and thermal loss, but it is independent of dust-neutral collision frequency. The stability of the considered configuration is analysed using the Routh–Hurwitz criterion. The growth rates of Jeans instability are illustrated, and stabilizing influence of viscoelasticity and dust-neutral collision frequency while destabilizing effect of electron radiative condensation, polarization force, and Jeans dust-neutral frequency ratio is observed. This work is applied to understand the gravitational collapse of SCDP with dust-neutral collisions.
Shimada, Yoshinori; Uchida, Shigeaki; Yamanaka, Chiyoe; Ogata, Akihisa; Yamanaka, Tatsuhiko; Kawasaki, Zen-ichiro; Fujiwara, Etsuo; Ishikubo, Yuji; Kawabata, Kinya
2000-01-01
Generation of a long laser-plasma channel capable of triggering and guiding an electrical discharge is a crucial issue for laser-triggering protection system. We make a long plasma channel to increase the probability of triggered lightning by laser. To produce a long laser plasma channel, we propose da new technique called hybrid plasma channel method which combines weakly and strongly ionized plasma channels to maximize laser-energy efficiency of discharge guiding. We investigate the characteristics of the hybrid plasma channels to maximize laser-energy efficiency of discharge guiding. We investigate the characteristics of the hybrid plasma channel method through several laboratory experiments. The weakly ionized channel was generated by UV laser pulses in air. As the number density of electrons in weakly ionized channel is proportional to 1.1 power of laser intensity, nitrogen and oxygen molecules can not attributed to the source of ionized plasma. It is suggested that dissociation process of impurities in air whose density is 1011 - 1012 cm-3 plays an important role in plasma formation and leader triggering effect. The 50 percent flashover voltage using the hybrid plasma channel method is lower than that without the weakly ionized plasma channel. It was also found that higher repetition rate of the plasma generation on lowers the V50 furthermore.
Indian Academy of Sciences (India)
Sourabh Bal; M Bose
2009-10-01
We have investigated analytically the stimulated Brillouin scattering (SBS) of an electromagnetic wave in non-dissipative weakly magnetized plasma in the presence of dust particles with variable charge.
Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas
Niemiec, Jacek; Bret, Antoine; Wieland, Volkmar
2012-01-01
We present results of 2D3V particle-in-cell simulations of non-relativistic plasma collisions with absent or parallel large-scale magnetic field for parameters applicable to the conditions at young supernova remnants. We study the collision of plasma slabs of different density, leading to two different shocks and a contact discontinuity. Electron dynamics play an important role in the development of the system. While non-relativistic shocks in both unmagnetized and magnetized plasmas can be mediated by Weibel-type instabilities, the efficiency of shock-formation processes is higher when a large-scale magnetic field is present. The electron distributions downstream of the forward and reverse shocks are generally isotropic, whereas that is not always the case for the ions. We do not see any significant evidence of pre-acceleration, neither in the electron population nor in the ion distribution.
Finite-amplitude shear-Alfv\\'en waves do not propagate in weakly magnetized collisionless plasmas
Squire, J; Schekochihin, A A
2016-01-01
It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfv\\'en fluctuations above a critical amplitude $\\delta B_{\\perp}/B_{0} \\sim \\beta^{\\,-1/2}$, where $\\beta$ is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfv\\'en-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-$\\beta$ conditions prevalent in many astrophysical plasmas, as well as for the solar wind at $\\sim 1 \\mathrm{AU}$ where $\\beta \\gtrsim 1$.
Intrinsic rotation driven by non-Maxwellian equilibria in Tokamak plasmas.
Barnes, M; Parra, F I; Lee, J P; Belli, E A; Nave, M F F; White, A E
2013-08-02
The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnetic effects, introduce a strong dependence of the radial flux of cocurrent toroidal angular momentum on collisionality: As the plasma goes from nearly collisionless to weakly collisional, the flux reverses direction from radially inward to outward. This indicates a collisionality-dependent transition from peaked to hollow rotation profiles, consistent with experimental observations of intrinsic rotation.
Intrinsic rotation driven by non-Maxwellian equilibria in tokamak plasmas
Barnes, M; Lee, J P; Belli, E A; Nave, M F F; White, A E
2013-01-01
The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnetic effects, introduce a strong dependence of the radial flux of co-current toroidal angular momentum on collisionality: As the plasma goes from nearly collisionless to weakly collisional, the flux reverses direction from radially inward to outward. This indicates a collisionality-dependent transition from peaked to hollow rotation profiles, consistent with experimental observations of intrinsic rotation.
Kourakis, I.; Elkamash, I. S.
2016-10-01
In a recent article (J. Plasma Phys., vol. 82, 2009, 905820104), weakly dissipative dust-ion acoustic wave modulation in dusty plasmas was considered. It is shown in this Comment that the analysis therein involved severe fallacies, and is in fact based on an erroneous plasma fluid model, which fails to satisfy an equilibrium condition, among other shortcomings. The subsequent analysis therefore is dubious and of limited scientific value.
Strong Helioseismic Constraints on Weakly-Coupled Plasmas
Nayfonov, Alan
The extraordinary accuracy of helioseismic data allows detailed theoretical studies of solar plasmas. The necessity to produce solar models matching the experimental results in accuracy imposes strong constrains on the equations of state of solar plasmas. Several discrepancies between the experimental data and models have been successfully identified as the signatures of various non-ideal phenomena. Of a particular interest are questions of the position of the energy levels and the continuum edge and of the effect of the excited states in the solar plasma. Calculations of energy level and continuum shifts, based on the Green function formalism, appeared recently in the literature. These results have been used to examine effects of the shifts on the thermodynamic quantities. A comparison with helioseismic data has shown that the calculations based on lower-level approximations, such as the static screening in the effective two-particle wave equation, agree very well with the experimental data. However, the case of full dynamic screening produces thermodynamic quantities inconsistent with observations. The study of the effect of different internal partition functions on a complete set of thermodynamic quantities has revealed the signature of the excited states in the MHD (Mihalas, Hummer, Dappen) equation of state. The presence of exited states causes a characteristic 'wiggle' in the thermodynamic quantities due to the density-dependent occupation probabilities. This effect is absent if the ACTEX (ACTivity EXpansion) equation of state is used. The wiggle has been found to be most prominent in the quantities sensitive to density. The size of this excited states effect is well within the observational power of helioseismology, and very recent inversion analyses of helioseismic data seem to indicate the presence of the wiggle in the sun. This has a potential importance for the helioseismic determination of the helium abundance of the sun.
Evdokimov, K. E.; Konishchev, M. E.; Pichugin, V. F.; Pustovalova, A. A.; Ivanova, N. M.; Sun', Ch.
2017-09-01
A method for determining the electron temperature and electron density in a plasma is proposed that is based on minimization of the difference between the experimental relative intensities of the spectral argon (Ar) lines and those same intensities calculated with the aid of the collisional-radiative model. The model describes the kinetics of the ground state and 40 excited states of the Ar atom and takes into account the following processes: excitation and deactivation of the states of the atom by electron impact, radiative decay of the excited states, self-absorption of radiation, ionization of excited states by electron impact, and quenching of metastable states as a consequence of collisions with the chamber walls. Using the given method, we have investigated the plasma of a magnetron discharge on a laboratory setup for intermediate-frequency magnetron sputtering for a few selected operating regimes.
Alekseeva, L M
2015-01-01
The dynamical coupling between the solar chromospheric plasma and magnetic field is investigated by numerically solving a fully self-consistent, two-dimensional initial-value problem for the nonlinear collisional MHD equations including electric resistivity, thermal conduction, and, in some cases, gas-dynamic viscosity. The processes in the contact zone between two horizontal magnetic fields of opposite polarities are considered. The plasma is assumed to be initially motionless and having a temperature of 50,000 K uniform throughout the plasma volume; the characteristic magnetic field corresponds to a plasma $\\beta\\gtrsim 1$. In a physical-time interval of 17~seconds typically covered by a computational run, the plasma temperature gradually increases by a factor of two to three. Against this background, an impulsive (in 0.1 seconds or less) increase in the current-aligned plasma velocity occurs at the site of the current-layer thinning (sausage-type deformation, or $m=0$ pinch instability). Such a "velocity b...
Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field
Ratushnaya, Valeria
2016-12-17
We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.
Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field
Ratushnaya, Valeria; Samtaney, Ravi
2016-12-01
We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.
Yanai, Ryoma; Kaminou, Yasuhiro; Nishida, Kento; Inomoto, Michiaki
2016-10-01
Magnetic reconnection is a universal phenomenon which determines global structure and energy conversion in magnetized plasmas. Many experimental studies have been carried out to explore the physics of magnetic reconnection in fully ionized condition. However, it is predicted that the behavior of magnetic reconnection in weakly ionized plasmas such as solar chromosphere plasma will show different behavior such as ambipolar diffusion caused by interaction with neutral particles. In this research, we are developing a new experimental device to uncover the importance of ambipolar diffusion during magnetic reconnection in weakly ionized plasmas. We employ an inverter-driven rotating magnetic fields technique, which is used for generating steady azimuthal plasma current, to establish long-duration ( 1 ms) anti-parallel reconnection with magnetic field of 5 mT in weakly ionized plasma. We will present development status and initial results from the new experimental setup. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus'', Giant-in Aid for Scientific Research (KAKENHI) 15H05750, 15K14279, 26287143 and the NIFS Collaboration Research program (NIFS14KNWP004).
Hafez, M. G.; Talukder, M. R.; Hossain Ali, M.
2017-04-01
The Burgers equation is obtained to study the characteristics of nonlinear propagation of ionacoustic shock, singular kink, and periodic waves in weakly relativistic plasmas containing relativistic thermal ions, nonextensive distributed electrons, Boltzmann distributed positrons, and kinematic viscosity of ions using the well-known reductive perturbation technique. This equation is solved by employing the ( G'/ G)-expansion method taking unperturbed positron-to-electron concentration ratio, electron-to-positron temperature ratio, strength of electrons nonextensivity, ion kinematic viscosity, and weakly relativistic streaming factor. The influences of plasma parameters on nonlinear propagation of ion-acoustic shock, periodic, and singular kink waves are displayed graphically and the relevant physical explanations are described. It is found that these parameters extensively modify the shock structures excitation. The obtained results may be useful in understanding the features of small but finite amplitude localized relativistic ion-acoustic shock waves in an unmagnetized plasma system for some astrophysical compact objects and space plasmas.
Scaling theory of relative diffusion of charged particles in a weakly magneto-turbulent plasma
Energy Technology Data Exchange (ETDEWEB)
Haida Wang (University of Science and Technology of China, Hefei, Anhui. Dept. of Modern Physics); Xiaoming Qui (Southwest Inst. of Physics, Leshan, SC (China))
1989-02-01
Stochastic motion of charged particles in a magneto-turbulent plasma is studied for the whole time region. A set of nonlinear differential equations for describing relative spatial diffusion of charged particles is derived and some explicit results are obtained in the case of a weak magnetic field. It is found that, for the diffusion in the present system there are some new and interesting properties which do not exist in an unmagnetized plasma. The clump effect is also discussed. (author).
Vauzour, B; Santos, J J; Debayle, A; Hulin, S; Schlenvoigt, H-P; Vaisseau, X; Batani, D; Baton, S D; Honrubia, J J; Nicolaï, Ph; Beg, F N; Benocci, R; Chawla, S; Coury, M; Dorchies, F; Fourment, C; d'Humières, E; Jarrot, L C; McKenna, P; Rhee, Y J; Tikhonchuk, V T; Volpe, L; Yahia, V
2012-12-21
We present experimental and numerical results on intense-laser-pulse-produced fast electron beams transport through aluminum samples, either solid or compressed and heated by laser-induced planar shock propagation. Thanks to absolute K(α) yield measurements and its very good agreement with results from numerical simulations, we quantify the collisional and resistive fast electron stopping powers: for electron current densities of ≈ 8 × 10(10) A/cm(2) they reach 1.5 keV/μm and 0.8 keV/μm, respectively. For higher current densities up to 10(12)A/cm(2), numerical simulations show resistive and collisional energy losses at comparable levels. Analytical estimations predict the resistive stopping power will be kept on the level of 1 keV/μm for electron current densities of 10(14)A/cm(2), representative of the full-scale conditions in the fast ignition of inertially confined fusion targets.
Energy Technology Data Exchange (ETDEWEB)
Smith, R F; Dunn, J; Filevich, J; Moon, S; Nilsen, J; Keenan, R; Shlyaptsev, V N; Rocca, J J; Hunter, J R; Marconi, M C
2004-10-04
We have directly probed the plasma conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates by measuring the near-field image and by utilizing picosecond resolution soft x-ray laser interferometry of the preformed Pd plasma gain medium. The electron density and gain region of the plasma have been determined experimentally and are found to be in good agreement with simulations. We observe a strong dependence of the laser pump-gain medium coupling on the laser pump parameters. The most efficient coupling of laser pump energy into the gain region occurs with the formation of lower density gradients in the pre-formed plasma and when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for mid-Z Ni-like schemes). This increases the output intensity by more than an order of magnitude relative to the commonly utilized case where the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). In contrast, the higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions where steep density gradients limit the effective length of the gain medium.
Lattice-Boltzmann simulation of laser interaction with weakly ionized helium plasmas.
Li, Huayu; Ki, Hyungson
2010-07-01
This paper presents a lattice Boltzmann method for laser interaction with weakly ionized plasmas considering electron impact ionization and three-body recombination. To simulate with physical properties of plasmas, the authors' previous work on the rescaling of variables is employed and the electromagnetic fields are calculated from the Maxwell equations by using the finite-difference time-domain method. To calculate temperature fields, energy equations are derived separately from the Boltzmann equations. In this way, we attempt to solve the full governing equations for plasma dynamics. With the developed model, the continuous-wave CO2 laser interaction with helium is simulated successfully.
Polarization forces in the vicinity of nanoparticles in weakly ionized plasma
Shneider, M N
2016-01-01
It is shown that the polarization forces in a weakly ionized plasma lead to a substantial increase in the fluxes of neutral atoms and molecules to the surface of charged nanoparticles. Thus, the nanoparticles can change thermal balance due to the acceleration of atoms and molecules in the dipole potential and subsequent inelastic collisions to the nanoparticles.
Optimal electric potential profile in a collisional magnetized thruster
Fruchtman, Amnon; Makrinich, Gennady
2016-10-01
A major figure of merit in propulsion in general and in electric propulsion in particular is the thrust per unit of deposited power, the ratio of thrust over power. We have recently demonstrated experimentally and theoretically that for a fixed deposited power in the ions, the momentum delivered by the electric force is larger if the accelerated ions collide with neutrals during the acceleration. As expected, the higher thrust for given power is achieved for a collisional plasma at the expense of a lower thrust per unit mass flow rate. Operation in the collisional regime can be advantageous for certain space missions. We analyze a Hall thruster configuration in which the flow is only weakly ionized but there are frequent ion-neutral collisions. With a variational method we seek an electric potential profile that maximizes thrust over power. We then examine what radial magnetic field profile should determine such a potential profile. Supported by the Israel Science Foundation Grant 765/11.
Nonlinear propagation of weakly relativistic ion-acoustic waves in electron–positron–ion plasma
Indian Academy of Sciences (India)
M G HAFEZ; M R TALUKDER; M HOSSAIN ALI
2016-11-01
This work presents theoretical and numerical discussion on the dynamics of ion-acoustic solitary wave for weakly relativistic regime in unmagnetized plasma comprising non-extensive electrons, Boltzmann positrons and relativistic ions. In order to analyse the nonlinear propagation phenomena, the Korteweg–de Vries(KdV) equation is derived using the well-known reductive perturbation method. The integration of the derived equation is carried out using the ansatz method and the generalized Riccati equation mapping method. The influenceof plasma parameters on the amplitude and width of the soliton and the electrostatic nonlinear propagation of weakly relativistic ion-acoustic solitary waves are described. The obtained results of the nonlinear low-frequencywaves in such plasmas may be helpful to understand various phenomena in astrophysical compact object and space physics.
Gangwar, Reetesh K.; Dipti; Srivastava, Rajesh; Stafford, Luc
2016-06-01
A collisional-radiative (C-R) model for krypton plasma using fully relativistic distorted-wave cross sections for electron excitations was developed. The model was applied to the characterization of inductively coupled Kr plasma with cylindrical geometry over the pressure regime 1-50 mTorr. Radially averaged emission intensities from transitions of Kr (4p55p → 4p55s) in the range 500-900 nm were recorded at 17 cm from the planar RF-driven coil, with the plasma operated in the inductive regime (H mode). The measured emission intensities were then fitted by varying the electron density, n e, and electron temperature, T e, in the C-R model. At both low and high pressures, variations of the electron density by over two orders of magnitude had only a minor role on the relative emission intensities. On the other hand, T e values deduced from the comparison between experiment and model decreased from 6.7 to 2.6 eV as pressure increased from 1 to 50 mTorr. These results are found to be in good agreement with the effective electron temperature determined from Langmuir probe measurements and the predictions of a model based on the particle balance equation of charged particles.
Longitudinal singular response of dusty plasma medium in weak and strong coupling limits
Energy Technology Data Exchange (ETDEWEB)
Kumar Tiwari, Sanat; Das, Amita; Kaw, Predhiman; Sen, Abhijit [Institute for Plasma Research, Bhat, Gandhinagar - 382428 (India)
2012-01-15
The longitudinal response of a dusty plasma medium in both weak and strong coupling limits has been investigated in detail using analytic as well as numerical techniques. In particular, studies on singular response of the medium have been specifically investigated here. A proper Galilean invariant form of the generalized hydrodynamic fluid model has been adopted for the description of the dusty plasma medium. For weak non-linear response, analytic reductive perturbative approach has been adopted. It is well known that in the weak coupling regime for the dusty plasma medium, such an analysis leads to the Korteweg-de Vries equation (KdV) equation and predicts the existence of localized smooth soliton solutions. We show that the strongly coupled dust fluid with the correct Galilean invariant form does not follow the KdV paradigm. Instead, it reduces to the form of Hunter-Saxton equation, which does not permit soliton solutions. The system in this case displays singular response with both conservative as well as dissipative attributes. At arbitrary high amplitudes, the existence and spontaneous formation of sharply peaked cusp structures in both weak and strong coupling regimes has been demonstrated numerically.
Three species one-dimensional kinetic model for weakly ionized plasmas
Gonzalez, J; Tierno, S P
2016-01-01
A three species one-dimensional kinetic model is presented for a spatially homogeneous weakly ionized plasma subjected to the action of a time varying electric field. Planar geometry is assumed, which means that the plasma dynamics evolves in the privileged direction of the field. The energy transmitted to the charges is be channelized to the neutrals thanks to collisions and impacting the plasma dynamics. Charge-charge interactions have been designed as a one dimensional collision term equivalent to the Landau operator used for fully ionized plasmas. Charge-neutral collisions are modelled by a conservative drift diffusion operator in the Doughertys form. The resulting set of coupled drift diffusion equations is solved with the stable and robust Propagator Integral Method. This method feasibility accounts for non-linear effects without appealing to linearisation or simplifications, providing conservative physically meaningful solutions. It is found that charge neutral collisions exert a significant effect sin...
Mass Hierarchy of Collisional Energy Loss
Kolevatov, Rodion
2008-01-01
Collisional parton energy loss is revisited within a simple model assuming incoherent elastic scattering of on-shell projectile partons on partonic constituents of the QGP with HTL screening. The thermal motion of plasma particles is carefully taken into account. Results on $dE/dx$ are found to be consistent with other authors. There is a significant discrepancy in the energy loss pattern for the cases with thermal motion on and off, which illustrates the importance of taking the kinematics into account exactly. The dependence on the mass of the partons forming the plasma is included in the calculations and its influence on the collisional energy loss is studied. The mass hierarchy of collisional energy loss is found to have a strong dependence on the mass introduced for plasma particles. Due to difference in the mass hierarchy with radiative energy loss, the collisional one when included increases the relative suppression of heavy quarks compared to light quarks.
Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma
Energy Technology Data Exchange (ETDEWEB)
Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Roychoudhury, Rajkumar [Indian Statistical Institute, Kolkata-700 108 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar Kolkata-700 064 (India)
2013-01-15
Nonlinear propagation of electron acoustic waves in homogeneous, dispersive plasma medium with two temperature electron species is studied in presence of externally applied magnetic field. The linear dispersion relation is found to be modified by the externally applied magnetic field. Lagrangian transformation technique is applied to carry out nonlinear analysis. For small amplitude limit, a modified KdV equation is obtained, the modification arising due to presence of magnetic field. For weakly magnetized plasma, the modified KdV equation possesses stable solitary solutions with speed and amplitude increasing temporally. The solutions are valid upto some finite time period beyond which the nonlinear wave tends to wave breaking.
Chen, Qiang; Chen, Bin
2012-10-01
In this paper, a hybrid electrodynamics and kinetics numerical model based on the finite-difference time-domain method and lattice Boltzmann method is presented for electromagnetic wave propagation in weakly ionized hydrogen plasmas. In this framework, the multicomponent Bhatnagar-Gross-Krook collision model considering both elastic and Coulomb collisions and the multicomponent force model based on the Guo model are introduced, which supply a hyperfine description on the interaction between electromagnetic wave and weakly ionized plasma. Cubic spline interpolation and mean filtering technique are separately introduced to solve the multiscalar problem and enhance the physical quantities, which are polluted by numerical noise. Several simulations have been implemented to validate our model. The numerical results are consistent with a simplified analytical model, which demonstrates that this model can obtain satisfying numerical solutions successfully.
Collisional Excitation and De-Excitation of N2 and N2+ in High-Pressure Discharge Plasmas
Kurunczi, P.; Abramzon, N.; Figus, M.; Becker, K.
2003-05-01
Emission spectroscopy using the 2nd positive system of N2 and the 1st negative system of N2+ can be used to determine important plasma parameters such the translational, vibrational, and rotational temperatures of the plasma species. The rotational temperature is perhaps the most frequently determined quantity as its determination may reflect the gas temperature in the plasma and/or provide insight into the reaction kinetics of important plasma species. If the emitting species are in equilibrium with the bulk gas in the plasma, then this temperature can be interpreted as the gas kinetic temperature in the plasma. We determined rotational temperatures for N2 and N2+ in high-pressure (400 Torr) discharges in mixtures in Ne with a trace admixture of N2. Significantly different values were obtained for respectively N2 and N2+. The relation of these rotational temperatures to the gas kinetic temperature and to the reaction kinetics leading to the formation and the decay of the emitting species will be discussed. We also carried out a rotational analysis of the unresolved N2 second positive system emitted by an atmospheric-pressure capillary plasma electrode (CPE) discharge in ambient air. Work supported by the US National Science Foundation.
Energy Technology Data Exchange (ETDEWEB)
Morrison, P.J., E-mail: morrison@physics.utexas.edu [Department of Physics and Institute for Fusion Studies, University of Texas, Austin (United States); Vanneste, J. [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh (United Kingdom)
2016-05-15
A method, called beatification, is presented for rapidly extracting weakly nonlinear Hamiltonian systems that describe the dynamics near equilibria of systems possessing Hamiltonian form in terms of noncanonical Poisson brackets. The procedure applies to systems like fluids and plasmas in terms of Eulerian variables that have such noncanonical Poisson brackets, i.e., brackets with nonstandard and possibly degenerate form. A collection of examples of both finite and infinite dimensions is presented.
Weakly nonlinear ion-acoustic excitations in a relativistic model for dense quantum plasma.
Behery, E E; Haas, F; Kourakis, I
2016-02-01
The dynamics of linear and nonlinear ionic-scale electrostatic excitations propagating in a magnetized relativistic quantum plasma is studied. A quantum-hydrodynamic model is adopted and degenerate statistics for the electrons is taken into account. The dispersion properties of linear ion acoustic waves are examined in detail. A modified characteristic charge screening length and "sound speed" are introduced, for relativistic quantum plasmas. By employing the reductive perturbation technique, a Zakharov-Kuznetzov-type equation is derived. Using the small-k expansion method, the stability profile of weakly nonlinear slightly supersonic electrostatic pulses is also discussed. The effect of electron degeneracy on the basic characteristics of electrostatic excitations is investigated. The entire analysis is valid in a three-dimensional as well as in two-dimensional geometry. A brief discussion of possible applications in laboratory and space plasmas is included.
Vaishnav, Bhushit; Joshipura, K. N.; Gangopadhyay, S.
2007-10-01
Plasma screening effects on electron induced atomic collision properties have attracted considerable research attention, because of applications in inertial confinement fusion and X-ray lasers etc. The theoretical interest is to examine the ionization of atomic/molecular targets by the impact of electrons in plasma. Basically the electron scattering problem is treated in a semi-empirical approach in the complex scattering potential ionization contribution (CSP-ic), to calculate total ionization cross section as a dominant part of total inelastic cross sections. This approach has been successful for number of (free) atomic and molecular targets in [1]. This paper extends the method to the collision processes in plasma and the relative contribution of ionization has been identified. We consider He^+ ion embedded in weak plasma. The static potential of the e-He^+ system in plasma environment is derived by us. Results will be discussed in the Conference. References: [1] K N Joshipura, Bhushit G Vaishnav and Sumona Gangopadhyay, Int. J. Mass. Spectrom. 261 (2007) 146.
Studies of instability and transport in tokamak plasmas with very weak magnetic shear
Energy Technology Data Exchange (ETDEWEB)
Dong, J.Q.; Zhang, Y.Z. [Southwestern Inst. of Physics, Chengdu (China)]|[International Center for Theoretical Physics, Trieste (Italy); Mahajan, S.M. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies
1997-04-01
Ion temperature gradient (ITG or {eta}{sub i}) driven microinstabilities are studied, using kinetic theory, for tokamak plasmas with very weak (positive or negative) magnetic shear (VWS). The gradient of magnetic shear as well as the effects of parallel and perpendicular velocity shear (v{prime}{sub {parallel}} and v{prime}{sub E}) are included in the defining equations. Two eigenmodes: the double (D) and the global (G) are found to coexist. Parametric dependence of these instabilities, and of the corresponding quasilinear transport is systematically analyzed. It is shown that, in VWS plasmas, a parallel velocity shear (PVS) may stabilize or destabilize the modes, depending on the individual as well as the relative signs of PVS and of the gradient of magnetic shear. The quasilinear transport induced by the instabilities may be significantly reduced with PVS in VWS plasmas. The v{prime}{sub E} values required to completely suppress the instabilities are much lower in VWS plasmas than they are in normal plasmas. Possible correlations with tokamak experiments are discussed.
Nobuto, Kyosuke; Mizui, Yasutaka; Miyagi, Shigeyuki; Sakai, Osamu; Murakami, Tomoyuki
2016-09-01
We visualize complicated chemical reaction systems in weakly-ionized plasmas by analysing network structure for chemical processes, and calculate some indexes by assuming interspecies relationships to be a network to clarify them. With the current social evolution, the mean size of general data which we can use in computers grows huge, and significance of the data analysis increases. The methods of the network analysis which we focus on in this study do not depend on a specific analysis target, but the field where it has been already applied is still limited. In this study, we analyse chemical reaction systems in plasmas for configuring the network structure. We visualize them by expressing a reaction system in a specific plasma by a directed graph and examine the indexes and the relations with the characteristic of the species in the reaction system. For example, in the methane plasma network, the centrality index reveals importance of CH3 in an influential position of species in the reaction. In addition, silane and atmospheric pressure plasmas can be also visualized in reaction networks, suggesting other characteristics in the centrality indexes.
Three species one-dimensional kinetic model for weakly ionized plasmas
Gonzalez, J.; Donoso, J. M.; Tierno, S. P.
2016-06-01
A three species one-dimensional kinetic model is presented for a spatially homogeneous weakly ionized plasma subjected to the action of a time varying electric field. Planar geometry is assumed, which means that the plasma evolves in the privileged direction of the field. The energy transmitted to the electric charges is channelized to the neutrals thanks to collisions, a mechanism that influences the plasma dynamics. Charge-charge interactions have been designed as a one-dimensional collision term equivalent to the Landau operator used for fully ionized plasmas. Charge-neutral collisions are modelled by a conservative drift-diffusion operator in the Dougherty's form. The resulting set of coupled integro-differential equations is solved with the stable and robust propagator integral method. This semi-analytical method feasibility accounts for non-linear effects without appealing to linearisation or simplifications, providing conservative physically meaningful solutions even for initial or emerging sharp velocity distribution function profiles. It is found that charge-neutral collisions exert a significant effect since a quite different plasma evolution arises if compared to the collisionless limit. In addition, substantial differences in the system motion are found for constant and temperature dependent collision frequencies cases.
Three species one-dimensional kinetic model for weakly ionized plasmas
Energy Technology Data Exchange (ETDEWEB)
Gonzalez, J., E-mail: jorge.gonzalez@upm.es; Donoso, J. M.; Tierno, S. P. [Department of Applied Physics, Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio, Universidad Politécnica de Madrid, 28040 Madrid (Spain)
2016-06-15
A three species one-dimensional kinetic model is presented for a spatially homogeneous weakly ionized plasma subjected to the action of a time varying electric field. Planar geometry is assumed, which means that the plasma evolves in the privileged direction of the field. The energy transmitted to the electric charges is channelized to the neutrals thanks to collisions, a mechanism that influences the plasma dynamics. Charge-charge interactions have been designed as a one-dimensional collision term equivalent to the Landau operator used for fully ionized plasmas. Charge-neutral collisions are modelled by a conservative drift-diffusion operator in the Dougherty's form. The resulting set of coupled integro-differential equations is solved with the stable and robust propagator integral method. This semi–analytical method feasibility accounts for non–linear effects without appealing to linearisation or simplifications, providing conservative physically meaningful solutions even for initial or emerging sharp velocity distribution function profiles. It is found that charge-neutral collisions exert a significant effect since a quite different plasma evolution arises if compared to the collisionless limit. In addition, substantial differences in the system motion are found for constant and temperature dependent collision frequencies cases.
Guo, Shimin; Mei, Liquan; He, Ya-Ling; Ma, Chenchen; Sun, Youfa
2016-10-01
The nonlinear behavior of an ion-acoustic wave packet is investigated in a three-component plasma consisting of warm ions, nonthermal electrons and positrons. The nonthermal components are assumed to be inertialess and hot where they are modeled by the kappa distribution. The relevant processes, including the kinematic viscosity amongst the plasma constituents and the collision between ions and neutrals, are taken into consideration. It is shown that the dynamics of the modulated ion-acoustic wave is governed by the generalized complex Ginzburg-Landau equation with a linear dissipative term. The dispersion relation and modulation instability criterion for the generalized complex Ginzburg-Landau equation are investigated numerically. In the general dissipation regime, the effect of the plasma parameters on the dissipative solitary (dissipative soliton) and shock waves is also discussed in detail. The project is supported by NSF of China (11501441, 11371289, 11371288), National Natural Science Foundation of China (U1261112), China Postdoctoral Science Foundation (2014M560756), and Fundamental Research Funds for the Central Universities (xjj2015067).
Rincon, F; Schekochihin, A A; Valentini, F
2015-01-01
Magnetic fields pervade the entire Universe and, through their dynamical interactions with matter, affect the formation and evolution of astrophysical systems from cosmological to planetary scales. How primordial cosmological seed fields arose and were further amplified to $\\mu$Gauss levels reported in nearby galaxy clusters, near equipartition with kinetic energy of plasma motions and on scales of at least tens of kiloparsecs, is a major theoretical puzzle still largely unconstrained by observations. Extragalactic plasmas are weakly collisional (as opposed to collisional magnetohydrodynamic fluids), and whether magnetic-field growth and its sustainment through an efficient dynamo instability driven by chaotic motions is possible in such plasmas is not known. Fully kinetic numerical simulations of the Vlasov equation in a six-dimensional phase space necessary to answer this question have until recently remained beyond computational capabilities. Here, we show by means of such simulations that magnetic-field a...
Jeans stability in collisional quantum dusty magnetoplasmas
Energy Technology Data Exchange (ETDEWEB)
Jamil, M.; Asif, M. [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Mir, Zahid [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Faculty of Engineering and Technology, Superior University, Lahore 54000 (Pakistan); Salimullah, M. [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh)
2014-09-15
Jeans instability is examined in detail in uniform dusty magnetoplasmas taking care of collisional and non-zero finite thermal effects in addition to the quantum characteristics arising through the Bohm potential and the Fermi degenerate pressure using the quantum hydrodynamic model of plasmas. It is found that the presence of the dust-lower-hybrid wave, collisional effects of plasma species, thermal effects of electrons, and the quantum mechanical effects of electrons have significance over the Jeans instability. Here, we have pointed out a new class of dissipative instability in quantum plasma regime.
The diffusion of charged particles in the weakly ionized plasma with power-law kappa-distributions
Wang, Lan; Du, Jiulin
2017-10-01
We study the diffusion of charged particles in the weakly ionized plasma with the power-law κ-distributions and without the magnetic field. The electrons and ions have different κ-parameters. We obtain the expressions of both diffusion and mobility coefficients of electrons and ions respectively in the plasma. We find that these new transport coefficient formulae depend strongly on the κ-parameters in the power-law distributed plasma. When we take κ→∞, these formulae reduce to the classical forms in the weakly ionized plasma with a Maxwellian distribution.
Existence of Global Weak Solutions to a Hybrid Vlasov-MHD Model for Magnetized Plasmas
Cheng, Bin; Tronci, Cesare
2016-01-01
We prove the global-in-time existence of large-data finite-energy weak solutions to an incompressible hybrid Vlasov-magnetohydrodynamic model in three space dimensions. The model couples three essential ingredients of magnetized plasmas: a transport equation for the probability density function, which models energetic rarefied particles of one species; the incompressible Navier--Stokes system for the bulk fluid; and a parabolic evolution equation, involving magnetic diffusivity, for the magnetic field. The physical derivation of our model is given. It is also shown that the weak solution, whose existence is established, has nonincreasing total energy, and that it satisfies a number of physically relevant properties, including conservation of the total momentum, conservation of the total mass, and nonnegativity of the probability density function for the energetic particles. The proof is based on a one-level approximation scheme, which is carefully devised to avoid increase of the total energy for the sequence...
Instability saturation by the oscillating two-stream instability in a weakly relativistic plasma
Energy Technology Data Exchange (ETDEWEB)
Pal, Barnali; Poria, Swarup, E-mail: swarup-p@yahoo.com [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Sahu, Biswajit, E-mail: biswajit-sahu@yahoo.co.in [Department of Mathematics, West Bengal State University, Barasat, Kolkata 700126 (India)
2015-04-15
The two-stream instability has wide range of astrophysical applications starting from gamma-ray bursts and pulsar glitches to cosmology. We consider one dimensional weakly relativistic Zakharov equations and describe nonlinear saturation of the oscillating two-stream instability using a three dimensional dynamical system resulting form a truncation of the nonlinear Schrodinger equation to three modes. The equilibrium points of the model are determined and their stability natures are discussed. Using the tools of nonlinear dynamics such as the bifurcation diagram, Poincaré maps, and Lyapunav exponents, existence of periodic, quasi-periodic, and chaotic solutions are established in the dynamical system. Interestingly, we observe the multistable behavior in this plasma model. The system has multiple attractors depending on the initial conditions. We also notice that the relativistic parameter plays the role of control parameter in the model. The theoretical results presented in this paper may be helpful for better understanding of space and astrophysical plasmas.
Institute of Scientific and Technical Information of China (English)
Song Falun; Cao Jinxiang; Wang Ge
2005-01-01
The purpose of the present work is to present a full-wave analysis of scattering from the weakly ionized plasma in the plane geometry. We have yielded an approximate solution in an analytic form to the electromagnetic wave scattering from the weakly ionizsd plasma. In the normal and oblique incidence, the analytic solution works well, as compared with the exact solution and the solution based on the Wenzell-Kramers-Brillouin-Jeffreys (WKBJ) approximation to the uniform density profile.
Chaoticity threshold in magnetized plasmas: Numerical results in the weak coupling regime
Energy Technology Data Exchange (ETDEWEB)
Carati, A., E-mail: andrea.carati@unimi.it; Benfenati, F.; Maiocchi, A.; Galgani, L. [Università degli Studi di Milano, Milano (Italy); Zuin, M., E-mail: matteo.zuin@igi.cnr.it [Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, Padova (Italy)
2014-03-15
The present paper is a numerical counterpart to the theoretical work [Carati et al., Chaos 22, 033124 (2012)]. We are concerned with the transition from order to chaos in a one-component plasma (a system of point electrons with mutual Coulomb interactions, in a uniform neutralizing background), the plasma being immersed in a uniform stationary magnetic field. In the paper [Carati et al., Chaos 22, 033124 (2012)], it was predicted that a transition should take place when the electron density is increased or the field decreased in such a way that the ratio ω{sub p}/ω{sub c} between plasma and cyclotron frequencies becomes of order 1, irrespective of the value of the so-called Coulomb coupling parameter Γ. Here, we perform numerical computations for a first principles model of N point electrons in a periodic box, with mutual Coulomb interactions, using as a probe for chaoticity the time-autocorrelation function of magnetization. We consider two values of Γ (0.04 and 0.016) in the weak coupling regime Γ ≪ 1, with N up to 512. A transition is found to occur for ω{sub p}/ω{sub c} in the range between 0.25 and 2, in fairly good agreement with the theoretical prediction. These results might be of interest for the problem of the breakdown of plasma confinement in fusion machines.
