Invited Article: Relation between electric and magnetic field structures and their proton-beam images

Kugland, N. L.; Ryutov, D. D.; Plechaty, C.; Ross, J. S.; Park, H.-S.

doi:10.1063/1.4750234

Cited by 114 publications

(212 citation statements)

References 103 publications

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“…[11]). This is in reasonable agreement with the proton caustic formation by magnetic deflection [20], which requires ∇ ⊥ B × dℓ ∼ 60 T for typical proton energies and the experimental proton magnification factors. Here the line integral is along the proton trajectories and the gradient is taken in the object plane.…”

supporting

confidence: 73%

“…The first image, at t = 3.8 ns relative to the start of the driver pulse, shows a prominent and sharp"X"-like structure at the midplane, with the protons deflected into pairs of thin lines, reminiscent of the caustic proton structures observed in experiments in a similar laser-energy regime with larger initial target separation [19,20]. However, for the present discussion, we focus on the filamentary instability visible above the "X" structure.…”

mentioning

confidence: 99%

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Filamentation Instability of Counterstreaming Laser-Driven Plasmas

et al. 2013

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Filamentation due to the growth of a Weibel-type instability was observed in the interaction of a pair of counter-streaming, ablatively-driven plasma flows, in a supersonic, collisionless regime relevant to astrophysical collisionless shocks. The flows were created by irradiating a pair of opposing plastic (CH) foils with 1.8 kJ, 2-ns laser pulses on the omega ep laser system. Ultrafast laserdriven proton radiography was used to image the Weibel-generated electromagnetic fields. The experimental observations are in good agreement with the analytical theory of the Weibel instability and with particle-in-cell simulations.Astrophysical shock waves play diverse roles, including energizing cosmic rays in the blast waves of astrophysical explosions [1], and generating primordial magnetic fields during the formation of galaxies and clusters [2]. These shocks are typically collisionless, and require collective electromagnetic fields [3], as Coulomb collisions alone are too weak to sustain shocks in high-temperature astrophysical plasmas. The class of Weibel-type instabilities [4][5][6] (including the classical Weibel and currentfilamentation instabilities) is one such collective mechanism that has been proposed to generate a turbulent magnetic field in the shock front and thereby mediate shock formation in cosmological shocks [7] and blast wave shocks in gamma ray bursts [8][9][10] and supernova remnants [11]. These instabilities generate magnetic field de novo by tapping into non-equilibrium features in the electron and ion distributions functions. The classical form of the Weibel instability is driven by temperature anisotropy [4], but counterstreaming ion beams, as occurs in the present context, provides an equivalent drive mechanism [6]. A related current filamentation instability of relativistic electron beams [12] has also previously been observed in experiments driven by ultraintense lasers [13].We report experimental identification an ion-driven Weibel-type instability generated in the interaction of two counterstreaming laser-produced plasma plumes. A pair of opposing CH targets was irradiated by kJ-class laser pulses on the OMEGA EP laser laser system, driving a pair of ablative flows toward the collision region at the midplane between the two foils. Due to the long mean-free-path between ions in opposing streams, the streams interpenetrate, establishing supersonic counterstreaming conditions in the ion populations, while the electrons form a single thermalized cloud. Meanwhile, the plasma density is also sufficient so that the the ion skin depth d i = (m i /µ 0 ne 2 ) 1/2 , is much smaller than the system size L. These conditions allow the growth of an ion-driven Weibel instability, for which d i is the characteristic wavelength [14][15][16]. The Weibel-generated electromagnetic fields were observed with an ultrafast pro- ton radiography technique [17], and identified through good agreement with analytic theory [6] and particle-incell simulations, discussed below. Figure 1 shows a schematic of the experiments...

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confidence: 73%

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confidence: 99%

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

et al. 2013

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“…The extracted electric field profiles are shown in Figures 1(c)-(e), indicating that the electric field evolves from a bell-shaped profile to an asymmetric bipolar profile, while maintaining a peak amplitude of the order of 100 MV m −1 . The potential associated with the thin shell is of the order of a kV that, while being sufficiently strong to reflect the nitrogen ions of the background plasma has a small effect on the multi-MeV probing protons, confirming that the formation of caustics (as discussed in Kugland et al 2012) has no relevance here.…”

Section: Resultsmentioning

confidence: 53%

Experimental Observation of Thin-shell Instability in a Collisionless Plasma

Ahmed

Doria

Dieckmann

et al. 2017

ApJL

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We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.

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“…We have conducted the Weibel-instability mediated collisionless EM shock experiments with Omega and Omega EP laser systems (Rochester U., U.S.A), and measured plasma parameters such as electron and ion temperatures, electron density, and flow velocity of counter-streaming plasmas [60][61][62] with collective Thomson scattering (CTS) [63], and filamentary structure produced by the Weibel instability [62,64,65] with proton radiography [66,67]. Now the NIF experiment is going on.…”

Section: Introductionmentioning

confidence: 99%

Collisionless electrostatic shock generation using high-energy laser systems

Sakawa

Morita

Kuramitsu

et al. 2016

Advances in Physics: X

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Collisionless shock is ubiquitous in space and astrophysical plasmas, and is believed to be a source of cosmic rays. In this review article, historical achievements of three different types of collisionless shocks, i.e. magnetohydrodynamic, electromagnetic, and electrostatic (ES) shocks, in theory/simulation, observation in space and astrophysical plasmas, and laboratory experiments are shown. An overview is given on recent progress of collisionless ES shock experiments using high-energy laser systems for two schemes. One is an interaction between laser-produced highdensity ablating plasma and a low-density ambient plasma, and the other is an interaction between laser-ablated counterstreaming plasmas using double-plane target. For the former scheme, detailed measurements of structures of collisionless ES shock and ion-acoustic soliton, and the transition from double-layer to collisionless ES shock are conducted by proton radiography. For the latter scheme, optical diagnostics are used to observe global structures of plasmas and shocks; collective laser Thomson scattering method is applied to clarify local plasma parameters, such as electron and ion temperatures, flow velocity, and electron density; and proton radiography is employed to measure a shock electric field. The measured large density-jump, steepening of self-emission profile, plasma parameters in the upand down-stream regions of a shock, and the narrow width of the shock electric field compared with the ion-ion Coulomb meanfree-path reveal the evidence for the formation of collisionless ES shock. ARTICLE HISTORY

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Invited Article: Relation between electric and magnetic field structures and their proton-beam images

Cited by 114 publications

References 103 publications

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

Filamentation Instability of Counterstreaming Laser-Driven Plasmas

Experimental Observation of Thin-shell Instability in a Collisionless Plasma

Collisionless electrostatic shock generation using high-energy laser systems

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