Analytic study of azimuthal asymmetries in relativistic hollow <i>e</i>-beams

Epstein, B. G.; Poukey, J. W.

doi:10.1063/1.863172

Cited by 5 publications

(2 citation statements)

References 15 publications

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“…Not only is the shear layer weakest here, but also the image vorticity (plasma image charge) exerts the least influence at this point due to the larger distance to the wall, Bunching and thinning develop on either side of this flow velocity minimum (figure 2b). This effect has been predicted numerically by Epstein & Poukey (1980) for the early development of an offcentre, circular shear layer. In addition, Poukey & Freeman (1981) numerically studied the initial stages of asymmetry driven beam breakup.…”

Section: The Active Phasementioning

confidence: 60%

“…We report here the observation of new, rapid, and dramatic dynamics in annular shear layers with sufficient asymmetry. Since many electron beam experiments use annular beams, asymmetry-driven instabilities may hinder beam propagation (Epstein & Poukey 1980). Asymmetry can result from misalignment of the cathode, magnetic field, or guide tubes or from instabilities like the resistive wall instability (White, Malmberg & Driscoll 1982) and the ion resonance instability (Levy, Daugherty & Buneman 1969;Peurrung, Notte & Fajans 1993).…”

Section: Introductionmentioning

confidence: 99%

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Collapse and winding of an asymmetric annulus of vorticity

1993

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The dynamics of an asymmetric annulus of vorticity in an incompressible, inviscid twodimensional fluid are experimentally studied using a pure electron plasma. A strict fluid analogy requires that the plasma system behave like an ideal fluid in a frictionless cylindrical container. For certain parameters the asymmetric annulus undergoes a complex evolution which is quite different from that of a symmetric annulus. During the first ‘active’, phase the symmetries grow until the annulus collapses, leaving a large vortex at the device centre. In the second, ‘passive’, phase the remainder of the annulus winds around this central vortex into an ever tighter spiral. Finally, slow shear instabilities destroy the structure of the highly evolved spiral.

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Section: The Active Phasementioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Collapse and winding of an asymmetric annulus of vorticity

1993

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Radial oscillations of a relativistic electron beam in an accelerating gap

Genoni

Franz

Epstein

et al. 1981

Journal of Applied Physics

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Radial oscillations of hollow, relativistic electron beams have been observed on Sandia’s RADLAC I, a multistage high-current linear induction accelerator. These oscillations, which arise because the presence of the accelerating gaps prevents radial force balance, can be responsible for poor beam quality and low current-transport efficiency. The method of magnetic field shaping to suppress oscillations is investigated. Two analytical models are formulated to derive nonuniform fields necessary to maintain force balance in a single-gap geometry. Particle code simulations have been made to test beam propagation in contoured fields. Field shaping does suppress oscillations and is not sensitive to fluctuations in beam and gap parameters.

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Limitation of accelerating process in the partly neutralized relativistic electron hollow beam

Chen

1984

Journal of Applied Physics

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A fluid-Maxwell thoery of the diocotron instability is developed for a relativistic electron hollow beam which is assumed in rigid-rotor and cold laminar flow equilibria. Stability analysis is performed for a sharp boundary electron density profile including the influence of positive ions which can accumulate in a long pulse device, and which form a partially neutralizing background. In the case of the strong magnetic field and tenuous electron beam (plasma frequency ωpb ≪gyrofrequency ωc) a partially neutralizing ion background staying uniformly within the beam annulus (R1<r<R2) has a stabilizing effect on the diocotron instability, R1 and R2 are the inner and outer radius of the annular hollow beam, respectively. However, the ions accumulating in the center of the beam (0<r<R1) have a destabilizing effect on the diocotron instability. Most importantly the kink mode becomes unstable with a growth rate several tenths of the diocotron frequency ωD ≡ ω2pb/2γ2ωc, where γ is the relativistic scaling factor.

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Analytic study of azimuthal asymmetries in relativistic hollow e-beams

Abstract: Stability of charged beam propagation through a relativistic hollow electron beam

Cited by 5 publications

References 15 publications

Collapse and winding of an asymmetric annulus of vorticity

Collapse and winding of an asymmetric annulus of vorticity

Radial oscillations of a relativistic electron beam in an accelerating gap

Limitation of accelerating process in the partly neutralized relativistic electron hollow beam

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