Alfvenic Ion Temperature Gradient Activities in a Weak Magnetic Shear Plasma
Chen, W; Li, Y Y; Shi, Z B; Du, H R; Jiang, M; Yu, L M; Yuan, B S; Li, Y G; Yang, Z C; Shi, P W; Ding, X T; Dong, J Q; Liu, Yi; Xu, M; Xu, Y H; Yang, Q W; Duan, X R
2016-01-01
We report the first experimental evidence of Alfvenic ion temperature gradient (AITG) modes in HL-2A Ohmic plasmas. A group of oscillations with $f=15-40$ kHz and $n=3-6$ is detected by various diagnostics in high-density Ohmic regimes. They appear in the plasmas with peaked density profiles and weak magnetic shear, which indicates that corresponding instabilities are excited by pressure gradients. The time trace of the fluctuation spectrogram can be either a frequency staircase, with different modes excited at different times or multiple modes may simultaneously coexist. Theoretical analyses by the extended generalized fishbone-like dispersion relation (GFLDR-E) reveal that mode frequencies scale with ion diamagnetic drift frequency and $\\eta_i$, and they lie in KBM-AITG-BAE frequency ranges. AITG modes are most unstable when the magnetic shear is small in low pressure gradient regions. Numerical solutions of the AITG/KBM equation also illuminate why AITG modes can be unstable for weak shear and low pressure...
Electrical conductivity of a methane-air burning plasma under the action of weak electric fields
Colonna, G.; Pietanza, L. D.; D'Angola, A.; Laricchiuta, A.; Di Vita, A.
2017-02-01
This paper focuses on the calculation of the electrical conductivity of a methane-air flame in the presence of weak electric fields, solving the Boltzmann equation for free electrons self-consistently coupled with chemical kinetics. The chemical model GRI-Mech 3.0 has been completed with chemi-ionization reactions to model ionization in the absence of fields, and a database of cross sections for electron-impact-induced processes to account for reactions and transitions activated in the flame during discharge. The dependence of plasma properties on the frequency of an oscillating field has been studied under different pressure and gas temperature conditions. Fitting expressions of the electrical conductivity as a function of gas temperature and methane consumption are provided for different operational conditions in the Ansaldo Energia burner.
Spin Polarized Photons from Axially Charged Plasma at Weak Coupling: Complete Leading Order
Mamo, Kiminad A
2015-01-01
In the presence of (approximately conserved) axial charge in the QCD plasma at finite temperature, the emitted photons are spin-aligned, which is a unique P- and CP-odd signature of axial charge in the photon emission observables. We compute this "P-odd photon emission rate" in weak coupling regime at high temperature limit to complete leading order in the QCD coupling constant: the leading log as well as the constant under the log. As in the P-even total emission rate in the literature, the computation of P-odd emission rate at leading order consists of three parts: 1) Compton and Pair Annihilation processes with hard momentum exchange, 2) soft t- and u-channel contributions with Hard Thermal Loop re-summation, 3) Landau-Pomeranchuk-Migdal (LPM) re-summation of collinear Bremstrahlung and Pair Annihilation. We present analytical and numerical evaluations of these contributions to our P-odd photon emission rate observable.
The efficiency of fast wave current drive for a weakly relativistic plasma
Chiu, S. C.; Lin-Liu, Y. R.; Karney, C. F. F.
1994-10-01
Current drive by fast waves (FWCD) is an important candidate for steady-state operation of tokamaks. Major experiments using this scheme are being carried out on DIII-D. There has been considerable study of the theoretical efficiency of FWCD. In Refs. 4 and 5, the nonrelativistic efficiency of FWCD at arbitrary frequencies was studied. For DIII-D parameters, the results can be considerably different from the Landau and Alfvén limits. At the high temperatures of reactors and DIII-D upgrade, relativistic effects become important. In this paper, the relativistic FWCD efficiency for arbitrary frequencies is studied. Assuming that the plasma is weakly relativistic, i.e., Te/mc2 is small, an analytic expression for FWCD is obtained for high resonant energies (uph/uTe≫1). Comparisons with the results from a numerical code ADJ and the nonrelativistic results shall be made and analytical fits in the whole range of velocities shall be presented.
Islam, Rokibul; Xie, Shuzheng; Englund, Karl; Pedrow, Patrick
2014-10-01
A grounded screen with short needle-like protrusions has been designed to generate back corona in an Atmospheric Pressure Weakly Ionized Plasma (APWIP) reactor. The grounded screen with protrusions is placed downstream at a variable gap length from an array of needles that is energized with 60 Hz high voltage. The excitation voltage is in the range 0--10 kV RMS and the feed gas mixture consists of argon and acetylene. A Lecroy 9350AL 500 MHz digital oscilloscope is used to monitor the reactor voltage and current using a resistive voltage divider and a current viewing resistor, respectively. The current signal contains many positive and negative current pulses associated with corona discharge. Analysis of the current signal shows asymmetry between positive and negative corona discharge currents. Photographs show substantial back corona generated near the tips of the protrusions situated at the grounded screen. The back corona activates via bond scission acetylene radicals that are transported downstream to form a plasma-polymerized film on a substrate positioned downstream from the grounded screen. The oscillograms will be used to generate corona mode maps that show the nature of the corona discharge as a function of gap spacing, applied voltage and many other reactor parameters.
Oblique non-neutral solitary Alfven modes in weakly nonlinear pair plasmas
Energy Technology Data Exchange (ETDEWEB)
Verheest, Frank [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium); School of Physics, Howard College Campus, University of KwaZulu-Natal, Durban 4041 (South Africa); Lakhina, G S [Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410218 (India); Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
2005-04-01
The equal charge-to-mass ratio for both species in pair plasmas induces a decoupling of the linear eigenmodes between waves that are charge neutral or non-neutral, also at oblique propagation with respect to a static magnetic field. While the charge-neutral linear modes have been studied in greater detail, including their weakly and strongly nonlinear counterparts, the non-neutral mode has received less attention. Here the nonlinear evolution of a solitary non-neutral mode at oblique propagation is investigated in an electron-positron plasma. Employing the framework of reductive perturbation analysis, a modified Korteweg-de Vries equation (with cubic nonlinearity) for the lowest-order wave magnetic field is obtained. In the linear approximation, the non-neutral mode has its magnetic component orthogonal to the plane spanned by the directions of wave propagation and of the static magnetic field. The linear polarization is not maintained at higher orders. The results may be relevant to the microstructure in pulsar radiation or to the subpulses.
Energy Technology Data Exchange (ETDEWEB)
Yoshikawa, Jun, E-mail: jun.yoshikawa@tel.com; Susa, Yoshio; Ventzek, Peter L. G. [Tokyo Electron Ltd., Akasaka Biz Tower, 3-1 Akasaka 5-chome, Minato-ku, Tokyo 107-6325 (Japan)
2015-05-15
The radial line slot antenna plasma source is a type of surface wave plasma source driven by a planar slot antenna. Microwave power is transmitted through a slot antenna structure and dielectric window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This renders the source useful for soft etch applications and thin film deposition processes requiring low ion energy. Another property of the diffusion zone is that the plasma density tends to decrease from the axis to the walls under the action of ambipolar diffusion at distances far from where the plasma is generated. A previous simulation study [Yoshikawa and. Ventzek, J. Vac. Sci. Technol. A 31, 031306 (2013)] predicted that the anisotropy in transport parameters due to weak static magnetic fields less than 50 G could be leveraged to manipulate the plasma profile in the radial direction. These simulations motivated experimental tests in which weak magnetic fields were applied to a radial line slot antenna source. Plasma absorption probe measurements of electron density and etch rate showed that the magnetic fields remote from the wafer were able to manipulate both parameters. A summary of these results is presented in this paper. Argon plasma simulation trends are compared with experimental plasma and etch rate measurements. A test of the impact of magnetic fields on charge up damage showed no perceptible negative effect.
Robson, R E; Winkler, R; Sigeneger, F
2002-05-01
The Boltzmann equation corresponding to a general "multiterm" representation of the phase space distribution function f(r,c,t) for charged particles in a gas in an electric field was reformulated entirely in terms of spherical tensors f(l)(m) some time ago, and numerous applications, including extension to time varying and crossed electric and magnetic fields, have followed. However, these applications have, by and large, been limited to the hydrodynamic conditions that prevail in swarm experiments and the full potential of the tensor formalism has thus never been realized. This paper resumes the discussion in the context of the more general nonhydrodynamic situation. Geometries for which a simple Legendre polynomial expansion suffices to represent f are discussed briefly, but the emphasis is upon cylindrical geometry, where such simplification does not arise. In particular, we consider an axisymmetric cylindrical column of weakly ionized plasma, and derive an infinite hierarchy of integrodifferential equations for the expansion coefficients of the phase space distribution function, valid for both electrons and ions, and for all types of binary interaction with neutral gas molecules.
Magnetorotational instability of weakly ionized and magnetized electron-positron-ion plasma
Mehdian, H.; Hajisharifi, K.; Azadnia, F.; Tajik-Nezhad, S.
2016-10-01
The magnetorotational instability in a differential rotating weakly ionized and magnetized plasma consisting of electron, positron, ion, and neutral particles has been investigated by using the multi-fluid model. Satisfying the current neutrality and homogeneity of the system in the equilibrium state by assuming the same unperturbed angular velocity for charge species and neutrals, the general local dispersion relation (DR) has been derived by taking into account the collision effects. By analytical examination of the obtained DR in the arbitrary and high frequency regimes, the instability conditions have been found in which the presence of light positive species (positrons) plays an important role in the instability criteria. Moreover, numerical investigation shows the broadening of instability range as well as increasing the maximum growth rate of instability (especially for the small number density ratio of light to heavy positive species) in the presence of positrons. The obtained results of the present investigation will greatly contribute to the understanding of the particles' dynamics as well as dissipation mechanism in some astrophysical environments, such as the region of accretion disks surrounding the central of black holes and protoplanetary disks.
Directory of Open Access Journals (Sweden)
S. A. El-Wakil
2012-01-01
Full Text Available The reductive perturbation method has been employed to derive the Korteweg-de Vries (KdV equation for small- but finite-amplitude electrostatic ion-acoustic waves in weakly relativistic plasma consisting of warm ions and isothermal electrons. An algebraic method with computerized symbolic computation is applied in obtaining a series of exact solutions of the KdV equation. Numerical studies have been made using plasma parameters which reveal different solutions, that is, bell-shaped solitary pulses, rational pulses, and solutions with singularity at finite points, which called “blowup” solutions in addition to the propagation of an explosive pulses. The weakly relativistic effect is found to significantly change the basic properties (namely, the amplitude and the width of the ion-acoustic waves. The result of the present investigation may be applicable to some plasma environments, such as ionosphere region.
Hafez, M. G.; Roy, N. C.; Talukder, M. R.; Hossain Ali, M.
2016-09-01
This work investigates the oblique nonlinear propagation of ion acoustic (IA) shock waves for both weakly and highly relativistic plasmas composed of nonthermal electrons and positrons with relativistic thermal ions. The KdVB-like equation, involving dispersive, weakly transverse dispersive, nonlinearity and dissipative coefficients, is derived employing the well known reductive perturbation method. The integration of this equation is carried out by the {tanh} method taking the stable shock formation condition into account. The effects of nonthermal electrons and positrons, nonthermal electrons with isothermal positrons, isothermal electrons with nonthermal positrons, and isothermal electrons and positrons on oblique propagation of IA shock waves in weakly relativistic regime are described. Furthermore, the effects of plasma parameters on oblique propagation of IA shock waves in highly relativistic regime are discussed and compared with weakly relativistic case. It is seen that the plasma parameters within certain limits significantly modify the structures of the IA shock waves in both cases. The results may be useful for better understanding of the interactions of charged particles with extra-galactic jets as well as astrophysical compact objects.
Collisional Effects on Nonlinear Ion Drag Force for Small Grains
Hutchinson, I H
2013-01-01
The ion drag force arising from plasma flow past an embedded spherical grain is calculated self-consistently and non-linearly using particle in cell codes, accounting for ion-neutral collisions. Using ion velocity distribution appropriate for ion drift driven by a force field gives wake potential and force greatly different from a shifted Maxwellian distribution, regardless of collisionality. The low-collisionality forces are shown to be consistent with estimates based upon cross-sections for scattering in a Yukawa (shielded) grain field, but only if non-linear shielding length is used. Finite collisionality initially enhances the drag force, but only by up to a factor of 2. Larger collisionality eventually reduces the drag force. In the collisional regime, the drift distribution gives larger drag than the shift distribution even at velocities where their collisionless drags are equal. Comprehensive practical analytic formulas for force that fit the calculations are provided.
Macpherson, Neil; Shabala, Lana; Rooney, Henrietta; Jarman, Marcus G; Davies, Julia M
2005-06-01
The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means; Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H(+). Measurement of H(+) extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae, this yeast uses a plasma membrane H(+)-ATPase to expel H(+) when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H(+) and K(+) fluxes showed that net K(+) influx accompanies net H(+) efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K(+) on long-term exposure to benzoic acid. Analysis of S. cerevisiae K(+) transporter mutants revealed that loss of the high affinity K(+) uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.
Waade, Ragnhild Birkeland; Molden, Espen; Martinsen, Mette Irene; Hermann, Monica; Ranhoff, Anette Hylen
2017-07-01
To determine use of psychotropic drugs and weak opioids in hip fracture patients by analysing plasma samples at admission, and compare detected drug frequencies with prescription registry data and drug records. Plasma from 250 hip fracture patients aged ≥65 years sampled at hospital admission were analysed by ultra-performance liquid chromatography-tandem mass spectrometry methods for detection of psychotropic drugs and weak opioid analgesics (alcohol also determined). Odds ratios for drugs detected in plasma of hip fracture patients vs. prescription frequencies of the same drugs in an age-, time- and region-matched reference population were calculated. Moreover, recorded and measured drugs were compared. Psychotropic drugs and/or weak opioid analgesics were detected in 158 (63%) of the patients (median age 84 years; 76% females), while alcohol was found in 19 patients (7.6%). The occurrence of diazepam (odds ratio 1.6; 95% confidence interval 1.1-2.4), nitrazepam (2.3; 1.3-4.1), selective serotonin reuptake inhibitors (1.9; 1.3-2.9) and mirtazapine (2.3; 1.2-4.3) was significantly higher in plasma samples of hip fracture patients than in prescription data from the reference population. Poor consistency between recorded and measured drugs was disclosed for z-hypnotics and benzodiazepines; e.g. diazepam was detected in 29 (11.6%), but only recorded in six (2.4%) of the patients. Plasma analysis shows that use of antidepressants and benzodiazepines in hip fracture patients is significantly more frequent than respective prescription frequencies in the general elderly population. Moreover, consistency between recorded and actual use of psychotropic fall-risk drugs is poor at hospital admission of hip fracture patients. © 2017 The British Pharmacological Society.
SOLAR WIND COLLISIONAL AGE FROM A GLOBAL MAGNETOHYDRODYNAMICS SIMULATION
Energy Technology Data Exchange (ETDEWEB)
Chhiber, R; Usmanov, AV; Matthaeus, WH [Department of Physics and Astronomy and Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Goldstein, ML [NASA Goddard Space Flight Center, Greenbelt MD 20771 (United States)
2016-04-10
Simple estimates of the number of Coulomb collisions experienced by the interplanetary plasma to the point of observation, i.e., the “collisional age”, can be usefully employed in the study of non-thermal features of the solar wind. Usually these estimates are based on local plasma properties at the point of observation. Here we improve the method of estimation of the collisional age by employing solutions obtained from global three-dimensional magnetohydrodynamics simulations. This enables evaluation of the complete analytical expression for the collisional age without using approximations. The improved estimation of the collisional timescale is compared with turbulence and expansion timescales to assess the relative importance of collisions. The collisional age computed using the approximate formula employed in previous work is compared with the improved simulation-based calculations to examine the validity of the simplified formula. We also develop an analytical expression for the evaluation of the collisional age and we find good agreement between the numerical and analytical results. Finally, we briefly discuss the implications for an improved estimation of collisionality along spacecraft trajectories, including Solar Probe Plus.
Energy Technology Data Exchange (ETDEWEB)
Nagata, M.
2002-04-01
Compared with the interest in the magneto-resistance effect in solid conductors, the effect in a gas plasma has hardly been addressed. In this work, a theoretical result that a magneto-resistance in an infinite plasma decreases is examined experimentally in an actual discharge plasma. Furthermore, a modified expression for the ambipolar diffusion coefficient in the case where electrons are scattered by heavy neutral atoms is presented. (author)
Lu, Ding; Xie, Bai-Song
2013-01-01
Effects of ion mobility and positron fraction on solitary waves of envelop of laser field and potential of electrostatic field in weak relativistic electron-positron-ion plasma are investigated. The parameter region for the existence of solitary waves is obtained analytically, and the reasonable choice of parameters is clarified. Both cases of mobile and immobile ions are considered. It is found that the amplitudes of solitary waves in the former case are larger compared to the latter case. For small plasma density, the localized solitary wave solutions in terms of approximate perturbation analytical method are consistent well with that by exact numerical calculations. However as the plasma density increases the analytical method loses its validity more and more. The influence of the positron fraction on the amplitudes of solitary waves shows a monotonous increasing relation. Implication of our results to the particle acceleration is also discussed briefly.
Lu, Ding; Li, Zi-Liang; Xie, Bai-Song
2013-09-01
The effects of ion mobility and positron fraction on the solitary waves of the laser field envelope and the potential of the electrostatic field in weak relativistic electron-positron-ion plasma are investigated. The parameter region for the existence of solitary waves is obtained analytically, and a reasonable choice of parameters is clarified. Both cases of mobile and immobile ions are considered. It is found that the amplitudes of solitary waves in the former case are larger compared to the latter case. For small plasma density, the localized solitary wave solutions in terms of the approximate perturbation analytical method are very consistent with those by exact numerical calculations. However, as the plasma density increases the analytical method loses its validity more and more. The influence of the positron fraction on the amplitudes of solitary waves shows a monotonous increasing relation. The implications of our results to particle acceleration are also discussed briefly.
Lekobou, William Pimakouon
Atmospheric pressure plasmas have gained considerable interest from researchers recently for their unique prospective of engineering surfaces with plasma without the need of vacuum systems. They offer the advantage of low energy consumption, minimal capital cost and their simplicity as compared to conventional low pressure plasmas make them easy to upscale from laboratory to industry size. The present dissertation summarizes results of our attempt at applying atmospheric pressure weakly ionized plasma (APWIP) to the engineering of plastic composites filled with cellulose based substrates. An APWIP reactor was designed and built based on a multipoint-to-grounded ring and screen configurations. The carrier gas was argon and acetylene serves as the precursor molecule. The APWIP reactors showed capability of depositing plasma polymerized coating rich in carbon on substrates positioned within the electrode gap as well as downstream of the plasma discharge into the afterglow region. Our findings show that films grow by forming islands which for prolonged deposition time grow into thin films showing nodules, aggregates of nodules and microspheres. They also show chemical structure similar to films deposited from hydrocarbons with other conventional plasma techniques. The plasma polymerized deposits were used on substrates to modify their surface properties. Results show the surface of wood veneer and wood flour can be finely tuned from hydrophilic to hydrophobic. It was achieved by altering the topography of the surfaces along with their chemical composition. The wettability of wood veneer was investigated with contact angle measurements on capacitive drops and the capillary effect was utilized to assess surface properties of wood flour exposed to the discharges.
On nonlinear evolution of low-frequency Alfvén waves in weakly-expanding solar wind plasmas
Energy Technology Data Exchange (ETDEWEB)
Nariyuki, Y. [Faculty of Human Development, University of Toyama, 3190 Toyama City, Toyama 930-8555 (Japan)
2015-02-15
A multi-dimensional nonlinear evolution equation for Alfvén waves in weakly-expanding solar wind plasmas is derived by using the reductive perturbation method. The expansion of solar wind plasma parcels is modeled by an expanding box model, which includes the accelerating expansion. It is shown that the resultant equation agrees with the Wentzel-Kramers-Brillouin prediction of the low-frequency Alfvén waves in the linear limit. In the cold and one-dimensional limit, a modified derivative nonlinear Schrodinger equation is obtained. Direct numerical simulations are carried out to discuss the effect of the expansion on the modulational instability of monochromatic Alfvén waves and the propagation of Alfvén solitons. By using the instantaneous frequency, it is quantitatively shown that as far as the expansion rate is much smaller than wave frequencies, effects of the expansion are almost adiabatic. It is also confirmed that while shapes of Alfvén solitons temporally change due to the expansion, some of them can stably propagate after their collision in weakly-expanding plasmas.
Refined Study of ECR Wave Propagation and Absorption in the Weakly Relativistic Plasma
Institute of Scientific and Technical Information of China (English)
SHIBingren; LONGYongxin
2001-01-01
The ECR wave heating is now a routine method for plasma heating and profile control in fusion devices and also in plasma applications. Theoretical study of ECR wave propagation and absorption began very early in 1950's. Basic theoretical work had accomplished in 1970～1980. For toroidal devices like the tokamak, the fundamental O-mode and X-mode with nearly perpendicular propagation were used very often. For pure O-mode and X-mode with kx=O,
Energy Technology Data Exchange (ETDEWEB)
Hafeez-Ur-Rehman; Mahmood, S. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Department of Physics and Applied Mathematics, PIEAS, Nilore, 44000 Islamabad (Pakistan); Shah, Asif; Haque, Q. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)
2011-12-15
Two dimensional (2D) solitons are studied in a plasma system comprising of relativistically streaming ions, kappa distributed electrons, and positrons. Kadomtsev-Petviashvili (KP) equation is derived through the reductive perturbation technique. Analytical solution of the KP equation has been studied numerically and graphically. It is noticed that kappa parameters of electrons and positrons as well as the ions relativistic streaming factor have an emphatic influence on the structural as well as propagation characteristics of two dimensional solitons in the considered plasma system. Our results may be helpful in the understanding of soliton propagation in astrophysical and laboratory plasmas, specifically the interaction of pulsar relativistic wind with supernova ejecta and the transfer of energy to plasma by intense electric field of laser beams producing highly energetic superthermal and relativistic particles [L. Arons, Astrophys. Space Sci. Lib. 357, 373 (2009); P. Blasi and E. Amato, Astrophys. Space Sci. Proc. 2011, 623; and A. Shah and R. Saeed, Plasma Phys. Controlled Fusion 53, 095006 (2011)].
Berrehrah, Hamza; Aichelin, Jörg; Cassing, Wolfgang; Bratkovskaya, Elena
2014-01-01
In this study we evaluate the dynamical collisional energy loss of heavy quarks, their interaction rate as well as the different transport coefficients (drag and diffusion coefficients, $\\hat{q}$, etc). We calculate these different quantities for i) perturbative partons (on-shell particles in the vacuum with fixed and running coupling) and ii) for dynamical quasi-particles (off-shell particles in the QGP medium at finite temperature $T$ with a running coupling in temperature as described by the dynamical quasi-particles model). We use the perturbative elastic $(q(g) Q \\rightarrow q (g) Q)$ cross section for the first case, and the Infrared Enhanced Hard Thermal Loop cross sections for the second. The results obtained in this work demonstrate the effects of a finite parton mass and width on the heavy quark transport properties and provide the basic ingredients for an explicit study of the microscopic dynamics of heavy flavors in the QGP - as formed in relativistic heavy-ion collisions - within transport approa...
Anomalous Viscosity of the Quark-Gluon Plasma
Hong, Juhee
2013-01-01
The shear viscosity of the quark-gluon plasma is predicted to be lower than the collisional viscosity for weak coupling. The estimated ratio of the shear viscosity to entropy density is rather close to the ratio calculated by N = 4 super Yang-Mills theory for strong coupling, which indicates that the quark-gluon plasma might be strongly coupled. However, in presence of momentum anisotropy, the Weibel instability can arise and affect transport properties. Shear viscosity can be lowered by enhanced collisionality due to turbulence, but the decorrelation time and its relation to underlying dynamics and color-magnetic fields have not been calculated self-consistently. In this paper, we use resonance broadening theory for strong turbulence to calculate the anomalous viscosity of the quark-gluon plasma for nonequilibrium. For saturated Weibel instability, we estimate the scalings of the decorrelation rate and viscosity and compare these with collisional transport. This calculation yields an explicit connection betw...
The Dependence of H-mode Energy Confinement and Transport on Collisionality in NSTX
Energy Technology Data Exchange (ETDEWEB)
Kaye, S. M.; Gerhardt, S.; Guttenfelder, W.; Maingi, R.; Bell, R. E.; Diallo, A.; LeBlanc, B. P.; Podesta, M.
2012-11-27
Understanding the dependence of confi nement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong and favorable dependence of normalized con nement on collisionality. Discharges with lithium conditioning discussed in the present study gen- erally achieved lower collisionality, extending the accessible range of collisionality by almost an order of unity. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confi nement time with decreasing collisionality when other dimension less variables were held as fi xed as possible. This increase of confi nement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and Electron Temperature Gradient modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma.
The Dependence of H-mode Energy Confinement and Transport on Collisionality in NSTX
Energy Technology Data Exchange (ETDEWEB)
Kaye, S. M.; Gerhardt, S.; Guttenfelder, W.; Maingi, R.; Bell, R. E.; Diallo, A.; LeBlanc, B. P.; Podesta, M.
2012-11-28
Understanding the dependence of confi nement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong and favorable dependence of normalized con nement on collisionality. Discharges with lithium conditioning discussed in the present study gen- erally achieved lower collisionality, extending the accessible range of collisionality by almost an order of unity. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confi nement time with decreasing collisionality when other dimension less variables were held as fi xed as possible. This increase of confi nement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and Electron Temperature Gradient modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma
Saini, N. S.; Singh, Kuldeep
2016-10-01
A head-on collision between two dust ion acoustic solitary waves (DIASWs) travelling in the opposite direction in a weakly relativistic plasma composed of four distinct particle populations, namely, weakly relativistic ion fluid, superthermal electrons as well as positrons, and immobile dust, is investigated. By employing extended Poincaré-Lighthill-Kuo method, two Korteweg-de Vries (KdV) equations are derived. The analytical phase shift after a head-on collision of two dust ion acoustic (DIA) solitary waves is also obtained. The combined effects of relativistic factor (β), electron to positron temperature ratio (α), ion to electron temperature ratio (σ), positron to electron density ratio (P), dust density ratio (d), and superthermality of electrons as well as positrons (via κ) on the phase shifts are numerically studied. All these physical parameters have also changed the potential amplitude and the width of colliding solitary waves. It is found that the presence of superthermal electrons as well as positrons and dust grains has emphatic influence on the phase shifts and potential pulse profiles of compressive DIA solitons. Our results are general and may be helpful in understanding a head-on collision between two DIASWs in astrophysical and laboratory plasmas, especially the interaction of pulsar relativistic winds with supernova ejecta that produces the superthermal particles and relativistic ions.
On the perpendicular propagating modes in the ultra-relativistic weakly magnetized plasma
Energy Technology Data Exchange (ETDEWEB)
Abbas, Gohar; Iqbal, Z. [Department of Physics, GC University Lahore, Lahore 54000 (Pakistan); Murtaza, G. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)
2015-03-15
The dispersion relations for the weakly magnetized perpendicular propagating modes (O-mode, X-mode, and upper hybrid mode) based on the ultra-relativistic Fermi-Dirac distribution function with chemical potential are derived using the Vlasov–Maxwell model. The results are presented in terms of Polylog functions without making any approximation. It is found that as the ratio μ/T is increased, the cutoff points shift downward. A comparison is also performed with the previously derived results for ultra-relativistic Maxwellian distribution.
Dynamics of low dimensional model for weakly relativistic Zakharov equations for plasmas
Energy Technology Data Exchange (ETDEWEB)
Sahu, Biswajit [Department of Mathematics, West Bengal State University, Barasat, Kolkata-700126 (India); Pal, Barnali; Poria, Swarup [Department of Applied Mathematics, University of Calcutta, Kolkata-700009 (India); Roychoudhury, Rajkumar [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)
2013-05-15
In the present paper, the nonlinear interaction between Langmuir waves and ion acoustic waves described by the one-dimensional Zakharov equations (ZEs) for relativistic plasmas are investigated formulating a low dimensional model. Equilibrium points of the model are found and it is shown that the existence and stability conditions of the equilibrium point depend on the relativistic parameter. Computational investigations are carried out to examine the effects of relativistic parameter and other plasma parameters on the dynamics of the model. Power spectrum analysis using fast fourier transform and also construction of first return map confirm that periodic, quasi-periodic, and chaotic type solution exist for both relativistic as well as in non-relativistic case. Existence of supercritical Hopf bifurcation is noted in the system for two critical plasmon numbers.
Propagation of dust-acoustic waves in weakly ionized plasmas with dust-charge fluctuation
Indian Academy of Sciences (India)
K K Mondal
2004-11-01
For an unmagnetized partially ionized dusty plasma containing electrons, singly charged positive ions, micron-sized massive negatively charged dust grains and a fraction of neutral atoms, dispersion relations for both the dust-ion-acoustic and the dust-acoustic waves have been derived, incorporating dust charge fluctuation. The dispersion relations, under various conditions, have been exhaustively analysed. The explicit expressions for the growth rates have also been derived.
Kinetic Theory of Instability-Enhanced Collisional Effects
Baalrud, Scott D.
2009-11-01
A generalization of the Lenard-Balescu collision operator is derived which accounts for the scattering of particles by instability amplified fluctuations that originate from the thermal motion of discrete particles (in contrast to evoking a fluctuation level externally, as is done in quasilinear kinetic theory) [1]. Emphasis is placed on plasmas with convective instabilities. It is shown that an instability-enhanced collective response results which can be the primary mechanism for scattering particles, being orders of magnitude more frequent than conventional Coulomb collisions, even though the fluctuations are in a linear growth phase. The resulting collision operator is shown to obey conservation laws (energy, momentum, and density), Galilean invariance, and the Boltzmann H-theorem. It has the property that Maxwellian is the unique equilibrium distribution function; again in contrast to weak turbulence or quasilinear theories. Instability-enhanced collisional effects can dominate particle scattering and cause strong frictional forces. For example, this theory has been applied to two outstanding problems: Langmuir's paradox [2] and determining Bohm's criterion for plasmas with multiple ion species [3]. Langmuir's paradox is a measurement of anomalous electron scattering rapidly establishing a Maxwellian distribution in gas discharges with low temperature and pressure. This may be explained by instability-enhanced scattering in the plasma-boundary transition region (presheath) where convective ion-acoustic instabilities are excited. Bohm's criterion for multiple ion species is a single condition that the ion fluid speeds must obey at the sheath edge; but it is insufficient to determine the speed of individual species. It is shown that an instability-enhanced collisional friction, due to streaming instabilities in the presheath, determines this criterion.[4pt] [1] S.D. Baalrud, J.D. Callen, and C.C. Hegna, Phys. Plasmas 15, 092111 (2008).[0pt] [2] S.D. Baalrud, J
Collisional blockade in microscopic optical dipole traps.
Schlosser, N; Reymond, G; Grangier, P
2002-07-08
We analyze the operating regimes of a very small optical dipole trap, loaded from a magneto-optical trap, as a function of the atom loading rate, i.e., the number of atoms per second entering the dipole trap. We show that, when the dipole trap volume is small enough, a "collisional blockade" mechanism locks the average number of trapped atoms on the value 0.5 over a large range of loading rates. We also discuss the "weak loading" and "strong loading" regimes outside the blockade range, and we demonstrate experimentally the existence of these three regimes.
Reznikov, Roman; Diwan, Mustansir; Nobrega, José N; Hamani, Clement
2015-02-01
Most of the available preclinical models of PTSD have focused on isolated behavioural aspects and have not considered individual variations in response to stress. We employed behavioural criteria to identify and characterize a subpopulation of rats that present several features analogous to PTSD-like states after exposure to classical fear conditioning. Outbred Sprague-Dawley rats were segregated into weak- and strong-extinction groups on the basis of behavioural scores during extinction of conditioned fear responses. Animals were subsequently tested for anxiety-like behaviour in the open-field test (OFT), novelty suppressed feeding (NSF) and elevated plus maze (EPM). Baseline plasma corticosterone was measured prior to any behavioural manipulation. In a second experiment, rats underwent OFT, NSF and EPM prior to being subjected to fear conditioning to ascertain whether or not pre-stress levels of anxiety-like behaviours could predict extinction scores. We found that 25% of rats exhibit low extinction rates of conditioned fear, a feature that was associated with increased anxiety-like behaviour across multiple tests in comparison to rats showing strong extinction. In addition, weak-extinction animals showed low levels of corticosterone prior to fear conditioning, a variable that seemed to predict extinction recall scores. In a separate experiment, anxiety measures taken prior to fear conditioning were not predictive of a weak-extinction phenotype, suggesting that weak-extinction animals do not show detectable traits of anxiety in the absence of a stressful experience. These findings suggest that extinction impairment may be used to identify stress-vulnerable rats, thus providing a useful model for elucidating mechanisms and investigating potential treatments for PTSD.
Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study
Directory of Open Access Journals (Sweden)
N. Gortsas
2009-04-01
Full Text Available The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many comets is ascertained to be anisotropic. However, most plasma simulation studies deploy a spherically symmetric activity pattern. In this paper anisotropy is studied by considering three different coma shape models. The first model is derived from the Haser model and is characterised by spherically symmetry. This reference model is then compared with two different neutral gas shape models: the dayside restricted model with no nightside activity and a cone shaped model with opening angle of π/2. In all models the integrated surface activity is kept constant. The simulations have been done for the Rosetta target comet 67P/Churyumov-Gerasimenko for two heliocentric distances, 1.30 AU and 3.25 AU. It is found that shock formation processes are modified as a result of increasing spatial confinement. Characteristic plasma structures of comets such as the bow shock, magnetic barrier region and the ion composition boundary exhibit a shift towards the sun. In addition, the cone shaped model leads to a strong increase of the mass-loaded region which in turn leads to a smooth deceleration of the solar wind flow and an increasing degree of mixture between the solar wind and cometary ion species. This creates an additional transport channel of the magnetic field from the magnetic barrier region away which in turn leads to a broadening of this region. In addition, it leads to an ion composition boundary which is only gradually developed.
Laosunthara, Ampan; Akatsuka, Hiroshi
2016-09-01
In previous study, we experimentally examined physical properties of supersonic flow of weakly ionized expanding arc-jet plasma through an open magnetic field line (Bmax 0.16T). We found supersonic velocity of helium plasma up to Mach 3 and the space potential drop at the end of the magnets. To understand the plasma in numerical point of view, the flows of ion and neutral are treated by particle-based Direct Simulation Monte Carlo (DSMC) method, electron is treated as a fluid. The previous numerical study, we assumed 2 conditions. Ion and electron temperatures were the same (LTE condition). Ion and electron velocities were the same (current-free condition). We found that ion velocity decreased by collision with residual gas molecules (background pressure). We also found that space potential changing with background pressure. In other words, it was indicated that electric field exists and the current-free assumption is not proper. In this study, we add electron continuity and electron momentum equations to obtain electron velocity and space potential. We find that space potential changing with background pressure slightly. It is indicated that electron is essential to space potential formation than ion.
Solitary waves in dusty plasmas with weak relativistic effects in electrons and ions
Energy Technology Data Exchange (ETDEWEB)
Kalita, B. C., E-mail: bckalita123@gmail.com [Gauhati University, Department of Mathematics (India); Choudhury, M., E-mail: choudhurymamani@gmail.com [Handique Girls’ College, Department of Mathematics (India)
2016-10-15
Two distinct classes of dust ion acoustic (DIA) solitary waves based on relativistic ions and electrons, dust charge Z{sub d} and ion-to-dust mass ratio Q’ = m{sub i}/m{sub d} are established in this model of multicomponent plasmas. At the increase of mass ratio Q’ due to increase of relativistic ion mass and accumulation of more negative dust charges into the plasma causing decrease of dust mass, relativistic DIA solitons of negative potentials are abundantly observed. Of course, relativistic compressive DIA solitons are also found to exist simultaneously. Further, the decrease of temperature inherent in the speed of light c causes the nonlinear term to be more active that increases the amplitude of the rarefactive solitons and dampens the growth of compressive solitons for relatively low and high mass ratio Q’, respectively. The impact of higher initial streaming of the massive ions is observed to identify the point of maximum dust density N{sub d} to yield rarefactive relativistic solitons of maximum amplitude.
Modeling of collisional excited x-ray lasers using short pulse laser pumping
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Akira; Moribayashi, Kengo; Utsumi, Takayuki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment
1998-03-01
A simple atomic kinetics model of electron collisional excited x-ray lasers has been developed. The model consists of a collisional radiative model using the average ion model (AIM) and a detailed term accounting (DTA) model of Ni-like Ta. An estimate of plasma condition to produce gain in Ni-like Ta ({lambda}=44A) is given. Use of the plasma confined in a cylinder is proposed to preform a uniform high density plasma from 1-D hydrodynamics calculations. (author)
Jet-Medium Interactions at NLO in a Weakly-Coupled Quark-Gluon Plasma
Ghiglieri, Jacopo; Teaney, Derek
2015-01-01
We present an extension to next-to-leading order in the strong coupling constant $g$ of the AMY effective kinetic approach to the energy loss of high momentum particles in the quark-gluon plasma. At leading order, the transport of jet-like particles is determined by elastic scattering with the thermal constituents, and by inelastic collinear splittings induced by the medium. We reorganize this description into collinear splittings, high-momentum-transfer scatterings, drag and diffusion, and particle conversions (momentum-preserving identity-changing processes). We show that this reorganized description remains valid to NLO in $g$, and compute the appropriate modifications of the drag, diffusion, particle conversion, and inelastic splitting coefficients. In addition, a new kinematic regime opens at NLO for wider-angle collinear bremsstrahlung. These semi-collinear emissions smoothly interpolate between the leading order high-momentum-transfer scatterings and collinear splittings. To organize the calculation, w...
