Dynamics of Heterogeneous Liners with Prolonged Plasma Creation

Александров, В. В.; Branitskii, A. V.; Volkov, G. S.; Grabovskiĭ, E. V.; Zurin, M. V.; Nedoseev, S. L.; Oleinik, G. M.; Samokhin, A. A.; Sasorov, P. V.; Smirnov, V. P.; Fedulov, M. V.; Frolov, I. N.

doi:10.1134/1.1348487

Cited by 102 publications

(48 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Generally, it is possible to divide the evolution of their dynamics into a set of four discrete phases; initiation, ablation, implosion, and stagnation. [3][4][5] During the initiation phase, the wires are heated ohmically, causing them to vaporise and expand. The wires electrically break down and a heterogeneous structure is formed; the wire cores remain relatively cold, dense and resistive, but are surrounded by sheaths of hot, low density, highly conductive coronal plasma.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

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

show abstract

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

show abstract

“…In general, their evolution can be divided into a sequence of four reasonably distinct phases; initiation, ablation, implosion, and stagnation. [7][8][9] The ablation phase is by far the longest of the four phases; at 1 MA it has been shown to account for $80% (Ref. 7) of the total implosion time (the period from current start to the peak of x-ray output) and $65% at 20 MA.…”

Section: Introductionmentioning

confidence: 99%

Shock-less interactions of ablation streams in tungsten wire array z-pinches

et al. 2013

View full text Add to dashboard Cite

Shock-less dynamics were observed during the ablation phase in tungsten wire array experiments carried out on the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. This behaviour contrasts with the shock structures which were seen to dominate in previous experiments on aluminium arrays [Swadling et al., Phys. Plasmas 20, 022705 (2013)]. In this paper, we present experimental results and make comparisons both with calculations of the expected mean free paths for collisions between the ablation streams and with previously published Thomson scattering measurements of the plasma parameters in these arrays [Harvey-Thompson et al., Phys. Plasmas 19, 056303 (2012)]. V C 2013 AIP Publishing LLC. [http://dx

show abstract

“…Experiments on the 20 MA Z pulsed power generator [1] have achieved peak powers of 280-300 TW with a >2 MJ yield at 20% efficiency [2] by imploding cylindrical arrays consisting of hundreds of fine metallic wires. It was found [3][4] [5] that in wire array Z pinches the wires remain stationary for the first 60-80% of the implosion time and steadily ablate plasma which is accelerated by the j×B force. This ablation flow distributes mass in the array interior which sets the initial conditions for the implosion phase.…”

mentioning

confidence: 99%

Optical Thomson Scattering Measurements of Plasma Parameters in the Ablation Stage of Wire ArrayZPinches

et al. 2012

View full text Add to dashboard Cite

A Thomson scattering diagnostic has been used to measure the parameters of cylindrical wire array Z pinch plasmas during the ablation phase. The scattering operates in the collective regime (α>1) allowing spatially localised measurements of the ion or electron plasma temperatures and of the plasma bulk velocity. The ablation flow is found to accelerate towards the axis reaching peak velocities of 1.2-1.3×10 7 cm/s in aluminium and ∼1×10 7 cm/s in tungsten arrays. Precursor ion temperature measurements made shortly after formation are found to correspond to the kinetic energy of the converging ablation flow.Wire array Z pinch implosions can efficiently convert stored electrical energy into powerful bursts of soft xrays. Experiments on the 20 MA Z pulsed power generator [1] have achieved peak powers of 280-300 TW with a >2 MJ yield at 20% efficiency [2] by imploding cylindrical arrays consisting of hundreds of fine metallic wires. It was found [3][4][5] that in wire array Z pinches the wires remain stationary for the first 60-80% of the implosion time and steadily ablate plasma which is accelerated by the j×B force. This ablation flow distributes mass in the array interior which sets the initial conditions for the implosion phase. The ablation mass distribution depends on the ablation rate, dm/dt, and on the flow velocity, which are related via force -momentum balance. However, the flow velocity was not measured in past experiments apart from the velocity of the initial part of the flow which was inferred from the time of plasma appearance on the array axis and from end-on interferometry measurements, giving V∼1.5×10 7 cm/s [6] [7]. The velocity of the ablation flow in the later stages, when the majority of the ablated material is moving into the array interior, is not known. Instead, the ablation rate and mass redistribution is often discussed using the so-called 'ablation velocity', introduced in the rocket model [3] via momentum balance arguments, which is inferred from the implosion dynamics or from unfolds of x-ray radiography measurements of mass distribution in the array interiorNumerical simulations [10][11] show that velocity is changing both with time and with the radial position of the flow, indicating that the flow is accelerated by the j×B force acting on the plasma in the array interior. However, these simulations do not model the initial heating of the wires and the process of conversion of initially cold metallic wires into a plasma. Instead, simulations start from wire material already converted into plasma at some initial temperature and density, and these initial conditions are adjusted to produce agreement of the simulated implosion dynamics with experimental observations. Direct measurements of the ablation flow velocity and density are needed to allow verification of these numerical models. Knowledge of the flow velocity is also important for other applications of different wire array Z pinch configurations, used e.g. in laboratory astrophysics [12] and other HEDP basic science research.In th...

show abstract

Dynamics of Heterogeneous Liners with Prolonged Plasma Creation

Cited by 102 publications

References 21 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

Shock-less interactions of ablation streams in tungsten wire array z-pinches

Optical Thomson Scattering Measurements of Plasma Parameters in the Ablation Stage of Wire ArrayZPinches

Contact Info

Product

Resources

About