Ablation Studies of Low-Number Wire Arrays at 200 kA Using A Linear Transformer Driver

Bott, S. C.; Haas, David M.; Eshaq, Y.; Ueda, U.; Madden, R.; Collins, Gilbert; Beg, F. N.

doi:10.1109/tps.2009.2034166

Cited by 13 publications

(5 citation statements)

References 21 publications

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“…These features are discussed by Mazarakis et al [476]. Already small LTD experiments are being undertaken in universities: Bott et al [477] have made ablation studies of low number wire arrays at currents of 200 kA employing laser imaging techniques to measure the wavelength of the axial density variations and ablation velocities. A larger LTD-driven Z-pinch is being commissioned at the University of Michigan [478], while a load current multiplier is being tested at the University of Nevada [479].…”

Section: Technology Of Pulsed Power; Longer Pulsesmentioning

confidence: 99%

A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

387

184

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The Z-pinch, perhaps the oldest subject in plasma physics, has achieved a remarkable renaissance in recent years, following a few decades of neglect due to its basically unstable MHD character. Using wire arrays, a significant transition at high wire number led to a great improvement in both compression and uniformity of the Z-pinch. Resulting from this the Z-accelerator at Sandia at 20 MA in 100 ns has produced a powerful, short pulse, soft x-ray source >230 TW for 4.5 ns) at a high efficiency of ∼15%. This has applications to inertial confinement fusion. Several hohlraum designs have been tested. The vacuum hohlraum has demonstrated the control of symmetry of irradiation on a capsule, while the dynamic hohlraum at a higher radiation temperature of 230 eV has compressed a capsule from 2 mm to 0.8 mm diameter with a neutron yield >3 × 10 11 thermal DD neutrons, a record for any capsule implosion. World record ion temperatures of >200 keV have recently been measured in a stainless-steel plasma designed for Kα emission at stagnation, due, it was predicted, to ion-viscous heating associated with the dissipation of fast-growing short wavelength nonlinear MHD instabilities. Direct fusion experiments using deuterium gas-puffs have yielded 3.9×10 13 neutrons with only 5% asymmetry, suggesting for the first time a mainly thermal source. The physics of wire-array implosions is a dominant theme. It is concerned with the transformation of wires to liquid-vapour expanding cores; then the generation of a surrounding plasma corona which carries most of the current, with inward flowing low magnetic Reynolds number jets correlated with axial instabilities on each wire; later an almost constant velocity, snowplough-like implosion occurs during which gaps appear in the cores, leading to stagnation on the axis, and the production of the main soft-x-ray pulse. These studies have been pursued also with smaller facilities in other laboratories around the world. At Imperial College, conical and radial wire arrays have led to highly collimated tungsten plasma jets with a Mach number of >20, allowing laboratory astrophysics experiments to be undertaken. These highlights will be underpinned in this review with the basic physics of Z-pinches including stability, kinetic effects, and finally its applications.

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Section: Technology Of Pulsed Power; Longer Pulsesmentioning

confidence: 99%

A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

387

184

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“…These include hydrodynamic jet experiments, in both adiabatic [10][11][12][13][14] and radiatively cooled [15][16][17][18] regimes, and experiments relevant to the study of the interaction of protostellar jets with an ambient medium [19][20][21] far away from the jet source.…”

Section: Introductionmentioning

confidence: 99%

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

et al. 2010

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We present experimental results of the formation of magnetically driven plasma jets, showing for the first time a way of producing episodic jet/ouflows in the laboratory. The jets are produced using a 6.5 µm thick aluminum disc (a radial foil), which is subjected to the 1 MA, 250 ns current pulse from the MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533(1996]. The early time motion of the foil is characterized by the bulk motion of the mass due to the magnetic pressure, together with the formation of a surface plasma following the direction of the J × B force. A low density plasma fills the region above the foil preceding the formation of subsequent magnetically driven jets on the axis of expanding magnetic bubbles. The outflows emerge in timescales of ∼30-40 ns and their episodic nature is the result of current reconnection in the foil, aided by the formation of current-driven instabilities in the jet and the distribution of mass available from the foil. The additional inductance due to the new current path inside the cavities was measured using an inductive probe, allowing to estimate the energy balance associated with the episodes. The measured temperature of the compressed jet resulted in Te∼300 eV and a magnetic Reynolds number of ReM ∼200-1000, allowing the experiments to be in the regime relevant for scaled representations of astrophysical outflows.

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“…Such experiments are planned on the 250 kA, 150 ns GenASIS machine at University of California, San Diego. 17 Controls of the dimensionless parameters in Table I can also be gained by modifying the array setup, and simple changes can optimize the experimental parameters for specific regimes.…”

Section: Discussionmentioning

confidence: 99%

Bow shocks in ablated plasma streams for nested wire array z-pinches: A laboratory astrophysics testbed for radiatively cooled shocks

et al. 2010

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Astrophysical observations have demonstrated many examples of bow shocks, for example, the head of protostellar jets or supernova remnants passing through the interstellar medium or between discrete clumps in jets. For such systems where supersonic and super-Alfvénic flows and radiative cooling are all important, carefully scaled laboratory experiments can add insight into the physical processes involved. The early stage of a wire array z-pinch implosion consists of the steady ablation of material from fine metallic wires. Ablated material is accelerated toward the array axis by the J ϫ B force. This flow is highly supersonic ͑M Ͼ 5͒ and becomes super-Alfvénic ͑M A Ͼ 2͒. Radiative cooling is significant in this flow and can be controlled by varying the material in the ablated plasma. The introduction of wires as obstructions in this steady flow leads to the formation of bow shocks, which can be used as a laboratory testbed for astrophysical bow shocks. The magnetic field associated with this obstruction wire can be controlled by varying the current through it. Differences in the shock for different cooling rates and different magnetic fields associated with the obstruction will be discussed, along with comparisons of dimensionless parameters in the experiments to astrophysical systems.

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Ablation Studies of Low-Number Wire Arrays at 200 kA Using A Linear Transformer Driver

Cited by 13 publications

References 21 publications

A review of the denseZ-pinch

A review of the denseZ-pinch

Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

Bow shocks in ablated plasma streams for nested wire array z-pinches: A laboratory astrophysics testbed for radiatively cooled shocks

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