Tallents, G. J.
2016-09-01
Collisional-radiative models enable average ionization and ionization populations, plus the rates of absorption and emission of radiation to be calculated for plasmas not in thermal equilbrium. At high densities and low temperatures, electrons may have a high occupancy of the free electron quantum states and evaluations of rate coefficients need to take into account the free electron degeneracy. We demonstrate that electron degeneracy can reduce collisional rate coefficients by orders-of-magnitude from values calculated neglecting degeneracy. We show that assumptions regarding the collisional differential cross-section can alter collisional ionization and recombination rate coefficients by a further factor two under conditions relevant to inertial fusion.
M, G. Hafez; N, C. Roy; M, R. Talukder; M Hossain, Ali
2017-01-01
A comparative study is carried out for the nonlinear propagation of ion acoustic shock waves both for the weakly and highly relativistic plasmas consisting of relativistic ions and q-distributed electrons and positions. The Burgers equation is derived to reveal the physical phenomena using the well known reductive perturbation technique. The integration of the Burgers equation is performed by the (G\\prime /G)-expansion method. The effects of positron concentration, ion–electron temperature ratio, electron–positron temperature ratio, ion viscosity coefficient, relativistic streaming factor and the strength of the electron and positron nonextensivity on the nonlinear propagation of ion acoustic shock and periodic waves are presented graphically and the relevant physical explanations are provided.
FLYCHK Collisional-Radiative Code
SRD 160 FLYCHK Collisional-Radiative Code (Web, free access) FLYCHK provides a capability to generate atomic level populations and charge state distributions for low-Z to mid-Z elements under NLTE conditions.
Energy Technology Data Exchange (ETDEWEB)
Bott-Suzuki, Simon
2014-11-05
We have developed a new experimental platform to study bow-shock formation in plasma flows generated using an inverse wire array z-pinch. We have made significant progress on the analysis of both hydrodynamic and magnetized shocks using this system. The hydrodynamic experiments show formation of a well-defined Mach cone, and highly localized shock strong associated with radiative losses and rapidly cooling over the shock. Magnetized shocks show that the balance of magnetic and ram pressures dominate the evolution of the shock region, generating a low plasma beta void around the target. Manuscripts are in preparation for publication on both these topics. We have also published the development of a novel diagnostic method which allow recovery of interferometry and self-emission data along the same line of sight. Finally, we have carried out work to integrate a kinetic routine with the 3D MHD code Gorgon, however it remains to complete this process. Both undergraduate and graduate students have been involved in both the experimental work and publications.
Modulational instability of electromagnetic waves in a collisional quantum magnetoplasma
Energy Technology Data Exchange (ETDEWEB)
Niknam, A. R., E-mail: a-niknam@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Rastbood, E.; Bafandeh, F.; Khorashadizadeh, S. M., E-mail: smkhorashadi@birjand.ac.ir [Physics Department of Birjand University, Birjand (Iran, Islamic Republic of)
2014-04-15
The modulational instability of right-hand circularly polarized electromagnetic electron cyclotron (CPEM-EC) wave in a magnetized quantum plasma is studied taking into account the collisional effects. Employing quantum hydrodynamic and nonlinear Schrödinger equations, the dispersion relation of modulated CPEM-EC wave in a collisional plasma has been derived. It is found that this wave is unstable in such a plasma system and the growth rate of the associated instability depends on various parameters such as electron Fermi temperature, plasma number density, collision frequency, and modulation wavenumber. It is shown that while the increase of collision frequency leads to increase of the growth rate of instability, especially at large wavenumber limit, the increase of plasma number density results in more stable modulated CPEM-EC wave. It is also found that in contrast to collisionless plasma in which modulational instability is restricted to small wavenumbers, in collisional plasma, the interval of instability occurrence can be extended to a large domain.
Sarwar, M. Adnan; Mirza, Arshad M.
2007-03-01
A simple derivation of the electrostatic potential and energy loss of N×M test charge projectiles traveling through dusty plasma has been presented. The effect of dust-charge fluctuations, dust neutral collisions, and self-gravitation on the shielded potential and energy loss of charge projectiles has been investigated both analytically as well as numerically. An interference contribution of these projectiles to the shielded potential and energy loss has been observed, which depends upon their relative orientation and separation distance. A comparison has been made for correlated and uncorrelated motion of the two projectiles. The amplitude of the shielded potential is enhanced with the increase of dust Jeans frequency for separation less than the effective Debye length. The dust-charge fluctuations produce a potential well for a slow charge relaxation rate and energy is gained, not lost, by the test charge projectiles. However, a fast charge relaxation rate with a fixed value of Jeans frequency enhances the energy loss. The dust neutral collisions are also found to enhance the energy loss for the test charge velocities greater than the dust acoustic speeds. The present investigation might be useful to explain the coagulation of dust particles such as those in molecular clouds, the interstellar medium, comet tails, planetary rings, etc.
Isotropic inelastic and superelastic collisional rates in a multiterm atom
Belluzzi, L; Bueno, J Trujillo
2013-01-01
The spectral line polarization of the radiation emerging from a magnetized astrophysical plasma depends on the state of the atoms within the medium, whose determination requires considering the interactions between the atoms and the magnetic field, between the atoms and photons (radiative transitions), and between the atoms and other material particles (collisional transitions). In applications within the framework of the multiterm model atom (which accounts for quantum interference between magnetic sublevels pertaining either to the same J-level or to different J-levels within the same term) collisional processes are generally neglected when solving the master equation for the atomic density matrix. This is partly due to the lack of experimental data and/or of approximate theoretical expressions for calculating the collisional transfer and relaxation rates (in particular the rates for interference between sublevels pertaining to different J-levels, and the depolarizing rates due to elastic collisions). In th...
Latyshev, A V
2013-01-01
Formulas for the longitudinal dielectric permeability in quantum degenerate collisional plasma with the frequency of collisions proportional to the module of the wave vector, in Mermin's approach, are received. Equation of Shr\\"{o}dinger - Boltzmann with integral of collisions relaxation type in Mermin's approach is applied. It is spent numerical and graphic comparison of the real and imaginary parts of dielectric function of non-degenerate and maxwellian collisional quantum plasma with a constant and a variable frequencies of collisions. It is shown, that the longitudinal dielectric function weakly depends on a wave vector.
Protoplanetary Accretion by Collisional Fusion
Wettlaufer, J S
2009-01-01
The formation of a solar system is believed to have followed a multi-stage process around a protostar. Whipple first noted that planetesimal growth by particle agglomeration is strongly influenced by gas drag; there is a ``bottleneck'' at the meter scale with such bodies rapidly spiraling into the central star, whereas much smaller or larger particles do not. Thus, successful planetary accretion requires rapid planetesimal growth to km scale. A commonly accepted picture is that for collisional velocities $V_c$ above a certain threshold collisional velocity, ${V_{th}} \\sim$ 0.1-10 cm s$^{-1}$, particle agglomeration is not possible; elastic rebound overcomes attractive surface and intermolecular forces. However, if perfect sticking is assumed for all collisions the bottleneck can be overcome by rapid planetesimal growth. While previous work has dealt explicitly with the influences of collisional pressures and the possibility of particle fracture or penetration, the basic role of the phase behavior of matter--p...
Energy Technology Data Exchange (ETDEWEB)
Misguich, J.H
2004-04-01
As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation.
Pandey, Mukesh Kumar; Lin, Yen-Chang; Ho, Yew Kam
2017-02-01
The effects of weakly coupled or classical and dense quantum plasmas environment on charge exchange and ionization processes in Na+ + Rb(5s) atom collision at keV energy range have been investigated using classical trajectory Monte Carlo (CTMC) method. The interaction of three charged particles are described by the Debye-Hückel screen potential for weakly coupled plasma, whereas exponential cosine-screened Coulomb potential have been used for dense quantum plasma environment and the effects of both conditions on the cross sections are compared. It is found that screening effects on cross sections in high Debye length condition is quite small in both plasma environments. However, enhanced screening effects on cross sections are observed in dense quantum plasmas for low Debye length condition, which becomes more effective while decreasing the Debye length. Also, we have found that our calculated results for plasma-free case are comparable with the available theoretical results. These results are analyzed in light of available theoretical data with the choice of model potentials.
Silantyev, Denis A.; Lushnikov, Pavel M.; Rose, Harvey A.
2017-04-01
We consider two kinds of pumped Langmuir waves (LWs) in the kinetic regime, k λ D ≳ 0.2 , where k is the LW wavenumber and λD is the Debye length, driven to finite amplitude by a coherent external potential whose amplitude is either weak or strong. These dynamically prepared nonlinear LWs develop a transverse (filamentation) instability whose nonlinear evolution destroys the LW's transverse coherence. Instability growth rates in the weakly pumped regime are the same as those of Bernstein-Greene-Kruskal modes considered in Part I (D. A. Silantyev et al., Phys. Plasmas 24, 042104 (2017)), while strongly pumped LWs have higher filamentation grow rates.
Latyshev, A V
2013-01-01
Formulas for the longitudinal dielectric permeability in quantum non-degenerate and maxwellian collisional plasma with the frequency of collisions proportional to the module of the wave vector, in Mermin's approach, are received. Equation of Shr\\"{o}dinger - Boltzmann with integral of collisions relaxation type in Mermin's approach is applied. It is spent numerical and graphic comparison of the real and imaginary parts of dielectric function of non-degenerate and maxwellian collisional quantum plasma with a constant and a variable frequencies of collisions. It is shown, that the longitudinal dielectric function weakly depends on a wave vector.
Surface wave and linear operating mode of a plasma antenna
Energy Technology Data Exchange (ETDEWEB)
Bogachev, N. N., E-mail: bgniknik@yandex.ru; Bogdankevich, I. L.; Gusein-zade, N. G.; Rukhadze, A. A. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)
2015-10-15
The relation between the propagation conditions of a surface electromagnetic wave along a finiteradius plasma cylinder and the linear operating mode of a plasma antenna is investigated. The solution to the dispersion relation for a surface wave propagating along a finite-radius plasma cylinder is analyzed for weakly and strongly collisional plasmas. Computer simulations of an asymmetrical plasma dipole antenna are performed using the KARAT code, wherein the dielectric properties of plasma are described in terms of the Drude model. The plasma parameters corresponding to the linear operating mode of a plasma antenna are determined. It is demonstrated that the characteristics of the plasma antenna in this mode are close to those of an analogous metal antenna.
Modulating toroidal flow stabilization of edge localized modes with plasma density
Cheng, Shikui; Banerjee, Debabrata
2016-01-01
Recent EAST experiments have demonstrated mitigation and suppression of edge localized modes (ELMs) with toroidal rotation flow in higher collisionality regime, suggesting potential roles of plasma density. In this work, the effects of plasma density on the toroidal flow stabilization of the high-$n$ edge localized modes have been extensively studied in linear calculations for a circular-shaped limiter H-mode tokamak, using the extended MHD code NIMROD. In the single MHD model, toroidal flow has a weak stabilizing effects on the high-$n$ modes. Such a stabilization, however, can be significantly enhanced with the increase in plasma density. Furthermore, our calculations show that the enhanced stabilization of high-$n$ modes from toroidal flow with higher edge plasma density persists in the 2-fluid MHD model. These findings may explain the ELM mitigation and suppression by toroidal rotation in higher collisionality regime due to the enhancement of plasma density obtained in recent EAST experiments.
Simulation of transient collisional x-ray lasers
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Akira; Utsumi, Takayuki; Moribayashi, Kengo; Zhidkov, A.; Kawachi, Tetsuya; Kado, Masataka; Hasegawa, Noboru [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Institute, Neyagawa, Osaka (Japan)
2000-03-01
We have developed a collisional radiative model of electron collisional excited x-ray lasers. We calculate the ion abundance and soft x-ray gain for the Ne-like 3s-3p transition and Ni-like 4d-4p transition, in short pulse laser irradiated plasmas. We combine a detailed model using the atomic data calculated by the HULLAC code and the averaged model based on the screened hydrogenic approximation to develop a compact model. Effects of dielectronic recombination channels and radiation trapping of the lower laser level are investigated. The calculation of the transient gain is carried out using the plasma temperature and density obtained from a 1D hydrodynamics code. (author)
Yang, Gengliang; Feng, Sha; Liu, Haiyan; Yin, Junfa; Zhang, Li; Cai, Liping
2007-07-01
A weak ion exchange monolithic column prepared by modifying the GMA-MAA-EDMA (glycidyl methacrylate-methacrylic acid-ethylene glycol dimethacrylate) monoliths with ethylenediamine was applied to remove matrix compounds in biological fluid. Using this monolithic column, on-line clean-up and screening of oxacillin and cloxacillin in human urine and plasma samples had been investigated. Chromatography was performed by reversed-phase HPLC on a C(18) column with ultraviolet detection at 225 nm. Results showed that the ion exchange monolithic column could be used for deproteinization and retaining oxacillin and cloxacillin in human urine and plasma, which provided a simple and fast method for assaying drugs in human urine and plasma.
Turbulent transport and heating of trace heavy ions in hot, magnetized plasmas
Barnes, M; Dorland, W
2012-01-01
Scaling laws for the transport and heating of trace heavy ions in low-frequency, magnetized plasma turbulence are derived and compared with direct numerical simulations. The predicted dependences of turbulent fluxes and heating on ion charge and mass number are found to agree with numerical results for both stationary and differentially rotating plasmas. Heavy ion momentum transport is found to increase with mass, and heavy ions are found to be preferentially heated, implying a mass-dependent ion temperature for very weakly collisional plasmas and for partially-ionized heavy ions in strongly rotating plasmas.
Double layers in a modestly collisional electronegative discharge
Sheridan, T E
1999-01-01
The effect of ion-neutral collisions on the structure and ion flux emanating from a steady-state, planar discharge with two negative components is investigated. The positive ion component is modelled as a cold fluid subject to constant-mobility collisions, while the electrons and negative ions obey Boltzmann relations. The model includes the collisionless limit. When the negative ions are sufficiently cold three types of discharge structures are found. For small negative ion concentrations or high collisionality, the discharge is 'stratified', with an electronegative core and an electropositive edge. For the opposite conditions, the discharge is 'uniform' with the negative ion density remaining significant at the edge of the plasma. Between these cases lies the special case of a double-layer-stratified discharge, where quasi-neutrality is violated at the edge of the electronegative core. Double-layer-stratified solutions are robust in that they persist for moderate collisionality. Numerical solutions for fini...
Collisional Energy Loss of Non Asymptotic Jets in a QGP
Adil, A; Horowitz, W A; Wicks, S
2006-01-01
We calculate the collisional energy loss suffered by a heavy (charm) quark created at a finite time within a Quark Gluon Plasma (QGP) in the classical linear response formalism. We pay close attention to the problem of formulating a conserved current and accounting for binding and radiative energy loss effects. We find that the finite time correction is on the order of a Debye length as expected and the overall energy loss is similar in magnitude to the energy loss suffered by a charge created in the asymptotic past. This result has significant implications for the relative contribution to energy loss from collisional and radiative sources and will have ramifications for the ``single electron puzzle'' at RHIC as well as other experimental observables.
Collisional effects on Rayleigh-Taylor-induced magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Manuel, M. J.-E. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Flaig, M.; Plewa, T. [Florida State University, Tallahassee, Florida 32306 (United States); Li, C. K.; Séguin, F. H.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hu, S. X.; Betti, R.; Hager, J.; Meyerhofer, D. D.; Smalyuk, V. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
2015-05-15
Magnetic-field generation from the Rayleigh-Taylor (RT) instability was predicted more than 30 years ago, though experimental measurements of this phenomenon have only occurred in the past few years. These pioneering observations demonstrated that collisional effects are important to B-field evolution. To produce fields of a measurable strength, high-intensity lasers irradiate solid targets to generate the nonaligned temperature and density gradients required for B-field generation. The ablation process naturally generates an unstable system where RT-induced magnetic fields form. Field strengths inferred from monoenergetic-proton radiographs indicate that in the ablation region diffusive effects caused by finite plasma resistivity are not negligible. Results from the first proof-of-existence experiments are reviewed and the role of collisional effects on B-field evolution is discussed in detail.
Directory of Open Access Journals (Sweden)
M. G. Hafez
2016-01-01
Full Text Available Two-dimensional three-component plasma system consisting of nonextensive electrons, positrons, and relativistic thermal ions is considered. The well-known Kadomtsev-Petviashvili-Burgers and Kadomtsev-Petviashvili equations are derived to study the basic characteristics of small but finite amplitude ion acoustic waves of the plasmas by using the reductive perturbation method. The influences of positron concentration, electron-positron and ion-electron temperature ratios, strength of electron and positrons nonextensivity, and relativistic streaming factor on the propagation of ion acoustic waves in the plasmas are investigated. It is revealed that the electrostatic compressive and rarefactive ion acoustic waves are obtained for superthermal electrons and positrons, but only compressive ion acoustic waves are found and the potential profiles become steeper in case of subthermal positrons and electrons.
Understanding the core density profile in TCV H-mode plasmas
Wágner, Dávid; Pitzschke, Andreas; Sauter, Olivier; Weisen, Henri
2012-01-01
Results from a database analysis of H-mode electron density profiles on the Tokamak \\`a Configuration Variable (TCV) in stationary conditions show that the logarithmic electron density gradient increases with collisionality. By contrast, usual observations of H-modes showed that the electron density profiles tend to flatten with increasing collisionality. In this work it is reinforced that the role of collisionality alone, depending on the parameter regime, can be rather weak and in these, dominantly electron heated TCV cases, the electron density gradient is tailored by the underlying turbulence regime, which is mostly determined by the ratio of the electron to ion temperature and that of their gradients. Additionally, mostly in ohmic plasmas, the Ware-pinch can significantly contribute to the density peaking. Qualitative agreement between the predicted density peaking by quasi-linear gyrokinetic simulations and the experimental results is found. Quantitative comparison would necessitate ion temperature meas...
Low Collisionality Neoclassical Toroidal Viscosity in Tokamaks and Quasi-symmetric Stellarators
Cole, A. J.; Hegna, C. C.; Callen, J. D.
2008-11-01
Non-resonant magnetic perturbations can affect plasma rotation in toroidally confined plasmas through their modification to |B|. Variations along a field line induce nonambipolar radial transport and produce a global neoclassical toroidal viscous force [NTV]. In this work, previously calculated radial particle fluxes for the low-collisionality ``ν'' and ``1/ν'' regimes [1] are unified into a single particle flux (or toroidal viscous force). Provided pitch-angle scattering dominates over collisional energy exchange, the energy component of phase space can be decoupled into independent regions (E >Ec. for ν regime, E Callen, Phys. Fluids 19, 667 (1976).
THE COLLISIONAL EVOLUTION OF DEBRIS DISKS
Energy Technology Data Exchange (ETDEWEB)
Gaspar, Andras; Rieke, George H. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Balog, Zoltan, E-mail: agaspar@as.arizona.edu, E-mail: grieke@as.arizona.edu, E-mail: balog@mpia.de [Max-Plank Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
2013-05-01
We explore the collisional decay of disk mass and infrared emission in debris disks. With models, we show that the rate of the decay varies throughout the evolution of the disks, increasing its rate up to a certain point, which is followed by a leveling off to a slower value. The total disk mass falls off {proportional_to}t {sup -0.35} at its fastest point (where t is time) for our reference model, while the dust mass and its proxy-the infrared excess emission-fades significantly faster ({proportional_to}t {sup -0.8}). These later level off to a decay rate of M{sub tot}(t){proportional_to}t {sup -0.08} and M{sub dust}(t) or L{sub ir}(t){proportional_to}t {sup -0.6}. This is slower than the {proportional_to}t {sup -1} decay given for all three system parameters by traditional analytic models. We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100 {mu}m observations. Assuming a log-normal distribution of initial disk masses, we generate model population decay curves for the fraction of stars harboring debris disks detected at 24 {mu}m. We also model the distribution of measured excesses at the far-IR wavelengths (70-100 {mu}m) at certain age regimes. We show general agreement at 24 {mu}m between the decay of our numerical collisional population synthesis model and observations up to a Gyr. We associate offsets above a Gyr to stochastic events in a few select systems. We cannot fit the decay in the far-infrared convincingly with grain strength properties appropriate for silicates, but those of water ice give fits more consistent with the observations (other relatively weak grain materials would presumably also be successful). The oldest disks have a higher incidence of large excesses than predicted by the model; again, a plausible explanation is very late phases of high dynamical activity around a small number of stars. Finally, we constrain the variables of our numerical model by comparing the evolutionary trends generated from the exploration
Collisional Aggregation due to Turbulence
Pumir, Alain
2015-01-01
Collisions between particles suspended in a fluid play an important role in many physical processes. As an example, collisions of microscopic water droplets in clouds are a necessary step in the production of macroscopic raindrops. Collisions of dust grains are also conjectured to be important for planet formation in the gas surrounding young stars, and also to play a role in the dynamics of sand storms. In these processes, collisions are favoured by fast turbulent motions. Here we review recent advances in the understanding of collisional aggregation due to turbulence. We discuss the role of fractal clustering of particles, and caustic singularities of their velocities. We also discuss limitations of the Smoluchowski equation for modelling these processes. These advances lead to a semi-quantitative understanding on the influence of turbulence on collision rates, and point to deficiencies in the current understanding of rainfall and planet formation.
Alam, M. S.; Hafez, M. G.; Talukder, M. R.; Hossain Ali, M.
2017-07-01
A comparative study of the interactions between nonlinear ion acoustic solitary waves (IASWs) propagating toward each other, and the electrostatic nonlinear propagation of IASWs, both for the weakly and relativistic regimes consisting of relativistic warm ions, nonthermal electrons, and positrons, is carried out. Two-sided Korteweg-de Vries (KdV) equations are derived using the extended Poincaré-Lighthill-Kuo (PLK) method to reveal the physical issues concerned. The effects of positron concentration, ion-electron temperature ratio, electron-positron temperature ratio, relativistic streaming factor, the population of electron, and positron nonthermality on the electrostatic resonances and their phase shifts are investigated for both regimes. It is found that the plasma parameters significantly modify the phase shifts, electrostatic resonances, hump-shaped electrostatic potential profiles, and the electric fields on the nonlinear propagation characteristics of IASWs. The results obtained may be useful for clarifications of interaction between IASWs in astrophysical and laboratory plasmas, especially in pulsar magnetosphere, laser produced, inertial confinement plasmas, and pulsar relativistic winds with supernova ejecta that produce nonthermal electrons, positrons, and relativistic ions.
Collisional stochastic ripple diffusion of alpha particles and beam ions on TFTR
Energy Technology Data Exchange (ETDEWEB)
Redi, M.H.; Zarnstorff, M.C.; White, R.B.; Budny, R.V.; Janos, A.C.; Owens, D.K.; Schivell, J.F.; Scott, S.D.; Zweben, S.J.
1995-07-01
Predictions for ripple loss of fast ions from TFTR are investigated with a guiding center code including both collisional and ripple effects. A synergistic enhancement of fast ion diffusion is found for toroidal field ripple with collisions. The total loss is calculated to be roughly twice the sum of ripple and collisional losses calculated separately. Discrepancies between measurements and calculations of plasma beta at low current and large major radius are resolved when both effects are included for neutral beam ions. A 20--30% reduction in alpha particle heating is predicted for q{sub a} = 6--14, R = 2.6 m DT plasmas on TFTR due to first orbit and collisional stochastic ripple diffusion.
Lyon, M.; Rolston, S. L.
2017-01-01
By photoionizing samples of laser-cooled atoms with laser light tuned just above the ionization limit, plasmas can be created with electron and ion temperatures below 10 K. These ultracold neutral plasmas have extended the temperature bounds of plasma physics by two orders of magnitude. Table-top experiments, using many of the tools from atomic physics, allow for the study of plasma phenomena in this new regime with independent control over the density and temperature of the plasma through the excitation process. Characteristic of these systems is an inhomogeneous density profile, inherited from the density distribution of the laser-cooled neutral atom sample. Most work has dealt with unconfined plasmas in vacuum, which expand outward at velocities of order 100 m/s, governed by electron pressure, and with lifetimes of order 100 μs, limited by stray electric fields. Using detection of charged particles and optical detection techniques, a wide variety of properties and phenomena have been observed, including expansion dynamics, collective excitations in both the electrons and ions, and collisional properties. Through three-body recombination collisions, the plasmas rapidly form Rydberg atoms, and clouds of cold Rydberg atoms have been observed to spontaneously avalanche ionize to form plasmas. Of particular interest is the possibility of the formation of strongly coupled plasmas, where Coulomb forces dominate thermal motion and correlations become important. The strongest impediment to strong coupling is disorder-induced heating, a process in which Coulomb energy from an initially disordered sample is converted into thermal energy. This restricts electrons to a weakly coupled regime and leaves the ions barely within the strongly coupled regime. This review will give an overview of the field of ultracold neutral plasmas, from its inception in 1999 to current work, including efforts to increase strong coupling and effects on plasma properties due to strong coupling.
Analysis of the transient collisional x-ray lasers
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Akira; Utsumi, Takayuki; Moribayashi, Kengo; Zhidkov, Alexei; Kawachi, Tetsuya; Kado, Masataka; Tanaka, Momoko; Hasegawa, Noboru; Daido, Hiroyuki [Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan). Kansai Research Establishment
2001-10-01
The spatial and temporal evolution of the gain of a transient collisional x-ray lasers had been investigated using a plasma hydrodynamics code coupled with a detailed atomic kinetics code. The calculated gain of a Ni-like Ag laser pumped by two 100ps laser pulses agrees qualitatively with the experiment. Calculations for a thin foil target irradiated by two 2ps laser pulses shows that a high gain (>50/cm) can be obtained by adjusting the temporal interval between the two pump pulses. (author)
Influence of collisional dephasing processes on superfluorescence
Maki, Jeffery J.; Malcuit, Michelle S.; Raymer, Michael G.; Boyd, Robert W.; Drummond, Peter D.
1989-11-01
We present a quantum-mechanical treatment of the influence of collisional dephasing processes on the statistical properties of superfluorescence (SF). The theory, which treats nonlinear propagation effects as well as quantum noise, shows how the nature of the cooperative emission process changes from that of SF to that of amplified spontaneous emission as the collisional dephasing rate is varied. The predictions of how the SF delay time varies with the collisional dephasing rate are in good agreement with the results of a recent experiment [M. S. Malcuit, J. J. Maki, D. J. Simkin, and R. W. Boyd, Phys. Rev. Lett. 59, 1189 (1987)].
Eigenvalue solution to the electron-collisional effect on ion-acoustic and entropy waves
Institute of Scientific and Technical Information of China (English)
ZHENG; Jian
2001-01-01
［1］Braginskii,S.I.,Transport processes in a plasma,in Reviews of Plasma Physics,Vol.1,New York:Consultants Bureau,1965,205-311.［2］Ono,M.,Kulsrud,R.M.,Frequency and damping of ion acoustic waves,Phys.Fluids,1975,18(10):1287-1293.［3］Randall,C.J.,Effect of ion collisionality on ion-acoustic waves,Phys.Fluids,1982,25(12):2231-2233.［4］Tracy,M.D.,Williams,E.A.,Estabrook,K.G.et al.,Eigenvalue solution for the ion-collisional effects on ion-acoustic and entropy waves,Phys.Fluids,1993,B5(5):1430.［5］Bell,A.R.,Electron energy transport in ion waves and its relevance to laser produced plasmas,Phys.Fluids,1983,26(1):279-284.［6］Epperlein,E.M.,Short,R.W.,Simon,A.,Damping of ion-acoustic waves in the presence of electron-ion collisions,Phys.Rev.Lett.,1992,69(12):1765-1768.［7］Epperlein,E.M.,Effect of electron collisions on ion-acoustic waves and heat flow,Phys.Plasmas,1994,1(1):109-115.［8］Bychenkov,V.Y.,Myatt,J.,Rozmus,W.et al.,Quasihydrodynamic description of ion acoustic waves in a collisional plasmas,Phys.Plasmas,1994,1(8):2419-2429.［9］Bychenkov,V.Y.,Myatt,J.,Rozmus,W.et al.,Ion acoustic waves in plasmas with collisional electrons,Phys.Rev.E,1994,50(6):5134-5137.［10］Bychenkov,V.Y.,Rozmus,W.,Tikhonchuk,V.T.et al.,Nonlocal electron transport in a plasma,Phys.Rev.Lett.,1995,75(24):4405-4408.［11］Zhang,Y.Q.et al.,Density fluctuation spectra of a collision-dominated plasma measured by light scattering,Phys.Rev.Lett.,1989,62(16):1848-1851.［12］Hinton,F.L.,Collisional transport in plasma,in Handbook of Plasma Physics,Vol.1,Amsterdam:North-Holland,1983,147-199.［13］Zheng Jian,Yu Changxuan,A numerical approach to the frequencies and damping rates of ion-acoustic waves in ion-collisional plasmas,Chin.Phys.Lett.,1999,16(12):905-907.［14］Hammett,G.W.,Perkins,F.,Fluid moment models for Landau damping with application to the ion-temperature-gradient instability,Phys.Rev.Lett.,1990,64(25):3019-3022.
Ghorbanalilu, M.; Sadegzadeh, S.
2017-01-01
Counter-streaming plasma structures are ubiquitous in astrophysical sources of non-thermal radiations. We discuss the dispersion properties and the stability of this non-thermal particle distribution, which is modeled on the basis of the relativistic Jüttner-Maxwell distribution function in the correct laboratory frame of reference. In this work, we aim to construct analytical solutions of the dispersion relations and investigate the properties of the growth rate of the filamentation and two-stream instabilities in an unmagnetized and homogeneous counter-propagating plasma. The Maxwell and the relativistic Vlasov equations are used to derive the covariant dispersion relations that are valid in any (conveniently chosen) reference frame. Aperiodic solutions ( ℜ(ω)≃0 ) to the covariant dispersion relations of the growing modes ( ℑ(ω)>0 ) are demonstrated with the aid of analytical calculations. The dependence of the growth rate on the normalized bulk velocity β0=V0/c and thermal parameter μ=m c2/KBT is shown in graphic illustrations. We found that for both kinds of instabilities, growth rates are decreased by increasing the temperature and decreasing the bulk velocity. Therefore, the electrons at sufficiently low temperatures and with relativistic streams are capable of increasing the range of unstable wave numbers and consequently prevent the instability to cease at small wave numbers. The results indicate that under the same condition and in contrast to the non-relativistic regime, the filamentation instability has the largest growth rate and the electrostatic two-stream instability is in the next place.
Briefi, S.; Gutmann, P.; Rauner, D.; Fantz, U.
2016-06-01
The discharge properties of a weakly magnetized inductively coupled hydrogen discharge (operating pressure 1 Pa) are evaluated by using optical emission spectroscopy. The behaviour of the electron density n e, temperature T e and the density ratio of atomic to molecular hydrogen n H/{{n}{{\\text{H}2}}} with varying magnetic field strength (up to 12 mT) is investigated. The results obtained from the OES measurements performed with a line of sight directed along the central axis of the cylindrical discharge vessel are compared to the case when the ICP antenna is replaced by a Nagoya-type-III Helicon antenna. In the ICP case, the electron temperature and density at the axis of the cylindrical discharge vessel decrease with increasing magnetic field due to the hindered radial electron diffusion. This results in a gradual transition from a homogeneous radial emission profile to a hollow profile with minimal emission in the discharge centre. Concerning the density ratio of atomic to molecular hydrogen, one obtains very high values of up to 0.32 at low B field and a decreasing behaviour with higher magnetic fields. For the Helicon case, the obtained values of n e and T e are virtually unaffected by the external magnetic field. Furthermore, a hollow radial emission profile is observed already at low B field strengths. In the Helicon setup one obtains an increasing trend for n H/{{n}{{\\text{H}2}}} with a maximum of about 0.2 at 12 mT.
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, T., E-mail: t.yamamoto@ppl.appi.keio.ac.jp; Shibata, T.; Ohta, M.; Yasumoto, M.; Nishida, K.; Hatayama, A. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan); Mattei, S.; Lettry, J. [CERN, 1211 Geneva 23 (Switzerland); Sawada, K. [Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Fantz, U. [Max-Plank-Instutut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, D-85748 Garching (Germany)
2014-02-15
To control the H{sup 0} atom production profile in the H{sup −} ion sources is one of the important issues for the efficient and uniform surface H{sup −} production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H{sup 0} atoms from H{sub 2} molecules in the model geometry of the radio-frequency (RF) H{sup −} ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H{sup 0} production and the Balmer H{sub α} photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H{sup −} ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established.
Weak Convergence and Weak Convergence
Directory of Open Access Journals (Sweden)
Narita Keiko
2015-09-01
Full Text Available In this article, we deal with weak convergence on sequences in real normed spaces, and weak* convergence on sequences in dual spaces of real normed spaces. In the first section, we proved some topological properties of dual spaces of real normed spaces. We used these theorems for proofs of Section 3. In Section 2, we defined weak convergence and weak* convergence, and proved some properties. By RNS_Real Mizar functor, real normed spaces as real number spaces already defined in the article [18], we regarded sequences of real numbers as sequences of RNS_Real. So we proved the last theorem in this section using the theorem (8 from [25]. In Section 3, we defined weak sequential compactness of real normed spaces. We showed some lemmas for the proof and proved the theorem of weak sequential compactness of reflexive real Banach spaces. We referred to [36], [23], [24] and [3] in the formalization.
Screening length in dusty plasma crystals
Nikolaev, V. S.; Timofeev, A. V.
2016-11-01
Particles interaction and value of the screening length in dusty plasma systems are of great interest in dusty plasma area. Three inter-particle potentials (Debye potential, Gurevich potential and interaction potential in the weakly collisional regime) are used to solve equilibrium equations for two dusty particles suspended in a parabolic trap. The inter-particle distance dependence on screening length, trap parameter and particle charge is obtained. The functional form of inter-particle distance dependence on ion temperature is investigated and compared with experimental data at 200-300 K in order to test used potentials applicability to dusty plasma systems at room temperatures. The preference is given to the Yukawa-type potential including effective values of particle charge and screening length. The estimated effective value of the screening length is 5-15 times larger than the Debye length.
Collisional Scaling of the Energy Transfer in Drift-Wave Zonal Flow Turbulence.
Schmid, B; Manz, P; Ramisch, M; Stroth, U
2017-02-03
The collisionality scaling of density and potential coupling together with zonal flow energy transfer and spectral power is investigated at the stellarator experiment TJ-K. With a poloidal probe array, consisting of 128 Langmuir probes, density and potential fluctuations are measured on four neighboring flux surfaces simultaneously over the complete poloidal circumference. By analyzing Reynolds stress and pseudo-Reynolds stress, it is found that, for increasing collisionality, the coupling between density and potential decreases which hinders the zonal flow drive. Also, as a consequence, the nonlinear energy transfer, as well as the zonal flow contribution to the complete turbulent spectrum, decreases the same way. This is in line with theoretical expectations and is a first experimental verification of the importance of collisionality for large-scale structure formation in magnetically confined toroidal plasmas.
Collisional transport across the magnetic field in drift-fluid models
DEFF Research Database (Denmark)
Madsen, Jens; Naulin, Volker; Nielsen, Anders Henry;
2016-01-01
Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without...... simulations. We further derive a computationally efficient, two-dimensional model, which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field...... located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model employs a computational expedient model for collisional transport. Numerical simulations show good agreement between the full and the simplified model for collisional transport....
A dynamical model of plasma turbulence in the solar wind.
Howes, G G
2015-05-13
A dynamical approach, rather than the usual statistical approach, is taken to explore the physical mechanisms underlying the nonlinear transfer of energy, the damping of the turbulent fluctuations, and the development of coherent structures in kinetic plasma turbulence. It is argued that the linear and nonlinear dynamics of Alfvén waves are responsible, at a very fundamental level, for some of the key qualitative features of plasma turbulence that distinguish it from hydrodynamic turbulence, including the anisotropic cascade of energy and the development of current sheets at small scales. The first dynamical model of kinetic turbulence in the weakly collisional solar wind plasma that combines self-consistently the physics of Alfvén waves with the development of small-scale current sheets is presented and its physical implications are discussed. This model leads to a simplified perspective on the nature of turbulence in a weakly collisional plasma: the nonlinear interactions responsible for the turbulent cascade of energy and the formation of current sheets are essentially fluid in nature, while the collisionless damping of the turbulent fluctuations and the energy injection by kinetic instabilities are essentially kinetic in nature.
Collisional quenching of highly rotationally excited HF
Yang, Benhui; Forrey, R C; Stancil, P C; Balakrishnan, N
2015-01-01
Collisional excitation rate coefficients play an important role in the dynamics of energy transfer in the interstellar medium. In particular, accurate rotational excitation rates are needed to interpret microwave and infrared observations of the interstellar gas for nonlocal thermodynamic equilibrium line formation. Theoretical cross sections and rate coefficients for collisional deexcitation of rotationally excited HF in the vibrational ground state are reported. The quantum-mechanical close-coupling approach implemented in the nonreactive scattering code MOLSCAT was applied in the cross section and rate coefficient calculations on an accurate 2D HF-He potential energy surface. Estimates of rate coefficients for H and H$_2$ colliders were obtained from the HF-He collisional data with a reduced-potential scaling approach. The calculation of state-to-state rotational quenching cross sections for HF due to He with initial rotational levels up to $j=20$ were performed for kinetic energies from 10$^{-5}$ to 15000...
