Current-induced implosion of a multiwire array as a radial plasma rainstorm

Alexandrov, V. V.; Grabovsky, E. V.; Zukakishvili, G. G.; Zurin, M. V.; Komarov, N.N.; Krasovsky, I. V.; Mitrofanov, K. N.; Nedoseev, S. L.; Oleĭnik, G. M.; Porofeev, I. Yu.; Samokhin, A. A.; Sasorov, P. V.; Smirnov, V. P.; Fedulov, M. V.; Frolov, I. N.; Chernov, A. A.

doi:10.1134/1.1625064

Cited by 31 publications

(5 citation statements)

References 5 publications

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“…To this end, the Z accelerator has just completed an upgrade to 26 MA, and preliminary tests/experiments have begun. 22 In parallel with activity on Z, wire-array Z-pinch experiments have been taking place on lower-current machines such as the 8-MA Saturn accelerator at Sandia, 23,24 the 4-MA Angara-5-1 facility in Russia, 25,26 and 1-MA ma-chines found at universities, such as the MAGPIE facility at Imperial College, London, 18,27 the Zebra facility at the University of Nevada, Reno, 28,29 and the COBRA facility at Cornell. 19,20,[30][31][32] Remarkably, many of the wire-array Z-pinch phenomena observed at 1 MA, such as wire ablation, a delayed implosion of the bulk of the wire mass, and the presence of trailing mass, 28,32,33 are also seen at 20 MA.…”

Section: Implosion Dynamics and Radiation Characteristics Of Wire-arrmentioning

confidence: 99%

Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator

et al. 2009

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Experimental results are presented that characterize the implosion dynamics and radiation output of wire-array Z pinches on the 1-MA, 100-ns rise-time Cornell Beam Research Accelerator ͑COBRA͒ ͓J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 ͑2008͔͒. The load geometries investigated include 20-mm-tall cylindrical arrays ranging from 4 to 16 mm in diameter, and consisting of 8, 16, or 32 wires of either tungsten, aluminum, or Invar ͑64% iron, 36% nickel͒. Diagnostics fielded include an optical streak camera, a time-gated extreme-ultraviolet framing camera, a laser shadowgraph system, time-integrated pinhole cameras, an x-ray wide-band focusing spectrograph with spatial resolution, an x-ray streak camera, a load voltage monitor, a Faraday cup, a bolometer, silicon diodes, and diamond photoconducting detectors. The data produced by the entire suite of diagnostics are analyzed and presented to provide a detailed picture of the overall implosion process and resulting radiation output on COBRA. The highest x-ray peak powers ͑300-500 GW͒ and total energy yields ͑6-10 kJ͒ were obtained using 4-mm-diameter arrays that stagnated before peak current. Additional findings include a decrease in soft x-ray radiation prior to stagnation as the initial wire spacing was changed from 1.6 mm to 785 m, and a timing correlation between the onset of energetic electrons, hard x-ray generation, and the arrival of trailing current on axis-a correlation that is likely due to the formation of micropinches. The details of these and other findings are presented and discussed.

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Section: Implosion Dynamics and Radiation Characteristics Of Wire-arrmentioning

confidence: 99%

Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator

et al. 2009

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“…Multiplying this electron line density by the width of the region (2×2.5 mm) yields an upper limit on the mass in this region of ∼0.5-2% of the array mass (assuming Z=4 or Z=1, respectively). This is in contrast to implosions of standard wire arrays, where a significant fraction of the array mass remains at the initial array radius [4] [11]. The interferogram in Fig.…”

mentioning

confidence: 93%

Suppression of the Ablation Phase in Wire Array Z Pinches Using a Tailored Current Prepulse

