Power enhancement by increasing the initial array radius and wire number of tungsten<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math>pinches

Deeney, C.; Nash, T. J.; Spielman, R. B.; Seaman, J. F.; Chandler, G. C.; Struve, K. W.; Porter, J. L.; Stygar, W. A.; McGurn, J.; Jobe, D.; Gilliland, T. L.; Torres, J. A.; Vargas, M.; Ruggles, L. E.; Breeze, S. P.; Mock, R. C.; Douglas, M. R.; Fehl, D. L.; McDaniel, D. H.; Matzen, M. K.; Peterson, Darrell L.; Matuska, W.; Roderick, N. F.; Macfarlane, J. J.

doi:10.1103/physreve.56.5945

Cited by 123 publications

(81 citation statements)

References 23 publications

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“…(10) and (11) reveals that l a=b s scales inversely with n b . This is most likely to be the scaling that causes the change in the collisionality observed in the 16 wire array data in Fig.…”

Section: -9mentioning

confidence: 99%

“…6,7 Once the wires are broken the array undergoes a snowplough like implosion, 8,9 followed by the stagnation of the accrued kinetic energy as an intense pulse of soft x-ray radiation. 10,11 This paper presents the results of a series of experiments conducted in order to investigate the dynamics of wire array plasmas during the ablation phase. In particular, it focuses on the azimuthal ablation flow structures formed in aluminium wire arrays.…”

Section: Introductionmentioning

confidence: 99%

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Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

et al. 2013

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A series of experiments has been conducted in order to investigate the azimuthal structures formed by the interactions of cylindrically converging plasma flows during the ablation phase of aluminium wire array Z pinch implosions. These experiments were carried out using the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. The main diagnostic used in this study was a two-colour, end-on, Mach-Zehnder imaging interferometer, sensitive to the axially integrated electron density of the plasma. The data collected in these experiments reveal the strongly collisional dynamics of the aluminium ablation streams. The structure of the flows is dominated by a dense network of oblique shock fronts, formed by supersonic collisions between adjacent ablation streams. An estimate for the range of the flow Mach number (M ¼ 6.2-9.2) has been made based on an analysis of the observed shock geometry. Combining this measurement with previously published Thomson Scattering measurements of the plasma flow velocity by Harvey-Thompson et al. [Physics of Plasmas 19, 056303 (2012)] allowed us to place limits on the range of the ZT e of the plasma. The detailed and quantitative nature of the dataset lends itself well as a source for model validation and code verification exercises, as the exact shock geometry is sensitive to many of the plasma parameters. Comparison of electron density data produced through numerical modelling with the Gorgon 3D MHD code demonstrates that the code is able to reproduce the collisional dynamics observed in aluminium arrays reasonably well. V C 2013 American Institute of Physics. [http://dx

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Section: -9mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

et al. 2013

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“…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] that even 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].…”

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confidence: 99%

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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“…kJ, for about 4 TW/mm and 23 kJ/mm [26]. The 10 TW and 165±20 kJ made by our W X-pinch sources are comparable at roughly 3 TW/mm and 55 kJ/mm.…”

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confidence: 56%

Investigation of High-Temperature Bright Plasma X-ray Sources Produced in 5-MA X-Pinch Experiments

et al. 2012

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Power enhancement by increasing the initial array radius and wire number of tungstenZpinches

Cited by 123 publications

References 23 publications

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

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

Investigation of High-Temperature Bright Plasma X-ray Sources Produced in 5-MA X-Pinch Experiments

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