Collisional excitation of water by hydrogen atoms
Daniel, F; Dagdigian, P J; Dubernet, M -L; lique, F; forêts, G Pineau des
2014-01-01
We present quantum dynamical calculations that describe the rotational excitation of H$_2$O due to collisions with H atoms. We used a recent, high accuracy potential energy surface, and solved the collisional dynamics with the close-coupling formalism, for total energies up to 12 000 cm$^{-1}$. From these calculations, we obtained collisional rate coefficients for the first 45 energy levels of both ortho- and para-H$_2$O and for temperatures in the range T = 5-1500 K. These rate coefficients are subsequently compared to the values previously published for the H$_2$O / He and H$_2$O / H$_2$ collisional systems. It is shown that no simple relation exists between the three systems and that specific calculations are thus mandatory.
Expansion of Collisional Radiative Model for Helium line ratio spectroscopy
Cinquegrani, David; Cooper, Chris; Forest, Cary; Milhone, Jason; Munoz-Borges, Jorge; Schmitz, Oliver; Unterberg, Ezekial
2015-11-01
Helium line ratio spectroscopy is a powerful technique of active plasma edge spectroscopy. It enables reconstruction of plasma edge parameters like electron density and temperature by use of suitable Collisional Radiative Models (CRM). An established approach is successful at moderate plasma densities (~1018m-3 range) and temperature (30-300eV), taking recombination and charge exchange to be negligible. The goal of this work is to experimentally explore limitations of this approach to CRM. For basic validation the Madison Plasma Dynamo eXperiment (MPDX) will be used. MPDX offers a very uniform plasma and spherical symmetry at low temperature (5-20 eV) and low density (1016 -1017m-3) . Initial data from MPDX shows a deviation in CRM results when compared to Langmuir probe data. This discrepancy points to the importance of recombination effects. The validated model is applied to first time measurement of electron density and temperature in front of an ICRH antenna at the TEXTOR tokamak. These measurements are important to understand RF coupling and PMI physics at the antenna limiters. Work supported in part by start up funds of the Department of Engineering Physics at the UW - Madison, USA and NSF CAREER award PHY-1455210.
Evolution of a Gaussian laser beam in warm collisional magnetoplasma
Jafari, M. J.; Jafari Milani, M. R.; Niknam, A. R.
2016-07-01
In this paper, the spatial evolution of an intense circularly polarized Gaussian laser beam propagated through a warm plasma is investigated, taking into account the ponderomotive force, Ohmic heating, external magnetic field, and collisional effects. Using the momentum transfer and energy equations, both modified electron temperature and electron density in plasma are obtained. By introducing the complex dielectric permittivity of warm magnetized plasma and using the complex eikonal function, coupled differential equations for beam width parameter are established and solved numerically. The effects of polarization state of laser and magnetic field on the laser spot size evolution are studied. It is observed that in case of the right-handed polarization, an increase in the value of external magnetic field causes an increase in the strength of the self-focusing, especially in the higher values, and consequently, the self-focusing occurs in shorter distance of propagation. Moreover, the results demonstrate the existence of laser intensity and electron temperature ranges where self-focusing can occur, while the beam diverges outside of these regions; meanwhile, in these intervals, there exists a turning point for each of intensity and temperature in which the self-focusing process has its strongest strength. Finally, it is found that the self-focusing effect can be enhanced by increasing the plasma frequency (plasma density).
Study of Coupling between a Plasma Source and Plasma Fluctuations
Berumen, Jorge; Chu, Feng; Hood, Ryan; Mattingly, Sean; Rogers, Anthony; Skiff, Fred
2014-10-01
An experimental study on the coupling between a plasma source and plasma fluctuations in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional is presented. Typical plasma conditions are n ~1010 cm-3 Te ~ 3 eV and B ~ 1 kG. Amplitude Modulation (AM) of the inductively-coupled RF plasma source is produced near the fundamental-mode ion-acoustic wave frequency (~1 kHz) to study the effects of the source-wave interaction and plasma production. Density fluctuation measurements are implemented using Laser-Induced Fluorescence techniques and Langmuir probes. We apply coherent detection with respect to the wave frequency to obtain the perturbed ion distribution function associated with the waves. Measurements of fluctuating I-V traces from a Langmuir probe array and antenna current load are also used to show the effects of the interaction. We would like to acknowledge DOE DE-FG02-99ER54543 for their financial support throughout this research.
Chen, Jiunn-Wei; Song, Yu-Kun; Wang, Qun
2012-01-01
We calculate the shear (eta) and bulk (zeta) viscosities of a weakly coupled quark gluon plasma at the leading-log order with finite temperature T and quark chemical potential mu. We find that the shear viscosity to entropy density ratio eta/s increases monotonically with mu and eventually scales as (mu/T)^2 at large mu. In contrary, zeta/s is insensitive to mu. Both eta/s and zeta/s are monotonically decreasing functions of the quark flavor number N_f when N_f \\geq 2. This property is also observed in pion gas systems. Our perturbative calculation suggests that QCD becomes the most perfect (i.e. with the smallest eta/s) at mu=0 and N_f = 16 (the maximum N_f with asymptotic freedom). It would be interesting to test whether the currently smallest eta/s computed close to the phase transition with mu=0 and N_f = 0 can be further reduced by increasing N_f.
Propinquity of current and vortex structures: effects on collisionless plasma heating
Parashar, Tulasi N
2016-01-01
Intermittency of heating in weakly collisional plasma turbulence is an active subject of research, with significant potential impact on understanding of the solar wind, solar corona and astrophysical plasmas. Recent studies suggest a role of vorticity in plasma heating. In magnetohydrodynamics small scale vorticity is generated near current sheets and this effect persists in kinetic plasma, as demonstrated here with hybrid and fully kinetic Particle-In-Cell (PIC) simulations. Furthermore, vorticity enhances local kinetic effects, with a generalized resonance condition selecting sign-dependent enhancements or reductions of proton heating and thermal anisotropy. In such plasmas heating is correlated with vorticity and current density, but more strongly with vorticity. These results help explain several prior results that find kinetic effects and energization near to, but not centered on, current sheets. Evidently intermittency in kinetic plasma involves multiple physical quantities, and the associated coherent ...
Spatial structure of a collisionally inhomogeneous Bose-Einstein condensate
Energy Technology Data Exchange (ETDEWEB)
Li, Fei, E-mail: wiself@gmail.com [Hunan First Normal University, Department of Education Science (China); Zhang, Dongxia; Rong, Shiguang; Xu, Ying [Hunan University of Science and Technology, Department of Physics (China)
2013-11-15
The spatial structure of a collisionally inhomogeneous Bose-Einstein condensate (BEC) in an optical lattice is studied. A spatially dependent current with an explicit analytic expression is found in the case with a spatially dependent BEC phase. The oscillating amplitude of the current can be adjusted by a Feshbach resonance, and the intensity of the current depends heavily on the initial and boundary conditions. Increasing the oscillating amplitude of the current can force the system to pass from a single-periodic spatial structure into a very complex state. But in the case with a constant phase, the spatially dependent current disappears and the Melnikov chaotic criterion is obtained via a perturbative analysis in the presence of a weak optical lattice potential. Numerical simulations show that a strong optical lattice potential can lead BEC atoms to a state with a chaotic spatial distribution via a quasiperiodic route.
Dependence of intermittent density fluctuations on collisionality in TJ-K
Energy Technology Data Exchange (ETDEWEB)
Reuther, Kyle; Garland, Stephen; Ramisch, Mirko [Institut fuer Grenzflaechenverfahrenstechnikund Plasmatechnologie, Universitaet Stuttgart (Germany); Manz, Peter [Physik-Department E28, Technische Universitaet Muenchen, Garching (Germany)
2016-07-01
Particle and heat transport losses due to edge turbulence are well known phenomena commonly seen in toroidal magnetic confinement devices. Furthermore in the scrape-off layer (SOL), turbulent density fluctuations are often observed to be intermittent and dominate particle transport to the vessel walls. In the adiabatic limit (small collisionality), of the two-field Hasegawa-Wakatani model, simulated turbulent density fluctuations are observed to couple to potential fluctuations and exhibit Gaussian behavior. However, in the hydrodynamic limit (large collisionality) the density and potential decouple. As a result, the density becomes passively advected, evolves towards the vorticity, and exhibits intermittent behavior. The relationship between collisionality and intermittency is investigated experimentally at the stellarator TJ-K. To vary the plasma collisionality, which is related to electron density and temperature, parameters such as gas type, neutral gas pressure, magnetic field, and heating power are varied. Radial profiles of plasma density, temperature, floating potential, and vorticity are recorded via a scanning 7-tip Langmuir probe array. First results are presented.
Without the weak force, the sun wouldn't shine. The weak force causes beta decay, a form of radioactivity that triggers nuclear fusion in the heart of the sun. The weak force is unlike other forces: it is characterised by disintegration. In beta decay, a down quark transforms into an up quark and an electron is emitted. Some materials are more radioactive than others because the delicate balance between the strong force and the weak force varies depending on the number of particles in the atomic nucleus. We live in the midst of a natural radioactive background that varies from region to region. For example, in Cornwall where there is a lot of granite, levels of background radiation are much higher than in the Geneva region. Text for the interactive: Move the Geiger counter to find out which samples are radioactive - you may be surprised. It is the weak force that is responsible for the Beta radioactivity here. The electrons emitted do not cross the plastic cover. Why do you think there is some detected radioa...
Collisional evolution of eccentric planetesimal swarms
Wyatt, M C; Payne, M J; Churcher, L J
2009-01-01
Models for the steady state collisional evolution of low eccentricity planetesimal belts identify debris disks with hot dust at 1AU, like eta Corvi and HD69830, as anomalous since collisional processing should have removed most of the planetesimal mass over their >1 Gyr lifetimes. This paper looks at the effect of large planetesimal eccentricities (e>>0.3) on their collisional lifetime and the amount of mass that can remain at late times M_{late}. For an axisymmetric planetesimal disk with common pericentres and eccentricities e, we find that M_{late} \\propto e^{-5/3}(1+e)^{4/3}(1-e)^{-3}. For a scattered disk-like population (i.e., common pericentres), in the absence of dynamical evolution, the mass evolution at late times would be as if only planetesimals with the largest eccentricity were present. Despite the increased remaining mass, higher eccentricities do not increase the hot emission from the collisional cascade until e>0.99, partly because most collisions occur near pericentre thus increasing the dus...
Analyses of the short pulse laser pumped transient collisional excited X-ray lasers
Energy Technology Data Exchange (ETDEWEB)
Sasaki, A.; Utsumi, T.; Moribayashi, K.; Zhidkov, A.; Kado, M.; Tanaka, M.; Hasegawa, N.; Kawachi, T. [Japan Atomic Energy Research Inst., Osaka (Japan). Advanced Photon Research Center
2001-07-01
The soft X-ray gain of the transient collisional excited (TCE) Ni-like Ag laser is investigated using the plasma hydrodynamics and atomic kinetics codes. The gain is calculated for a plasma produced from two 100ps laser irradiated solid target to show qualitative agreement with the experiment. The calculation shows significant improvement of the gain using a thin foil target pumped by two short laser pulses, because of a better coupling of the pump laser energy into the gain region of the plasma. The codes will provide performance prediction as well as optimization of the experimental studies of the TCE X-ray lasers. (orig.)
[Plasma properties research: Task 3
Energy Technology Data Exchange (ETDEWEB)
1992-12-31
The principal research activities of the Magneto-Fluid Dynamics Division relate to magnetic fusion plasma physics. In addition, there is a modest amount of work in closely related areas, including space plasma physics, fluid dynamics, and dynamical systems. Members of the Magneto-Fluid Dynamics Division maintain close contacts with fusion researchers in the US and abroad. Some of the work of the Division is clearly directed towards ITER and TPX, while other problems relate to the broader development of fusion plasma physics and to the support of other issues arising in the many experimental programs. Topics of some note in the last year that are discussed in this report are: Application of sophisticated statistical techniques to tokamak data reduction, including time series analysis of TFTR fluctuation data and spline analysis of profile data. Continuing development of edge plasma and divertor modelling, including initial ergodic divertor studies. Analysis of energetic fusion products losses from TFTR plasmas. Examination of anomalous transport in dynamical systems induced by chaotic-like Hamiltonian motion. Numerical simulation of the development of singular MHD equilibria. Exploration of the validity of moment expansions of kinetic equations for weakly collisional systems. Studies of RF- and ripple-induced helium ash removal. Ballooning mode studies in fluids and rotating stars. Studies in dynamical systems, including explosive instabilities, development of chaos, and motion of collisionless particles in a domain with overlapping islands.
[Plasma properties research: Task 3
Energy Technology Data Exchange (ETDEWEB)
1992-01-01
The principal research activities of the Magneto-Fluid Dynamics Division relate to magnetic fusion plasma physics. In addition, there is a modest amount of work in closely related areas, including space plasma physics, fluid dynamics, and dynamical systems. Members of the Magneto-Fluid Dynamics Division maintain close contacts with fusion researchers in the US and abroad. Some of the work of the Division is clearly directed towards ITER and TPX, while other problems relate to the broader development of fusion plasma physics and to the support of other issues arising in the many experimental programs. Topics of some note in the last year that are discussed in this report are: Application of sophisticated statistical techniques to tokamak data reduction, including time series analysis of TFTR fluctuation data and spline analysis of profile data. Continuing development of edge plasma and divertor modelling, including initial ergodic divertor studies. Analysis of energetic fusion products losses from TFTR plasmas. Examination of anomalous transport in dynamical systems induced by chaotic-like Hamiltonian motion. Numerical simulation of the development of singular MHD equilibria. Exploration of the validity of moment expansions of kinetic equations for weakly collisional systems. Studies of RF- and ripple-induced helium ash removal. Ballooning mode studies in fluids and rotating stars. Studies in dynamical systems, including explosive instabilities, development of chaos, and motion of collisionless particles in a domain with overlapping islands.
Plasma effect of the Houston horse
Pavlov, V. A.; Tryaskin, Ya. V.
2015-05-01
The effect of a strong shock wave on a weakly ionized collisional plasma was studied. The structure of the ion-acoustic perturbation caused by the shock wave was numerically investigated. The effect of the nonlinearity, dispersion, and dissipation on the formation of an oscillating wave profile was shown. It is found that in some modes, an increase in the shock wave velocity leads to a sharp increase in the concentration of charged particles and a reduction in the number of perturbation maxima. This change of the flow structure can be preceded by the formation of localized regions with an increased degree of plasma ionization. It is shown that the presence of plasmoids can lead to a strong influence of charges on the neutral component.
Eigenvalue solution to the electron-collisional effect on ion-acoustic and entropy waves
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The linearized electron Fokker-Planck and cold-ion fluid equations are solved as an eigenvalue problem in the quasineutral limit for ionization state,Z=1,8,and 64 for ion-acoustic and entropy waves.The perturbed electron distribution function is written as a moment expansion of eigenvectors,and is used to compute collisionality-dependence macroscopic quantities in the plasma such as the generalized specific heat ratio,and the electron thermal conductivity.
Ambient tremors in a collisional orogenic belt
Chuang, Lindsay Yuling; Chen, Kate Huihsuan; Wech, Aaron G.; Byrne, Timothy; Peng, Wei
2014-01-01
Deep-seated tectonic tremors have been regarded as an observation tied to interconnected fluids at depth, which have been well documented in worldwide subduction zones and transform faults but not in a collisional mountain belt. In this study we explore the general features of collisional tremors in Taiwan and discuss the possible generation mechanism. In the 4 year data, we find 231 ambient tremor episodes with durations ranging from 5 to 30 min. In addition to a coseismic slip-induced stress change from nearby major earthquake, increased tremor rate is also highly correlated with the active, normal faulting earthquake swarms at the shallower depth. Both the tremor and earthquake swarm activities are confined in a small, area where the high attenuation, high thermal anomaly, the boundary between high and low resistivity, and localized veins on the surfaces distributed, suggesting the involvement of fluids from metamorphic dehydration within the orogen.
Collisional Simulations of Neptune's Ring Arcs
Hänninen, J.; Porco, C.
1997-03-01
The currently accepted model for Neptune arc confinement relies on the radial and azimuthal confining perturbations due to the nearby satellite, Galatea. This model calls for arc particle orbits exhibiting a negative eccentricity gradient and crossing at quadrature, a configuration that paradoxically leads to collisions energetic enough to disrupt arc confinement. We confirm with numerical collisional N-body simulations that the confinement mechanism relying on a 42:43 corotation-inclination resonance and a 42:43 outer Lindblad resonance with Galatea is indeed capable of confining a large population of 10-m-size and bigger particles over short time scales. Moreover, we find that an 84:86 outer vertical resonance, also due to Galatea, falling within 20 m of the arcs' radial position, effectively reduces the collision frequency and relative collisional velocities and consequently stabilizes the arcs over long time scales against the disruptive effects of collisions.
Collisional and collisionless expansion of Yukawa balls.
Piel, Alexander; Goree, John A
2013-12-01
The expansion of Yukawa balls is studied by means of molecular dynamics simulations of collisionless and collisional situations. High computation speed was achieved by using the parallel computing power of graphics processing units. When the radius of the Yukawa ball is large compared to the shielding length, the expansion process starts with the blow-off of the outermost layer. A rarefactive wave subsequently propagates radially inward at the speed of longitudinal phonons. This mechanism is fundamentally different from Coulomb explosions, which employ a self-similar expansion of the entire system. In the collisionless limit, the outer layers carry away most of the available energy. The simulations are compared with analytical estimates. In the collisional case, the expansion process can be described by a nonlinear diffusion equation that is a special case of the porous medium equation.
Molecular spectroscopy and collisional excitation. [in astrophysics
Green, S.
1975-01-01
The paper examines the basic principles underlying the molecular transitions responsible for interstellar molecular spectra. The energy levels of molecules are discussed in detail with special attention given to the Born-Oppenheimer approximation, the electronic Hamiltonian, and the parameters of vibrational and rotational energy. The probabilities for radiative and collisional transitions are calculated. A brief review of techniques for molecular spectroscopy is presented along with methods used to determine collision cross sections on both an experimental and a theoretical basis.
Collisionally induced atomic clock shifts and correlations
Energy Technology Data Exchange (ETDEWEB)
Band, Y. B.; Osherov, I. [Departments of Chemistry and Electro-Optics and the Ilse Katz Center for Nano-Science, Ben-Gurion University, Beer-Sheva 84105 (Israel)
2011-07-15
We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.
Introduction to Plasma Physics
Gurnett, Donald A.; Bhattacharjee, Amitava
2017-03-01
Preface; 1. Introduction; 2. Characteristic parameters of a plasma; 3. Single particle motions; 4. Waves in a cold plasma; 5. Kinetic theory and the moment equations; 6. Magnetohydrodynamics; 7. MHD equilibria and stability; 8. Discontinuities and shock waves; 9. Electrostatic waves in a hot unmagnetized plasma; 10. Waves in a hot magnetized plasma; 11. Nonlinear effects; 12. Collisional processes; Appendix A. Symbols; Appendix B. Useful trigonometric identities; Appendix C. Vector differential operators; Appendix D. Vector calculus identities; Index.
Selleri, Franco
2015-01-01
Weak Relativity is an equivalent theory to Special Relativity according to Reichenbach’s definition, where the parameter epsilon equals to 0. It formulates a Neo-Lorentzian approach by replacing the Lorentz transformations with a new set named “Inertial Transformations”, thus explaining the Sagnac effect, the twin paradox and the trip from the future to the past in an easy and elegant way. The cosmic microwave background is suggested as a possible privileged reference system. Most importantly, being a theory based on experimental proofs, rather than mutual consensus, it offers a physical description of reality independent of the human observation.
Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry
Energy Technology Data Exchange (ETDEWEB)
Koh, S.; Choe, W. [Korea Advanced Institute of Science and Technology, Department of Physics, Daejeon 305-701 (Korea, Republic of); Chang, C. S.; Ku, S.; Menard, J. E. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Weitzner, H. [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)
2012-07-15
The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A drift-kinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al., Phys. Plasmas 6, 2834 (1999)] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity
Mobility in a strongly coupled dusty plasma with gas
Liu, Bin; Goree, J.
2014-04-01
The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force F, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity up. The mobility μp=up/F of the projectile's motion is obtained. Two regimes depending on F are identified. In the high-force regime, μp∝F0.23, and the scattering cross section σs diminishes as up-6/5. Results for σs are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.
Mobility in a strongly coupled dusty plasma with gas
Liu, Bin
2014-01-01
The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force $F$, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity $u_p$. The mobility $\\mu_p=u_p/F$ of the projectile's motion is obtained. Two regimes depending on $F$ are identified. In the high force regime, $\\mu_p \\propto F^{0.23}$, and the scattering cross section $\\sigma_s$ diminishes as $u_p^{-6/5}$. Results for $\\sigma_s$ are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.
Excitation and ionization of hydrogen Rydberg states in a plasma
Energy Technology Data Exchange (ETDEWEB)
Glab, W.; Nayfeh, M.H.
1982-08-01
Hydrogen Rydberg states in a hydrogen plasma are optically excited from the plasma-excited n = 2 state. Photoionization and optogalvanic, which are due to electron-impact ionization and other collisional processes, are used to monitor the Rydberg states. This process may be used to study collisional ionization of the Rydberg states.
Excitation and ionization of hydrogen Rydberg states in a plasma.
Glab, W; Nayfeh, M H
1982-08-01
Hydrogen Rydberg states in a hydrogen plasma are optically excited from the plasma-excited n = 2 state. Photoionization and optogalvanic ionization, which is due to electron-impact ionization and other collisional processes, are used to monitor the Rydberg states. This process may be used to study collisional ionization of the Rydberg states.
Energy Technology Data Exchange (ETDEWEB)
Wang, G. Q.; Ma, J. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Centre for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei 230031 (China); Weiland, J.; Zang, Q. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)
2013-10-15
We have made the first drift wave study of particle transport in the Experimental Advanced Superconducting Tokamak (Wan et al., Nucl. Fusion 49, 104011 (2009)). The results reveal that collisions make the particle flux more inward in the high collisionality regime. This can be traced back to effects that are quadratic in the collision frequency. The particle pinch is due to electron trapping which is not very efficient in the high collisionality regime so the approach to equilibrium is slow. We have included also the electron temperature gradient (ETG) mode to give the right electron temperature gradient, since the Trapped Electron Mode (TE mode) is weak in this regime. However, at the ETG mode number ions are Boltzmann distributed so the ETG mode does not give particle transport.
Collisional-radiative model for the visible spectrum of W{sup 26+} ions
Energy Technology Data Exchange (ETDEWEB)
Ding, Xiaobin, E-mail: dingxb@nwnu.edu.cn [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu, Jiaxin [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Koike, Fumihiro [Department of Physics, Sophia University, Tokyo, 102-8554 (Japan); Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Nakamura, Nobuyuki [Institute for Laser Science, The University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Dong, Chenzhong [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)
2016-02-22
Plasma diagnostics in magnetic confinement fusion plasmas by using visible spectrum strongly depends on the knowledge of fundamental atomic properties. A detailed collisional-radiative model of W{sup 26+} ions has been constructed by considering radiative and electron excitation processes, in which the necessary atomic data had been calculated by relativistic configuration interaction method with the implementation of Flexible Atomic Code. The visible spectrum observed at an electron beam ion trap (EBIT) in Shanghai in the range of 332 nm to 392 nm was reproduced by present calculations. Some transition pairs of which the intensity ratio is sensitive to the electron density were selected as potential candidates of plasma diagnostics. Their electron density dependence is theoretically evaluated for the cases of EBIT plasmas and magnetic confinement fusion plasmas.
Collisional-Radiative Model for the visible spectrum of $W^{26+}$ ions
Ding, Xiaobin; Koike, Fumihiro; Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A; Nakamura, Nobuyuki; Dong, Chenzhong
2015-01-01
Plasma diagnostics in magnetic confinement fusion plasmas by using visible spectrum strongly depends on the knowledge of fundamental atomic properties. A detailed collisional-radiative model of W$^{26+}$ ions has been constructed by considering radiative and electron excitation processes, in which the necessary atomic data had been calculated by relativistic configuration interaction method with the implementation of Flexible Atomic Code. The visible spectrum observed at an electron beam ion trap (EBIT) in Shanghai in the range of 332 nm to 392 nm was reproduced by present calculations. Some transition pairs of which the intensity ratio are sensitive to the electron density were selected as potential candidate of plasma diagnostics. Their electron density dependence are theoretically evaluated for the cases of EBIT plasmas and magnetic confinement fusion plasmas.
Measuring Kinetic Plasma Eigenmodes
Mattingly, Sean; Berumen, Jorge; Chu, Feng; Hood, Ryan; Skiff, Fred
2015-11-01
We present a method for measuring kinetic plasma eigenmodes of a cylindrical axially magnetized (1 kG) laboratory plasma (n ~109cm-3 , Te ~ 5eV , Ti ~ 0 . 06eV) by measuring velocity space correlation functions. This method simultaneously observes two separate laser induced fluorescence schemes. Each scheme has its own indepedently tunable laser and its own set of collection optics. With this setup, we are able to measure the time - averaged correlation function as a function of position on the cylindrical axis parallel to the magnetic field (z) and velocity on the deconvolved ion velocity distribution function (v) : C (z , v ,z' ,v' , τ) = t. The freedom of two lasers allows us to measure a two dimensional velocity correlation matrix. This matrix is investigated with the Vlasov equation in the collisionless and weakly collisional regime. The former case, which is continuous, is diagonalized with an integral transform defined by P. J. Morrison while the latter case, which is discrete, is diagonalized through the use of Hermite polynomials.
Collisional-Radiative Modeling of Tungsten at Temperatures of 1200–2400 eV
Directory of Open Access Journals (Sweden)
James Colgan
2015-04-01
Full Text Available We discuss new collisional-radiative modeling calculations of tungsten at moderate temperatures of 1200 to 2400 eV. Such plasma conditions are relevant to ongoing experimental work at ASDEX Upgrade and are expected to be relevant for ITER. Our calculations are made using the Los Alamos National Laboratory (LANL collisional-radiative modeling ATOMIC code. These calculations formed part of a submission to the recent NLTE-8 workshop that was held in November 2013. This series of workshops provides a forum for detailed comparison of plasma and spectral quantities from NLTE collisional-radiative modeling codes. We focus on the LANL ATOMIC calculations for tungsten that were submitted to the NLTE-8 workshop and discuss different models that were constructed to predict the tungsten emission. In particular, we discuss comparisons between semi-relativistic configuration-average and fully relativistic configuration-average calculations. We also present semi-relativistic calculations that include fine-structure detail, and discuss the difficult problem of ensuring completeness with respect to the number of configurations included in a CR calculation.
Weakly relativistic dispersion of Bernstein waves
Robinson, P. A.
1988-01-01
Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.
Weakly relativistic dispersion of Bernstein waves
Robinson, P. A.
1988-01-01
Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.
Turbulent dynamo in a collisionless plasma.
Rincon, François; Califano, Francesco; Schekochihin, Alexander A; Valentini, Francesco
2016-04-12
Magnetic fields pervade the entire universe and affect the formation and evolution of astrophysical systems from cosmological to planetary scales. The generation and dynamical amplification of extragalactic magnetic fields through cosmic times (up to microgauss levels reported in nearby galaxy clusters, near equipartition with kinetic energy of plasma motions, and on scales of at least tens of kiloparsecs) are major puzzles largely unconstrained by observations. A dynamo effect converting kinetic flow energy into magnetic energy is often invoked in that context; however, extragalactic plasmas are weakly collisional (as opposed to magnetohydrodynamic fluids), and whether magnetic field growth and sustainment through an efficient turbulent dynamo instability are possible in such plasmas is not established. Fully kinetic numerical simulations of the Vlasov equation in a 6D-phase space necessary to answer this question have, until recently, remained beyond computational capabilities. Here, we show by means of such simulations that magnetic field amplification by dynamo instability does occur in a stochastically driven, nonrelativistic subsonic flow of initially unmagnetized collisionless plasma. We also find that the dynamo self-accelerates and becomes entangled with kinetic instabilities as magnetization increases. The results suggest that such a plasma dynamo may be realizable in laboratory experiments, support the idea that intracluster medium turbulence may have significantly contributed to the amplification of cluster magnetic fields up to near-equipartition levels on a timescale shorter than the Hubble time, and emphasize the crucial role of multiscale kinetic physics in high-energy astrophysical plasmas.
Al Kaissi, Ali; Ryabykh, Sergey; Ochirova, Polina; Kenis, Vladimir; Hofstätter, Jochen G.; Grill, Franz; Ganger, Rudolf; Kircher, Susanne Gerit
2017-01-01
Marked ligamentous hyperlaxity and muscle weakness/wasting associated with awkward gait are the main deficits confused with the diagnosis of myopathy. Seven children (6 boys and 1 girl with an average age of 8 years) were referred to our department because of diverse forms of skeletal abnormalities. No definitive diagnosis was made, and all underwent a series of sophisticated investigations in other institutes in favor of myopathy. We applied our methodology through the clinical and radiographic phenotypes followed by targeted genotypic confirmation. Three children (2 boys and 1 girl) were compatible with the diagnosis of progressive pseudorheumatoid chondrodysplasia. The genetic mutation was correlated with the WISP 3 gene actively expressed by articular chondrocytes and located on chromosome 6. Klinefelter syndrome was the diagnosis in 2 boys. Karyotyping confirmed 47,XXY (aneuploidy of Klinefelter syndrome). And 2 boys were finally diagnosed with Morquio syndrome (MPS type IV A) as both showed missense mutations in the N-acetylgalactosamine-sulfate sulfatase gene. Misdiagnosis can lead to the initiation of a long list of sophisticated investigations. PMID:28210640
Collisional evolution of the early asteroid belt
Gil-Hutton, Ricardo; Brunini, Adrián
1999-04-01
We present numerical results obtained by a simulation of the collisional process between asteroids and scattered comets from the Uranus-Neptune zone. This mechanism allows the use of single exponent incremental size distributions for the initial belt reaching a final distribution that matches the observed population very well. Since the cometary bombardment was extremely efficient removing mass from the primordial asteroid belt in a very short time, we always obtained belts with total masses less than 0.001 M ⊕ after ≈ 2×10 7 yrs. This result allows processes with an important initial mass preserving Vestas basaltic crust.
Missing Mass in Collisional Debris from Galaxies
Bournaud, F; Brinks, E; Boquien, M; Amram, P; Lisenfeld, U; Koribalski, B S; Walter, F; Charmandaris, V
2007-01-01
Recycled dwarf galaxies can form in the collisional debris of massive galaxies. Theoretical models predict that, contrary to classical galaxies, they should be free of non-baryonic Dark Matter. Analyzing the observed gas kinematics of such recycled galaxies with the help of a numerical model, we demonstrate that they do contain a massive dark component amounting to about twice the visible matter. Staying within the standard cosmological framework, this result most likely indicates the presence of large amounts of unseen, presumably cold, molecular gas. This additional mass should be present in the disks of their progenitor spiral galaxies, accounting for a significant part of the so-called missing baryons.
Drake, D J; Howes, G G; Kletzing, C A; Skiff, F; Carter, T A; Auerbach, D W
2013-01-01
Turbulence is a phenomenon found throughout space and astrophysical plasmas. It plays an important role in solar coronal heating, acceleration of the solar wind, and heating of the interstellar medium. Turbulence in these regimes is dominated by Alfven waves. Most turbulence theories have been established using ideal plasma models, such as incompressible MHD. However, there has been no experimental evidence to support the use of such models for weakly to moderately collisional plasmas which are relevant to various space and astrophysical plasma environments. We present the first experiment to measure the nonlinear interaction between two counterpropagating Alfven waves, which is the building block for astrophysical turbulence theories. We present here four distinct tests that demonstrate conclusively that we have indeed measured the daughter Alfven wave generated nonlinearly by a collision between counterpropagating Alfven waves.
Enhanced toroidal flow stabilization of edge localized modes with increased plasma density
Cheng, Shikui; Zhu, Ping; Banerjee, Debabrata
2017-09-01
Toroidal flow alone is generally thought to have an important influence on tokamak edge pedestal stability, even though theoretical analysis often predicts merely a weak stabilizing effect of toroidal flow on the edge localized modes (ELMs) in experimental parameter regimes. For the first time, we find from two-fluid MHD calculations that such a stabilization, however, can be significantly enhanced by increasing the edge plasma density. Our finding resolves a long-standing mystery whether or how toroidal rotation can indeed have an effective influence on ELMs, and explains why the ELM mitigation and suppression by toroidal rotation are more favorably achieved in higher collisionality regime in recent experiments. The finding suggests a new control scheme on modulating toroidal flow stabilization of ELMs with plasma density, along with a new additional constraint on the optimal level of plasma density for the desired edge plasma conditions.
Model for collisional fast ion diffusion into Tokamak Fusion Test Reactor loss cone
Energy Technology Data Exchange (ETDEWEB)
Chang, C.S. [New York Univ., NY (United States). Courant Inst. of Mathematical Sciences]|[Korea Advanced Inst. of Science and Technology, Seoul (Korea, Republic of); Zweben, S.J.; Schivell, J.; Budny, R.; Scott, S. [Princeton Univ., NJ (United States). Plasma Physics Lab.
1994-08-01
An analytic model is developed to estimate the classical pitch angle scattering loss of energetic fusion product ions into prompt loss orbits in a tokamak geometry. The result is applied to alpha particles produced by deutrium-tritium fusion reactions in a plasma condition relevant to Tokamak Fusion Test Reactor (TFTR). A poloidal angular distribution of collisional fast ion loss at the first wall is obtained and the numerical result from the TRANSP code is discussed. The present model includes the effect that the prompt loss boundary moves away from the slowing-down path due to reduction in banana thickness, which enables us to understand, for the first time. the dependence of the collisional loss rate on Z{sub eff}.
Collisional transport across the magnetic field in drift-fluid models
Madsen, Jens; Nielsen, Anders Henry; Rasmussen, Jens Juul
2015-01-01
Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum and pressures in drift-fluid turbulence models and thereby obviate the customary use of artificial diffusion in turbulence simulations. We further derive a computationally efficient, two-dimensional model which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model...
Collisional transport across the magnetic field in drift-fluid models
DEFF Research Database (Denmark)
Madsen, Jens; Naulin, Volker; Nielsen, Anders Henry
2016-01-01
Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without...... altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum, and pressures in drift-fluid turbulence models and, thereby, obviates the customary use of artificial diffusion in turbulence...... simulations. We further derive a computationally efficient, two-dimensional model, which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field...
On the effects of ion-neutral interactions in solar plasmas
Khomenko, Elena
2017-01-01
Solar photosphere and chromosphere are composed of weakly ionized plasma for which collisional coupling decreases with height. This implies a breakdown of some hypotheses underlying magnetohydrodynamics at low altitudes and gives rise to non-ideal MHD effects such as ambipolar diffusion, Hall effect, etc. Recently, there has been progress in understanding the role of these effects for the dynamics and energetics of the solar atmosphere. There are evidences that phenomena such as wave propagation and damping, magnetic reconnection, formation of stable magnetic field concentrations, magnetic flux emergence, etc can be affected. This paper reviews the current state-of-the-art of multi-fluid MHD modeling of the coupled solar atmosphere.
On the effects of ion-neutral interactions in solar plasmas
Khomenko, Elena
2016-01-01
Solar photosphere and chromosphere are composed of weakly ionized plasma for which collisional coupling decreases with height. This implies a breakdown of some hypotheses underlying magnetohydrodynamics at low altitudes and gives rise to non-ideal MHD effects such as ambipolar diffusion, Hall effect, etc. Recently, there has been progress in understanding the role of these effects for the dynamics and energetics of the solar atmosphere. There are evidences that such phenomena as wave propagation and damping, magnetic reconnection, formation of stable magnetic field concentrations, magnetic flux emergence, etc. can be affected. This paper reviews the current state-of-the-art of multi-fluid MHD modeling of the coupled solar atmosphere.
Energy Technology Data Exchange (ETDEWEB)
Gaufridy de Dortan, F. de
2003-03-15
Collisional excitation cross-sections are essential for the modeling of the properties of non equilibrium plasmas. There has been a lot of work on electron impact excitation of isolated ions, but in dense plasmas, neighboring particles are expected to widely disturb these electron transitions in atoms. Plasma modeling through a radially perturbed potential has already been done but is not satisfactory as it does not account for levels degeneracy breaking and its consequences. Introduction of a quasistatic electric micro-field of neighboring ions allows us to break spherical symmetry. Our original theoretical study has given birth to a numerical code that accurately computes collisional strengths and rates (in the Distorted Waves approach) in atoms submitted to a realistic micro-field. Hydrogen- and helium-like aluminium is studied. Stark mixing widely increases rates of transitions from high l levels and forbidden transitions are field-enhanced by many orders of magnitude until they reach allowed ones. Eventually, we conduct an elementary stationary collisional radiative study to investigate field-enhancement effects on corresponding line shapes. In cases we study (aluminium, hydrogen- and helium-like) we find a relatively weak increase of K-shell line broadening.
