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  • 1
    Electronic Resource
    Electronic Resource
    Upper bound for the space-charge limited current of relativistic electron beams in finite-length coaxial drift tubes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3108-3111 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional theory for calculating an upper bound for the space-charge limited current of relativistic electron beams is extended to coaxial drift tubes. The theory applies to annular beams of arbitrary radius, thickness and length travelling in a grounded coaxial drift tube of circular cross section. Poisson's equation for space-charge limited flow is replaced with a Sturm–Liouville-type eigenvalue problem. The problem reduces to numerically solving a determinantal equation rather than a partial differential equation. Under limiting cases, closed-form analytical expressions are derived. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874175
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  • 2
    Electronic Resource
    Electronic Resource
    Confinement of a neutral plasma using nested electric potential wells (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2313-2315 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent, two-dimensional analysis is presented on confining a region of neutral plasma with a Penning/Malmberg type plasma trap using a nested well configuration. It is found that a neutral plasma region having disparate electron and ion temperatures or having high charge state ions can be confined with static fields. For confining a neutral region comprised of electrons and equal temperature low charge state ions, a quasistatic approach appears promising. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872404
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  • 3
    Electronic Resource
    Electronic Resource
    Possibilities for achieving antihydrogen recombination and trapping using a nested Penning trap and a magnetic well (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 3289-3302 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical study is presented regarding some possibilities for achieving antihydrogen recombination and trapping using a nested Penning trap and a magnetic well. The work reported consists of a review, an extension, and applications of the relevant knowledge base. A nested Penning trap produces a magnetic field, which provides plasma confinement perpendicular to the magnetic field, and an electric field associated with a nested-well potential profile. The nested-well potential profile provides plasma confinement parallel to the magnetic field for oppositely signed plasma species that can have overlapping confinement regions. A configuration is considered in which the electric field is applied in two regions of uniform magnetic field that reside on opposite sides of a magnetic well region. The electric field confines overlapping positron and antiproton plasmas, which thread the magnetic well region. The magnetic well region would serve to trap a fraction of any antihydrogen atoms that are formed. Two different methods are considered for achieving overlap of positron and antiproton plasmas. For each, a set of conditions is predicted for achieving antihydrogen recombination and trapping. Although the study reported specifically considers simultaneous confinement of positron and antiproton plasmas in nested Penning traps, much of the information presented is also relevant to the prospect of merging other pairs of oppositely signed plasmas (e.g., electron and positron plasmas). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494822
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of the Coulomb logarithm using cutoff and screened Coulomb interaction potentials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2515-2518 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Coulomb logarithm is a fundamental plasma parameter which is commonly derived within the framework of the binary collision approximation. The conventional formula for the Coulomb logarithm, λ=ln Λ, takes into account a pure Coulomb interaction potential for binary collisions and is not accurate at small values (λ〈10). However, a more exact Fokker–Planck equation was recently presented by Li and Petrasso which is accurate at small Coulomb logarithm values (λ(approximately-greater-than)2) [Phys. Rev. Lett. 70, 3063 (1993)]. This theory and computer simulations which are accurate for small Coulomb logarithm values provide the motivation for a more precise evaluation of the Coulomb logarithm. In the present work, the Coulomb logarithm is evaluated more precisely by using a cutoff Coulomb interaction potential. The result is compared to an exact numerical evaluation of the Coulomb logarithm which considers a screened Coulomb interaction potential. Fits to the numerical results are also provided. The fitted formula λ=ln(0.6 Λ) is recommended for most applications providing values within 4% of the exact numerical values for λ(approximately-greater-than)2. This formula is easily implemented by using 0.6λD in place of λD (the Debye length) in the conventional formula for the Coulomb logarithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870578
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of a plasma sheath and ion injection on axial particle and energy confinement in a collisional mirror plasma (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1359-1361 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Continual scattering of particles into the loss cone of a simple magnetic mirror used to confine a collisional, fully Maxwellian plasma results in exceedingly large particle and energy loss rates. However, a considerable increase in confinement is found when a material wall is placed at the high field side of the mirror. A plasma sheath forms which reflects a large fraction of the electrons which pass through the mirror. Further, the sheath potential can be increased by axial ion injection. With optimized axial ion injection, the energy loss rate for a deuterium–tritium plasma decreases to 1.5% of its value without sheath reflection and near perfect electron confinement is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870735
