Dense Z-Pinches

Haines, M. G.

doi:10.1007/978-94-011-4758-3_1

Cited by 4 publications

(5 citation statements)

References 20 publications

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“…Assuming that the electrodes are perfect conductors and that at this time there is a current short across the AK gap the magnetic flux can only decay if the line integral K A E z dz along the axis is non-zero. If only axisymmetric m = 0 modes are present, and if the resistivity is negligible then this can only be achieved if there are many hot spots formed on the axis with a component of number density variation out of phase with the temperature variation [389]. A contribution from electron viscosity through the electron stress in Ohm's law might be important.…”

Section: = 0 Instabilities and Ion-viscous Heatingmentioning

confidence: 99%

“…Thus on the axis when the axial electric field has convected or diffused in (perhaps anomalously quickly by the vortices of the fine scale m = 0 instabilities discussed in section 5.8) the electron distribution function could be very non-Maxwellian. In the presence of fine-scale instabilities and viscous heating, the rapid conversion of magnetic energy to thermal energy will be accompanied by a greatly enhanced E z field, and hence enhanced Ettingshausen advection of hotter particles to the axis, leading to hot spots and runaway electrons [395].…”

Section: Atomic Physicsmentioning

confidence: 99%

“…Thus viscosity dominates over resistivity (S R) in contrast to Kroupp where R(∼ 10 4 ) S(∼ 90). A discussion of the distinction between viscous and resistive Z-pinches and the role of numerical viscosity in simulations is to be found in [395].…”

Section: Gas-puff Z-pinchmentioning

confidence: 99%

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A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

390

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: = 0 Instabilities and Ion-viscous Heatingmentioning

confidence: 99%

Section: Atomic Physicsmentioning

confidence: 99%

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A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

390

184

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“…Theory at the time [5] suggested that the cool, collapsed pinch might be resistively stabilized against violent MHD instability (sausage and kink modes) since the magnetic Reynolds number, the ratio of diffusion time to Alfven wave time scales, could be fairly small. While the final pinch might be stabilized, the collapse could be expected (and observed) to remain unstable so that high density could only occur in very localized regions.…”

Section: Fast Ignitionmentioning

confidence: 99%

Alternative Approaches to High Energy Density Fusion

Hammer¹

2016

Edward Teller Lectures

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Abstract. This paper explores selected approaches to High Energy Density (HED) fusion, beginning with discussion of ignition requirements at the National Ignition Facility (NIF). The needed improvements to achieve ignition are closely tied to the ability to concentrate energy in the implosion, manifested in the stagnation pressure, P stag . The energy that must be assembled in the imploded state to ignite varies roughly as P stag -2 , so among other requirements, there is a premium on reaching higher P stag to achieve ignition with the available laser energy. The U.S. inertial confinement fusion program (ICF) is pursuing higher P stag on NIF through improvements to capsule stability and symmetry. One can argue that recent experiments place an approximate upper bound on the ultimate ignition energy requirement. Scaling the implosions in spatial, temporal and energy scales shows that implosions of the demonstrated quality ignite robustly at 9-15 times the current energy of NIF. While lasers are unlikely to reach that bounding energy, it appears that pulsed power sources could plausibly do so, giving a range of paths forward for ICF depending on success in improving energy concentration. In this paper, I show the scaling arguments then discuss topics from my own involvement in HED fusion. The recent Viewfactor experiments at NIF have shed light on both the observed capsule drive deficit and errors in the detailed modelling of hohlraums. The latter could be an important factor in the inability to achieve the needed symmetry and energy concentration. The paper then recounts earlier work in Fast Ignition and the uses of pulsed power for HED and fusion applications. It concludes with a description of a method for improving pulsed power driven hohlraums that could potentially provide a factor of 10 in energy at NIF-like drive conditions and reach the energy bound for indirect drive ICF.

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“…In addition to its fundamental importance (see, e.g., original papers 1-4 and reviews 5,6 ) it has also a number of applications, especially in fusion research, e.g., Refs. 7-9 and in radiation generation, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

Evolution of helical perturbations in a thin-shell model of an imploding liner

Ryutov

Dorf

2014

Physics of Plasmas

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A thin-shell model of the liner stability has been revisited and applied to the stability of the helical perturbations. Several stages of the implosion have been identified, starting from a long initial "latent" phase of an almost resting liner, continuing to the second stage of a rapid contraction and significant perturbation growth, and then transitioning to the third stage where perturbations become ballistic and highly non-linear. The stage of stagnation and rebound is beyond the scope of this paper. An importance of vorticity conservation during the late stages is emphasized. Nonlinear evolution of perturbations is followed up to the point of the formation of cusp structures. Effects of in-surface flows and of their enhancement due to the vorticity conservation are discussed. It is shown that the pre-machined perturbations created only on the outer surface of the liner grow much slower than one could anticipate. The limitations on the thin-shell description are discussed. V C 2014 AIP Publishing LLC.

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Dense Z-Pinches

Cited by 4 publications

References 20 publications

A review of the denseZ-pinch

A review of the denseZ-pinch

Alternative Approaches to High Energy Density Fusion

Evolution of helical perturbations in a thin-shell model of an imploding liner

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