Silantyev, Denis A; Rose, Harvey A
2016-01-01
We consider two kinds of pumped Langmuir waves (LWs) in the kinetic regime, $k\\lambda_D\\gtrsim0.2,$ where $k$ is the LW wavenumber and $\\lambda_D$ is the Debye length. They are driven to finite amplitude by a coherent external potential whose amplitude is either weak or strong. These dynamically prepared nonlinear LWs develop a transverse (filamentation) instability whose nonlinear evolution destroys the LW's transverse coherence. Instability growth rates in the weakly pumped regime are the same as those of BGK modes considered in Part I, while strongly pumped LWs have higher filamentation grow rates.
Intense sediment transport: Collisional to turbulent suspension
Berzi, Diego; Fraccarollo, Luigi
2016-02-01
A recent simple analytical approach to the problem of steady, uniform transport of sediment by a turbulent shearing fluid dominated by interparticle collisions is extended to the case in which the mean turbulent lift may partially or totally support the weight of the sediment. We treat the granular-fluid mixture as a continuum and make use of constitutive relations of kinetic theory of granular gases to model the particle phase and a simple mixing-length approach for the fluid. We focus on pressure-driven flows over horizontal, erodible beds and divide the flow itself into layers, each dominated by different physical mechanisms. This permits a crude analytical integration of the governing equations and to obtain analytical expressions for the distribution of particle concentration and velocity. The predictions of the theory are compared with existing laboratory measurements on the flow of glass spheres and sand particles in water. We also show how to build a regime map to distinguish between collisional, turbulent-collisional, and fully turbulent suspensions.
The Creation of Haumea's Collisional Family
Schlichting, Hilke E
2009-01-01
Recently, the first collisional family was discovered in the Kuiper belt. The parent body of this family, Haumea, is one of the largest objects in the Kuiper belt and is orbited by two satellites. It has been proposed that the Haumea family was created from dispersed fragments that resulted from a giant impact. This proposed origin of the Haumea family is however in conflict with the observed velocity dispersion between the family members (\\sim 140 m/s) which is significantly less than the escape velocity from Haumea's surface (\\sim 900 m/s). In this paper we propose a different formation scenario for Haumea's collisional family. In our scenario the family members are ejected while in orbit around Haumea. This scenario, therefore, gives naturally rise to a lower velocity dispersion among the family members than expected from direct ejection from Haumea's surface. In our scenario Haumea's giant impact forms a single moon that tidally evolves outward until it suffers a destructive collision from which the famil...
Collisional deactivation of highly vibrationally excited pyrazine
Miller, Laurie A.; Barker, John R.
1996-07-01
The collisional deactivation of vibrationally excited pyrazine (C4N2H4) in the electronic ground state by 19 collider gases was studied using the time-resolved infrared fluorescence (IRF) technique. The pyrazine was photoexcited with a 308 nm laser and its vibrational deactivation was monitored following rapid radiationless transitions to produce vibrationally excited molecules in the electronic ground state. The IRF data were analyzed by a simple approximate inversion method, as well as with full collisional master equation simulations. The average energies transferred in deactivating collisions (d) exhibit a near-linear dependence on vibrational energy at lower energies and less dependence at higher energies. The deactivation of ground state pyrazine was found to be similar to that of ground state benzene [J. R. Barker and B. M. Toselli, Int. Rev. Phys. Chem. 12, 305 (1990)], but it is strikingly different from the deactivation of triplet state pyrazine [T. J. Bevilacqua and R. B. Weisman, J. Chem. Phys. 98, 6316 (1993)].
Collisional Features in Saturn's F Ring
Attree, Nicholas Oliver; Murray, Carl; Cooper, Nicholas; Williams, Gareth
2016-10-01
Saturn's highly dynamic F ring contains a population of small (radius ~ 1 km) moonlets embedded within its core or on nearby orbits. These objects interact, both gravitationally and collisionally, with the ring producing a range of features, some of which are unique to it. Here we present a brief overview of F ring collisional processes, investigated using a combination of Cassini imaging, simulations and orbital dynamics. Collisions produce linear debris clouds, known as 'jets' and 'mini-jets', which evolve, due to differential orbital motion, over periods ranging from hours to months. Mini-jet-forming collisions occur daily in the F ring whilst larger, more dramatic, events are rarer but produce jets that persist for many months, 'wrapping around' the ring to form almost parallel strands. Measuring jet properties, such as formation rates and relative orbits, allows us to infer a local population of order hundreds of objects colliding at relative velocities of a few metres per second. N-body modelling of the collisions shows good agreement with observations when two aggregates are allowed to impact and partially fragment (as opposed to a solid moonlet encountering dust), implying massive objects both in the core and nearby. Multiple, repeated collisions by the same, or fragments of the same, object are also important in explaining some jet morphology, showing that many objects survive the collisions. The F ring represents a natural laboratory for observing low-velocity collisions between icy objects as well as the ongoing aggregation and accretion that most-likely forms them.
Hydrodynamic Models for Multicomponent Plasmas with Collisional-Radiative Kinetics
2014-12-01
characteristics. Paper AIAA- 2011-61, January 2011. [18] J.-L. Cambier, T. Roth , C. Zeineh, and A. R. Karagozian. The pulse deto- nation rocket induced MHD...Cole, T. Roth , A. R. Karagozian, and J.-L. Cambier. Magnetohydrodynamic augmentation of pulse detonation rocket engines. Journal of Propulsion and...Glinsky, W. L. Kruer, S. C. Wilks, J. Wood- worth, E. M. Campbell, M. D. Perry, and R. J. Mason . Ignition and high gain with ultrapowerful lasers
Plasma Instabilities and Magnetic Field Growth in Clusters of Galaxies
Schekochihin, A. A.; Cowley, S. C.; Kulsrud, R. M.; Hammett, G. W.; Sharma, P.
2005-08-01
We show that under very general conditions, cluster plasmas threaded by weak magnetic fields are subject to very fast growing plasma instabilities driven by the anisotropy of the plasma pressure (viscous stress) with respect to the local direction of the magnetic field. Such an anisotropy will naturally arise in any weakly magnetized plasma that has low collisionality and is subject to stirring. The magnetic field must be sufficiently weak for the instabilities to occur, viz., β>~Re1/2. The instabilities are captured by the extended MHD model with Braginskii viscosity. However, their growth rates are proportional to the wavenumber down to the ion gyroscale, so MHD equations with Braginskii viscosity are not well posed and a fully kinetic treatment is necessary. The instabilities can lead to magnetic fields in clusters being amplified from seed strength of ~10-18 G to dynamically important strengths of ~10 μG on cosmologically trivial timescales (~108 yr). The fields produced during the amplification stage are at scales much smaller than observed. Predicting the saturated field scale and structure will require a kinetic theory of magnetized cluster turbulence.
Electron Capture Dissociation of Weakly Bound Polypeptide Polycationic Complexes
DEFF Research Database (Denmark)
Haselmann, Kim F; Jørgensen, Thomas J D; Budnik, Bogdan A;
2002-01-01
We have previously reported that, in electron capture dissociation (ECD), rupture of strong intramolecular bonds in weakly bound supramolecular aggregates can proceed without dissociation of weak intermolecular bonds. This is now illustrated on a series of non-specific peptide-peptide dimers...... as well as specific complexes of modified glycopeptide antibiotics with their target peptide. The weak nature of bonding is substantiated by blackbody infrared dissociation, low-energy collisional excitation and force-field simulations. The results are consistent with a non-ergodic ECD cleavage mechanism....
Energy transfer and dual cascade in kinetic magnetized plasma turbulence.
Plunk, G G; Tatsuno, T
2011-04-22
The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally.
Particle model for nonlocal heat transport in fusion plasmas.
Bufferand, H; Ciraolo, G; Ghendrih, Ph; Lepri, S; Livi, R
2013-02-01
We present a simple stochastic, one-dimensional model for heat transfer in weakly collisional media as fusion plasmas. Energies of plasma particles are treated as lattice random variables interacting with a rate inversely proportional to their energy schematizing a screened Coulomb interaction. We consider both the equilibrium (microcanonical) and nonequilibrium case in which the system is in contact with heat baths at different temperatures. The model exhibits a characteristic length of thermalization that can be associated with an interaction mean free path and one observes a transition from ballistic to diffusive regime depending on the average energy of the system. A mean-field expression for heat flux is deduced from system heat transport properties. Finally, it is shown that the nonequilibrium steady state is characterized by long-range correlations.
The mechanisms as well the genetics underlying bioavailability and metabolism of carotenoids in humans remains unclear. The individual temporal response of plasma carotenoids was analyzed in adults who consumed carotenoid-containing juices on a controlled-diet study using cluster analysis. Treatmen...
Thayer, Jeffrey; Hsu, Vicki
2015-04-01
The high-latitude regions of Earth’s upper atmosphere are strongly influenced by plasma-neutral interactions. These interactions couple electrodynamic processes of the ionosphere with hydrodynamic processes of the more abundant thermosphere neutral gas, consequently connecting the high-latitude upper atmosphere to distant regions of the geoplasma environment. This produces a complex spatial and temporal interplay of competing processes that results in a myriad of physical and chemical responses and a rich array of neutral and plasma morphologies that constitute the high-latitude thermosphere and ionosphere. The altitude extent from the lower thermosphere to the upper ionosphere (90km - 1000km) can be considered Earth’s space-atmosphere interaction region - likened to the solar chromosphere’s interaction region where radiative processes and hydrodynamic waves from the dense lower atmosphere produce a cold lower boundary that quickly transitions over a few 100 kilometers to neutral and plasma temperatures that are five times hotter. A thousand or more kilometers further in altitude, Earth's upper atmosphere becomes a hot, collisionless, geomagnetically controlled protonosphere whose neutral and plasma population originates from the thermosphere and ionosphere. A grand challenge in the study of Earth’s interaction region is how the collision-dominated thermosphere/ionosphere system exchanges energy, mass and momentum with the collisionless magnetosphere. This talk will focus primarily on collision-dominated processes of the high-latitude ionosphere and the electromagnetic energy transfer processes that lead to frictional heating of ions and neutrals, and plasma instability phenomenon that leads to extreme electron heating. Observations of the ionosphere response to these processes will be illustrated using incoherent scatter radar measurements. Relevance to the solar chromosphere will be identified where appropriate and outstanding issues in Earth
Kunz, M W; Cowley, S C; Binney, J J; Sanders, J S
2010-01-01
We consider the problem of self-regulated heating and cooling in galaxy clusters and the implications for cluster magnetic fields and turbulence. Viscous heating of a weakly collisional magnetised plasma is regulated by the pressure anisotropy with respect to the local direction of the magnetic field. The intracluster medium is a high-beta plasma, where pressure anisotropies caused by the turbulent stresses and the consequent local changes in the magnetic field will trigger very fast microscale instabilities. We argue that the net effect of these instabilities will be to pin the pressure anisotropies at a marginal level, controlled by the plasma beta parameter. This gives rise to local heating rates that turn out to be comparable to the radiative cooling rates. Furthermore, we show that a balance between this heating and Bremsstrahlung cooling is thermally stable, unlike the often conjectured balance between cooling and thermal conduction. Given a sufficient (and probably self-regulating) supply of turbulent ...
Weak Galois and Weak Cocleft Coextensions
Institute of Scientific and Technical Information of China (English)
J.N. Alonso (A)lvarez; J.M. Fernández Vilaboa; R. González Rodríguez; A.B. Rodríguez Raposo
2007-01-01
For a weak entwining structure (A, C,ψ) living in a braided monoidal category with equalizers and coequalizers, we formulate the notion of weak A-Galois coextension with normal basis and we show that these Galois coextensions are equivalent to the weak A-cocleft coextensions introduced by the authors.
Thermal conduction in a mirror-unstable plasma
Komarov, S. V.; Churazov, E. M.; Kunz, M. W.; Schekochihin, A. A.
2016-07-01
The plasma of galaxy clusters is subject to firehose and mirror instabilities at scales of order the ion Larmor radius. The mirror instability generates fluctuations of magnetic-field strength δB/B ˜ 1. These fluctuations act as magnetic traps for the heat-conducting electrons, suppressing their transport. We calculate the effective parallel thermal conductivity in the ICM in the presence of the mirror fluctuations for different stages of the evolution of the instability. The mirror fluctuations are limited in amplitude by the maximum and minimum values of the field strength, with no large deviations from the mean value. This key property leads to a finite suppression of thermal conduction at large scales. We find suppression down to ≈0.2 of the Spitzer value for the secular phase of the perturbations' growth, and ≈0.3 for their saturated phase. The effect operates in addition to other suppression mechanisms and independently of them. Globally, fluctuations δB/B ˜ 1 can be present on much larger scales, of the order of the scale of turbulent motions. However, we do not expect large suppression of thermal conduction by these, because their scale is considerably larger than the collisional mean free path of the ICM electrons. The obtained suppression of thermal conduction by a factor of ˜5 appears to be characteristic and potentially universal for a weakly collisional mirror-unstable plasma.
Impact of hydrogen isotope species on microinstabilities in helical plasmas
Nakata, Motoki; Nunami, Masanori; Sugama, Hideo; Watanabe, Tomo-Hiko
2016-07-01
The impact of isotope ion mass on ion-scale and electron-scale microinstabilities such as ion temperature gradient (ITG) mode, trapped electron mode (TEM), and electron temperature gradient (ETG) mode in helical plasmas are investigated by using gyrokinetic Vlasov simulations with a hydrogen isotope and real-mass kinetic electrons. Comprehensive scans for the equilibrium parameters and magnetic configurations clarify the transition from ITG mode to TEM instability, where a significant TEM enhancement is revealed in the case of inward-shifted plasma compared to that in the standard configuration. It is elucidated that the ion-mass dependence on the ratio of the electron-ion collision frequency to the ion transit one, i.e. {ν\\text{ei}}/{ω\\text{ti}}\\propto {{≤ft({{m}\\text{i}}/{{m}\\text{e}}\\right)}1/2} , leads to a stabilization of the TEM for heavier isotope ions. The ITG growth rate indicates a gyro-Bohm-like ion-mass dependence, where the mixing-length estimate of diffusivity yields γ /k\\bot2\\propto m\\text{i}1/2 . On the other hand, a weak isotope dependence of the ETG growth rate is identified. A collisionality scan also reveals that the TEM stabilization by the isotope ions becomes more significant for relatively higher collisionality in a banana regime.
Del Sarto, Daniele; Tenerani, Anna; Velli, Marco
2015-01-01
This paper discusses the transition to fast growth of the tearing instability in thin current sheets in the collisionless limit where electron inertia drives the reconnection process. It has been previously suggested that in resistive MHD there is a natural maximum aspect ratio (ratio of sheet length and breadth to thickness) which may be reached for current sheets with a macroscopic length L, the limit being provided by the fact that the tearing mode growth time becomes of the same order as the Alfv\\`en time calculated on the macroscopic scale (Pucci and Velli (2014)). For current sheets with a smaller aspect ratio than critical the normalized growth rate tends to zero with increasing Lundquist number S, while for current sheets with an aspect ratio greater than critical the growth rate diverges with S. Here we carry out a similar analysis but with electron inertia as the term violating magnetic flux conservation: previously found scalings of critical current sheet aspect ratios with the Lundquist number are...
Parker, Joseph T.
2015-02-03
Copyright © Cambridge University Press 2015. We study Landau damping in the 1+1D Vlasov-Poisson system using a Fourier-Hermite spectral representation. We describe the propagation of free energy in Fourier-Hermite phase space using forwards and backwards propagating Hermite modes recently developed for gyrokinetic theory. We derive a free energy equation that relates the change in the electric field to the net Hermite flux out of the zeroth Hermite mode. In linear Landau damping, decay in the electric field corresponds to forward propagating Hermite modes; in nonlinear damping, the initial decay is followed by a growth phase characterized by the generation of backwards propagating Hermite modes by the nonlinear term. The free energy content of the backwards propagating modes increases exponentially until balancing that of the forward propagating modes. Thereafter there is no systematic net Hermite flux, so the electric field cannot decay and the nonlinearity effectively suppresses Landau damping. These simulations are performed using the fully-spectral 5D gyrokinetics code SpectroGK, modified to solve the 1+1D Vlasov-Poisson system. This captures Landau damping via Hou-Li filtering in velocity space. Therefore the code is applicable even in regimes where phase mixing and filamentation are dominant.
Deterministic single-file dynamics in collisional representation.
Marchesoni, F; Taloni, A
2007-12-01
We re-examine numerically the diffusion of a deterministic, or ballistic single file with preassigned velocity distribution (Jepsen's gas) from a collisional viewpoint. For a two-modal velocity distribution, where half the particles have velocity +/-c, the collisional statistics is analytically proven to reproduce the continuous time representation. For a three-modal velocity distribution with equal fractions, where less than 12 of the particles have velocity +/-c, with the remaining particles at rest, the collisional process is shown to be inhomogeneous; its stationary properties are discussed here by combining exact and phenomenological arguments. Collisional memory effects are then related to the negative power-law tails in the velocity autocorrelation functions, predicted earlier in the continuous time formalism. Numerical and analytical results for Gaussian and four-modal Jepsen's gases are also reported for the sake of a comparison.
Evolution of Collisionally Merged Massive Stars
Suzuki, T K; Baumgardt, H; Ibukiyama, A; Makino, J; Ebisuzaki, & T; Suzuki, Takeru K; Nakasato, Naohito; Baumgardt, Holger; Ibukiyama, Akihiro; Makino, Junichiro
2007-01-01
We investigate the evolution of collisionally merged stars with mass of ~100 Msun which might be formed in dense star clusters. We assumed that massive stars with several tens Msun collide typically after ~1Myr of the formation of the cluster and performed hydrodynamical simulations of several collision events. Our simulations show that after the collisions, merged stars have extended envelopes and their radii are larger than those in the thermal equilibrium states and that their interiors are He-rich because of the stellar evolution of the progenitor stars. We also found that if the mass-ratio of merging stars is far from unity, the interior of the merger product is not well mixed and the elemental abundance is not homogeneous. We then followed the evolution of these collision products by a one dimensional stellar evolution code. After an initial contraction on the Kelvin-Helmholtz (thermal adjustment) timescale (~10^{3-4} yr), the evolution of the merged stars traces that of single homogeneous stars with co...
Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence
Schekochihin, A A; Highcock, E G; Dellar, P J; Dorland, W; Hammett, G W
2015-01-01
A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., drift-wave turbulence driven by temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating ExB flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. A consistent theory is constructed in which very little free energy leaks into high velocity moments of the distribution, rendering the turbulent cascade in the energetically relevant part of the wave-number space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also i...
Indian Academy of Sciences (India)
J N Mohanty; K C Baral; G Nath
2007-03-01
Boltzmann-transport equation is analytically solved for two-component magnetoplasma using Chapman-Enskog analysis to include collisional diffusion transport having anisotropies in both streaming velocity and temperature components. The modified collisional integrals are analytically solved with flux integrals and perturbed kinetic equation to arrive at drift diffusion velocity and resulting transport coefficients which are markedly affected by both streaming and temperature anisotropy. The early isotropic results are recovered in the limit $V_{0} = 0$ and $T_{\\|} = T_{\\bot}$ which reduce to eqs (11.30) and (11.31) of [1] and eqs (2.7) and (2.13) of [2]. The electrical resistivity (n_{\\bot}) diminishes sharply in fusion temperature limit $kT_{\\bot} = 1$ keV. The shape of the curves for both electrical resistivity and thermal conductivity is rectangular hyperbolic. However, for low thermal ratio $(T_{\\|}/T_{\\bot} < 1)$, the curves are raised up and for high thermal ratio $(T_{\\|}/T_{\\bot} > 1)$, they are lowered down the isotropic case $(T_{\\|}/T_{\\bot} > 1)$, showing comparatively diminished magnitudes of the quantities.
Institute of Scientific and Technical Information of China (English)
Yong Hua LI; Hai Bin KAN; Bing Jun YU
2004-01-01
In this paper, a special kind of partial algebras called projective partial groupoids is defined.It is proved that the inverse image of all projections of a fundamental weak regular *-semigroup under the homomorphism induced by the maximum idempotent-separating congruence of a weak regular *-semigroup has a projective partial groupoid structure. Moreover, a weak regular *-product which connects a fundamental weak regular *-semigroup with corresponding projective partial groupoid is defined and characterized. It is finally proved that every weak regular *-product is in fact a weak regular *-semigroup and any weak regular *-semigroup is constructed in this way.
Collisional interaction between metastable neon atoms
Energy Technology Data Exchange (ETDEWEB)
Drunen, Wouter Johannes van
2008-07-07
In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2]{sub 2} and the 3s'[1/2]{sub 0} metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. For the measurements described here, neon atoms have been confined in a magnetooptical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m{sub J} = +2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 10{sup 11} cm{sup -3}, and a central phase-space density of up to 2.2.10{sup -7}. After loading the optical dipole trap from the magnetic trap, 2.5.10{sup 6} atoms with typical temperatures of 0.1 mK, and central densities up to 5.10{sup 10} cm{sup -3} were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5.10{sup -5}. Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the {sup 3}D{sub 3} line a frequency dependence of laser enhanced Penning ionization was observed. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. The implementation of an optical dipole trap allowed us to trap the {sup 3}P{sub 0} metastable state. From the trap loss measurements we determined the two-body loss coefficient of the {sup 3}P{sub 0} metastable state for both bosonic isotopes {sup 20}Ne and {sup 22}Ne. For {sup 20}Ne we obtained {beta}=6{sup +5}{sub
Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.; Li, Z. Q.
2015-10-01
Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E ×B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs˜0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E ×B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E ×B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Moreover, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport in advanced ST
Phase mixing versus nonlinear advection in drift-kinetic plasma turbulence
Schekochihin, A. A.; Parker, J. T.; Highcock, E. G.; Dellar, P. J.; Dorland, W.; Hammett, G. W.
2016-04-01
> A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g. drift-wave turbulence driven by ion temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. It is found that it is possible to construct a consistent theory in which very little free energy leaks into high velocity moments of the distribution function, rendering the turbulent cascade in the energetically relevant part of the wavenumber space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also in contrast with the linear problem, in which it occurs at the finite rate equal to the Landau damping rate). The ability of the free energy to stay in the low velocity moments of the distribution function is facilitated by the `anti-phase-mixing' effect, whose presence in the nonlinear system is due to the stochastic version of the plasma echo (the advecting velocity couples the phase-mixing and anti-phase-mixing perturbations). The partitioning of the wavenumber space between the (energetically dominant) region where this is the case and the region where linear phase mixing wins its competition with nonlinear advection is governed by the `critical balance' between linear and nonlinear time scales (which for high Hermite moments splits into two thresholds, one demarcating the wavenumber region where phase mixing predominates, the other where plasma echo does).
Winters, Victoria; Green, Jonathan; Hershkowitz, Noah; Schmitz, Oliver; Severn, Greg
2015-11-01
The versatile helicon plasma device, MARIA (Magnetized AnisotRopic Ion-distribution Apparatus), was upgraded with stronger magnetic field B planned as well as design of an ion cyclotron-heating antenna. To quantify the plasma characteristics, diagnostics including a Triple Langmuir Probe, Emissive Probe, and Laser Induced Fluorescence were established. We show first results from characterization of the device. The coupling of the helicon mode in the electron temperature and density parameter space in Argon was mapped out with regard to neutral pressure, B-field and RF power. In addition, validity of the Bohm Criterion and of the Chodura model starting in the weakly collisional regime is tested. A key goal in all efforts is to develop methods of quantitative spectroscopy based on cutting-edge models and active laser spectroscopy. This work was funded by Startup funds of the Department of Engineering Physics at UW Madison, the NSF CAREER award PHY-1455210 and NSF grant PHY-1206421.
Characterization of Ion-Acoustic Wave Reflection Off A Plasma Chamber Wall
Berumen, Jorge; Chu, Feng; Hood, Ryan; Mattingly, Sean; Rogers, Anthony; Skiff, Fred
2015-11-01
We present an experimental characterization of the ion acoustic wave reflection coefficient off a plasma chamber wall. The experiment is performed in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional with typical conditions: n ~ 1010cm-3 Te ~ 3 eV and B ~ 1 kG. The main diagnostics are laser-induced fluorescence and Langmuir probe measurements. A survey of the ion velocity distribution function's zeroth and first order as well as density fluctuations at different wave excitation frequencies is obtained. Analysis of the reflection coefficient's dependence on the phase velocity and frequency of the wave is done through the characterization of waves utilizing Case-Van Kampen modes and the use of Morrison's G-transform. This research is supported by the Department of Energy under grant No. DOE DE-FG02-99ER54543.
Measuring Collisionless Damping in Heliospheric Plasmas using Field-Particle Correlations
Klein, Kristopher G
2016-01-01
An innovative field-particle correlation technique is proposed that uses single-point measurements of the electromagnetic fields and particle velocity distribution functions to investigate the net transfer of energy from fields to particles associated with the collisionless damping of turbulent fluctuations in weakly collisional plasmas, such as the solar wind. In addition to providing a direct estimate of the local rate of energy transfer between fields and particles, it provides vital new information about the distribution of that energy transfer in velocity space. This velocity-space signature can potentially be used to identify the dominant collisionless mechanism responsible for the damping of turbulent fluctuations in the solar wind. The application of this novel field-particle correlation technique is illustrated using the simplified case of the Landau damping of Langmuir waves in an electrostatic 1D-1V Vlasov-Poisson plasma, showing that the procedure both estimates the local rate of energy transfer f...
Plasma Polarization Spectroscopy and collision cross sections
Energy Technology Data Exchange (ETDEWEB)
Fujimoto, Takashi; Nakai, Manabu [Dept. of Engineering Physics and Mechanics, Graduate School of Engineering, Kyoto Univ. (Japan)
2000-01-01
In Plasma Polarization Spectroscopy (PPS), we observe the polarized spectral lines emitted from a plasma. For berylliumlike oxygen lines from a tokamak plasma the polarization feature is interpreted as due to the anisotropic velocity distribution of electrons which excite the ions. In this interpretation in terms of the population-alignment collisional-radiative (PACR) model various collision processes are involved concerning the population and the alignment, e.g., transfer of the alignment, and the coherence by collisional excitation and production of an alignment from a population by elastic collisions. These latter processes are little known so far. (author)
Zhao, Miao; Wu, Xiao-Jie; Fan, Ya-Xin; Guo, Bei-Ning; Zhang, Jing
2016-05-30
A rapid ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) assay method was developed for determination of CMS and formed colistin in human plasma and urine. After extraction on a 96-well SPE Supra-Clean Weak Cation Exchange (WCX) plate, the eluents were mixed and injected into the UHPLC-MS/MS system directly. A Phonomenex Kinetex XB-C18 analytical column was employed with a mobile phase consisting of solution "A" (acetonitrile:methanol, 1:1, v/v) and solution "B" (0.1% formic acid in water, v/v). The flow rate was 0.4 mL/min with gradient elution over 3.5 min. Ions were detected in ESI positive ion mode and the precursor-product ion pairs were m/z 390.7/101.3 for colistin A, m/z 386.0/101.2 for colistin B, and m/z 402.3/101.2 for polymyxin B1 (IS), respectively. The lower limit of quantification (LLOQ) was 0.0130 and 0.0251 mg/L for colistin A and colistin B in both plasma and urine with accuracy (relative error, %) <± 12.6% and precision (relative standard deviation, %) <± 10.8%. Stability of CMS was demonstrated in biological samples before and during sample treatment, and in the extract. This new analytical method provides high-throughput treatment and optimized quantification of CMS and colistin, which offers a highly efficient tool for the analysis of a large number of clinical samples as well as routine therapeutic drug monitoring.
Shear Viscosity of Turbulent Chiral Plasma
Kumar, Avdhesh; Das, Amita; Kaw, P K
2016-01-01
It is well known that the difference between the chemical potentials of left-handed and right-handed particles in a parity violating (chiral) plasma can lead to an instability. We show that the chiral instability may drive turbulent transport. Further we estimate the anomalous viscosity of chiral plasma arising from the enhanced collisionality due to turbulence.
Collins, C; Wallace, J; Jara-Almonte, J; Reese, I; Zweibel, E; Forest, C B; 10.1103/PhysRevLett.108.115001
2012-01-01
A new concept for spinning unmagnetized plasma is demonstrated experimentally. Plasma is confined by an axisymmetric multi-cusp magnetic field and biased cathodes are used to drive currents and impart a torque in the magnetized edge. Measurements show that flow viscously couples momentum from the magnetized edge (where the plasma viscosity is small) into the unmagnetized core (where the viscosity is large) and that the core rotates as a solid body. To be effective, collisional viscosity must overcome the ion-neutral drag due to charge exchange collisions.
Cofinitely weak supplemented modules
Alizade, Rafail; Büyükaşık, Engin
2003-01-01
We prove that a module M is cofinitely weak supplemented or briefly cws (i.e., every submodule N of M with M/N finitely generated, has a weak supplement) if and only if every maximal submodule has a weak supplement. If M is a cws-module then every M-generated module is a cws-module. Every module is cws if and only if the ring is semilocal. We study also modules, whose finitely generated submodules have weak supplements.
Institute of Scientific and Technical Information of China (English)
丁夏畦; 罗佩珠
2004-01-01
In this paper the authors introduce some new ideas on generalized numbers and generalized weak functions. They prove that the product of any two weak functions is a generalized weak function. So in particular they solve the problem of the multiplication of two generalized functions.
Chemistry and Physics of Weakly Ionized Plasmas
2010-01-22
constants k(E,J) for the dissociation of molecular ions J. Troe, V. G. Ushakov, and A. A. Viggiano Zeitschrift für Physikalische Chemie 219, 715-741 (May...energy distributions in the dissociation of n-propylbenzene cations (invited) J. Troe, V. G. Ushakov, and A. A. Viggiano Zeitschrift für Physikalische
Laser-induced collisional autoionization in europium and strontium atoms.
Buffa, R
1995-01-15
An experiment that involves laser-induced collisional autoionization in europium and strontium atoms is proposed and the spectral line shape of the cross section is calculated on the basis of data available in the literature. The feasibility of the experiment both in oven cells and in a crossed-atomic-beam geometry is discussed.
Subcritical excitation of plasma turbulence
Energy Technology Data Exchange (ETDEWEB)
Itoh, K.; Itoh, S.; Yagi, M.; Fukuyama, A.
1996-01-01
Theory of current-diffusive interchange mode turbulence in plasmas is developed in the presence of collisional transport. Double-valued amplitude of stationary fluctuations is expressed in terms of the pressure gradient. The backward bifurcation is shown to appear near the linear stability boundary. The subcritical nature of the turbulence is explicitly illustrated. Critical pressure gradient at which the transition from collisional transport to the turbulent one is to occur is predicted. This provides a prototype of the transport theory for nonlinear-non-equilibrium systems. (author).
Subcritical excitation of plasma turbulence
Energy Technology Data Exchange (ETDEWEB)
Itoh, Kimitaka [National Inst. for Fusion Science, Nagoya (Japan); Itoh, Sanae; Yagi, Masatoshi; Fukuyama, Atsushi
1996-09-01
Theory of current-diffusive interchange mode turbulence in plasmas in the presence of collisional transport is developed. Amplitude of stationary fluctuations is expressed in terms of the double-valued function of the pressure gradient. The backward bifurcation is shown to appear near the linear stability boundary. The subcritical nature of the turbulence is explicitly illustrated. The critical pressure gradient at which the transition from collisional transport to the turbulent one is to occur is predicted. This work provides a prototype of the transport theory for nonlinear-nonequilibrium systems. (author)
On the two weighting scheme for {delta}f collisional transport simulation
Energy Technology Data Exchange (ETDEWEB)
Okamoto, M.; Nakajima, N.; Wang, W. [National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-08-01
The validity is given to the newly proposed two weighting {delta}f scheme (Wang et al., Research Report of National Institute for Fusion Science NIFS-588, 1999) for collisional or neoclassical transport calculations, which can solve the drift kinetic equation taking account of effects of steep plasma gradients, large radial electric field, finite banana width, and the non-standard orbit topology near the axis. The marker density functions in weight equations are successively solved by using the idea of {delta}f method and a hierarchy of equations for weight and marker density functions is obtained. These hierarchy equations are solved by choosing an appropriate source function for each marker density. Thus the validity of the two weighting {delta}f scheme is mathematically proved. (author)
Optimization of CFETR confinement by controlling rotation shear and pedestal collisionality
Jian, Xiang; Chen, Jiale; Chan, Vincent; Li, Guoqiang; Zhuang, Ge; Cfetr Physics Team
2016-10-01
Optimization of a CFETR baseline scenario (Chan et al. 2015 Nucl. Fusion. 55) with EC and NB H&CD is performed using a multi-dimensional code suite. Rotation shear is controlled using NB, with injection angle being constrained to avoid edge heating and to maintain q_min >2. The NB power is adjusted to keep the plasma fully non-inductive. The NB energy that maximize the fusion gain Q is identified. Trade-off between the pedestal density and temperature is performed with the pedestal pressure fixed. It is found that Q increases with pedestal density, while the density peaking factor (DPF) remains unchanged. Linear analysis shows that the transport is dominated by TEM and ITG turbulence. Collisionality affects these turbulences in such a way that the induced changes in DPF cancel out. A weaker dependence of DPF makes higher density operation more favorable for fusion gain.
Collisional effect on the Weibel instability with the bi-Maxwellian distribution function
Energy Technology Data Exchange (ETDEWEB)
Mahdavi, M.; Khanzadeh, H. [Physics Department, Mazandaran University, P. O. Box 47415-416, Babolsar (Iran, Islamic Republic of)
2013-05-15
In this paper, the Coulomb collision effect of electron-ion is investigated based on the equilibrium bi-Maxwellian anisotropic distribution function in dense and unmagnetized plasma. An analytical expression is derived for the real frequency and the growth rate of the Weibel instability for two limiting cases |ξ=(ω{sup ′}/k{sub ||}θ{sub ||})|≫1 and |ξ|≪1. In the limit |ξ|≪1, the quantity η that is due to a collisional term will appear in the growth and condition of the rate of the Weibel instability, which leads to a constraining condition of the growth rate. When η increases, the growth rate will increase and the wave instability will be distant from its own damping mode.
ELECTRON HEAT FLUX IN THE SOLAR WIND: ARE WE OBSERVING THE COLLISIONAL LIMIT IN THE 1 AU DATA?
Energy Technology Data Exchange (ETDEWEB)
Landi, S. [Dipartimento di Fisica e Astronomia Università degli Studi di Firenze Largo E. Fermi 2, I-50125 Firenze (Italy); Matteini, L. [The Blackett Laboratory, Imperial College London Prince Consort Road, London SW7 2AZ (United Kingdom); Pantellini, F. [LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot 5, place J. Janssen, F-92195 Meudon Cedex (France)
2014-07-20
Using statistically significant data at 1 AU, it has recently been shown (Bale et al.) that in the solar wind, when the Knudsen number K {sub T} (the ratio between the electron mean free path and the electron temperature scale height) drops below about 0.3, the electron heat flux q intensity rapidly approaches the classical collisional Spitzer-Härm limit. Using a fully kinetic model including the effect of Coulomb collisions and the expansion of the solar wind with heliocentric distance, we observe that the heat flux strength does indeed approach the collisional value for Knudsen numbers smaller than about 0.3 in very good agreement with the observations. However, closer inspection of the heat flux properties, such as its variation with the heliocentric distance and its dependence on the plasma parameters, shows that for Knudsen numbers between 0.02 and 0.3 the heat flux is not conveniently described by the Spitzer-Härm formula. We conclude that even though observations at 1 AU seem to indicate that the electron heat flux intensity approaches the collisional limit when the Knudsen drops below ∼0.3, the collisional limit is not a generally valid closure for a Knudsen larger than 0.01. Moreover, the good agreement between the heat flux from our model and the heat flux from solar wind measurements in the high-Knudsen number regime seems to indicate that the heat flux at 1 AU is not constrained by electromagnetic instabilities as both wave-particle and wave-wave interactions are neglected in our calculations.
Simplifying plasma chemistry via ILDM
Rehman, T.; Kemaneci, E.; Graef, W.; van Dijk, J.
2016-02-01
A plasma fluid model containing a large number of chemical species and reactions yields a high computational load. One of the methods to overcome this difficulty is to apply Chemical Reduction Techniques as used in combustion engineering. The chemical reduction technique that we study here is ILDM (Intrinsic Lower Dimensional Manifold). The ILDM method is used to simplify an argon plasma model and then a comparison is made with a CRM (Collisional Radiative Model).
Thomson scattering off a pair (electron-positron) plasma
Institute of Scientific and Technical Information of China (English)
Zheng Jian
2006-01-01
Thomson scattering off a pair (electron-positron) plasma is theoretically investigated in the collisionless and collisional limits respectively. Our calculations show that the power spectrum of the Thomson scattering offa collisionless pair plasma is just proportional to the velocity distribution function of the particles in the plasma. Collective modes in the plasma do not have any effects on the Thomson scattering spectrum because of the correlation between the negatively- and positively-charged particles. In the collisional limit, the power spectrum of the Thomson scattering presents three spikes: two peaks correspond to two contra-propagating sound waves and one peak corresponds to an entropy wave.
