Three regimes of relativistic beam - plasma interaction

Muggli, P.; Allen, Brian; Fang, Yu; Yakimenko, V.; Babzien, M.; Kusche, K.; Fedurin, M.; Vieira, Jorge; Martins, Joana; Silva, L.

doi:10.1063/1.4773764

Cited by 4 publications

(3 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The MI was also shown to be robust against a variety of nonideal (realistic) shear conditions: (i) operating under relativistic thermal effects, (ii) different densities between shearing flows, (iii) smooth velocity shear profiles (L v ω pe /c 1), and, quite surprisingly, (iv) even in the absence of contact between flows (L g ω pe /c ≫ 1 for highly relativistic shears). Relativistic collisionless sheared flow conditions, capable of triggering the MI, may be reproduced in the laboratory by propagating a globally neutral relativistic e − e + beam [38] in a hollow plasma or dielectric channel [39,40], allowing experimental access to the MI and sheared flow dynamics on the electron scale. We have begun to explore this configuration in [41].…”

Section: -3mentioning

confidence: 99%

Transverse electron-scale instability in relativistic shear flows

et al. 2015

View full text Add to dashboard Cite

Electron-scale surface waves are shown to be unstable in the transverse plane of a sheared flow in an initially unmagnetized collisionless plasma, not captured by (magneto)hydrodynamics. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroomlike electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. This transverse electron-scale instability may play an important role in relativistic and supersonic sheared flow scenarios, which are stable at the (magneto)hydrodynamic level. Macroscopic ( c/ω pe ) fields are shown to be generated by this microscopic shear instability, which are relevant for particle acceleration, radiation emission, and to seed magnetohydrodynamic processes at long time scales. A fundamental question in plasma physics concerns the stability of a given plasma configuration. Unstable plasma configurations are ubiquitous and constitute important dissipation sites via the operation of plasma instabilities, which typically convert plasma kinetic energy into thermal and electric or magnetic field energy. Plasma instabilities can occur at microscopic (particle kinetic) and macroscopic [magnetohydrodynamic (MHD)] scales, and are generally studied separately using simplified frameworks that focus on a particular scale and neglect the other. This approach conceals the role that microscopic processes may have on the macroscopic plasma dynamics, which in many scenarios cannot be disregarded. It is now recognized, for instance, that collisionless plasma instabilities operating on the electron scale in unmagnetized plasmas, such as the Weibel [1] and streaming instabilities [2], play a crucial role in the formation of (macroscopic) collisionless shocks in astrophysical [3][4][5][6][7] and laboratory conditions [8,9]. These microscopic instabilities result from the bulk interpenetration between plasmas and are believed to be intimately connected to important questions such as particle acceleration and radiation emission in astrophysical scenarios [10,11].Sheared plasma flow configurations can host both microscopic and macroscopic instabilities simultaneously, although the former have been largely overlooked. Sheared flow settings have been traditionally studied using the MHD framework [12][13][14], where the Kelvin-Helmholtz instability (KHI) is the only instability known to develop [15]. Only very recently have collisionless unmagnetized sheared plasma flows been addressed experimentally [16] and using particle-in-cell (PIC) simulations, revealing a rich variety of electron-scale processes, such as the electron-scale KHI (ESKHI), dc magnetic field generation, and unstable transverse dynamics [17][18][19][20][21][22]. The generated fields and modif...

show abstract

Section: -3mentioning

confidence: 99%

Transverse electron-scale instability in relativistic shear flows

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Weibel-mediated shocks in the jet could generate fields of sufficient strength, but are expected to decay rapidly, on timescales comparable to the inverse plasma frequency [13]. On the other hand, analytical [10] and numerical [21][22][23][24] studies give significant evidence that magnetic fields of sufficient strength and persistence might be generated by strong current filamentation of the EPB.To date, there is no direct evidence of these phenomena, either in the laboratory or in astrophysical observations. This lack of experimental data is ultimately due to the difficulty of generating neutral EPBs in the laboratory despite considerable dedicated efforts worldwide [25][26][27].…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam

et al. 2017

View full text Add to dashboard Cite

We report on the first experimental observation of a current-driven instability developing in a quasineutral matter-antimatter beam. Strong magnetic fields (amp;gt;= 1 T) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma. The experimentally determined equipartition parameter of epsilon(B) approximate to 10(-3) is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. The data, supported by particle-in-cell simulations and simple analytical estimates, indicate that these magnetic fields persist in the background plasma for thousands of inverse plasma frequencies. The existence of such long-lived magnetic fields can be related to analog astrophysical systems, such as those prevalent in lepton-dominated jets.

Funding Agencies|EPSRC [EP/N022696/1, EP/N027175/1, EP/L013975/1, EP/N002644/1, EP/P010059/1]; DOE [DE-NA0002372]; ARO [W911NF-16-1-0044]

show abstract

Effect of beam emittance on self-modulation of long beams in plasma wakefield accelerators

Lotov

2015

Physics of Plasmas

View full text Add to dashboard Cite

The initial beam emittance determines the maximum wakefield amplitude that can be reached as a result of beam self-modulation in the plasma. The wakefield excited by the fully self-modulated beam decreases linearly with the increase of the beam emittance. There is a value of initial emittance beyond which the selfmodulation does not develop even if the instability is initiated by a strong seed perturbation. The emittance scale at which the wakefield is twice suppressed with respect to the zero-emittance case (the so called critical emittance) is determined by inability of the excited wave to confine beam particles radially and is related to beam and plasma parameters by a simple formula. The effect of beam emittance can be observed in several discussed self-modulation experiments.

show abstract

Three regimes of relativistic beam - plasma interaction

Cited by 4 publications

References 15 publications

Transverse electron-scale instability in relativistic shear flows

Transverse electron-scale instability in relativistic shear flows

Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam

Effect of beam emittance on self-modulation of long beams in plasma wakefield accelerators

Contact Info

Product

Resources

About