On the Role of the Plasma Composition in the Magnetic Field Evolution in Plasma Opening Switches

Osin, D.; Doron, R.; Arad, R.; Tsigutkin, K.; Starobinets, A.; Bernshtam, V.; Fisher, A.; Fruchtman, A.; Maron, Y.; Tauschwitz, A.

doi:10.1109/tps.2004.835941

Cited by 4 publications

(4 citation statements)

References 29 publications

(34 reference statements)

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“…Previous investigations of the POS operation, in which a novel method was implemented for producing plasmas of controllable purity, have been reported on. 47,48 Currently, better control of the plasma composition is pursued 49,50 in the present configuration in order to study the dependence of the phenomena observed here on this parameter. Also, improved doping capabilities should allow for further studying the mechanisms responsible for the ion velocities in the normal directions.…”

Section: Discussionmentioning

confidence: 99%

Investigation of the ion dynamics in a multispecies plasma under pulsed magnetic fields

et al. 2004

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The interaction between a moving magnetic-field front and a low-collisionality plasma consisting of different ion species is investigated using spatially and temporally resolved spectroscopic techniques. The experiment is carried out in a plasma-opening-switch configuration, in which a current rising to 150 kA in 400 ns is conducted through a plasma that prefills the region between two planar electrodes. Ion-species separation is found to occur, similarly to the results reported for a 80 ns duration plasma-opening-switch experiment of cylindrical geometry, which was not necessarily expected since in the present experiment plasma pushing is more substantial. The separation, in which the light-ion plasma (protons) is reflected while the heavy-ion plasma (carbon) is penetrated by the propagating magnetic-field, is investigated by determining the electron density from the temporal evolution of spectral lines, the nonprotonic ion velocities from line-emission Doppler shifts, and the proton velocity distribution from Doppler shifts of line emissions from hydrogen atoms produced by proton charge exchange. The ion dynamics is shown to be consistent with the acceleration expected from the one-dimensional Hall electric field, based on the previously published magnetic-field and electron density evolutions. Significant acceleration of the nonprotonic ions behind the magnetic-field front is observed. It is found that a significant fraction of the protons acquire a velocity that is more than twice the velocity of the magnetic piston. This phenomenon is shown to result from the time dependence of the accelerating electric field and the broad acceleration region. The lateral motion of the nonprotonic ions is also discussed.

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Section: Discussionmentioning

confidence: 99%

Investigation of the ion dynamics in a multispecies plasma under pulsed magnetic fields

et al. 2004

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“…The possibility that the proton reflection is sufficient for generating the instabilities leading to rapid field penetration raises a more general question regarding the role of the plasma composition in the plasma-magnetic field interaction. An effort to study this subject is now under way, 39 and perhaps use of controllable plasma sources ͑e.g., Ref. 45͒ can be considered.…”

Section: Discussionmentioning

confidence: 99%

“…In order to control the plasma composition, we make use of the different times of flight of ions with different charge-to-mass ratios ejected from the flashboard. In this method, 39 we mount the flashboard plasma source 4.5 cm away from the anode ͑instead of 3 cm in the previous setup͒. Due to the larger distance, the faster protons reach the A-K gap earlier than the carbon ions.…”

Section: Electron Density Distributionmentioning

confidence: 99%

Plasma dynamics in pulsed strong magnetic fields

et al. 2004

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Recent investigations of the interaction of fast-rising magnetic fields with multi-species plasmas at densities of 1013–1015 cm−3 are described. The configurations studied are planar or coaxial interelectrode gaps pre-filled with plasmas, known as plasma opening switches. The diagnostics are based on time-dependent, spatially resolved spectroscopic observations. Three-dimensional spatial resolution is obtained by plasma-doping techniques. The measurements include the propagating magnetic field structure, ion velocity distributions, electric field strengths, and non-Maxwellian electron energy distribution across the magnetic field front. It is found that the magnetic field propagation velocity is faster than expected from diffusion. The magnetic field evolution cannot be explained by the available theoretical treatments based on the Hall field (that could, in principle, explain the fast field propagation). Moreover, detailed observations reveal that magnetic field penetration and plasma reflection occur simultaneously, leading to ion-species separation, which is also not predicted by the available theories. A possible mechanism that is based on the formation of small-scale density fluctuations, previously formulated for astrophysical plasmas, may explain these results.

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“…This has the geometry more of a plasma opening switch, and cases could be found where the ions acquired a velocity component perpendicular to the J × B force. In a plasma opening switch geometry Osin et al [676] with 150 kA of 400 ns duration showed a marked difference of behaviour of the two ion species; rapid magnetic field penetration into the heavy-ion plasma and specular reflection of the light-ion plasma, leading to ion-species separation.…”

Section: Multi-species Ion Separationmentioning

confidence: 99%

A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

386

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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On the Role of the Plasma Composition in the Magnetic Field Evolution in Plasma Opening Switches

Cited by 4 publications

References 29 publications

Investigation of the ion dynamics in a multispecies plasma under pulsed magnetic fields

Investigation of the ion dynamics in a multispecies plasma under pulsed magnetic fields

Plasma dynamics in pulsed strong magnetic fields

A review of the denseZ-pinch

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