Practical beta limit in ITER-shaped discharges in DIII-D and its increase by higher collisionality
Energy Technology Data Exchange (ETDEWEB)
La Haye, R.J.; Chu, M.S. [General Atomics, San Diego, CA (United States); Callen, J.D. [Univ. of Wisconsin, Madison, WI (United States)] [and others
1996-10-01
The maximum beta which can be sustained for a long pulse in ITER-shaped plasmas in DIII-D with q{sub 95} {approx_gt} 3, ELMs, and sawteeth is found to be limited by resistive tearing modes, particularly m/n = 3/2 and 2/1. At low collisionality comparable to that which will occur in ITER, the beta limit is a factor of two below the usually expected n = {infinity} ballooning and n = 1 kink ideal limits.
On Weakly Semicommutative Rings*
Institute of Scientific and Technical Information of China (English)
CHEN WEI-XING; CUI SHU-YING
2011-01-01
A ring R is said to be weakly scmicommutative if for any a, b ∈ R,ab = 0 implies aRb C_ Nil(R), where Nil(R) is the set of all nilpotcnt elements in R.In this note, we clarify the relationship between weakly semicommutative rings and NI-rings by proving that the notion of a weakly semicommutative ring is a proper generalization of NI-rings. We say that a ring R is weakly 2-primal if the set of nilpotent elements in R coincides with its Levitzki radical, and prove that if R is a weakly 2-primal ring which satisfies oα-condition for an endomorphism α of R (that is, ab = 0 （←→） aα(b) ＝ 0 where a, b ∈ R) then the skew polynomial ring R[π; αα]is a weakly 2-primal ring, and that if R is a ring and I is an ideal of R such that I and R/I are both weakly semicommutative then R is weakly semicommutative.Those extend the main results of Liang et al. 2007 (Taiwanese J. Math., 11(5)(2007),1359-1368) considerably. Moreover, several new results about weakly semicommutative rings and NI-rings are included.
Shock Formation by Plasma Filaments of Microwave Discharge under Atmospheric Pressure
Takahashi, Masayuki; Ohnishi, Naofumi
2016-03-01
A one-dimensional compressible fluid calculation was coupled with a finite- difference time-domain code and a particle-in-cell code with collision to reproduce propagation of electromagnetic wave, ionization process of plasma, and shock wave formation in atmospheric microwave discharge. Plasma filaments are driven toward the microwave source at 1 atm, and the distance between each filament is one-fifth of the wavelength of the incident microwave. The strong shock wave is generated due to the high plasma density at the atmospheric pressure. A simple analysis of the microwave propagation into the plasma shows that cut-off density of the microwave becomes smaller with the pressure decrease in a collisional plasma. At the lower pressure, the smaller density plasma is obtained with a diffusive pattern because of the smaller cut-off density and the larger diffusion effect. In contrast with the 1-atm case, the weak shock wave is generated at a rarefied condition, which lowers performance of microwave thruster.
Using Field-Particle Correlations to Diagnose the Collisionless Damping of Plasma Turbulence
Howes, Gregory; Klein, Kristropher
2016-10-01
Plasma turbulence occurs ubiquitously throughout the heliosphere, yet our understanding of how turbulence governs energy transport and plasma heating remains incomplete, constituting a grand challenge problem in heliophysics. In weakly collisional heliospheric plasmas, such as the solar corona and solar wind, damping of the turbulent fluctuations occurs due to collisionless interactions between the electromagnetic fields and the individual plasma particles. A particular challenge in diagnosing this energy transfer is that spacecraft measurements are typically limited to a single point in space. Here we present an innovative field-particle correlation technique that can be used with single-point measurements to estimate the energization of the plasma particles due to the damping of the electromagnetic fields, providing vital new information about this how energy transfer is distributed as a function of particle velocity. This technique has the promise to transform our ability to diagnose the kinetic plasma physical mechanisms responsible for not only the damping of turbulence, but also the energy conversion in both collisionless magnetic reconnection and particle acceleration. The work has been supported by NSF CAREER Award AGS-1054061, NSF AGS-1331355, and DOE DE-SC0014599.
Collisional and collision-less surface heating in intense laser matter interaction
Kemp, Andreas; Divol, Laurent
2015-11-01
We explore the interaction of high-contrast intense sub-100 fs laser pulses with solid density tar- gets, using numerically converged collisional particle-in-cell simulations in one two and three dimen- sions. We observe a competition between two mechanisms that can lead to plasma heating. Inverse bremsstrahlung at solid density on one hand, and electrons scattering off plasma waves on the other, can both heat the skin layer to keV temperatures on a femtosecond time scale, facilitating a heat wave and a source of MeV electrons that penetrate and heat the bulk target. Collision-less effects heat the surface effectively starting at the relativistic intensity threshold, independent of plasma density. Our numerical results show that a high-contrast 1J/100fs laser can drive a solid target into the warm dense matter regime. This system is suitable to ab-initio modeling and experimental probing. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Observation of Up-gradient Particle Flux in Collisional Drift-ITG Turbulence
Cui, Lang
2015-11-01
We report the observation of a net inward, up-gradient turbulent particle flux from two independent diagnostics in collisional drift-ITG plasma turbulence. At low magnetic fields (B = 1.2 kG) the drift-waves persist, an up-gradient inward particle flux develops, fluctuations propagating in the ion diamagnetic drift direction develop and a pronounced steepening of the ion temperature and mean density gradients occurs. The two different types of fluctuation features modulate and compete with each other and dominate in different radial location and magnetic field region. Linear stability analyses show that a robust ITG instability is excited for these conditions. The onset of net inward flux also coincides with the development of a strong intrinsic parallel flow shear that can drive an inward pinch when it is coupled with grad-Ti. However, we find that the ITG-driven inward pinch is more dominant in our experiments. This basic experiment provides for a detailed examination of turbulent-driven particle pinches and up-gradient fluxes in the presence of multiple free-energy sources. Moreover, the coexistence and competition of DWs and ITG have been observed to influence tokamak transport and remains a topic of interest for both magnetically confined fusion plasmas and space plasma systems. A detailed experimental study complemented by theory and linear and nonlinear simulations of these experiments is used to elucidate the physics of up-gradient particle transport. Supported by DOE (DE- SC0001961).
Collective instabilities and collisional effects for space charge dominated beams
Energy Technology Data Exchange (ETDEWEB)
Benedetti, C. [Dipartimento di Fisica, Universita di Bologna and INFN, Via Irnerio 46, 40126 Bologna (Italy)]. E-mail: benedetti@bo.infn.it; Turchetti, G. [Dipartimento di Fisica, Universita di Bologna and INFN, Via Irnerio 46, 40126 Bologna (Italy)
2007-07-01
This paper is organized into two parts. In the first one we analyze the equipartitioning process in the presence of collisions for a Gaussian anisotropic beam. Far from instabilities the equipartition process can be described correctly by using Landau's collisional theory, whereas when the dynamics of the system is strongly nonlinear (e.g. in the vicinity of a resonance) a hybrid dynamical-collisional equipartition mechanism occurs. In the second part of the paper we discuss shortly a systematic study of the collective instabilities in a symmetric periodic focusing channel for a KV beam by using the moments method. We emphasize differences occurring when the periodic focusing lattice is replaced by the corresponding constant focusing one.
On the maximal efficiency of the collisional Penrose process
Leiderschneider, Elly
2015-01-01
The center of mass (CM) energy in a collisional Penrose process - a collision taking place within the ergosphere of a Kerr black hole - can diverge under suitable extreme conditions (maximal Kerr, near horizon collision and suitable impact parameters). We present an analytic expression for the CM energy, refining expressions given in the literature. Even though the CM energy diverges, we show that the maximal energy attained by a particle that escapes the black hole's gravitational pull and reaches infinity is modest. We obtain an analytic expression for the energy of an escaping particle resulting from a collisional Penrose process, and apply it to derive the maximal energy and the maximal efficiency for several physical scenarios: pair annihilation, Compton scattering, and the elastic scattering of two massive particles. In all physically reasonable cases (in which the incident particles initially fall from infinity towards the black hole) the maximal energy (and the corresponding efficiency) are only one o...
Collisional broadening of angular correlations in a multiphase transport model
Edmonds, Terrence; Wang, Fuqiang
2016-01-01
Systematic comparisons of jetlike correlation data to radiative and collisional energy loss model calculations are essential to extract transport properties of the quark-gluon medium created in relativistic heavy ion collisions. This paper presents a transport study of collisional broadening of jetlike correlations, by following parton-parton collision history in a multiphase transport (AMPT) model. The correlation shape is studied as a function of the number of parton-parton collisions suffered by a high transverse momentum probe parton ($N_{\\rm coll}$) and the azimuth of the probe relative to the reaction plane ($\\phi_{\\rm fin.}^{\\rm probe}$). Correlation is found to broaden with increasing $N_{\\rm coll}$ and $\\phi_{\\rm fin.}^{\\rm probe}$ from in- to out-of-plane direction. This study provides a transport model benchmark for future jet-medium interaction studies.
Idiopathic isolated orbicularis weakness
MacVie, O P; Majid, M A; Husssin, H M; Ung, T; Manners, R M; Ormerod, I; Pawade, J; Harrad, R A
2012-01-01
Purpose Orbicularis weakness is commonly associated with seventh nerve palsy or neuromuscular and myopathic conditions such as myotonic dystrophy and myasethenia gravis. We report four cases of idiopathic isolated orbicularis weakness. Methods All four cases were female and the presenting symptoms of ocular irritation and epiphora had been present for over 7 years in three patients. All patients had lagophthalmos and three had ectropion. Three patients underwent full investigations which excluded known causes of orbicularis weakness. Two patients underwent oribularis oculi muscle biopsy and histological confirmation of orbicularis atrophy. Results All patients underwent surgery to specifically address the orbicularis weakness with satisfactory outcomes and alleviation of symptoms in all cases. Isolated orbicularis weakness may be a relatively common entity that is frequently overlooked. Conclusion Early recognition of this condition may lead to better management and prevent patients undergoing unnecessary surgical procedures. PMID:22322997
Comets as collisional fragments of a primordial planetesimal disk
Morbidelli, Alessandro
2015-01-01
The Rosetta mission and its exquisite measurements have revived the debate on whether comets are pristine planetesimals or collisionally evolved objects. We investigate the collisional evolution experienced by the precursors of current comet nuclei during the early stages of the Solar System, in the context of the so-called "Nice Model". We consider two environments for the collisional evolution: (1) the trans-planetary planetesimal disk, from the time of gas removal until the disk was dispersed by the migration of the ice giants, and (2) the dispersing disk during the time that the scattered disk was formed. Simulations have been performed, using different methods in the two cases, to find the number of destructive collisions typically experienced by a comet nucleus of 2km radius. In the widely accepted scenario, where the dispersal of the planetesimal disk occurred at the time of the Late Heavy Bombardment about 4Gy ago, comet-sized planetesimals have a very small chance to survive against destructive colli...
Collisional Processing of Olivine and Pyroxene in Cometary Dust
Lederer, S. M.; Cintala, M. J.; Olney, R. D.; Keller, L. P.; Nakamura-Messenger, K.; Zolensky, M.
2008-01-01
According to the nebular theory of solar-system formation, collisions between bodies occurred frequently early in the solar system s history and continue at a lower rate even today. Collisions have reworked the surface compositions and structures of cometary nuclei, though to an unknown degree. The majority of the collisional history of a typical Jupiter-family comet takes place while it resides in the Kuiper Belt. Impacts occur on the surfaces of small bodies over a large range of velocities by impactors of all sizes, but typical encounter speeds within the Kuiper Belt are 1.5 to 2.0 km/s[1]. Durda and Stern suggest that the interiors of most cometary nuclei with diameters 8 m would rework up to one-third of that TNO s surface. In fact, it has been proposed that most short-period comets from the Kuiper Belt (90%) are collisional fragments from larger TNOs - not primordial objects themselves [3] - and that most short-period comets from the Kuiper Belt will be collisionally processed both on their surfaces as well as in their interiors.
A collisional extension of time-dependent Hartree-Fock
Lacombe, L.; Reinhard, P.-G.; Dinh, P. M.; Suraud, E.
2016-12-01
We propose a collisional extension of time-dependent mean-field theories on the basis of a recently proposed stochastic extension of mean-field dynamics (stochastic time-dependent Hartree-Fock, STDHF). The latter theory is unfortunately too involved to envision practical applications in realistic systems in the near future and is thus bound to model systems. It is also hard to explore moderate to low energies with STDHF, because of vanishing transition probabilities that are impossible to sample properly. For such moderately excited situations covering small fluctuations, we compactify sampling by employing the same average mean field for all STDHF trajectories. The new approach, coined average STDHF (ASTDHF), ignores the fluctuations of the mean field but still accounts correctly for the collisional correlations responsible for dissipative features on top of mean-field dynamics. We detail the main features of the new approach in relation to existing equations, in particular quantum kinetic theories. The new theory is directly connected to STDHF, both formally and practically. We thus discuss in detail how the two approaches are related to each other. We apply the new scheme to illustrative examples taking as benchmark STDHF dynamics in 1D. ASTDHF provides results that are in remarkable agreement with the more elaborate STDHF. It makes it a promising approach to deal with dissipative dynamics in finite quantum systems, because of its moderate cost allowing applications in realistic systems and the possibility of exploring any excitation energy range where collisional correlations are expected to play a role.
Collisional processes and size distribution in spatially extended debris discs
Thebault, Philippe
2007-01-01
We present a new multi-annulus code for the study of collisionally evolving extended debris discs. We first aim to confirm results obtained for a single-annulus system, namely that the size distribution in "real" debris discs always departs from the theoretical collisional equilibrium $dN\\proptoR^{-3.5}dR$ power law, especially in the crucial size range of observable particles (<1cm), where it displays a characteristic wavy pattern. We also aim at studying how debris discs density distributions, scattered light luminosity profiles, and SEDs are affected by the coupled effect of collisions and radial mixing due to radiation pressure affected small grains. The size distribution evolution is modeled from micron-sized grains to 50km-sized bodies. The model takes into account the crucial influence of radiation pressure-affected small grains. We consider the collisional evolution of a fiducial a=120AU radius disc with an initial surface density in $\\Sigma(a)\\propto a^{\\alpha}$. We show that the system's radial e...
No-Hair Theorem for Weak Pulsar
Gruzinov, Andrei
2015-01-01
It is proposed that there exists a class of pulsars, called weak pulsars, for which the large-scale magnetosphere, and hence the gamma-ray emission, are independent of the detailed pattern of plasma production. The weak pulsar magnetosphere and its gamma-ray emission are uniquely determined by just three parameters: spin, dipole, and the spin-dipole angle. We calculate this supposedly unique pulsar magnetosphere in the axisymmetric case. The magnetosphere is found to be very close to (although interestingly not fully identical with) the magnetosphere we have previously calculated, explaining the phenomenological success of the old calculation. We offer only a highly tentative proof of this "Pulsar No-Hair Theorem". Our analytics, while convincing in its non-triviality, is incomplete, and counts only as a plausibility argument. Our numerics, while complete, is dubious. The plasma flow in the weak pulsar magnetosphere turns out to be even more intricate than what we have previously proposed: some particles, aft...
Weak decays. [Lectures, phenomenology
Energy Technology Data Exchange (ETDEWEB)
Wojcicki, S.
1978-11-01
Lectures are given on weak decays from a phenomenological point of view, emphasizing new results and ideas and the relation of recent results to the new standard theoretical model. The general framework within which the weak decay is viewed and relevant fundamental questions, weak decays of noncharmed hadrons, decays of muons and the tau, and the decays of charmed particles are covered. Limitation is made to the discussion of those topics that either have received recent experimental attention or are relevant to the new physics. (JFP) 178 references
Weakly asymptotically hyperbolic manifolds
Allen, Paul T; Lee, John M; Allen, Iva Stavrov
2015-01-01
We introduce a class of "weakly asymptotically hyperbolic" geometries whose sectional curvatures tend to $-1$ and are $C^0$, but are not necessarily $C^1$, conformally compact. We subsequently investigate the rate at which curvature invariants decay at infinity, identifying a conformally invariant tensor which serves as an obstruction to "higher order decay" of the Riemann curvature operator. Finally, we establish Fredholm results for geometric elliptic operators, extending the work of Rafe Mazzeo and John M. Lee to this setting. As an application, we show that any weakly asymptotically hyperbolic metric is conformally related to a weakly asymptotically hyperbolic metric of constant negative curvature.
New insights into main belt asteroid collisional lifetimes
Henych, Tomas; Holsapple, Keith
2016-10-01
We are developing a new Monte Carlo code to study the collisional and spin evolution of main belt asteroids. A byproduct is information on asteroid lifetimes. We find new interpretations and values of those lifetimes.In the conventional approach, the "collisional lifetime" is measured by the time when an asteroid is struck by an impactor large enough to remove one-half of the target's mass. That event is called a catastrophic disruption (CD). From an assumed population of impactors and Poisson statistics, one can estimate the largest expected impactor to impact in a given time interval to get its expected collisional lifetime. However, our Monte Carlo simulations give lifetimes that are distinctly shorter. That raises questions about the basic definition of catastrophic disruption.During its presence in the main belt, many other asteroids of all sizes continually strike a target asteroid. Before the CD one happens, there are many small impacts, and a few less than but not equal to the CD one. Each impact erodes the target asteroid. Very commonly, it is eroded to a much smaller mass before some CD event. We will present examples.So what shall we define as its collisional lifetime? Should it be the time for which its mass is reduced to one-half of its original mass, irrespective of how that happened, perhaps from many impacts? Or when any single impact reduces its mass to one-half of its original mass? Or when a single impact reduces it to one-half of its current mass?We propose that collisional lifetime is defined as the time at which it reaches 50% of its original mass, from any combination of small and/or large events. We use cratering and ejecta scaling formulas (e.g. Holsapple, 1993, Housen and Holsapple, 2011) to calculate the eroded mass history of the target for a history of impactors and calculate the outcome of any impact using the current size. In the gravity regime, the eroded body is easier to disrupt. We will present our lifetime estimates and those of
Hosoya, Akio
2010-01-01
We develop a formal theory of the weak values with emphasis on the consistency conditions and a probabilistic interpretation in the counter-factual processes. We present the condition for the choice of the post-selected state to give a negative weak value of a given projection operator and strange values of an observable in general. The general framework is applied to Hardy's paradox and the spin $1/2$ system to explicitly address the issues of counter-factuality and strange weak values. The counter-factual arguments which characterize the paradox specifies the pre-selected state and a complete set of the post-selected states clarifies how the strange weak values emerge.
Bandyopadhyay, P; Sen, A; Kaw, P K
2016-01-01
The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and $MnO_2$ dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of $\\partial\\omega/\\partial k < 0$ are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.
Stability and evolution of wave packets in strongly coupled degenerate plasmas
Misra, A P
2011-01-01
We study the nonlinear propagation of electrostatic wave packets in a collisional plasma composed of strongly coupled ions and relativistically degenerate electrons. The equilibrium of ions is maintained by an effective temperature associated with their strong coupling, whereas that of electrons is provided by the relativistic degeneracy pressure. Using a multiple scale technique, a (3+1)-dimensional coupled set of nonlinear Schr\\"{o}dinger-like equations with nonlocal nonlinearity is derived from a generalized viscoelastic hydrodynamic model. These coupled equations, which govern the dynamics of wave packets, are used to study the oblique modulational instability of a Stoke's wave train to a small plane wave perturbation. We show that the wave packets, though stable to the parallel modulation, becomes unstable against oblique modulations. In contrast to the long-wavelength carrier modes, the wave packets with short-wavelengths are shown to be stable in the weakly relativistic case, whereas they can be stable...
The Structure of Plasma Heating in Gyrokinetic Alfv\\'enic Turbulence
Navarro, A B; Told, D; Groselj, D; Crandall, P; Jenko, F
2016-01-01
We analyze plasma heating in weakly collisional kinetic Alfv\\'en wave (KAW) turbulence using high resolution gyrokinetic simulations spanning the range of scales between the ion and the electron gyroradii. Real space structures that have a higher than average heating rate are shown not to be confined to current sheets. This novel result is at odds with previous studies, which use the electromagnetic work in the local electron fluid frame, i.e. $\\mathbf{J} \\!\\cdot\\! (\\mathbf{E} + \\mathbf{v}_e\\times\\mathbf{B})$, as a proxy for turbulent dissipation to argue that heating follows the intermittent spatial structure of the electric current. Furthermore, we show that electrons are dominated by parallel heating while the ions prefer the perpendicular heating route. We comment on the implications of the results presented here.
Energy Loss of a Heavy Fermion in an Anisotropic QED Plasma
Romatschke, P; Romatschke, Paul; Strickland, Michael
2004-01-01
We compute the leading-order collisional energy loss of a heavy fermion propagating in a QED plasma with an electron distribution function which is anisotropic in momentum space. We show that in the presence of such anisotropies there can be a significant directional dependence of the heavy fermion energy loss with the effect being quite large for highly-relativistic velocities. We also repeat the analysis of the isotropic case more carefully and show that the final result depends on the intermediate scale used to separate hard and soft contributions to the energy loss. We then show that the canonical isotropic result is obtained in the weak-coupling limit. For intermediate-coupling we use the residual scale dependence as a measure of our theoretical uncertainty. We also discuss complications which could arise due to the presence of unstable soft photonic modes and demonstrate that the calculation of the energy loss is safe.
Derouich, M; Barklem, P S
2015-01-01
Interpretation of solar polarization spectra accounting for partial or complete frequency redistribution requires data on various collisional processes. Data for depolarization and polarization transfer are needed but often missing, while data for collisional broadening are usually more readily available. Recent work by Sahal-Br\\'echot and Bommier concluded that despite underlying similarities in the physics of collisional broadening and depolarization processes, relationships between them are not possible to derive purely analytically. We aim to derive accurate numerical relationships between the collisional broadening rates and the collisional depolarization and polarization transfer rates due to hydrogen atom collisions. Such relationships would enable accurate and efficient estimation of collisional data for solar applications. Using earlier results for broadening and depolarization processes based on general (i.e. not specific to a given atom), semi-classical calculations employing interaction potentials...
Plasma density perturbation caused by probes at low gas pressure
Sternberg, Natalia; Godyak, Valery
2017-09-01
An analysis of plasma parameter perturbations caused by a spherical probe immersed into a spherical plasma is presented for arbitrary collisionality and arbitrary ratios of probe to plasma dimensions. The plasma was modeled by the fluid plasma equations with ion inertia and nonlinear ion friction force that dominate plasma transport at low gas pressures. Significant depletion of the plasma density around the probe surface has been found. The area of plasma depletion coincides with the sensing area of different kinds of magnetic and microwave probes and will therefore lead to errors in data inferred from measurements with such probes.
Joyal, André
2009-01-01
We define weak units in a semi-monoidal 2-category $\\CC$ as cancellable pseudo-idempotents: they are pairs $(I,\\alpha)$ where $I$ is an object such that tensoring with $I$ from either side constitutes a biequivalence of $\\CC$, and $\\alpha: I \\tensor I \\to I$ is an equivalence in $\\CC$. We show that this notion of weak unit has coherence built in: Theorem A: $\\alpha$ has a canonical associator 2-cell, which automatically satisfies the pentagon equation. Theorem B: every morphism of weak units is automatically compatible with those associators. Theorem C: the 2-category of weak units is contractible if non-empty. Finally we show (Theorem E) that the notion of weak unit is equivalent to the notion obtained from the definition of tricategory: $\\alpha$ alone induces the whole family of left and right maps (indexed by the objects), as well as the whole family of Kelly 2-cells (one for each pair of objects), satisfying the relevant coherence axioms.
The collisional history of dwarf planet Ceres revealed by Dawn
Marchi, S.; Williams, D. A.; Mest, S. C.; Schenk, P.; O'Brien, D. P.; De Sanctis, M. C.; Ermakov, A.; Castillo, J. C.; Jaumann, R.; Neesemann, A.; Hiesinger, H.; Park, R. S.; Kneissl, T.; Schmedemann, N.; Raymond, C. A.; Russell, C. T.
2015-12-01
Impact craters are a ubiquitous feature of solid surfaces of celestial objects. Craters are oftentimes used to constrain the past evolution of their host objects, as well as to assess their crustal structures. The Dawn spacecraft, currently in orbit around the dwarf planet Ceres, has revealed a surface peppered with impact craters. Two important facts emerge from their global spatial distribution: i) significant longitudinal and latitudinal asymmetries in the crater areal density, ii) and the lack of well-preserved craters larger than 400 km in imaging data. Interestingly, most of the low crater density terrains are found in the vicinity of the three largest, well-preserved impact craters ranging from ~160 to ~290 km in diameter. These low crater areal density terrains expand over a greater distance than observed for large craters on rocky bodies and icy satellites, which typically are confined within one crater radius from the rim. To assess the collisional history of Ceres we developed a Monte Carlo model that tracks the timing, size and number of collisions throughout the history of the solar system. The model shows that Ceres' collisional evolution should have resulted typically in a factor of 10 more craters than observed, with some ~10 craters larger than 400 km expected to have formed over the last 4.5 Gyr ago. While small craters may have reached an equilibrium level, which does not allow then to further increase in number, the lack of evident large craters is a puzzle. A possibility is that the scars of large craters have been obliterated by topography relaxation due to an ice-rich crust. Here we will present an overview of the Ceres' crater spatial distribution and compare it to other siblings (such as the asteroid Vesta), and collisional evolution models. We will also discuss how these results pose important constraints on the internal structure of the dwarf planet in conjunction with surface composition and gravity data acquired by Dawn.
Hybrid accretionary/collisional mechanism of Paleozoic Asian continental growth
Schulmann, Karel; Lexa, Ondrej; Janousek, Vojtech; Pavla, Stipska; Yingde, Jiang; Alexandra, Guy; Min, Sun
2016-04-01
Continental crust is formed above subduction zones by well-known process of "juvenile crust growth". This new crust is in modern Earth assembled into continents by two ways: (i) short-lived collisions of continental blocks with the Eurasian continent along the "Alpine-Himalayan collisional/interior orogens" in the heart of the Pangean continental plates realm; and (ii) long lived lateral accretion of ocean-floor fragments along "circum-Pacific accretionary/peripheral orogens" at the border of the Pacific oceanic plate. This configuration has existed since the late Proterozoic, when the giant accretionary Terra Australis Orogen developed at periphery of an old Palaeo-Pacific ocean together with collisional Caledonian and Variscan orogens. At the same time, the large (ca. 9 millions km2) Central Asian Orogenic Belt (CAOB) developed in the NE part of the Pangea. This orogen reveals features of both peripheral and interior orogens, which implies that the generally accepted "peripheral-accretionary" and "interior- collisional" paradigm is not applicable here. To solve this conundrum a new model of unprecedented Phanerozoic continental growth is proposed. In this model, the CAOB precursor evolved at the interface of old exterior and young interior oceans. Subsequently, the new lithospheric domain was transferred by advancing subduction into the interior of the Pangean mostly continental realm. During this process the oceanic crust was transformed into continental crust and it was only later when this specific lithosphere was incorporated into the Asian continent. If true, this concept represents revolutionary insight into processes of crustal growth explaining the enigma of anchoring hybrid lithosphere inside a continent without its subduction or Tibetan-type thickening.
Progress and records in the study of endogenetic mineralization during collisional orogenesis
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
To develop and perfect the theory of plate tectonics and regional metallogeny,metallogenesis during collisional orogenesis should be thoroughly studied and will attract increasing attention of more and more scientists.This paper presents the main aspects of research and discussions on metallogenesis during collisional orogenesis after the development of plate tectonics,and accordingly divides the study history into two stages,i.e.the junior stage during 1971-1990 and the senior stage after 1990.Beginning with the negation of mineralization in the collision regime by Guild (1971),the focus of study was put on whether there occurred any mineralization during collisional orogenesis at the junior stage.At the senior stage,which is initiated by the advance of metallogenic and petrogenic model for collisional orogenesis,scientists begin to pay their attention to the geodynamic mechanism of metallogenesis,spatial and temporal distribution of ore deposits,ore-forming fluidization,relationship between petrogenesis and mineralization in collisional orogenesis,etc.Abundance of typical collisional orogens such as Himalayan,China has best natural conditions to study collisional metallogenesis.Great progress in the study of metallogenesis during collisional orogenesis has been made by Chinese geologists.Therefore,we hope that the Chinese geologists and Chinese governments at various levels to pay more attention to the study of collisional metallogenesis.Some urgent problems are suggested to be solved so as to bring about breakthroughs in the aspects concerned.
Comparison of secondary islands in collisional reconnection to Hall reconnection.
Shepherd, L S; Cassak, P A
2010-07-02
Large-scale resistive Hall-magnetohydrodynamic simulations of the transition from Sweet-Parker (collisional) to Hall (collisionless) magnetic reconnection are presented; the first to separate secondary islands from collisionless effects. Three main results are described. There exists a regime with secondary islands but without collisionless effects, and the reconnection rate is faster than Sweet-Parker, but significantly slower than Hall reconnection. This implies that secondary islands do not cause the fastest reconnection rates. The onset of Hall reconnection ejects secondary islands from the vicinity of the X line, implying that energy is released more rapidly during Hall reconnection. Coronal applications are discussed.
Collisional transfer of population and orientation in sodium potassium
Wolfe, Christopher Matthew
Collisional spectral satellite lines have been identified in recent optical-optical double resonance (OODR) excitation spectra of the NaK molecule. These satellite lines represent both a transfer of population, and a partial preservation of angular momentum orientation, to a rotational level adjacent to the one directly excited by the pump laser beam. A rate equation model was used to study the intensities of these satellite lines as a function of argon pressure and heat pipe oven temperature, in order to separate the collisional effects of argon and potassium atoms (being the most populous species in the vapor by an order of magnitude over the third most populous). Using a fit of this rate equation model to the data, it was found that collisions between NaK and potassium are more likely to transfer population and destroy orientation than argon collisions, and also more likely to transfer population to rotational levels higher in energy than the one being pumped (i.e. a propensity for positive Delta J collisions). Also, collisions between NaK and argon atoms show a propensity toward even-numbered changes in J. In addition to the above study, an analysis of collisional line broadening and velocity-changes in J-changing collisions was performed, showing potassium has a higher line broadening rate coefficient, as well as a smaller velocity change in J-changing collisions, than argon. A program was also written in Fortran 90/95 which solves the density matrix equations of motion in steady state for a coupled system of 3 (or 4) energy levels with their constituent degenerate magnetic sublevels. The solution to these equations yields the populations of each sublevel in steady state, as well as the laser-induced coherences between each sublevel (which are needed to model the polarization spectroscopy lineshape precisely). Development of an appropriate theoretical model for collisional transfer will yield a more rigorous study of the problem than the empirical rate
Collisional Excitation of Automotive Fuel Components (ethanol and Isooctane)
Cobb, Rachelle H.; White, Allen R.; Devasher, Rebecca B.
2009-06-01
It is possible to excite fuel components indirectly via a 10.6 um CO2 laser. A 9% solution of isopropanol in ethanol was used, as it has a strong absorption cross section at 10.6 um. CO2 laser excitation of pure ethanol caused little or no change in absorption in the C-H stretch region. However, the ethanol/isopropanol mixture did show a response proportional to laser excitation. Further studies indicate that excitation of isooctane/isopropanol mixture is also possible via collisional energy transfer between the laser excited isopropanol and isooctane.
Impact of nonlinear absorption on propagation of microwave in a plasma filled rectangular waveguide
Sobhani, H.; Vaziri, M.; Rooholamininejad, H.; Bahrampour, A. R.
2016-07-01
In collisional and ponderomotive predominant regimes, the propagation of microwave in rectangular waveguide filled with collisional plasma is investigated numerically. The dominant mode is excited through an evacuated waveguide and then enters a similar and co-axis waveguide filled with plasma. In collisional predominant regime, the amplitude of electric field is oscillated along propagation path; outset of propagation path due to the electron-ion collision, the intensity oscillations are reduced. Afterward, under competition between the collisional nonlinearity and absorption, the intensity is increased, so the electron density peak is created in middle of waveguide. In ponderomotive predominant regime, the intensity is slowly decreased due to collision, so the electron density is ramped. Control parameters, like the frequency, input power, collision frequency, and background electron density are surveyed that can be used to control propagation characteristics of microwave. This method can be used to control heating of fusion plasma and accelerate charged particle.
Simulation of weak and strong Langmuir collapse regimes
Energy Technology Data Exchange (ETDEWEB)
Hadzievski, L.R.; Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Kono, M.; Sato, T.
1998-01-01
In order to check the validity of the self-similar solutions and the existence of weak and strong collapse regimes, direct two dimensional simulation of the time evolution of a Langmuir soliton instability is performed. Simulation is based on the Zakharov model of strong Langmuir turbulence in a weakly magnetized plasma accounting for the full ion dynamics. For parameters considered, agreement with self-similar dynamics of the weak collapse type is found with no evidence of the strong Langmuir collapse. (author)
WEAK CONVERGENCE OF SOME SERIES
Institute of Scientific and Technical Information of China (English)
2000-01-01
This paper continues the study of [1] on weak functions.The weak convergence theory is investigated in complex analysis,Fourier transform and Mellin transform.A Mobius inverse formula of weak functions is obtained.
DEFF Research Database (Denmark)
Kohlenbach, Ulrich Wilhelm
2002-01-01
We show that the so-called weak Markov's principle (WMP) which states that every pseudo-positive real number is positive is underivable in E-HA + AC. Since allows one to formalize (atl eastl arge parts of) Bishop's constructive mathematics, this makes it unlikely that WMP can be proved within the...
Varying and inverting the mass hierarchy in collisional energy loss
Kolevatov, Rodion
2008-01-01
Heavy ion collisions at RHIC and at the LHC give access to the medium-induced suppression patterns of heavy-flavored single inclusive hadron spectra at high transverse momentum. This opens novel opportunities for a detailed characterization of the medium produced in the collision. In this note, we point out that the capacity of a QCD medium to absorb the recoil of a partonic projectile is an independent signature, which may differ for different media at the same density. In particular, while the mass hierarchy (i.e., the projectile mass dependence) of radiative energy loss depends solely on a property of the projectile, the mass hierarchy of collisional energy loss depends significantly on properties of the medium. By varying these properties in a class of models, we find that the mass hierarchy of collisional parton energy loss can be modified considerably and can even be inverted, compared to that of radiative parton energy loss. This may help to disentangle the relative strengths of radiative and collision...
Experimental study of collisional granular flows down an inclined plane
Azanza, Emmanuel; Chevoir, François; Moucheront, Pascal
1999-12-01
The collisional flow of a slightly inelastic granular material down a rough inclined plane is usually described by kinetic theories. We present an experimental study aimed at analysing the assumptions and the quantitative predictions of such theories. A two-dimensional channel coupled to a model granular material and image analysis allow detailed and complete measurement of the kinematics and structure of the flows. We determine the range of inclination and particle flux for which the flow is stationary and uniform. The characteristic profiles of solid fraction, mean velocity and granular temperature are systematically measured. Both the true collisional and the dilute kinetic regimes are examined. We show that a quasi-hydrodynamic description of these regimes seems relevant, and that the pressure and the viscosity terms are in good qualitative agreement with the prediction of the kinetic theory. The profiles are well described by the kinetic theory near the top of the flow, at low solid fraction. Conversely there are large discrepancies near the rough plane, where the material is structured in layers.
The Collisional Divot in the Kuiper belt Size Distribution
Fraser, Wesley C
2009-01-01
This paper presents the results of collisional evolution calculations for the Kuiper belt starting from an initial size distribution similar to that produced by accretion simulations of that region - a steep power-law large object size distribution that breaks to a shallower slope at r ~1-2 km, with collisional equilibrium achieved for objects r ~0.5 km. We find that the break from the steep large object power-law causes a divot, or depletion of objects at r ~10-20 km, which in-turn greatly reduces the disruption rate of objects with r> 25-50 km, preserving the steep power-law behavior for objects at this size. Our calculations demonstrate that the roll-over observed in the Kuiper belt size distribution is naturally explained as an edge of a divot in the size distribution; the radius at which the size distribution transitions away from the power-law, and the shape of the divot from our simulations are consistent with the size of the observed roll-over, and size distribution for smaller bodies. Both the kink r...
GAP CLEARING BY PLANETS IN A COLLISIONAL DEBRIS DISK
Energy Technology Data Exchange (ETDEWEB)
Nesvold, Erika R. [Department of Physics, University of Maryland Baltimore County 1000 Hilltop Circle Baltimore, MD 21250 (United States); Kuchner, Marc J., E-mail: Erika.Nesvold@umbc.edu, E-mail: Marc.Kuchner@nasa.gov [NASA Goddard Space Flight Center Exoplanets and Stellar Astrophysics Laboratory, Code 667 Greenbelt, MD 21230 (United States)
2015-01-10
We apply our 3D debris disk model, SMACK, to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (α = 2/7). We find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index α of the power law depends on the age of the system t relative to the collisional timescale t {sub coll} of the disk by α = 0.32(t/t {sub coll}){sup –0.04}, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion resonances near the chaotic zone. We investigate the effects of the initial eccentricity distribution of the disk particles and find a negligible effect on the gap size at Jovian planet masses, since collisions tend to erase memory of the initial particle eccentricity distributions. Finally, we find that the presence of Trojan analogs is a potentially powerful diagnostic of planets in the mass range ∼1-10 M {sub Jup}. We apply our model to place new upper limits on planets around Fomalhaut, HR 4796 A, HD 202628, HD 181327, and β Pictoris.