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  • 6
    Electronic Resource
    Electronic Resource
    Simplification of the Boltzmann collision integral (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2947-2949 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Close collision events play an important role in situations where the Coulomb logarithm approaches unity. The five-fold Boltzmann collision integral takes into account close collision events. However, the five-fold Boltzmann collision integral is generally considered too complex for practical use. In a previous paper [Y. Chang, Phys. Fluids B 4, 313 (1992)], the Boltzmann integral with a Maxwellian velocity distribution function for the field particles was reduced to a three-fold integral with a kernel function. However, the kernel function was expressed in the form of an infinite series. In this brief communication, a finite form for the kernel function is obtained and the Boltzmann integral is finally reduced to a simple form exactly. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873546
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  • 7
    Electronic Resource
    Electronic Resource
    Secondary electron emission at anode, cathode, and floating plasma-facing surfaces (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2270-2274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The secondary electron emission coefficient is evaluated for electron impact on anode, cathode, and electrically floating plasma-facing surfaces. Two energy and angle distribution functions for electron impact on a plasma-facing surface are derived and different relations for the secondary electron emission coefficient which functionally depend on energy and angle are integrated over the distributions. One integration is in closed form and provides a parametric expression for the secondary electron emission coefficient of a plasma-facing surface. The other integrations are carried out numerically. Evaluation of the secondary electron emission coefficient for a variety of commonly-used plasma-facing materials shows that its value is near or above unity over a significant range of plasma temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361151
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  • 8
    Electronic Resource
    Electronic Resource
    Dirac and reduced quantization: A Lagrangian approach and application to coset spaces (1995)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 36 (1995), S. 1146-1165 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A Lagrangian treatment of the quantization of first class Hamiltonian systems with constraints and Hamiltonian linear and quadratic in the momenta, respectively, is performed. The "first reduce and then quantize'' and the "first quantize and then reduce'' (Dirac's) methods are compared. A source of ambiguities in this latter approach is pointed out and its relevance on issues concerning self-consistency and equivalence with the "first reduce'' method is emphasized. One of the main results is the relation between the propagator obtained à la Dirac and the propagator in the full space. As an application of the formalism developed, quantization on coset spaces of compact Lie groups is presented. In this case it is shown that a natural selection of a Dirac quantization allows for full self-consistency and equivalence. Finally, the specific case of the propagator on a two-dimensional sphere S2 viewed as the coset space SU(2)/U(1) is worked out. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531111
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of fusion reactions on the stopping power of a non-neutral plasma (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1367-1369 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional scattering theory based on the binary-collision approximation is used to evaluate the effect of fusion reactions on the energy loss of energetic ions which pass through an ion non-neutral plasma. The effect appears as a term in a generalized expression for the Coulomb logarithm. Using the general form of the Coulomb logarithm, fusion reactions are calculated to change the stopping power of a pure triton plasma by up to 12% for energetic (≤10 MeV) deuterons which pass through the plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860926
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  • 10
    Electronic Resource
    Electronic Resource
    Fully kinetic plasma-sheath theory for a cold-electron emitting surface (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 778-783 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fully kinetic, one-dimensional, plasma-sheath theory by Schwager and Birdsall [Phys. Fluids B 2, 1057 (1990)] is further developed. A cold-electron emitting surface is included and a three-dimensional plasma is considered. The sheath potential is not assumed to equal the floating potential so that the theory applies to a current-carrying sheath. Appropriate values are found for higher-order moments of the velocity distribution which depend on the three-dimensional velocity distribution width. Distribution functions in terms of energy and angle are derived. The (effective) temperature, the total energy flux, and the heat flux are evaluated in terms of exact analytic functions. The normalized magnitude of the floating potential for a deuterium plasma with equal ion and electron temperatures is calculated to be ψf=3.2 for δ=0 and ψf=1.8 for δ=0.75 where δ is the electron emission coefficient. The normalized magnitude of the sheath potential for the same plasma (with δ=0) is calculated to be ψs=3.9 for γ=0.02 and ψs=2.8 for γ=−0.02 where γ is the normalized current density. A self-consistent integral solution for the electrostatic potential profile within the sheath is derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860232
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