et al. 2011

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A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array for the first time. The setup introduces a ∼5 kA, ∼25 ns current prepulse followed by a ∼140 ns current-free interval before the application of the main (∼1 MA) current pulse. The prepulse volumetrically heats the wires which expand to ∼1 mm diameter leaving no dense wire core and without development of instabilities. The main current pulse then ionises all the array mass resulting in suppression of the ablation phase, an accelerating implosion and no trailing mass. Rayleigh-Taylor instability growth in the imploding plasma is inferred to be seeded by µm-scale perturbations on the surface of the wires. The absence of wire cores is found to be the critical factor in altering the implosion dynamics.Fast z-pinch plasma implosions driven by multi megaAmpere currents are very efficient at converting stored electrical energy into X-rays. Achieving high x-ray powers by releasing this energy in a short time requires a high degree of azimuthal symmetry of the imploding plasma and a low level of initial axial perturbations seeding the growth of magnetic Rayleigh-Taylor (MRT) instabilities. The highest x-ray powers in z-pinch implosions were achieved using cylindrical arrays made of large numbers of fine metallic wires (280-300 TW, >2 MJ at ∼20% efficiency on the Z facility at SNL [1] [2]). Experimental studies of wire array z-pinches have shown [3] [4] [5] thateven for large number of wires the arrays do not form a plasma shell imploding as a 2-D object. Instead, the wires remain as discrete, compact objects for the first 60-80% of the implosion and during this time only the coronal plasma, continuously ablated from the stationary cores, are accelerated towards the axis by the J×B force [4]. This ablation phase determines the initial conditions for the implosion in two ways. Firstly, the ablated plasma fills the interior of the array which contributes to the mitigation of the growth of the MRT instability. Secondly, the quasi-periodic modulation of the ablation rate along each individual wire occurring at the 'natural' wavelength (∼250 μm for W and ∼500 μm for Al) is responsible for the large level of axial perturbations at the start of the implosion phase. The existence of the ablation phase is observed in all known wire array z-pinch experiments (currents between ∼1 MA and 26 MA, and implosion times between ∼50 ns and ∼800 ns) and occurs because current is initially carried by the small amount of plasma formed on the wire surfaces, and not by the wire cores themselves.In this letter we report on experiments where, for the first time, the ablation phase in wire array z-pinches was suppressed, including dramatic suppression of the axial perturbations in the wires and suppression of the precursor plasma flow. This was achieved by using a short duration low-level current pre-pulse (∼25 ns, ∼5 kA) followed by a ∼140 ns current-free interval before the main (∼1 MA, 100 ns) current pulse driving the implosion is applied. Th...

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“…This complication will alter those expressions which depend on c, such as Eqs. (26) and (27). However, those predictions which are independent of c remain valid.…”

Section: Comparison Of 1d Generalized Noh To Simulation a Pre-stamentioning

confidence: 93%

“…[15][16][17][18][19][20][21] While such models are excellent for developing physical intuition, the applicability to a wire-array Z pinch is uncertain, owing to its three-dimensional (3D) nature, which is well-documented experimentally. [22][23][24][25][26] At early time, rather than vaporizing into a plasma shell, the wires develop a heterogeneous core-corona structure and undergo a prolonged ablation phase during which cores cook material off their surface, which is then accelerated towards axis by the j Â B force. The ablation phase, coupled with an instability on the cores that modulates the ablation rate axially (see Ref.…”

Section: Introductionmentioning

confidence: 99%

Application of one-dimensional stagnation solutions to three-dimensional simulation of compact wire array in absence of radiation

Velikovich

Maron

2014

Physics of Plasmas

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We investigate the stagnation phase of a three-dimensional (3D), magnetohydrodynamic simulation of a compact, tungsten wire-array Z pinch, under the simplifying assumption of negligible radiative loss. In particular, we address the ability of one-dimensional (1D) analytic theory to describe the time evolution of spatially averaged plasma properties from 3D simulation. The complex fluid flows exhibited in the stagnated plasma are beyond the scope of 1D theory and result in centrifugal force as well as enhanced thermal transport. Despite these complications, a 1D homogeneous (i.e., shockless) stagnation solution can capture the increase of on-axis density and pressure during the initial formation of stagnated plasma. Later, when the stagnated plasma expands outward into the imploding plasma, a 1D shock solution describes the decrease of on-axis density and pressure, as well as the growth of the shock accretion region. V

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Current-induced implosion of a multiwire array as a radial plasma rainstorm

Cited by 31 publications

References 5 publications

Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator

Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator

Suppression of the Ablation Phase in Wire Array Z Pinches Using a Tailored Current Prepulse

Application of one-dimensional stagnation solutions to three-dimensional simulation of compact wire array in absence of radiation

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