On closed weak supplemented modules
Institute of Scientific and Technical Information of China (English)
ZENG Qing-yi; SHI Mei-hua
2006-01-01
A module M is called closed weak supplemented if for any closed submodule N of M, there is a submodule K of M such that M=K+N and K(c)N＜＜M. Any direct summand of closed weak supplemented module is also closed weak supplemented.Any nonsingular image of closed weak supplemented module is closed weak supplemented. Nonsingular V-rings in which all nonsingular modules are closed weak supplemented are characterized in Section 4.
Neutrino propagation in a weakly magnetized medium
Indian Academy of Sciences (India)
Sushan Konar; Subinoy Das
2004-06-01
Neutrino—photon processes, forbidden in vacuum, can take place in the presence of a thermal medium and/or an external electro-magnetic field, mediated by the corresponding charged leptons (real or virtual). Such interactions affect the propagation of neutrinos through a magnetized plasma. We investigate the neutrino—photon absorptive processes, at the one-loop level, for massless neutrinos in a weakly magnetized plasma. We find that there is no correction to the absorptive part of the axial-vector—vector amplitude due to the presence of a magnetic field, to the linear order in the field strength.
Experimental measurements of the collisional absorption of XUV radiation in warm dense aluminium
Kettle, B.; Dzelzainis, T.; White, S.; Li, L.; Dromey, B.; Zepf, M.; Lewis, C. L. S.; Williams, G.; Künzel, S.; Fajardo, M.; Dacasa, H.; Zeitoun, Ph.; Rigby, A.; Gregori, G.; Spindloe, C.; Heathcote, R.; Riley, D.
2016-08-01
The collisional (or free-free) absorption of soft x rays in warm dense aluminium remains an unsolved problem. Competing descriptions of the process exist, two of which we compare to our experimental data here. One of these is based on a weak scattering model, another uses a corrected classical approach. These two models show distinctly different behaviors with temperature. Here we describe experimental evidence for the absorption of 26-eV photons in solid density warm aluminium (Te≈1 eV). Radiative x-ray heating from palladium-coated CH foils was used to create the warm dense aluminium samples and a laser-driven high-harmonic beam from an argon gas jet provided the probe. The results indicate little or no change in absorption upon heating. This behavior is in agreement with the prediction of the corrected classical approach, although there is not agreement in absolute absorption value. Verifying the correct absorption mechanism is decisive in providing a better understanding of the complex behavior of the warm dense state.
Weak Polarized Electron Scattering
Erler, Jens; Mantry, Sonny; Souder, Paul A
2014-01-01
Scattering polarized electrons provides an important probe of the weak interactions. Precisely measuring the parity-violating left-right cross section asymmetry is the goal of a number of experiments recently completed or in progress. The experiments are challenging, since A_{LR} is small, typically between 10^(-4) and 10^(-8). By carefully choosing appropriate targets and kinematics, various pieces of the weak Lagrangian can be isolated, providing a search for physics beyond the Standard Model. For other choices, unique features of the strong interaction are studied, including the radius of the neutron density in heavy nuclei, charge symmetry violation, and higher twist terms. This article reviews the theory behind the experiments, as well as the general techniques used in the experimental program.
von K\\'arm\\'an energy decay and heating of protons and electrons in a kinetic plasma
Wu, P; Matthaeus, W H; Shay, M A; Swisdak, M
2013-01-01
Decay in time of undriven weakly collisional kinetic plasma turbulence in systems large compared to the ion kinetic scales is investigated using fully electromagnetic particle-in-cell simulations initiated with transverse flow and magnetic disturbances, constant density, and a strong guide field. The observed energy decay is consistent with the von K\\'arm\\'an hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics (MHD). Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics. At small turbulence amplitude the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in large amplitude turbulence regime.
Von Kármán energy decay and heating of protons and electrons in a kinetic turbulent plasma.
Wu, P; Wan, M; Matthaeus, W H; Shay, M A; Swisdak, M
2013-09-20
Decay in time of undriven weakly collisional kinetic plasma turbulence in systems large compared to the ion kinetic scales is investigated using fully electromagnetic particle-in-cell simulations initiated with transverse flow and magnetic disturbances, constant density, and a strong guide field. The observed energy decay is consistent with the von Kármán hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics. Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics. At small turbulence amplitudes the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in the large amplitude turbulence regime.
Institute of Scientific and Technical Information of China (English)
WU Guang; SUN Fengyue; ZHAO Caisheng; LI Zhitong; ZHAO Ailin; PANG Qingbang; LI Guangyuan
2005-01-01
The Luoguhe intrusion, located in Mohe County, Heilongjiang Province, is mainly composed of monzogranite, quartz diorite and granodiorite, with minor diorite, tonalite, quartz monzodiorite, quartz monzonite, syenogranite and alkali-feldspar granite. The intrusion can be divided into two lithological units, I.e. Quartz diorite and monzogranite units, with affinities to high-K calc-alkaline series. The quartz diorite unit (SiO2: 54.79%―58.30%, Na2O/CaO: 0.79―1.53 and Shand index: 0.77―0.82) belongs to metaluminous rocks. And the monzogranite unit (SiO2: 65.29%―66.45%, Na2O/CaO:1.73―3.43 and Shand index <1.05) can be considered as weakly peraluminous rocks. The intrusion is characterized by high REE abundance (∑REE = 180.2―344.3 μg/g), medium-strong negative Eu anomalies (δEu = 0.33―0.82), weak REE fractionation [(La/Yb)N = 4.12―10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, Hf, Zr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and Ti. These characteristics of major, REE and trace elements indicate that the intrusion was formed in a transitional tectonic setting from compressional to extensional regime, which can be classified as post-collisional granitoids. SHRIMP U-Pb zircon analyses yield ages of 517±9 and 504±8 Ma for the quartz diorite and monzogranite units, respectively. The discovery of Early Paleozoic post-collisional granites in the northern margin of the Erguna massif indicates that the northern branch of Paleo-Asian Ocean between Siberian plate and Erguna massif was closed in the Early Paleozoic and the Salair orogeny ended ca. 500 Ma ago.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, M.
1988-04-01
Dynamical mechanism of composite W and Z is studied in a 1/N field theory model with four-fermion interactions in which global weak SU(2) symmetry is broken explicitly by electromagnetic interaction. Issues involved in such a model are discussed in detail. Deviation from gauge coupling due to compositeness and higher order loop corrections are examined to show that this class of models are consistent not only theoretically but also experimentally.
Oikonomou, V K; Park, Miok
2014-01-01
We study some aspects of cosmological evolution in a universe described by a viable curvature corrected exponential $F(R)$ gravity model, in the presence of matter fluids consisting of collisional matter and radiation. Particularly, we express the Friedmann-Robertson-Walker equations of motion in terms of parameters that are appropriate for describing the dark energy oscillations and compare the dark energy density and the dark energy equation of state parameter corresponding to collisional and non-collisional matter. In addition to these, and owing to the fact that the cosmological evolution of collisional and non-collisional matter universes, when quantified in terms of the Hubble parameter and the effective equation of states parameters, is very much alike, we further scrutinize the cosmological evolution study by extending the analysis to the study of matter perturbations in the matter domination era. We quantify this analysis in terms of the growth factor of matter perturbations, in which case the result...
Nonlinear Alfvén wave dynamics in plasmas
Energy Technology Data Exchange (ETDEWEB)
Sarkar, Anwesa; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Schamel, Hans [Theoretical Physics, University of Bayreuth, D-95440 Bayreuth (Germany)
2015-07-15
Nonlinear Alfvén wave dynamics is presented using Lagrangian fluid approach in a compressible collisional magnetized plasma. In the framework of two fluid dynamics, finite electron inertia is shown to serve as a dispersive effect acting against the convective nonlinearity. In a moving frame, the Alfvén wave can, therefore, form an arbitrarily strong amplitude solitary wave structure due to the balance between nonlinearity and dispersion. Weak amplitude Alfvén waves are shown to be governed by a modified KdV equation, which extends for finite dissipation to a mKdV-Burgers equation. These equations have well known solutions. Next, we have analyzed the fourth order nonlinear Alfvén wave system of equations both numerically and by approximation method. The results indicate a collapse of the density and magnetic field irrespective of the presence of dispersion. The wave magnetic field, however, appears to be less singular showing collapse only when the dispersive effects are negligible. These results may contribute to our understanding of the generation of strongly localized magnetic fields (and currents) in plasmas and are expected to be of special importance in the astrophysical context of magnetic star formation.
Nonlinear Alfvén wave dynamics in plasmas
Sarkar, Anwesa; Chakrabarti, Nikhil; Schamel, Hans
2015-07-01
Nonlinear Alfvén wave dynamics is presented using Lagrangian fluid approach in a compressible collisional magnetized plasma. In the framework of two fluid dynamics, finite electron inertia is shown to serve as a dispersive effect acting against the convective nonlinearity. In a moving frame, the Alfvén wave can, therefore, form an arbitrarily strong amplitude solitary wave structure due to the balance between nonlinearity and dispersion. Weak amplitude Alfvén waves are shown to be governed by a modified KdV equation, which extends for finite dissipation to a mKdV-Burgers equation. These equations have well known solutions. Next, we have analyzed the fourth order nonlinear Alfvén wave system of equations both numerically and by approximation method. The results indicate a collapse of the density and magnetic field irrespective of the presence of dispersion. The wave magnetic field, however, appears to be less singular showing collapse only when the dispersive effects are negligible. These results may contribute to our understanding of the generation of strongly localized magnetic fields (and currents) in plasmas and are expected to be of special importance in the astrophysical context of magnetic star formation.
Energy Technology Data Exchange (ETDEWEB)
Xu, X. Q., E-mail: xxu@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ma, J. F. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States); Li, G. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China)
2014-12-15
The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.
DEFF Research Database (Denmark)
Haagerup, Uffe; Knudby, Søren
2015-01-01
The weak Haagerup property for locally compact groups and the weak Haagerup constant were recently introduced by the second author [27]. The weak Haagerup property is weaker than both weak amenability introduced by Cowling and the first author [9] and the Haagerup property introduced by Connes [6......] and Choda [5]. In this paper, it is shown that a connected simple Lie group G has the weak Haagerup property if and only if the real rank of G is zero or one. Hence for connected simple Lie groups the weak Haagerup property coincides with weak amenability. Moreover, it turns out that for connected simple...... Lie groups the weak Haagerup constant coincides with the weak amenability constant, although this is not true for locally compact groups in general. It is also shown that the semidirect product R2 × SL(2,R) does not have the weak Haagerup property....
Weak martingale Hardy spaces and weak atomic decompositions
Institute of Scientific and Technical Information of China (English)
HOU; Youliang; REN; Yanbo
2006-01-01
In this paper we define some weak martingale Hardy spaces and three kinds of weak atoms. They are the counterparts of martingale Hardy spaces and atoms in the classical martingale Hp-theory. And then three atomic decomposition theorems for martingales in weak martingale Hardy spaces are proved. With the help of the weak atomic decompositions of martingale, a sufficient condition for a sublinear operator defined on the weak martingale Hardy spaces to be bounded is given. Using the sufficient condition, we obtain a series of martingale inequalities with respect to the weak Lp-norm, the inequalities of weak (p ,p)-type and some continuous imbedding relationships between various weak martingale Hardy spaces. These inequalities are the weak versions of the basic inequalities in the classical martingale Hp-theory.
LAD Dissertation Prize Talk: Molecular Collisional Excitation in Astrophysical Environments
Walker, Kyle M.
2017-06-01
While molecular excitation calculations are vital in determining particle velocity distributions, internal state distributions, abundances, and ionization balance in gaseous environments, both theoretical calculations and experimental data for these processes are lacking. Reliable molecular collisional data with the most abundant species - H2, H, He, and electrons - are needed to probe material in astrophysical environments such as nebulae, molecular clouds, comets, and planetary atmospheres. However, excitation calculations with the main collider, H2, are computationally expensive and therefore various approximations are used to obtain unknown rate coefficients. The widely-accepted collider-mass scaling approach is flawed, and alternate scaling techniques based on physical and mathematical principles are presented here. The most up-to-date excitation data are used to model the chemical evolution of primordial species in the Recombination Era and produce accurate non-thermal spectra of the molecules H2+, HD, and H2 in a primordial cloud as it collapses into a first generation star.
Collisional Processing of Comet Surfaces: Impact Experiments into Olivine
Lederer, S. M.; Jensen, E. A.; Cintala, M. J.; Smith, D. C.; Nakamura-Messenger, K.; Keller, L. P.; Wooden, D. H.; Fernandez, Y. R.; Zolensky, M. E.
2011-01-01
A new paradigm has emerged where 3.9 Ga ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. In addition, objects in the Kuiper Belt are believed to undergo extensive collisional processing while in the Kuiper Belt. Physical manifestations of shock effects (e.g., planar dislocations) in minerals typically found in comets will be correlated with spectral changes (e.g. reddening, loss and shift of peaks, new signatures) to allow astronomers to better understand geophysical impact processing that has occurred on small bodies. Targets will include solid and granular olivine (forsterite), impacted over a range of impact speeds with the Experimental Impact Laboratory at NASA JSC. Analyses include quantification of the dependence of the spectral changes with respect to impact speed, texture of the target, and temperature.
Modeling Collisional Cascades In Debris Disks: The Numerical Method
Gaspar, Andras; Ozel, Feryal; Rieke, George H; Cooney, Alan
2011-01-01
We develop a new numerical algorithm to model collisional cascades in debris disks. Because of the large dynamical range in particle masses, we solve the integro-differential equations describing erosive and catastrophic collisions in a particle-in-a-box approach, while treating the orbital dynamics of the particles in an approximate fashion. We employ a new scheme for describing erosive (cratering) collisions that yields a continuous set of outcomes as a function of colliding masses. We demonstrate the stability and convergence characteristics of our algorithm and compare it with other treatments. We show that incorporating the effects of erosive collisions results in a decay of the particle distribution that is significantly faster than with purely catastrophic collisions.
MODELING COLLISIONAL CASCADES IN DEBRIS DISKS: THE NUMERICAL METHOD
Energy Technology Data Exchange (ETDEWEB)
Gaspar, Andras; Psaltis, Dimitrios; Oezel, Feryal; Rieke, George H.; Cooney, Alan, E-mail: agaspar@as.arizona.edu, E-mail: dpsaltis@as.arizona.edu, E-mail: fozel@as.arizona.edu, E-mail: grieke@as.arizona.edu, E-mail: acooney@physics.arizona.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
2012-04-10
We develop a new numerical algorithm to model collisional cascades in debris disks. Because of the large dynamical range in particle masses, we solve the integro-differential equations describing erosive and catastrophic collisions in a particle-in-a-box approach, while treating the orbital dynamics of the particles in an approximate fashion. We employ a new scheme for describing erosive (cratering) collisions that yields a continuous set of outcomes as a function of colliding masses. We demonstrate the stability and convergence characteristics of our algorithm and compare it with other treatments. We show that incorporating the effects of erosive collisions results in a decay of the particle distribution that is significantly faster than with purely catastrophic collisions.
The violent collisional history of asteroid 4 Vesta.
Marchi, S; McSween, H Y; O'Brien, D P; Schenk, P; De Sanctis, M C; Gaskell, R; Jaumann, R; Mottola, S; Preusker, F; Raymond, C A; Roatsch, T; Russell, C T
2012-05-11
Vesta is a large differentiated rocky body in the main asteroid belt that accreted within the first few million years after the formation of the earliest solar system solids. The Dawn spacecraft extensively imaged Vesta's surface, revealing a collision-dominated history. Results show that Vesta's cratering record has a strong north-south dichotomy. Vesta's northern heavily cratered terrains retain much of their earliest history. The southern hemisphere was reset, however, by two major collisions in more recent times. We estimate that the youngest of these impact structures, about 500 kilometers across, formed about 1 billion years ago, in agreement with estimates of Vesta asteroid family age based on dynamical and collisional constraints, supporting the notion that the Vesta asteroid family was formed during this event.
Collisional effects in the dynamics of a dipolar gas
Sykes, Andrew
2016-05-01
In this talk, we discuss the role of collisions in dipolar gases which are far from equilibrium. We compare and contrast collisional mechanisms with mean-field effects. We consider several cases of dynamical behaviour. We begin with cross-dimensional relaxation, where the time-scale of equilibration is studied following a quench in the trap parameters. We also discuss the damping of monopole and quadrupole excitations. Finally we discuss time-of-flight expansion dynamics. Our results demonstrate that collisions can play a significant role. We use these results to extract an estimate of the deca-heptuplet s-partial-wave scattering length of bosonic dysprosium, and to improve the accuracy of experimental time-of-flight expansion imaging. Financial support from the Marie Sklodowska-Curie H2020 framework program.
Collisionally-activated dissociation in hyperthermal surface ionization of cholesterol
Dagan, Shai; Danon, Albert; Amirav, Aviv
1992-03-01
Cholesterol in a hydrogen-seeded supersonic molecular beam was scattered from a continuously oxidized rhenium foil. The hyperthermal surface scattering exhibited efficient molecular ionization with a controlled amount of molecular ion dissociation. At 5.3 eV incident molecular kinetic energy the hyperthermal surface ionization mass spectrum was dominated by the parent molecular ion. Upon the increase of the molecular kinetic energy, a gradual increase in the degree of ion dissociation was observed. At 22eV incident kinetic energy the parent ion was completely dissociated and the mass spectrum was dominated by an extensive consecutive fragmentation. An efficient kinetic-vibrational energy transfer was observed, and it is extimated to be over 18% of the available incident kinetic energy. The implication for surface collisionally-activated dissociation of polyatomic ions is discussed. Rhenium oxide is suggested as an optimal surface for this purpose, as well as for the hyperthermal surface ionization of neutral species.
Collisional Cascade Caclulations for Irregular Satellite Swarms in Fomalhaut b
Kenyon, Scott J
2015-01-01
We describe an extensive suite of numerical calculations for the collisional evolution of irregular satellite swarms around 1--300 M-earth planets orbiting at 120 AU in the Fomalhaut system. For 10--100 M-earth planets, swarms with initial masses of roughly 1% of the planet mass have cross-sectional areas comparable to the observed cross-sectional area of Fomalhaut b. Among 30--300 M-earth planets, our calculations yield optically thick swarms of satellites for ages of 1-10 Myr. Observations with HST and ground-based AO instruments can constrain the frequency of these systems around stars in the beta Pic moving group and possibly other nearby associations of young stars.
Karmakar, P. K.; Borah, B.
2013-09-01
We try to present a theoretical evolutionary model leading to the excitations of nonlinear pulsational eigenmodes in a planar (1D) collisional dust molecular cloud (DMC) on the Jeans scale. The basis of the adopted model is the Jeans assumption of self-gravitating homogeneous uniform medium for simplification. It is a self-gravitating multi-fluid consisting of the Boltzmann distributed warm electrons and ions, and the inertial cold dust grains with partial ionization. Dust-charge fluctuations, convections and all the possible collisions are included. The grain-charge behaves as a dynamical variable owing mainly to the attachment of the electrons and ions to the grain-surfaces randomly. The adopted technique is centered around a mathematical model based on new solitary spectral patterns within the hydrodynamic framework. The collective dynamics of the patterns is governed by driven Korteweg-de Vries ( d-KdV) and Korteweg-de Vries (KdV) equations obtained by a standard multiscale analysis. Then, simplified analytical and numerical solutions are presented. The grain-charge fluctuation and collision processes play a key role in the DMC stability. The sensitive dependence of the eigenmode amplitudes on diverse relevant plasma parameters is discussed. The significance of the main results in astrophysical, laboratory and space environments are concisely summarized.
Collisional modelling of the debris disc around HIP 17439
Schüppler, Ch.; Löhne, T.; Krivov, A. V.; Ertel, S.; Marshall, J. P.; Eiroa, C.
2014-07-01
We present an analysis of the debris disc around the nearby K2 V star HIP 17439. In the context of the Herschel DUNES key programme, the disc was observed and spatially resolved in the far-IR with the Herschel PACS and SPIRE instruments. In a previous study, we assumed that the size and radial distribution of the circumstellar dust are independent power laws. There, several scenarios capable of explaining the observations were suggested after exploring a very broad range of possible model parameters. In this paper, we perform a follow-up in-depth collisional modelling of these scenarios to further distinguish between them. In our models we consider collisions, direct radiation pressure, and drag forces, which are the actual physical processes operating in debris discs. We find that all scenarios discussed in the first paper are physically reasonable and can reproduce the observed spectral energy distribution along with the PACS surface brightness profiles reasonably well. In one model, the dust is produced beyond 120 au in a narrow planetesimal belt and is transported inwards by Poynting-Robertson and stellar wind drag. Good agreement with the observed radial profiles would require stellar winds by about an order of magnitude stronger than the solar value, which is not confirmed - although not ruled out - by observations. Another model consists of two spatially separated planetesimal belts, a warm inner and a cold outer one. This scenario would probably imply the presence of planets clearing the gap between the two components. Finally, we show qualitatively that the observations can be explained by assuming the dust is produced in a single, but broad planetesimal disc with a surface density of solids rising outwards, as expected for an extended disc that experiences a natural inside-out collisional depletion. Prospects of distinguishing between the competing scenarios by future observations are discussed.
Plasma physics an introduction
Fitzpatrick, Richard
2014-01-01
Plasma Physics: An Introduction is based on a series of university course lectures by a leading name in the field, and thoroughly covers the physics of the fourth state of matter. This book looks at non-relativistic, fully ionized, nondegenerate, quasi-neutral, and weakly coupled plasma. Intended for the student market, the text provides a concise and cohesive introduction to plasma physics theory, and offers a solid foundation for students wishing to take higher level courses in plasma physics.
Kirk, A; Liu, Yueqiang; Chapman, I T; Cahyna, P; Eich, T; Fuchs, C; Ham, C; Harrison, J R; Jakubowski, M W; Pamela, S; Peterka, M; Ryan, D; Saarelma, S; Scannell, R; Thornton, A J; Valovic, M; Sieglin, B; Orte, L Barrera; Willensdorfer, M; Kurzan, B; Fischer, R; Upgrade, ASDEX
2014-01-01
Sustained ELM mitigation has been achieved on MAST and AUG using RMPs with a range of toroidal mode numbers over a wide region of low to medium collisionality discharges. The ELM energy loss and peak heat loads at the divertor targets have been reduced. The ELM mitigation phase is typically associated with a drop in plasma density and overall stored energy. In one particular scenario on MAST, by carefully adjusting the fuelling it has been possible to counteract the drop in density and to produce plasmas with mitigated ELMs, reduced peak divertor heat flux and with minimal degradation in pedestal height and confined energy. While the applied resonant magnetic perturbation field can be a good indicator for the onset of ELM mitigation on MAST and AUG there are some cases where this is not the case and which clearly emphasise the need to take into account the plasma response to the applied perturbations. The plasma response calculations show that the increase in ELM frequency is correlated with the size of the e...
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
The study of weak scattering from inhomogeneous media or interface roughness has long been of interest in sonar applications. In an acoustic backscattering model of a stationary field of volume inhomogeneities, a stochastic description of the field is more useful than a deterministic description...... due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Erler, Jens
2013-01-01
This is a review of electroweak precision physics with particular emphasis on low-energy precision measurements in the neutral current sector of the electroweak theory and includes future experimental prospects and the theoretical challenges one faces to interpret these observables. Within the minimal Standard Model they serve as determinations of the weak mixing angle which are competitive with and complementary to those obtained near the Z-resonance. In the context of new physics beyond the Standard Model these measurements are crucial to discriminate between models and to reduce the allowed parameter space within a given model. We illustrate this for the minimal supersymmetric Standard Model with or without R-parity.
Measurement of weak radioactivity
Theodorsson , P
1996-01-01
This book is intended for scientists engaged in the measurement of weak alpha, beta, and gamma active samples; in health physics, environmental control, nuclear geophysics, tracer work, radiocarbon dating etc. It describes the underlying principles of radiation measurement and the detectors used. It also covers the sources of background, analyzes their effect on the detector and discusses economic ways to reduce the background. The most important types of low-level counting systems and the measurement of some of the more important radioisotopes are described here. In cases where more than one type can be used, the selection of the most suitable system is shown.
Weakly broken galileon symmetry
Energy Technology Data Exchange (ETDEWEB)
Pirtskhalava, David [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Santoni, Luca; Trincherini, Enrico [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); INFN, Sezione di Pisa, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Vernizzi, Filippo [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette cédex, F-91191 (France)
2015-09-01
Effective theories of a scalar ϕ invariant under the internal galileon symmetryϕ→ϕ+b{sub μ}x{sup μ} have been extensively studied due to their special theoretical and phenomenological properties. In this paper, we introduce the notion of weakly broken galileon invariance, which characterizes the unique class of couplings of such theories to gravity that maximally retain their defining symmetry. The curved-space remnant of the galileon’s quantum properties allows to construct (quasi) de Sitter backgrounds largely insensitive to loop corrections. We exploit this fact to build novel cosmological models with interesting phenomenology, relevant for both inflation and late-time acceleration of the universe.
MOL-D: A Collisional Database and Web Service within the Virtual Atomic and Molecular Data Center
Indian Academy of Sciences (India)
V. Vujčić; D. Jevremović; A. A. Mihajlov; Lj. M. Ignjatović; V. A. Srećković; M. S. Dimitrijević; M. Malović
2015-12-01
MOL-D database is a collection of cross-sections and rate coefficients for specific collisional processes and a web service within the Serbian Virtual Observatory (SerVO) and the Virtual Atomic and Molecular Data Center (VAMDC). This database contains photo-dissociation cross-sections for the individual ro-vibrational states of the diatomic molecular ions and rate coefficients for the atom-Rydberg atom chemiionization and inverse electron–ion–atom chemi-recombination processes. At the moment it contains data for photodissociation crosssections of hydrogen H+2 and helium H+2 molecular ions and the corresponding averaged thermal photodissociation cross-sections. The ro-vibrational energy states and the corresponding dipole matrix elements are provided as well. Hydrogen and helium molecular ion data are important for calculation of solar and stellar atmosphere models and for radiative transport, as well as for kinetics of other astrophysical and laboratory plasma (i.e. early Universe).
Alberico, W M
2004-01-01
The focus of these Lectures is on the weak decay modes of hypernuclei, with special attention to Lambda-hypernuclei. The subject involves many fields of modern theoretical and experimental physics, from nuclear structure to the fundamental constituents of matter and their interactions. The various weak decay modes of Lambda-hypernuclei are described: the mesonic mode and the non-mesonic ones. The latter are the dominant decay channels of medium--heavy hypernuclei, where, on the contrary, the mesonic decay is disfavoured by Pauli blocking effect on the outgoing nucleon. In particular, one can distinguish between one-body and two-body induced decays. Theoretical models employed to evaluate the (partial and total) decay widths of hypernuclei are illustrated, and their results compared with existing experimental data. Open problems and recent achievements are extensively discussed, in particular the determination of the ratio Gamma_n/Gamma_p, possible tests of the Delta I=1/2 rule in non-mesonic decays and the pu...
Jolley, Sarah E; Bunnell, Aaron E; Hough, Catherine L
2016-11-01
Survivorship after critical illness is an increasingly important health-care concern as ICU use continues to increase while ICU mortality is decreasing. Survivors of critical illness experience marked disability and impairments in physical and cognitive function that persist for years after their initial ICU stay. Newfound impairment is associated with increased health-care costs and use, reductions in health-related quality of life, and prolonged unemployment. Weakness, critical illness neuropathy and/or myopathy, and muscle atrophy are common in patients who are critically ill, with up to 80% of patients admitted to the ICU developing some form of neuromuscular dysfunction. ICU-acquired weakness (ICUAW) is associated with longer durations of mechanical ventilation and hospitalization, along with greater functional impairment for survivors. Although there is increasing recognition of ICUAW as a clinical entity, significant knowledge gaps exist concerning identifying patients at high risk for its development and understanding its role in long-term outcomes after critical illness. This review addresses the epidemiologic and pathophysiologic aspects of ICUAW; highlights the diagnostic challenges associated with its diagnosis in patients who are critically ill; and proposes, to our knowledge, a novel strategy for identifying ICUAW. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.
Kaplan, L
1998-01-01
We examine the consequences of classical ergodicity for the localization properties of individual quantum eigenstates in the classical limit. We note that the well known Schnirelman result is a weaker form of quantum ergodicity than the one implied by random matrix theory. This suggests the possibility of systems with non-gaussian random eigenstates which are nonetheless ergodic in the sense of Schnirelman and lead to ergodic transport in the classical limit. These we call "weakly quantum ergodic.'' Indeed for a class of "slow ergodic" classical systems, it is found that each eigenstate becomes localized to an ever decreasing fraction of the available state space, in the semiclassical limit. Nevertheless, each eigenstate in this limit covers phase space evenly on any classical scale, and long-time transport properties betwen individual quantum states remain ergodic due to the diffractive effects which dominate quantum phase space exploration.
Ross, James; Park, H.-S.; Huntington, C.; Ryutov, D.; Drake, R. P.; Froula, D.; Gregori, G.; Levy, M.; Lamb, D.; Fiuza, F.; Petrasso, R.; Li, C.; Zylastra, A.; Rinderknecht, H.; Sakawa, Y.; Spitkovsky, A.
2015-11-01
Shock formation from high-Mach number plasma flows is observed in many astrophysical objects such as supernova remnants and gamma ray bursts. These are collisionless shocks as the ion-ion collision mean free path is much larger than the system size. It is believed that seed magnetic fields can be generated on a cosmologically fast timescale via the Weibel instability when such environments are initially unmagnetized. Here we present laboratory experiments using high-power lasers whose ultimate goal is to investigate the dynamics of collisionless shock formation in two interpenetrating plasma streams. Particle-in-cell numerical simulations have confirmed that the strength and structure of the generated magnetic field are consistent with the Weibel mediated electromagnetic nature and that the inferred magnetization level could be as high as ~ 1%. This paper will review recent experimental results from various laser facilities as well as the simulation results and the theoretical understanding of these observations. Taken together, these results imply that electromagnetic instabilities can be significant in both inertial fusion and astrophysical conditions. We will present results from initial NIF experiments, where we observe the neutrons and x-rays generated from the hot plasmas at the center of weakly collisional, counterstreaming flows. Prepared by LLNL under Contract DE-AC52-07NA27344.
Collisional transfer of population and orientation in NaK
Wolfe, C. M.; Ashman, S.; Bai, J.; Beser, B.; Ahmed, E. H.; Lyyra, A. M.; Huennekens, J.
2011-05-01
Collisional satellite lines with |ΔJ| ≤ 58 have been identified in recent polarization spectroscopy V-type optical-optical double resonance (OODR) excitation spectra of the Rb2 molecule [H. Salami et al., Phys. Rev. A 80, 022515 (2009)]. Observation of these satellite lines clearly requires a transfer of population from the rotational level directly excited by the pump laser to a neighboring level in a collision of the molecule with an atomic perturber. However to be observed in polarization spectroscopy, the collision must also partially preserve the angular momentum orientation, which is at least somewhat surprising given the extremely large values of ΔJ that were observed. In the present work, we used the two-step OODR fluorescence and polarization spectroscopy techniques to obtain quantitative information on the transfer of population and orientation in rotationally inelastic collisions of the NaK molecules prepared in the 2(A)1Σ+(v' = 16, J' = 30) rovibrational level with argon and potassium perturbers. A rate equation model was used to study the intensities of these satellite lines as a function of argon pressure and heat pipe oven temperature, in order to separate the collisional effects of argon and potassium atoms. Using a fit of this rate equation model to the data, we found that collisions of NaK molecules with potassium atoms are more likely to transfer population and destroy orientation than collisions with argon atoms. Collisions with argon atoms show a strong propensity for population transfer with ΔJ = even. Conversely, collisions with potassium atoms do not show this ΔJ = even propensity, but do show a propensity for ΔJ = positive compared to ΔJ = negative, for this particular initial state. The density matrix equations of motion have also been solved numerically in order to test the approximations used in the rate equation model and to calculate fluorescence and polarization spectroscopy line shapes. In addition, we have measured rate
Long-Range Collisions in Magnetized Plasmas
Dubin, D.
2015-12-01
Astrophysical (and earthbound) plasmas in strong magnetic fields exhibit collisional effects that are not described by classical collision theory nor by the standard collision operators, such as the Landau or Balescu-Lenard operators. These theories implicitly neglect "long-range" collisions, i.e. collisions with impact parameters large compared to the cyclotron radius. This presentation will review several important physical effects such collisions have on various phenomena, including cross-magnetic field diffusion, heat conduction, and collisional slowing parallel to the magnetic field. Long-range collisions are analyzed as guiding-centers moving in one-dimension along the magnetic field, with parallel energy and momentum transferred to particles on separate field lines through the screened Coulomb interaction. This causes cross-field heat transport that is independent of magnetic field strength B (as opposed to the classical 1/B2 scaling), and enhances the rate of collisional slowing parallel to B. The Coulomb interaction between guiding centers on different field lines also produces random ExB drifts that enhance cross-magnetic field diffusion compared to the classical theory. The theory of long-range guiding center collisions must also include the novel effect of "collisional caging": plasma noise causes two colliding guiding centers to diffuse in relative parallel velocity, reversing their motion along B and colliding several times before becoming uncorrelated. This further enhances cross-field diffusion from long-range collisions by a factor of three, and enhances parallel slowing by a factor of approximately 1.5.
Gaussian beam diffraction in weakly anisotropic inhomogeneous media
Energy Technology Data Exchange (ETDEWEB)
Kravtsov, Yu.A., E-mail: kravtsov@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland); Space Research Institute, Russian Academy of Science, Moscow 117 997 (Russian Federation); Berczynski, P., E-mail: pawel.berczynski@ps.p [Institute of Physics, West Pomeranian University of Technology, Szczecin 70-310 (Poland); Bieg, B., E-mail: b.bieg@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland)
2009-08-10
Combination of quasi-isotropic approximation (QIA) of geometric optics with paraxial complex geometric optics (PCGO) is suggested, which allows describing both diffraction and polarization evolution of Gaussian electromagnetic beams in weakly anisotropic inhomogeneous media. Combination QIA/PCGO reduces Maxwell equations to the system of the ordinary differential equations of the first order and radically simplifies solution of various problems, related to microwave plasma diagnostics, including plasma polarimetry, interferometry and refractometry in thermonuclear reactors. Efficiency of the method is demonstrated by the example of electromagnetic beam diffraction in a linear layer of magnetized plasma with parameters, modeling tokamak plasma in the project ITER.
Anatexis witnessed post-collisional evolution of the Dabie orogen, China
Xu, Haijin; Zhang, Junfeng
2017-09-01
Crustal anatexis plays a significant role in the processes of orogenic evolution. We carried out a combined study of structure, U-Pb age and trace element on zircons from leucosome-based migmatites in the North Dabie zone to provide information on crustal anatexis during the evolution of the Dabie orogen. Protoliths of the migmatites are Middle Neoproterozoic (ca. 780-710 Ma) magmatic rocks that belong to the South China Block. They underwent a relatively low-T eclogite-facies metamorphism during the Middle to Late Triassic (235-225 Ma) continental subduction and collision. An over-thickened crustal root was formed and the Dabie orogen entered into the stage of post-collisional evolution after the Triassic. The earliest anatexis occurred at ca. 185 Ma; the anatexis in the Jurassic was weak and gentle due to episodic flow of metamorphic fluids with a prolonged interval. Nevertheless, it indicates that the crustal root started to become ductile and unstable at that time. Extensive epsodic anatexis occurred between ca. 160 Ma and 110 Ma. As the anatexis became stronger, more extensive and uninterrupted, the anatectic products changed gradually from low-degree migmatites to high-degree migmatites. The beginning of extensive anatexis at ∼160 Ma marks the beginning of orogenic activation. The duration of ca. 160-145 Ma corresponds to the orogenic activation when the collision-thickened crust still remained, whereas the period of ca. 145-110 Ma is in accordance with the orogenic collapse. The peak period of anatexis (ca. 145-125 Ma) was accompanied by plutonism, high-T granulite-facies metamorphism, extensional uplift and subsequent delamination of crustal root. After that, the anatexis trailed off until ca. 110 Ma. The long lasting multistage anatexis recorded in the migmatites has witnessed the evolution of the Dabie orogen in the postcollisional stage.
Thebault, Philippe
2011-01-01
Debris discs are traditionally studied using two distinct types of numerical models: statistical particle-in-a-box codes to study their collisional and size distribution evolution, and dynamical N-body models to study their spatial structure. The absence of collisions from N-body codes is in particular a major shortcoming, as collisional processes are expected to significantly alter the results obtained from pure N-body runs. We present a new numerical model, to study the spatial structure of perturbed debris discs at dynamical and collisional steady-state. We focus on the competing effects between gravitational perturbations by a massive body (planet or star), collisional production of small grains, and radiation pressure placing these grains in possibly dynamically unstable regions. We consider a disc of parent bodies at dynamical steady-state, from which small radiation-pressure-affected grains are released in a series of runs, each corresponding to a different orbital position of the perturber, where part...
