Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows

Swadling, G. F.; Лебедев, С. В.; Harvey‐Thompson, A. J.; Rozmus, W.; Burdiak, G.; Suttle, L.; Patankar, S.; Smith, R. A.; Bennett, M.; Hall, G. N.; Suzuki-Vidal, F.; Yuan, Jianhua

doi:10.1103/physrevlett.113.035003

Cited by 21 publications

(27 citation statements)

References 24 publications

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“…The position (y coordinate) at which the probing beam crossed the layer was adjusted between different experiments to sample different regions of the plasma. The scattered light was collected in the same plane, from 13 spatial positions along the beam, at scattering angles of θ ¼ 45°and 135°to the laser, using an imaging spectrometer and two linear arrays of optical fibers (see [20,21] for more details). Alignment of the TS diagnostic and determination of the scattering volume locations with respect to the interferogram was performed as described in [20], with a precision of ≤0.2 mm.…”

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confidence: 99%

“…A TS diagnostic [20,21] was used to record the ion feature of the collective TS spectrum, measuring the flow velocity and temperatures (T i ,ZT e ) of the plasma. The distribution of the magnetic field was measured using a polarimetry (Faraday rotation) diagnostic (1053 nm and 1 ns) [20], while the electron density was obtained in end-on (x-y) and side-on (x-z) directions via laser interferometry (532 and 355 nm, 0.3 ns, 1053 nm, and 1 ns) [20,22].…”

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Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows

et al. 2016

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We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure-two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T i ∼ZT e , with average ionizationZ ¼ 7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities. DOI: 10.1103/PhysRevLett.116.225001 The interaction of supersonic, counterstreaming plasma flows occurs in many astrophysical scenarios (e.g., astrophysical jets [1] and termination shocks [2,3]) and in laboratory experiments (e.g., colliding plasmas in inertial confinement fusion hohlraums [4]). The presence of frozenin magnetic fields advected by the colliding flows could play an important role in determining the structure of the interaction region in these systems. Collisions of magnetized plasmas with oppositely directed magnetic fields should eventually lead to annihilation of the flux via magnetic reconnection. In many astrophysical scenarios reconnection occurs in high beta plasmas and is strongly driven, with ram pressure significantly exceeding the magnetic pressure. The structure of the reconnection layer in these conditions is unknown, but is expected to adjust to accommodate the rate of magnetic flux delivered into the layer, where, for example, a pileup of the magnetic flux could contribute to controlling the reconnection rate [5,6]. A number of recent laser-driven, high energy density physics (HEDP) experiments [7][8][9][10] have investigated magnetic reconnection in the strongly driven regime, as well as the formation of astrophysically relevant collisionless shocks [11] and self-organized field structures [12]. Large-scale field structures produced by collisions between laser-driven plasma flows have, for example, been interpreted [11] as being due to the accumulation of advected toroidal magnetic fields generated via the Biermann battery mechanism at the laser spots [13]. Despite the importance of magnetic fields in defining the properties of shocks formed in HEDP plasmas, experimental information is still limited.In this Letter we present experimental data characterizing the structure of an interaction layer formed by the collision of two counterstreaming, supersonic (sonic Mach number M S > 3), magnetized plasma flows. These flows advect embedded magnetic fields (magnetic Reynolds number Re M > 30), orientated in opposing directions perpendicular to the flow, and their interaction is strongly driven [i.e., high dynamic beta regime,. The experiments provide detaile...

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Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows

et al. 2016

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“…The first experimental application for the horizontal wire array was a campaign designed to study the dynamics of ablation stream interactions in the precursor region of tungsten wire arrays [17], [18]. The main aim of these experiments was to use a novel scattering geometry which would allow simultaneous measurements of the radial and axial (with respect to the wire array) velocity components of the ion velocity distributions.…”

Section: Application To Thomson Scattering Experiments Smentioning

confidence: 99%

“…a). This configuration has recently been used to make detailed Thomson scattering measurements of the flow velocity vectors in tungsten wire arrays [17], [18] and has many other potential diagnostic applications. While the experiments carried out using this configuration so far have been designed primarily to study the interactions of plasma streams during the "ablation phase" (the phase where the wire cores remain stationary), this configuration also has potential applications in the study of implosion and stagnation phase physics .…”

Section: Introductionmentioning

confidence: 99%

Commissioning of a Rotated Wire Array Configuration for Improved Diagnostic Access

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et al. 2015

IEEE Trans. Plasma Sci.

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Abstract-A new rotated wire array z-pinch configuration has been developed for use in experiments on the Magpie generator at Imperial College London. The wire array is rotated onto its side such that the array axis lies perpendicular to the axis of the pulsed power electrodes. This arrangement provides greatly improved end-on diagnostic access to the array and has a number of potential experimental applications; the design has recently been used to make novel Thomson scattering measurements of ablation flow interactions in tungsten wire arrays. Turning the wire array on its side leads to an uneven distribution of current through the wires, due to the variation in the inductance of the current path through each wire. The forces acting on each wire will therefore be imbalanced, leading to uneven ablation of the wire cores. An experimental campaign was carried out in order to inductively re-tune the current distribution in the wire array. The results of these experiments are presented, along with discussion of potential future experimental applications.

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“…These are relevant as comparable environments for astrophysical processes. [15][16][17] Due to the azimuthal symmetry imposed on standard arrays, the ablation flows from each wire radially converge toward the array axis, where plasma accumulates forming a precursor plasma column. Even after most of the wires have been fully ablated and during the implosion phase as well, the null field region (and consequently, the precursor) remains at the array axis.…”

Section: Introductionmentioning

confidence: 99%

Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology

et al. 2015

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The dynamics of ablation streams and precursor plasma in cylindrical wire array Z-pinches under temporal variations of the global magnetic field topology is investigated through experiments and numerical simulations. The wire arrays in these experiments are modified by replacing a pair of consecutive wires with wires of a larger diameter. This modification leads to two separate effects, both of which impact the dynamics of the precursor plasma; firstly, current is unevenly distributed between the wires and secondly, the thicker wires take longer to fully ablate. The uneven distribution of current is evidenced in the experiments by the drift of the precursor off axis due to a variation in the global magnetic field topology which modifies the direction of the ablation streams tracking the precursor position. The variation of the global magnetic field due to the presence of thick wires is studied with three-dimensional magnetohydrodynamic (MHD) simulations, showing that the global field changes from the expected toroidal field to a temporally variable topology after breakages appear in the thin wires. This leads to an observed acceleration of the precursor column towards the region closer to the thick wires and later, when thick wires also present breakages, it continues moving away from the original array position as a complicated and disperse object subject to MHD instabilities

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Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows

Cited by 21 publications

References 24 publications

Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows

Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows

Commissioning of a Rotated Wire Array Configuration for Improved Diagnostic Access

Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology

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