Powerful relativistic electron beams in a plasma and in a vacuum (theory)

Brejzman, B. N.; Ryutov, D. D.

doi:10.1088/0029-5515/14/6/012

Cited by 153 publications

(24 citation statements)

References 62 publications

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“…However, the area of the unstable region is 20%-30% larger in the case of warm plasma. We do not expect a thermal reduction in the Buneman growth rate that would explain the lower wave intensity, and we cannot exclude the fact that the saturation level is lower on account of strong nonlinear Landau damping (Breǐzman & Ryutov 1974) or the modulation instability (Galeev et al 1977). The efficiency of electron acceleration is determined by the number of trapped electrons, and the volume fraction occupied by intense Buneman modes with the convective electric field that provides the acceleration.…”

Section: The Buneman Instabilitymentioning

confidence: 92%

Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks

Bohdan

Niemiec

Kobzar

et al. 2017

ApJ

114

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We perform particle-in-cell simulations of perpendicular nonrelativistic collisionless shocks to study electron heating and pre-acceleration for parameters that permit the extrapolation to the conditions at young supernova remnants. Our high-resolution large-scale numerical experiments sample a representative portion of the shock surface and demonstrate that the efficiency of electron injection is strongly modulated with the phase of the shock reformation. For plasmas with low and moderate temperature (plasma beta 5 10, we explore the nonlinear shock structure and electron pre-acceleration for various orientations of the large-scale magnetic field with respect to the simulation plane, while keeping it at 90°to the shock normal. Ion reflection off of the shock leads to the formation of magnetic filaments in the shock ramp, resulting from Weibel-type instabilities, and electrostatic Buneman modes in the shock foot. In all of the cases under study, the latter provides first-stage electron energization through the shock-surfing acceleration mechanism. The subsequent energization strongly depends on the field orientation and proceeds through adiabatic or second-order Fermi acceleration processes for configurations with the out-of-plane and in-plane field components, respectively. For strictly out-of-plane field, the fraction of suprathermal electrons is much higher than for other configurations, because only in this case are the Buneman modes fully captured by the 2D simulation grid. Shocks in plasma with moderate p b provide more efficient pre-acceleration. The relevance of our results to the physics of fully 3D systems is discussed.

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Section: The Buneman Instabilitymentioning

confidence: 92%

Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks

Bohdan

Niemiec

Kobzar

et al. 2017

ApJ

114

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“…Under optimal conditions, the beam excites the high-level Langmuir turbulence. [7][8][9] The beam-induced small-scale high-frequency turbulence evolves in plasma and finally transports the energy to plasma electrons. Practical consequences of evolution of the turbulence are not only the plasma heating, but also the change in transport coefficients within the beam cross-section.…”

Section: Introductionmentioning

confidence: 99%

Magnetohydrodynamically stable plasma with supercritical current density at the axis

2014

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In this work, an analysis of magnetic perturbations in the GOL-3 experiment is given. In GOL-3, plasma is collectively heated in a multiple-mirror trap by a high-power electron beam. During the beam injection, the beam-plasma interaction maintains a high-level microturbulence. This provides an unusual radial profile of the net current (that consists of the beam current, current of the preliminary discharge, and the return current). The plasma core carries supercritical current density with the safety factor well below unity, but as a whole, the plasma is stable with q(a) % 4. The net plasma current is counter-directed to the beam current; helicities of the magnetic field in the core and at the edge are of different signs. This forms a system with a strong magnetic shear that stabilizes the plasma core in good confinement regimes. We have found that the most pronounced magnetic perturbation is the well-known n ¼ 1, m ¼ 1 mode for both stable and disruptive regimes. V C 2014 AIP Publishing LLC. [http://dx.

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“…2 However, the use of the high intensity beam in the interaction process is somewhat difficult in Č erenkov-type devices, such as the traveling wave tube, backward wave oscillator, and dielectric Č erenkov maser, because the injected current of the beam must be lower than the spacecharge limit current. 3 At the early stages of the research, it was suggested that injection of a background plasma into the interaction region could help to overcome the space-charge limitations. And the early studies of the Č erenkov free-electron maser predicted also that due to the plasma in the interaction region the linear growth rate and the output power of the electromagnetic radiation would increase.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Čerenkov maser with a plasma column in a dielectric lined slow-wave waveguide

1997

Physics of Plasmas

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Dielectric Čerenkov maser with a plasma column in a dielectric lined slow-wave waveguide is studied in the absence of a longitudinal guided magnetic field by use of a fully self-consistent and relativistic field theory. Determinantal dispersion equations of the interaction of a thin annular relativistic electron beam (TAREB) with the wave are derived for the TAREB inside and surrounding the plasma column, respectively. These dispersion equations show that the beam–wave interaction results from the coupling of the transverse-magnetic (TM) mode in the dielectric lined slow-wave waveguide with the plasma column to the beam mode via the electron beam. Finally, the dispersion equations are directly solved numerically, and the cutoff frequency, the operation frequency, and the growth rate of the wave are obtained.

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Powerful relativistic electron beams in a plasma and in a vacuum (theory)

Cited by 153 publications

References 62 publications

Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks

Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks

Magnetohydrodynamically stable plasma with supercritical current density at the axis

Dielectric Čerenkov maser with a plasma column in a dielectric lined slow-wave waveguide

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