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  • 1
    Electronic Resource
    Electronic Resource
    An electron–positron beam–plasma instability (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4982-4994 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a new technique to generate cold electron beams, an electron-beam positron-plasma experiment was performed in a previously unexplored range of energies. An electron beam, formed from a thermalized room-temperature electron plasma, is transmitted through a positron plasma stored in a quadrupole Penning trap geometry. The transit-time instability, which is excited by the beam, was previously studied using a hot-cathode electron gun. The large beam energies produced by the cathode did not permit an investigation of the instability in the interesting range of energies near its onset. Using a new 0.1 eV energy width electron beam, we have reinvestigated the system. The experimental data are compared with the results of a theoretical model, also described in this paper. The theory employs a linearized cold fluid and Vlasov approach to model the plasma and beam dynamics, respectively. The data and predictions are in good agreement over the broad range of energies and beam currents studied. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1407284
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  • 2
    Electronic Resource
    Electronic Resource
    Theory of vortex crystal formation in two-dimensional turbulence : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1719-1722 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments on pure electron plasmas have found that the decay of two-dimensional (2D) turbulence can lead to spontaneous formation of "vortex crystals," which are symmetric arrays of strong vortices within a background of weaker vorticity. This paper presents a theory of these novel equilibrium states of 2D turbulence. The paper consists of two parts. In the first part, we show that the vortex crystals are well described as "regional" maximum fluid entropy (RMFE) states, which are equilibrium states reached through ergodic mixing of the background by the strong vortices. In the second part, a theory is advanced that allows us to predict from the initial conditions the approximate number of the strong vortices in the final state. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873990
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  • 3
    Electronic Resource
    Electronic Resource
    The phonon wake behind a charge moving relative to a two-dimensional plasma crystal (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3895-3903 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a recent experiment a wake was created in a two-dimensional lattice of charged dust grains by a charge moving parallel to the lattice plane. Multiple "Mach cones" were observed in the wake. This paper describes a linear theory of the phonon wake caused by a charge moving relative to a crystalline lattice. The theory predicts multiple structures in the wake that are qualitatively similar to those observed in the experiments. These structures are caused by constructive interference of compressional phonons excited by the moving charge, combined with the strongly dispersive nature of these phonons. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308078
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  • 4
    Electronic Resource
    Electronic Resource
    Collisional transport in non-neutral plasmas : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1688-1694 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several recent experiments have measured collisional transport in non-neutral plasmas (heat conduction, test particle diffusion, and viscosity) that is from 10 to 104 times larger than predicted by classical theory. New guiding center theories of collisional transport have been developed that agree with the measurements. The experiments operate in the guiding center regime rc(very-much-less-than)λD, where rc is the cyclotron radius and λD is the Debye length. In this regime, classical transport theory is irrelevant because it implicitly assumes the opposite ordering, λD(very-much-less-than)rc, although this ordering is not always satisfied in neutral plasmas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872837
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  • 5
    Electronic Resource
    Electronic Resource
    Non-neutral ion plasmas and crystals, laser cooling, and atomic clocksf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1403-1414 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental work which uses Penning and Paul traps to confine non-neutral ion plasmas is discussed. Penning traps use a static uniform magnetic field and a static electric field to confine ions. The Paul trap uses the ponderomotive force from inhomogeneous radio-frequency fields to confine ions to a region of minimum field strength. In many atomic physics experiments, these traps are designed to produce a harmonic restoring force for small numbers of stored ions (〈104). Under these conditions and at low temperatures, both traps produce plasmas with simple shapes whose mode properties can be calculated exactly. Laser cooling has been used to reduce the temperature of trapped ions to less than 10 mK with ion spacings less than 20 μm. At such temperatures and interion spacings, the Coulomb potential energy between nearest neighbor ions is greater than the ion thermal energy and the ions exhibit spatial correlations characteristic of a liquid or crystal. Laser beams also apply a torque which, by changing the plasma angular momentum, changes the plasma density. Atomic clocks are an important application of ion trap plasmas. Better control of the plasma dynamics will reduce fluctuations in the relativistic time dilation, yielding better clocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870690