Rosenberg, Claudio; Bellahsen, Nicolas
2016-04-01
The style of collision in the Alps varies along strike, reflecting different amounts and different modes of accommodation of collisional shortening. These differences control the patterns of exhumation during collision. Whereas the western Alps largely consist of a metamorphic complex formed during subduction and largely exhumed before the initiation of collision, the subduction nappe-stack of the Central and the Eastern Alps is strongly overprinted by collisional shortening and by Barrovian metamorphism. Based on compiled and new data we estimate amounts of collisional shortening along the strike of the chain and set it in relationship to the geometry of the collisional prism. The western Alpine collisional structures form a very large (in map view), but moderately shortened wedge, terminating in front of a poorly developed Molasse basin. Shortening of this wedge was mainly localized along its external parts, resulting in accretion of basement and cover units thrusted towards the foreland. Back-folding and back-thrusting are barely developed and no shortening takes place in the upper, Adriatic plate. In the Central Alps, the amount of collisional shortening is larger and it is distributed both in the lower and in the upper plate. The collisional prism is bivergent and partitioning of the amount of shortening between the upper and lower plates varies along strike, being most probably controlled by rheological, heterogeneities. The thickened accreted lower plate is strongly affected by Barrovian metamorphism where shortening is largest and localized within a confined area. A deep Molasse basin developed in front of the prism. In the Eastern Alps collisional kinematics vary from east to west, with orogen-parallel displacements dominating in the east and orogen-perpendicular ones in the West, where they culminate in the structural and metamorphic dome of the Tauern Window. Nowhere else in the Alps collisional shortening is so strongly localized in one and the same
A Collisional Origin to Earth's Non-chondritic Composition?
Bonsor, Amy; Carter, Philip J; Elliott, Tim; Walter, Michael J; Stewart, Sarah T
2014-01-01
Several lines of evidence indicate a non-chondritic composition for Bulk Earth. If Earth formed from the accretion of chondritic material, its non-chondritic composition, in particular the super-chondritic 142Nd/144Nd and low Mg/Fe ratios, might be explained by the collisional erosion of differentiated planetesimals during its formation. In this work we use an N-body code, that includes a state-of-the-art collision model, to follow the formation of protoplanets, similar to proto-Earth, from differentiated planetesimals (> 100 km) up to isolation mass (> 0.16 M_Earth). Collisions between differentiated bodies have the potential to change the core-mantle ratio of the accreted protoplanets. We show that sufficient mantle material can be stripped from the colliding bodies during runaway and oligarchic growth, such that the final protoplanets could have Mg/Fe and Si/Fe ratios similar to that of bulk Earth, but only if Earth is an extreme case and the core is assumed to contain 10% silicon by mass. This may indicat...
Consistent analytic approach to the efficiency of collisional Penrose process
Harada, Tomohiro; Miyamoto, Umpei
2016-01-01
We propose a consistent analytic approach to the efficiency of collisional Penrose process in the vicinity of a maximally rotating Kerr black hole. We focus on a collision with arbitrarily high centre-of-mass energy, which occurs if either of the colliding particles has its angular momentum finetuned to the critical value to enter the horizon. We show that if the finetuned particle is ingoing on the collision, the upper limit of the efficiency is $(2+\\sqrt{3})(2-\\sqrt{2})\\simeq 2.186$, while if the finetuned particle is bounced back before the collision, the upper limit is $(2+\\sqrt{3})^{2}\\simeq 13.93$. Despite earlier claims, the former can be attained for inverse Compton scattering if the finetuned particle is massive and starts at rest at infinity, while the latter for various particle reactions, such as inverse Compton scattering and pair annihilation, if the finetuned particle is either massless or highly relativistic at infinity. We discuss difference between the present and earlier analyses.
Collisional Grooming Models of the Kuiper Belt Dust Cloud
Kuchner, Marc J
2010-01-01
We modeled the 3-D structure of the Kuiper Belt dust cloud at four different dust production rates, incorporating both planet-dust interactions and grain-grain collisions using the collisional grooming algorithm. Simulated images of a model with a face-on optical depth of ~10^-4 primarily show an azimuthally-symmetric ring at 40-47 AU in submillimeter and infrared wavelengths; this ring is associated with the cold classical Kuiper Belt. For models with lower optical depths (10^-6 and 10^-7), synthetic infrared images show that the ring widens and a gap opens in the ring at the location of of Neptune; this feature is caused by trapping of dust grains in Neptune's mean motion resonances. At low optical depths, a secondary ring also appears associated with the hole cleared in the center of the disk by Saturn. Our simulations, which incorporate 25 different grain sizes, illustrate that grain-grain collisions are important in sculpting today's Kuiper Belt dust, and probably other aspects of the Solar System dust c...
Collisional modelling of the AU Microscopii debris disc
Schüppler, Ch; Krivov, A V; Ertel, S; Marshall, J P; Wolf, S; Wyatt, M C; Augereau, J -C; Metchev, S A
2015-01-01
The spatially resolved AU Mic debris disc is among the most famous and best-studied debris discs. We aim at a comprehensive understanding of the dust production and the dynamics of the disc objects with in depth collisional modelling including stellar radiative and corpuscular forces. Our models are compared to a suite of observational data for thermal and scattered light emission, ranging from the ALMA radial surface brightness profile at 1.3mm to polarisation measurements in the visible. Most of the data can be reproduced with a planetesimal belt having an outer edge at around 40au and subsequent inward transport of dust by stellar winds. A low dynamical excitation of the planetesimals with eccentricities up to 0.03 is preferred. The radial width of the planetesimal belt cannot be constrained tightly. Belts that are 5au and 17au wide, as well as a broad 44au-wide belt are consistent with observations. All models show surface density profiles increasing with distance from the star as inferred from observatio...
Collisional modelling of the debris disc around HIP 17439
Schüppler, Ch; Krivov, A V; Ertel, S; Marshall, J P; Eiroa, C
2014-01-01
We present an analysis of the debris disc around the nearby K2 V star HIP 17439. In the context of the Herschel DUNES key programme the disc was observed and spatially resolved in the far-IR with the Herschel PACS and SPIRE instruments. In a first model, Ertel et al. (2014) assumed the size and radial distribution of the circumstellar dust to be independent power laws. There, by exploring a very broad range of possible model parameters several scenarios capable of explaining the observations were suggested. In this paper, we perform a follow-up in-depth collisional modelling of these scenarios trying to further distinguish between them. In our models we consider collisions, direct radiation pressure, and drag forces, i.e. the actual physical processes operating in debris discs. We find that all scenarios discussed in Ertel et al. are physically sensible and can reproduce the observed SED along with the PACS surface brightness profiles reasonably well. In one model, the dust is produced beyond 120au in a narro...
Collisional disruption of gravitational aggregates in the tidal environment
Energy Technology Data Exchange (ETDEWEB)
Hyodo, Ryuki; Ohtsuki, Keiji [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan)
2014-05-20
The degree of disruption in collisions in free space is determined by specific impact energy, and the mass fraction of the largest remnant is a monotonically decreasing function of impact energy. However, it has not been shown whether such a relationship is applicable to collisions under the influence of a planet's tidal force, which is important in ring dynamics and satellite accretion. Here we examine the collisional disruption of gravitational aggregates in the tidal environment by using local N-body simulations. We find that outcomes of such a collision largely depend on the impact velocity, the direction of impact, and the radial distance from the planet. In the case of a strong tidal field corresponding to Saturn's F ring, collisions in the azimuthal direction are much more destructive than those in the radial direction. Numerical results of collisions sensitively depend on the impact velocity, and a complete disruption of aggregates can occur even in impacts with velocity much lower than their escape velocity. In such low-velocity collisions, the deformation of colliding aggregates plays an essential role in determining collision outcomes, because the physical size of the aggregate is comparable to its Hill radius. On the other hand, the dependence of collision outcomes on impact velocity becomes similar to the case in free space when the distance from the planet is sufficiently large. Our results are consistent with Cassini observations of the F ring, which suggest ongoing creation and disruption of aggregates within the ring.
3D multispecies collisional model of Ganymede's atmosphere
Leblanc, Francois; Leclercq, Ludivine; Oza, Apurva; Schmidt, Carl; Modolo, Ronan; Chaufray, Jean-Yves; Johnson, Robert E.
2016-10-01
Ganymede's atmosphere is produced by the interaction of the Sun and of the Jovian magnetosphere with its surface. It is a reflection of Ganymede's surface properties, but also of the complex interaction between the Ganymede and Jupiter magnetospheres. The Exospheric Global Model (EGM) has been developed in order to be able to integrate surface and magnetosphere processes with those in Ganymede's atmosphere. It is a 3D parallelized multi-species collisional model, coupled with LatHys, a hybrid multi-grid 3D multi-species model of Ganymede's magnetosphere (Leclercq et al., Geophys. Res. Let., Submitted, 2016). EGM's description of the species-dependent spatial distribution of Ganymede's atmosphere, its temporal variability during rotation around Jupiter, its connection to the surface, the role of collisions, and respective roles of sublimation and sputtering in producing Ganymede's exosphere, illustrates how modeling combined with in situ and remote sensing of Ganymede's atmosphere can contribute to our understanding of this unique surface-atmosphere-magnetosphere integrated system.
Hiding in the Shadows II: Collisional Dust as Exoplanet Markers
Dobinson, Jack; Lines, Stefan; Carter, Philip J; Dodson-Robinson, Sarah E; Teanby, Nick A
2016-01-01
Observations of the youngest planets ($\\sim$1-10 Myr for a transitional disk) will increase the accuracy of our planet formation models. Unfortunately, observations of such planets are challenging and time-consuming to undertake even in ideal circumstances. Therefore, we propose the determination of a set of markers that can pre-select promising exoplanet-hosting candidate disks. To this end, N-body simulations were conducted to investigate the effect of an embedded Jupiter mass planet on the dynamics of the surrounding planetesimal disk and the resulting creation of second generation collisional dust. We use a new collision model that allows fragmentation and erosion of planetesimals, and dust-sized fragments are simulated in a post process step including non-gravitational forces due to stellar radiation and a gaseous protoplanetary disk. Synthetic images from our numerical simulations show a bright double ring at 850 $\\mu$m for a low eccentricity planet, whereas a high eccentricity planet would produce a ch...
Direct and Collisional Excitation of Automotive Fuel Components)
White, Allen R.; Wilson, Kyle; Sakai, Stephen; Devasher, Rebecca B.
2010-06-01
Adding energy directly into the vibrational modes of automotive fuel may reduce the threshold energy required for combustion, without raising the combustion charge temperature. This energy can be supplied either directly via incident laser radiation or indirectly through collision with directly excited molecules. The most common chemical in commercial gasoline, isooctane, does not absorb infrared radiation sufficiently at any wavelength for which an infrared laser is readily available. However, CO2 lasers are relatively cheap, and are available at wavelengths which are absorbed by isopropanol as well as ethanol, which is also a component of commercial gasoline. In this study, the infrared absorption of isopropanol and ethanol in balance isooctane were measured at three wavelengths (10.6 m, 10.2 m, and 9.3 m) of incident CO2 laser radiation. Additional time-resolved emission measurements were performed for these mixtures. The data support the existence of the proposed collisional pathway for energy transfer from ethanol and isopropanol to isooctane.
Microgravity experiments on the collisional behavior of Saturnian ring particles
Heißelmann, Daniel; Fraser, Helen J; Wolling, Kristin; 10.1016/j.icarus.2009.08.009
2009-01-01
In this paper we present results of two novel experimental methods to investigate the collisional behavior of individual macroscopic icy bodies. The experiments reported here were conducted in the microgravity environments of parabolic flights and the Bremen drop tower facility. Using a cryogenic parabolic-flight setup, we were able to capture 41 near-central collisions of 1.5-cm-sized ice spheres at relative velocities between 6 and $22 \\mathrm{cm s^{-1}}$. The analysis of the image sequences provides a uniform distribution of coefficients of restitution with a mean value of $\\overline{\\varepsilon} = 0.45$ and values ranging from $\\varepsilon = 0.06$ to 0.84. Additionally, we designed a prototype drop tower experiment for collisions within an ensemble of up to one hundred cm-sized projectiles and performed the first experiments with solid glass beads. We were able to statistically analyze the development of the kinetic energy of the entire system, which can be well explained by assuming a granular `fluid' fo...
Collisional debris as laboratories to study star formation
Boquien, M; Wu, Y; Charmandaris, V; Lisenfeld, U; Braine, J; Brinks, E; Iglesias-Páramo, J; Xu, C K
2009-01-01
In this paper we address the question whether star formation is driven by local processes or the large scale environment. To do so, we investigate star formation in collisional debris where the gravitational potential well and velocity gradients are shallower and compare our results with previous work on star formation in non-interacting spiral and dwarf galaxies. We have performed multiwavelength spectroscopic and imaging observations (from the far-ultraviolet to the mid-infrared) of 6 interacting systems, identifying a total of 60 star-forming regions in their collision debris. Our analysis indicates that in these regions a) the emission of the dust is at the expected level for their luminosity and metallicity, b) the usual tracers of star formation rate display the typical trend and scatter found in classical star forming regions, and c) the extinction and metallicity are not the main parameters governing the scatter in the properties of intergalactic star forming regions; age effects and variations in the...
Consistent analytic approach to the efficiency of collisional Penrose process
Harada, Tomohiro; Ogasawara, Kota; Miyamoto, Umpei
2016-07-01
We propose a consistent analytic approach to the efficiency of collisional Penrose process in the vicinity of a maximally rotating Kerr black hole. We focus on a collision with arbitrarily high center-of-mass energy, which occurs if either of the colliding particles has its angular momentum fine-tuned to the critical value to enter the horizon. We show that if the fine-tuned particle is ingoing on the collision, the upper limit of the efficiency is (2 +√{3 })(2 -√{2 })≃2.186 , while if the fine-tuned particle is bounced back before the collision, the upper limit is (2 +√{3 })2≃13.93 . Despite earlier claims, the former can be attained for inverse Compton scattering if the fine-tuned particle is massive and starts at rest at infinity, while the latter can be attained for various particle reactions, such as inverse Compton scattering and pair annihilation, if the fine-tuned particle is either massless or highly relativistic at infinity. We discuss the difference between the present and earlier analyses.
HIDING IN THE SHADOWS. II. COLLISIONAL DUST AS EXOPLANET MARKERS
Energy Technology Data Exchange (ETDEWEB)
Dobinson, Jack; Leinhardt, Zoë M.; Lines, Stefan; Carter, Philip J. [University of Bristol, School of Physics, H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Dodson-Robinson, Sarah E. [University of Delaware, Department of Physics and Astronomy, 217 Sharp Lab, Newark, DE 19716 (United States); Teanby, Nick A. [University of Bristol, School of Earth Sciences, H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom)
2016-03-20
Observations of the youngest planets (∼1–10 Myr for a transitional disk) will increase the accuracy of our planet formation models. Unfortunately, observations of such planets are challenging and time-consuming to undertake, even in ideal circumstances. Therefore, we propose the determination of a set of markers that can preselect promising exoplanet-hosting candidate disks. To this end, N-body simulations were conducted to investigate the effect of an embedded Jupiter-mass planet on the dynamics of the surrounding planetesimal disk and the resulting creation of second-generation collisional dust. We use a new collision model that allows fragmentation and erosion of planetesimals, and dust-sized fragments are simulated in a post-process step including non-gravitational forces due to stellar radiation and a gaseous protoplanetary disk. Synthetic images from our numerical simulations show a bright double ring at 850 μm for a low-eccentricity planet, whereas a high-eccentricity planet would produce a characteristic inner ring with asymmetries in the disk. In the presence of first-generation primordial dust these markers would be difficult to detect far from the orbit of the embedded planet, but would be detectable inside a gap of planetary origin in a transitional disk.
Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; Nazikian, R.; Strait, E. J.; Chen, X.; Ferraro, N. M.; King, J. D.; Lyons, B. C.; Park, J.-K.
2016-05-01
The nature of the multi-modal n = 2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (Δ {φ\\text{UL}} ) between upper and lower in-vessel coils demonstrates that different n = 2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observed confinement degradation shares the same Δ {φ\\text{UL}} dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the Δ {φ\\text{UL}} dependence of both the global confinement and the n = 2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same Δ {φ\\text{UL}} dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap
Dosen, K
2010-01-01
An operad (this paper deals with non-symmetric operads) may be conceived as a partial algebra with a family of insertion operations, Gerstenhaber's circle-i products, which satisfy two kinds of associativity, one of them involving commutativity. A Cat-operad is an operad enriched over the category Cat of small categories, as a 2-category with small hom-categories is a category enriched over Cat. The notion of weak Cat-operad is to the notion of Cat-operad what the notion of bicategory is to the notion of 2-category. The equations of operads like associativity of insertions are replaced by isomorphisms in a category. The goal of this paper is to formulate conditions concerning these isomorphisms that ensure coherence, in the sense that all diagrams of canonical arrows commute. This is the sense in which the notions of monoidal category and bicategory are coherent. The coherence proof in the paper is much simplified by indexing the insertion operations in a context-independent way, and not in the usual manner. ...
Weak Total Resolvability In Graphs
Directory of Open Access Journals (Sweden)
Casel Katrin
2016-02-01
Full Text Available A vertex v ∈ V (G is said to distinguish two vertices x, y ∈ V (G of a graph G if the distance from v to x is di erent from the distance from v to y. A set W ⊆ V (G is a total resolving set for a graph G if for every pair of vertices x, y ∈ V (G, there exists some vertex w ∈ W − {x, y} which distinguishes x and y, while W is a weak total resolving set if for every x ∈ V (G−W and y ∈ W, there exists some w ∈ W −{y} which distinguishes x and y. A weak total resolving set of minimum cardinality is called a weak total metric basis of G and its cardinality the weak total metric dimension of G. Our main contributions are the following ones: (a Graphs with small and large weak total metric bases are characterised. (b We explore the (tight relation to independent 2-domination. (c We introduce a new graph parameter, called weak total adjacency dimension and present results that are analogous to those presented for weak total dimension. (d For trees, we derive a characterisation of the weak total (adjacency metric dimension. Also, exact figures for our parameters are presented for (generalised fans and wheels. (e We show that for Cartesian product graphs, the weak total (adjacency metric dimension is usually pretty small. (f The weak total (adjacency dimension is studied for lexicographic products of graphs.
Spectra of neutral carbon for plasma diagnostics
Energy Technology Data Exchange (ETDEWEB)
Wang, J.G.; Kato, M.; Kato, T.
2000-10-01
Recently, carbon pellet experiments have been performed on W-7AS and a few CI lines have been observed in the situation of the pellet cloud from the cold dense plasma to hot ambient plasma. In so large varied conditions, the collisional radiative (CR) model is needed to study the spectra. In this article, a CR model including 79 states with n {<=} 6 and l {<=} 4 is developed, and then the line spectra and line intensity ratios are evaluated in the ionizing and recombining plasma, respective. (author)
Kemaneci, Efe; Graef, Wouter; van Dijk, Jan; Kroesen, Gerrit M W
2015-01-01
Collisional and radiative dynamics of a plasma is exposed by so-called Collisional Radiative Models [1] that simplify the chemical kinetics by quasi-steady state assignment on certain types of particles. The assignment is conventionally based on the classification of the plasma species by the ratio of the transport to the local destruction frequencies. We show that the classification is not exact due to the role of the time-dependent local production, and a measure is necessary to confirm the validity of the assignment. The main goal of this study is to evaluate a measure on the quasi-steady state assumptions of these models. Inspired by a chemical reduction technique called Intrinsic Low Dimensional Manifolds [2, 3], an estimate local source is provided at the transport time-scale. This source is a deviation from the quasi-steady state for the particle and its value is assigned as an error of the quasi-steady state assumption. The propagation of this error on the derived quantities is formulated in the Colli...
Coupling Dynamical And Collisional Evolution Of Dust In Protoplanetary Disks
Charnoz, Sebastien
2010-10-01
Gaseous circumstellar disks are rich in dust and are thought to be both accretionaly and dynamically active. Unfortunately large bodies that could be embedded in these disks are still difficult to observe and their putative properties are indirectly inferred from the observable small dust content. It is why constraining the size distribution coupled with dust-dynamics is so critical. Unfortunately, coupling effects such as a realistic time-dependant dynamics, fragmentation and coagulation, has been recognized as numerically challenging and almost no attempt really succeeded with a generic approach. In these disks, the dust dynamics is driven by a variety of processes (gravity, gas drag, radiation pressure..) inducing a size-dependant dynamics, and, at the same time collisional evolution changes the local size distributions. These two effects are intimately coupled because the local dynamics and size-distribution determines the local collision rates, that, in-turn, determines the size-distribution and modifies the particle's dynamics. Here we report on a new algorithm that overcomes these difficulties by using a hybrid approach extending the work of Charnoz & Morbidelli (Icarus, 2004, 2007). We will briefly present the method and focus on gaseous protoplanetary disks either laminar or turbulent (the time dependant transport and dust evolution will be shown) . We will show how the taking into account of a 3D dynamics helps to determine disantengle the dust size-distribution in the disk's photosphere and in the midplane and thus may provide observational signatures of accretion. We will show how the coupling of turbulence with fragmentation may significantly affect the dust/ratio for the smallest bodies. Finally, we will show that an accurate description of the time dependant dynamics of larger dusts (those with Stokes numbers >= 1) may provide a possible path to the formation of bodies larger than the accretion barrier, through accretion in a transitory regime.
Collisional Disruption of Ice by High-Velocity Impact
Arakawa, Masahiko
1999-11-01
High-velocity impact among icy planetesimals is a physical phenomenon important to the planetary evolution process in the outer Solar System. In order to study this phenomenon, impact experiments on water ice were made by using a two-stage light gas gun installed in a cold room (-10°C) to clarify the elementary processes of collisional disruption and to study the reaccumulation and the escape conditions of the impact fragments. Cubic ice targets ranging in size from 15 to 100 mm were impacted by a nylon projectile of 7 mg with an impact velocity ( vi) from 2.3 to 4.7 km/s. The corresponding mass ratio of the projectile to the target ( mp/ Mt) ranged from 10 -3 to 10 -6, which is two orders of magnitude lower than that used in previous studies (Arakawa et al. 1995, Icarus118, 341-354). As a result, we obtained data on elementary processes such as attenuation of the shock wave and fragmentation dynamics. We found that the shock pressure attenuates in the ice target according to the relation of P∝( Lp/ r2, irrespective of the mass ratio between 10 -3 and 10 -5, where Lp is the projectile size and r is a propagation distance. The largest fragment mass ( ml) normalized by the original target mass has a good relationship to a nondimensional impact stress ( PI, NDIS) defined as the ratio of the antipodal pressure to the material strength. This relationship is described as ml/ Mt ∝ PI-1.7 for a wide range of impact conditions (50 m/s20 km) reaccumulated. On the other hand, when smaller icy bodies (radius<2 km) disrupted catastrophically, all fragments escaped and a rubble pile was never formed.
Weak compactness of biharmonic maps
Directory of Open Access Journals (Sweden)
Shenzhou Zheng
2012-10-01
Full Text Available This article shows that if a sequence of weak solutions of a perturbed biharmonic map satisfies $Phi_ko 0$ in $(W^{2,2}^*$ and $u_kightharpoonup u$ weakly in $W^{2,2}$, then $u$ is a biharmonic map. In particular, we show that the space of biharmonic maps is sequentially compact under the weak-$W^{2,2}$ topology.
Model of strong stationary vortex turbulence in space plasmas
Directory of Open Access Journals (Sweden)
G. D. Aburjania
2009-01-01
Full Text Available This paper investigates the macroscopic consequences of nonlinear solitary vortex structures in magnetized space plasmas by developing theoretical model of plasma turbulence. Strongly localized vortex patterns contain trapped particles and, propagating in a medium, excite substantial density fluctuations and thus, intensify the energy, heat and mass transport processes, i.e., such vortices can form strong vortex turbulence. Turbulence is represented as an ensemble of strongly localized (and therefore weakly interacting vortices. Vortices with various amplitudes are randomly distributed in space (due to collisions. For their description, a statistical approach is applied. It is supposed that a stationary turbulent state is formed by balancing competing effects: spontaneous development of vortices due to nonlinear twisting of the perturbations' fronts, cascading of perturbations into short scales (direct spectral cascade and collisional or collisionless damping of the perturbations in the short-wave domain. In the inertial range, direct spectral cascade occurs through merging structures via collisions. It is shown that in the magneto-active plasmas, strong turbulence is generally anisotropic Turbulent modes mainly develop in the direction perpendicular to the local magnetic field. It is found that it is the compressibility of the local medium which primarily determines the character of the turbulent spectra: the strong vortex turbulence forms a power spectrum in wave number space. For example, a new spectrum of turbulent fluctuations in k^{−8/3} is derived which agrees with available experimental data. Within the framework of the developed model particle diffusion processes are also investigated. It is found that the interaction of structures with each other and particles causes anomalous diffusion in the medium. The effective coefficient of diffusion has a square root dependence on the stationary level of noise.
Numerical simulation of dusty plasmas
Energy Technology Data Exchange (ETDEWEB)
Winske, D.
1995-09-01
The numerical simulation of physical processes in dusty plasmas is reviewed, with emphasis on recent results and unresolved issues. Three areas of research are discussed: grain charging, weak dust-plasma interactions, and strong dust-plasma interactions. For each area, we review the basic concepts that are tested by simulations, present some appropriate examples, and examine numerical issues associated with extending present work.
Magnetorotational Turbulence and Dynamo in a Collisionless Plasma
Kunz, Matthew W.; Stone, James M.; Quataert, Eliot
2016-12-01
We present results from the first 3D kinetic numerical simulation of magnetorotational turbulence and dynamo, using the local shearing-box model of a collisionless accretion disk. The kinetic magnetorotational instability grows from a subthermal magnetic field having zero net flux over the computational domain to generate self-sustained turbulence and outward angular-momentum transport. Significant Maxwell and Reynolds stresses are accompanied by comparable viscous stresses produced by field-aligned ion pressure anisotropy, which is regulated primarily by the mirror and ion-cyclotron instabilities through particle trapping and pitch-angle scattering. The latter endow the plasma with an effective viscosity that is biased with respect to the magnetic-field direction and spatiotemporally variable. Energy spectra suggest an Alfvén-wave cascade at large scales and a kinetic-Alfvén-wave cascade at small scales, with strong small-scale density fluctuations and weak nonaxisymmetric density waves. Ions undergo nonthermal particle acceleration, their distribution accurately described by a κ distribution. These results have implications for the properties of low-collisionality accretion flows, such as that near the black hole at the Galactic center.
Electron density and plasma dynamics of a colliding plasma experiment
Energy Technology Data Exchange (ETDEWEB)
Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J. [Plasma Physics Group, Institute of Applied Physics, Goethe University, 60438 Frankfurt am Main (Germany)
2016-07-15
We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.
Collisional-Radiative Modeling of Free-Burning Arc Plasma in Argon
2013-06-01
7) For the radiative transitions, data recommended by Wiese et al. [30] is used. The transition probabilities Amn (s -1...Atoms and Molecules, Published in the 20th Century: Argon, Rep. NIFS-DATA-72, National Institute for Fusion Science (Jpn), 2003. [30] W. L. Wiese , J
Physical Mechanism of the Lower-Hybrid-Drift Instability in a Collisional Plasma.
1981-01-30
ATTN R. CR.AwFORO DEFENSE TECHNICAL INFORMATION CENTER CAMERON STA’ION COmtiAVNDER/DIRECTOR ALEXANDRIA, VA. 22314 ATMOSP’-ERIC SCIENCES .ABOR.ATORY (12...S’REE 6565 ARE~ ~ OFLVER FHALS CHURl VRP AO TOY 22346 NEEZMAM MAl 02134 ,15(N.ONY 555 TECNOLOGY QUAREODCY A,’’N NEASAL ROSSCN’-O Y 01Cr A’-N D..N SP
A High-Order Transport Scheme for Collisional-Radiative and Nonequilibrium Plasma
2009-02-06
case. A master may want to tap into the resources of a Beowulf cluster for example, but may only do so through the head node of the cluster . In such a...Data (SPMD) programming applica- tions on clustered networks. In particular, the framework is aimed at solving hyperbolic conservation laws and other
Lyons, B. C.; Jardin, S. C.; Ramos, J. J.
2012-08-01
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f) in the conventional banana regime for both ions and electrons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h). We work in a 4D phase space in which ψ defines a flux surface, θ is the poloidal angle, v is the magnitude of the velocity referenced to the mean flow velocity, and λ is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and λ. The Rosenbluth potentials, Φ and Ψ, which define the integral part of the collision operator, are expanded in Legendre series in cosχ, where χ is the pitch angle, Fourier series in cosθ, and finite elements in v. At each ψ, we solve a block tridiagonal system for hi (independent of fe), then solve another block tridiagonal system for he (dependent on fi). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia et al., J. Comput. Phys. 37, 183-204 (1980)] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D -C1 [S. C. Jardin et al., Comput. Sci. Discovery 5, 014002 (2012)]).
Energy Technology Data Exchange (ETDEWEB)
Lyons, B. C. [Program in Plasma Physics, Princeton University, Princeton, New Jersey 08543-0451 (United States); Jardin, S. C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Ramos, J. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)
2012-08-15
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f) in the conventional banana regime for both ions and electrons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h). We work in a 4D phase space in which {psi} defines a flux surface, {theta} is the poloidal angle, v is the magnitude of the velocity referenced to the mean flow velocity, and {lambda} is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and {lambda}. The Rosenbluth potentials, {Phi} and {Psi}, which define the integral part of the collision operator, are expanded in Legendre series in cos{chi}, where {chi} is the pitch angle, Fourier series in cos{theta}, and finite elements in v. At each {psi}, we solve a block tridiagonal system for h{sub i} (independent of f{sub e}), then solve another block tridiagonal system for h{sub e} (dependent on f{sub i}). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia et al., J. Comput. Phys. 37, 183-204 (1980)] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D-C{sup 1}[S. C. Jardin et al., Comput. Sci. Discovery 5, 014002 (2012)]).
Energy Technology Data Exchange (ETDEWEB)
B.C. Lyons, S.C. Jardin, and J.J. Ramos
2012-06-28
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f ) in the conventional banana regime for both ions and elec trons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h ). We work in a 4D phase space in which Ψ defines a flux surface, θ is the poloidal angle, v is the total velocity referenced to the mean flow velocity, and λ is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and λ . The Rosenbluth potentials, φ and ψ, which define the integral part of the collision operator, are expanded in Legendre series in cos χ , where χ is the pitch angle, Fourier series in cos θ , and finite elements in v . At each ψ , we solve a block tridiagonal system for hi (independent of fe ), then solve another block tridiagonal system for he (dependent on fi ). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia, et al., J. Comput. Phys. 37 , pp 183-204 (1980).] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D-C1 [S.C. Jardin, et al ., Computational Science & Discovery, 4 (2012).]).
Analysis of Collisional Cross Sections of Rydberg nS and nD States of Ultracold Caesium Atoms
Feng, Zhigang; Miao, Jingyuan; Zhao, Kejia; Li, Difei; Yang, Zhijun; Wu, Fan; Wu, Zhaochun; Zhao, Jianming; Jia, Suotang
2016-05-01
We present a simple analytical formula derived from an existing theoretical model and a detailed theoretical investigation of effects of the van der Waals interaction and dipole-dipole interaction on collisional cross sections as functions of various parameters. We analyze the main mechanism leading to large collisional cross sections on the basis of our previous experimental results using the present formula and also analyze the effects of some other factors on collisional cross sections.
Wünderlich, D.; Wimmer, C.; Friedl, R.
2015-04-01
A collisional radiative (CR) model for caesium atoms in low-temperature, low-pressure hydrogen-caesium plasmas is introduced. This model includes the caesium ground state, 14 excited states, the singly charged caesium ion and the negative hydrogen ion. The reaction probabilities needed as input are based on data from the literature, using some scaling and extrapolations. Additionally, new cross sections for electron collision ionization and three-body recombination have been calculated. The relevance of mutual neutralization of positive caesium ions and negative hydrogen ions is highlighted: depending on the densities of the involved particle species, this excitation channel can have a significant influence on the population densities of excited states in the caesium atom. This strong influence is successfully verified by optical emission spectroscopy measurements performed at the IPP prototype negative hydrogen ion source for ITER NBI. As a consequence, population models for caesium in electronegative low-temperature, low-pressure hydrogen-caesium plasmas need to take into account the mutual neutralization process. The present CR model is an example for such models and represents an important prerequisite for deducing the total caesium density in surface production based negative hydrogen ion sources.
Energy Technology Data Exchange (ETDEWEB)
Wünderlich, D., E-mail: dirk.wuenderlich@ipp.mpg.de; Wimmer, C. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany); Friedl, R. [AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg (Germany)
2015-04-08
A collisional radiative (CR) model for caesium atoms in low-temperature, low-pressure hydrogen-caesium plasmas is introduced. This model includes the caesium ground state, 14 excited states, the singly charged caesium ion and the negative hydrogen ion. The reaction probabilities needed as input are based on data from the literature, using some scaling and extrapolations. Additionally, new cross sections for electron collision ionization and three-body recombination have been calculated. The relevance of mutual neutralization of positive caesium ions and negative hydrogen ions is highlighted: depending on the densities of the involved particle species, this excitation channel can have a significant influence on the population densities of excited states in the caesium atom. This strong influence is successfully verified by optical emission spectroscopy measurements performed at the IPP prototype negative hydrogen ion source for ITER NBI. As a consequence, population models for caesium in electronegative low-temperature, low-pressure hydrogen-caesium plasmas need to take into account the mutual neutralization process. The present CR model is an example for such models and represents an important prerequisite for deducing the total caesium density in surface production based negative hydrogen ion sources.
Schneider, P. A.; Bustos, A.; Hennequin, P.; Ryter, F.; Bernert, M.; Cavedon, M.; Dunne, M. G.; Fischer, R.; Görler, T.; Happel, T.; Igochine, V.; Kurzan, B.; Lebschy, A.; McDermott, R. M.; Morel, P.; Willensdorfer, M.; the ASDEX Upgrade Team; The EUROfusion MST1 Team
2017-06-01
In ASDEX Upgrade (AUG), the normalised gyroradius {ρ\\star} was varied via a hydrogen isotope scan while keeping other dimensionless parameters constant. This was done in L-mode, to minimise the impact of pedestal stability on confinement. Power balance and perturbative transport analyses reveal that the electron heat transport is unaffected by the differences in isotope mass. Nonlinear simulations with the Gene code suggest that these L-mode discharges are ion temperature gradient (ITG) dominated. The different gyroradii due to the isotope mass do not necessarily result in a change of the predicted heat fluxes. This result is used in simulations with the Astra transport code to match the experimental profiles. In these simulations the experimental profiles and confinement times are reproduced with the same transport coefficients for hydrogen and deuterium plasmas. The mass only enters in the energy exchange term between electrons and ions. These numerical observations are supported by additional experiments which show a lower ion energy confinement compared to that of the electrons. Additionally, hydrogen and deuterium plasmas have a similar confinement when the energy exchange time between electrons and ions is matched. This strongly suggests that the observed isotope dependence in L-mode is not dominated by a gyroradius effect, but a consequence of the mass dependence in the collisional energy exchange between electrons and ions.
Improved energy coupling into the gain region of the Ni-like Pd transient collisional x-ray laser
Energy Technology Data Exchange (ETDEWEB)
Smith, R; Dunn, J; Filevich, J; Moon, S; Nilsen, J; Keenan, R; Shlyaptsev, V; Rocca, J; Hunter, J; Shepherd, R; Booth, R; Marconi, M
2004-10-05
We present within this paper a series of experiments, which yield new observations to further our understanding of the transient collisional x-ray laser medium. We use the recently developed technique of picosecond x-ray laser interferometry to probe the plasma conditions in which the x-ray laser is generated and propagates. This yields two dimensional electron density maps of the plasma taken at different times relative to the peak of the 600ps plasma-forming beam. In another experimental campaign, the output of the x-ray laser plasma column is imaged with a spherical multilayer mirror onto a CCD camera to give a two-dimensional intensity map of the x-ray laser output. Near-field imaging gives insights into refraction, output intensity and spatial mode structure. Combining these images with the density maps gives an indication of the electron density at which the x-ray laser is being emitted at (yielding insights into the effect of density gradients on beam propagation). Experimental observations coupled with simulations predict that most effective coupling of laser pump energy occurs when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for Ni-like schemes). This can increase the output intensity by more than an order of magnitude relative to the case were the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). We have also conducted an experiment in which the output of the x-ray laser was imaged onto the entrance slit of a high temporal resolution streak camera. This effectively takes a one-dimensional slice of the x-ray laser spatial profile and sweeps it in time. Under some conditions we observe rapid movement of the x-ray laser ({approx} 3 {micro}m/ps) towards the target surface.
Transient and Capillary Collisional X-ray Laser
Energy Technology Data Exchange (ETDEWEB)
Shlyaptsev, V N; Dunn, J; Fournier, K B; Moon, S; Osterheld, A L; Rocca, J J; Detering, F; Rozmus, W; Matte, J P; Fiedorowicz, H; Bartnik, A; Kanouff, M
2001-12-17
In this work we report our numerical modeling results of laser-generated transient inversion and capillary discharge X-ray lasers. In the search for more efficient X-ray lasers we look closely at other approaches in conjunction with experiments at LLNL. In the search for improved X-ray lasers we perform modeling and experimental investigations of low density targets including gas puff targets. We have found the importance of plasma kinetics in transient X-ray lasers by expanding the physical model beyond hydrodynamics approach with Particle In Cell (PIC) and Fokker-Planck codes. The evidence of the Langdon effect was inferred from the recent experimental data obtained with the Ni-like Pd X-ray laser. We continue modeling different kinds of capillary discharge plasma configurations directed toward shorter wavelength X-ray lasers, plasma diagnostics and other applications.