Electron-Hose Instability in an Annular Plasma Sheath PDF Download
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Languages : en
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A relativistic electron beam propagating through an annular plasma sheath is subject to a transverse plasma-electron coupled electrostatic instability. From the linearized fluid equations, the beam-sheath interaction is resolved into three coupled equations. The corresponding wakefield is computed and the asymptotic linear evolution is noted. For illustration, numerical examples are given for a plasma accelerator employing such a sheath. While the coasting beam scalings are quite severe at low energy, single-bunch instability growth can in fact be reduced to nil, for a very high-gradient accelerator.
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Languages : en
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A relativistic electron beam propagating through an annular plasma sheath is subject to a transverse plasma-electron coupled electrostatic instability. From the linearized fluid equations, the beam-sheath interaction is resolved into three coupled equations. The corresponding wakefield is computed and the asymptotic linear evolution is noted. For illustration, numerical examples are given for a plasma accelerator employing such a sheath. While the coasting beam scalings are quite severe at low energy, single-bunch instability growth can in fact be reduced to nil, for a very high-gradient accelerator.
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Languages : en
Pages : 3
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In the FACET plasma-wakefield acceleration experiment a dense 23 GeV electron beam will interact with lithium and cesium plasmas, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons may lead to a fast growing electron hose instability. By using optics dispersion knobs to induce a controlled z-x tilt along the beam entering the plasma, we investigate the transverse behavior of the beam in the plasma as function of the tilt. We seek to quantify limits on the instability in order to further explore potential limitations on future plasma wakefield accelerators due to the electron hose instability. The FACET plasma-wakefield experiment at SLAC will study beam driven plasma wakefield acceleration. A dense 23 GeV electron beam will interact with lithium or cesium plasma, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons drives the electron hose instability, as first studied by Whittum. While Ref. [2] indicates the possibility of a large instability growth rate for typical beam and plasma parameters, other studies including have shown that several physical effects may mitigate the hosing growth rate substantially. So far there has been no quantitative benchmarking of experimentally observed hosing in previous experiments. At FACET we aim to perform such benchmarking by for example inducing a controlled z-x tilt along the beamentering the plasma, and observing the transverse behavior of the beam in the plasma as function. The long-term objective of these studies is to quantify potential limitations on future plasma wakefield accelerators due to the electron hose instability.
Author: Ferdinand F. Cap
Publisher: Academic Press
ISBN: 148327098X
Category : Science
Languages : en
Pages : 575
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Book Description
Handbook on Plasma Instabilities, Volume 2 consists of four chapters on plasma instabilities. Chapter 14 discusses the various aspects of microinstabilities. Beam-plasma systems are covered in Chapter 15, while the various stabilization methods are presented in Chapter 16. This book concludes with deliberations on parametric effects in Chapter 17. Other topics discussed include the microinstabilities of a homogeneous unmagnetized plasma; kinetic theory of macroscopic instabilities; basic beam physics; and beam-plasma instabilities. The magnetic field configuration stabilization; macroscopic nonmagnetic stabilization methods; parametric instabilities in homogeneous unmagnetized plasmas; and parametric effects in bounded and inhomogeneous plasmas are also elaborated in this text. This publication is beneficial to students and researchers conducting work on unstable plasma.
Author: Stanton Jerrold Peale
Publisher:
ISBN:
Category : Antennas (Electronics)
Languages : en
Pages : 154
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Book Description
In recent years there has been a growing interest in general plasma physics. Communications over long distances are affected by plasma clouds and any magnetic fields they contain. While radio sounding is currently used to explore the ionosphere, investigation of plasmas located at points far beyond the ionosphere demands that environmental sampling techniques be developed to produce reliable knowledge.
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Category : Controlled fusion
Languages : en
Pages : 596
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Category :
Languages : en
Pages :
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A condition for sheath instability due to secondary electron emission (SEE) is derived for low collisionality plasmas. When the SEE coefficient of the electrons bordering the depleted loss cone in energy space exceeds unity, the sheath potential is unstable to a negative perturbation. This result explains three different instability phenomena observed in Hall thruster simulations including a newly found state with spontaneous 2̃0MHz oscillations. When instabilities occur, the SEE propagating between the walls becomes the dominant contribution to the particle flux, energy loss and axial transport.
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Category : Power resources
Languages : en
Pages : 660
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Author: Stanley Humphries, JR.
Publisher: Courier Corporation
ISBN: 0486498689
Category : Science
Languages : en
Pages : 866
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Book Description
Detailed enough to serve as both text and reference, this volume addresses topics vital to understanding high-power accelerators and high-brightness-charged particle beams, including stochastic cooling, high-brightness injectors, and the free electron laser. 1990 edition.
Author: Kevin Joseph O'Brien
Publisher:
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Category :
Languages : en
Pages : 520
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Languages : en
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The Debye sheath is shown to be unstable under general conditions. For surface materials with sufficient secondary electron emission (SEE) yields, the surface's current-voltage characteristic has an unstable branch when the bulk plasma temperature (Te) exceeds a critical value, or when there are fast electron populations present. The plasma-surface interaction becomes dynamic where the sheath may undergo spontaneous transitions or oscillations. Using particle-in-cell simulations, we analyze sheath instabilities occurring in a high Te plasma slab bounded by walls with SEE. As the plasma evolves, whenever the sheath enters an unstable state, its amplitude rapidly collapses, allowing a large flux of previously trapped electrons to hit the wall. These hot electrons induce more than one secondary on average, causing a net loss of electrons from the wall. The sheath collapse quenches when the surface charge becomes positive because the attractive field inhibits further electrons from escaping. Sheath instabilities influence the current balance, energy loss, cross-B-field transport and even the bulk plasma properties. Implications for discharges including Hall thrusters are discussed. More generally, the results show that common theories that treat emission as a fixed (time-independent) "coefficient" do not capture the full extent of SEE effects.