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal equilibria and thermodynamics of trapped plasmas with a single sign of charge (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2163-2193 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasmas consisting exclusively of particles with a single sign of charge (e.g., pure electron plasmas and pure ion plasmas) can be confined by static electric and magnetic fields (e.g., in a Penning trap) and also be in a state of global thermal equilibrium. This important property distinguishes these totally un-neutralized plasmas from neutral and quasineutral plasmas. This paper reviews the conditions for and structure of the thermal equilibrium states and then develops a thermodynamic theory of the trapped plasmas. Thermodynamics provides hundreds of general relations (Maxwell relations) between partial derivatives of thermodynamic variables with respect to one another. Thermodynamic inequalities place general and useful bounds on various quantities. General and relatively simple expressions are provided for fluctuations of the thermodynamic variables. In practice, trapped plasmas are often made to evolve through a sequence of thermal equilibrium states through the slow addition (or subtraction) of energy and angular momentum (say, by laser cooling and torque beams). A thermodynamic approach to this late time transport describes the evolution through coupled ordinary differential equations for the thermodynamic variables, which is a huge reduction in complexity compared to the partial differential equations typically required to describe plasma transport. These evolution equations provide a theoretical basis for the dynamical control of the plasmas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872925
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  • 7
    Electronic Resource
    Electronic Resource
    Two-dimensional bounce-averaged collisional particle transport in a single species non-neutral plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1305-1314 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we describe a new theory of like particle collisional transport for a non-neutral plasma confined in a Penning trap. The theory is valid in the regime ωb〉ωE, ωb〉νc, and rc〈λD where ωb is the axial bounce frequency, ωE is the E×B rotation frequency, νc is the collision frequency, rc is the cyclotron radius, and λD is the Debye length. In this regime each particle can be bounce averaged into a long rod and the transport understood as arising from the E×B drift motion of the rods due to long-range mutual interactions. This is a very different mechanism than is considered in the classical theory of transport, where a particle guiding center undergoes a step of order rc as a result of a velocity scattering collision. For the parameter range considered, the new theory predicts transport rates that are orders of magnitude larger than those predicted by classical theory and that scale with magnetic field strength like 1/B rather than 1/B4. The new theory differs from a previous analysis of transport due to E×B drift interactions of charged rods, in that the finite length of the rods is taken into account. This enables transport to occur even for the case of an E×B drift rotation frequency that is a monotonic decreasing function of radius (as was the case in recent experiments). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872789
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  • 8
    Electronic Resource
    Electronic Resource
    Equilibration rate of spin temperature in a strongly magnetized pure electron plasma (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 691-710 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The equilibration of spin temperature Tspin with kinetic temperature T is examined in a weakly correlated pure electron plasma in the strongly magnetized limit, where the distance of closest approach is large compared to the Larmor radius. In this limit, the spin precession frequency Ωp=gΩc/2 is large so the component of spin along the magnetic field is an adiabatic invariant that is broken only by resonant magnetic fluctuations of frequency Ωp. (Here Ωc is the electron cyclotron frequency and g(approximately-equal-to)2.002.) In this case, the most important spin flip mechanism stems from electron–electron collisions in a spatially inhomogeneous magnetic field. Such collisions cause an exchange of spin and cyclotron quanta, and consequently the conventional many-electron adiabatic invariant (i.e., the total number of cyclotron quanta) is broken and is replaced by a new adiabatic invariant, equal to the sum of the spin and cyclotron actions. A quantum Boltzmann equation is derived to describe the equilibration of Tspin toward T.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860514
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal equilibrium of a cryogenic magnetized pure electron plasma (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 11-13 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal equilibrium correlation properties of a magnetically confined pure electron plasma (McPEP) are related to those of a one-component plasma (OCP). The N-particle spatial distribution ρs and the Helmholtz free energy F are evaluated for the McPEP to O(λ2d/a2), where λd is the thermal de Broglie wavelength and a is an interparticle spacing. The electron gyromotion is allowed to be fully quantized while the guiding center motion is quasiclassical. The distribution ρs is shown to be identical to that of a classical OCP with a slightly modified potential. To O(λ2d/a2) this modification does not affect that part of F which caused by correlations, as long as certain requirements concerning the size of the plasma are met. This theory is motivated by a current series of experiments that involve the cooling of a magnetically confined pure electron plasma to the cryogenic temperature range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865987
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  • 10
    Electronic Resource
    Electronic Resource
    Point vortex dynamics within a background vorticity patch (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 677-691 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments and simulations have observed that the interaction of strong vortices with a low vorticity background can strongly affect the dynamics of both vortices and background. This paper considers an idealized model of this interaction. The background is treated as a patch of uniform vorticity with a nearly circular shape. The strong vortices are treated as point vortices, and their total circulation λ is assumed to be small compared to that of the background. It is found that Kelvin waves on the boundary of the background patch can be driven to large amplitude by the strong vortices, eventually resulting in wave breaking and filamentation. A multiscale analysis finds that the wave-breaking time scales as λ−1 ln λ−1, in agreement with contour dynamics simulations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343484
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