Recent results on dense Z pinches

Hammel, J.E.; Scudder, D.W.; Shlachter, J.S.

doi:10.1016/0167-5087(83)90233-8

Cited by 39 publications

(36 citation statements)

References 6 publications

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“…It might at first be thought that discharging a current into a solid fiber would lead to a high density Z pinch. However, it is difficult to raise the current field fast enough to satisfy the Haines-Hammel curve, 27,28 and the coronal plasma explodes. Thus some Z pinches implode and others explode.…”

Section: Historymentioning

confidence: 98%

The past, present, and future of Z pinches

et al. 2000

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The Z pinch is enjoying a renaissance as the world's most powerful yet efficient soft x-ray source which can energize large volume hohlraums for indirectly driven inertial confinement fusion. It has the advantages of being efficient and having high energy and power density. Its early history will be traced from the 18th century to the present day. The most notable feature of the Z pinch is its instability. The various regimes of stability analysis will be reviewed, including resistive and finite ion Larmor radius effects. Work in the last 10 years on single fibres, especially of cryogenic deuterium, gave neutrons that were of the same origin, namely, beam-plasma interactions, as reported by Kurchatov. The renaissance has come about through the implosion of arrays of fine wires. Research at Sandia National Laboratory has shown that by using more and finer wires, the x-ray radiation emitted at stagnation increased in power and decreased in pulse width. The understanding of these results has been advanced considerably by theory, simulation and smaller-scale, well diagnosed experiments showing the early uncorrelated mϭ0 instabilities on each wire, the inward jetting of plasma to the axis, the global Rayleigh-Taylor instability and the mitigating effect of nested arrays.

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Section: Historymentioning

confidence: 98%

The past, present, and future of Z pinches

et al. 2000

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“…Initially (1977 -1984) experiments were conducted in a configuration referred to as a laser-initiated, gas-embedded Z-pinch (Hammel et al, 1983). A large (25 cm radius) load chamber at the output of a conventional electron-beam type pulsed power machine was filled with D2 gas at 1 atm pressure.…”

Section: Los Alamos Dense Z-pinch Plasma Programmentioning

confidence: 99%

BBO-crystal optical parametric oscillator tunable over the 300 — 2340 nm range and pumped by the 4th harmonic of a Nd:YAG laser

Kondratyuk¹,

Shagov²,

Demidchik³

et al. 2000

Quantum Electron.

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The Los Alamos Dense Z-Pinch program has recently completed construction of a new, high current (1.2 MA) pulsed power device for ohmically heating :>lid deuterium fibers and studying the dynanucs of these dense, magnetically confined plasmas. Experiments to date have been performed at half maximum bank energy (1OOkJ) and half current (650kA) with fiber diameters of -20 pm. Peak current is achieved in 100 ns in this three stage machine. A variety of optical, x-ray, neutron, and electrical diagnostics are employed to examine the plasma arameters. Motivation for these experiments, experimental results, and the program for Eture work are presented in this paper.

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“…tot . 2 The further extent of relaxation to a force-free, minimumenergy state is being computed. Figure 4 shows an average (B iotz ) over the outer wall, with S = 150, 500, and 1500.…”

Section: Gary D Doolen and Leaf Turnermentioning

confidence: 99%

Turbulent Relaxation to a Force-Free Field-Reversed State

et al. 1986

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The evolution of nonequilibrium initial conditions of an incompressible magnetohydrodynamic Z pinch is described by a three-dimensional, pseudospectral numerical code. Magnetohydrodynamic turbulence develops in the resistive, nonviscous magnetofluid, resulting in the selective decay of the energy relative to the magnetic helicity, at Lundquist numbers of only a few hundred. An interior force-free region grows with time and achieves spontaneous reversal of the toroidal magnetic field at the wall, without the necessity of an external electric field.PACS numbers: 52.55. Ez, 52.65. +z Theoretical or computational treatments of magnetohydrodynamic (MHD) pinches usually have been described in terms of the evolution of unstable normal modes of laminar equilibria. However, the formation of Z pinches can be violent, and there may be regimes in which laminar equilibrium conditions are never a good initial approximation. 1 " 3 The nonlinear evolution of the resulting magnetic and velocity fields is of interest. In explaining Z-pinch behavior, it has been conjectured 4 ' 6 that the resulting MHD turbulence leads to a "selective decay" 7 " 10 of energy relative to magnetic helicity. This idea has received some numerical support in two dimensions, 8 * 9 with axisymmetry, 10 and in three dimensions 1112 (see the recent review by Hasegawa 13 ). The physical bases of "selective decay" turbulent processes have been presented in Refs. 7-10 and 13.The nature of selective decay becomes clear from the spectral representations of the two ideal invariants, energy and magnetic helicity. The former derives a higher fraction of its contributions from the larger wave numbers, where the dissipation occurs, and so is more affected by the decay of the short-spatial-scale expansion coefficients. The result is a decrease in ratio of the energy to magnetic helicity. At the lower limit of this ratio, a "force-free" state results. 14 For high enough currents, and a given toroidal magnetic flux, this implies reversal of the toroidal component of the magnetic field near the outer wall, 4 " 6 thought to be desirable for the achievement of quiescence and confinement.We report nonlinear MHD turbulence computations of evolving Z pinches which achieve spontaneous self-reversal of the toroidal magnetic field at the wall. The computation does not contain (1) external electric fields, (2) initial regions of diminished toroidal flux near the wall ("aided" reversal), or (3) finite compressibility. We use broad-band-noise initial conditions not close to an equilibrium and a Lundquist number S of a few hundred. There is no viscous stress. Related, but significantly different, computations have been reported by Sykes and Wesson 11 ; Aydemir and Barnes 15 ; Schnack, Caramana, and Nebel 16 ; Werley, Nebel, and Wurden 17 ; and Horiuchi and Sato. 18 The present calculation is closest to that of Aydemir and Barnes 15 and Horiuchi and Sato. 12 Our novel features include (1) a demonstrable connection between field reversal and selective decay to a forcefree state; (2) m...

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Recent results on dense Z pinches

Cited by 39 publications

References 6 publications

The past, present, and future of Z pinches

The past, present, and future of Z pinches

BBO-crystal optical parametric oscillator tunable over the 300 — 2340 nm range and pumped by the 4th harmonic of a Nd:YAG laser

Turbulent Relaxation to a Force-Free Field-Reversed State

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