Ion Viscous Heating in a Magnetohydrodynamically Unstable<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math>Pinch at Over<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>9</mml:mn></mml:msup></mml:math>Kelvin

Haines, M. G.; LePell, P.D.; Coverdale, C. A.; Jones, B.; Deeney, C.; Apruzese, J. P.

doi:10.1103/physrevlett.96.075003

Cited by 87 publications

(66 citation statements)

References 15 publications

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“…It is clear that our optimistic estimation of jxB input energy does not explain the total x-ray yield. This is not particularly surprising; the same observation has been previously made for cylindrical wire array implosions [41,42], with proposed explanations including additional plasma compression and PdV work post-stagnation [43], m=0 [44,45,46] or m=1 [10] instabilities enhancing resistive or inductive energy deposition, and Hall effect enhancements in Ohmic heating [9]. It is interesting that the calculated coupled energy comes close to explaining the total yield for the highest mass case, while it does not even explain the yield to peak x-rays for the lightest load.…”

Section: Chapter 3 Discussion Of Experimental Resultsmentioning

confidence: 51%

Planar wire array performance scaling at multi-MA levels on the Saturn generator.

Chuvatin

Jones²,

Vesey³

et al. 2007

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A series of twelve shots were performed on the Saturn generator in order to conduct an initial evaluation of the planar wire array z-pinch concept at multi-MA current levels. Planar wire arrays, in which all wires lie in a single plane, could offer advantages over standard cylindrical wire arrays for driving hohlraums for inertial confinement fusion studies as the surface area of the electrodes in the load region (which serve as hohlraum walls) may be substantially reduced. In these experiments, mass and array width scans were performed using tungsten wires. A maximum total radiated x-ray power of 10±2 TW was observed with 20 mm wide arrays imploding in ∼100 ns at a load current of ∼3 MA, limited by the high inductance. Decreased power in the 4-6 TW range was observed at the smallest width studied (8 mm). 10 kJ of Al K-shell x-rays were obtained in one Al planar array fielded. This report will discuss the zero-dimensional calculations used to design the loads, the results of the experiments, and potential future research to determine if planar wire arrays will continue to scale favorably at current levels typical of the Z machine. Implosion dynamics will be discussed, including x-ray self-emission imaging used to infer the velocity of the implosion front and the potential role of trailing mass. Resistive heating has been previously cited as the cause for enhanced yields observed in excess of jxB-coupled energy. The analysis presented in this report suggests that jxBcoupled energy may explain as much as the energy in the first x-ray pulse but not the total yield, which is similar to our present understanding of cylindrical wire array behavior.4 Acknowledgment

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Section: Chapter 3 Discussion Of Experimental Resultsmentioning

confidence: 51%

Planar wire array performance scaling at multi-MA levels on the Saturn generator.

Chuvatin

Jones²,

Vesey³

et al. 2007

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“…the kinetic energy goes to zero in the center-of-mass system. In the second class, both (18), (19), (20) and (21) apply, and internal energy plays no independent role. The first class is discussed in Sec.…”

Section: The Scatteringmentioning

confidence: 99%

“…The contributions of η // and η ⊥ to P J add up to j · η (J) · j where RT ene provide also a vanishing contribution, in the limit of vanishing gradients of T and p e ∝ n e T . As for R f , the amplitude of magnetic fluctuations it takes into account is ∝ (|k|L) −1 where k is the wavenumber of the fluctuations [19]; if R f = 0 then (5) reduces to the well-known case discussed in [12]. In the following we assume |k|L ≫ 1, then we neglect R f (for instance, large-|k| modes play a crucial role at the birth of a plasmoid in the ionosphere [20]).…”

Section: ≈ 10mentioning

confidence: 99%

“…Before (after) the collision, the centers of mass of 1 and 2 move at velocity +v C z (−v C z) and −v C z (+v C z) respectively. In this head-on collision, relevant conservation laws are concerned with total mass, energy, magnetic flux and component of momentum along z; these 4 independent relationships correspond to the 4 independent equations (18), (19), (20) and (21).…”

Section: The Scatteringmentioning

confidence: 99%

“…Generally speaking, relaxation 8 to Taylor's state requires some level of turbulence [32]; turbulence-induced ion heating is therefore possible beyond collisional viscous effects, and P v may be affected. According to [50], this ion heating is fed by |k|L ≈ 10 2 MHD instabilities with wavenumber k whenever…”

mentioning

confidence: 99%

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On super-elastic collisions between magnetized plasmoids in the heliosphere

Vita

2018

Eur. Phys. J. D

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Recently, a unique collision between two large-scale magnetized plasmoids produced by coronal mass ejections in the heliosphere has been observed [C. Shen et al., Nature Physics 8, 923-928 (2012)]. Results suggest that the collision is super-elastic, i.e. the total linear kinetic energy of the two plasmoids after the collision is larger than before the collision, and that an anti-correlation exists, i.e. the lower the initial relative velocity of the plasmoids, the larger the relative increase in total kinetic energy. The problemCoronal mass ejections (CMEs) give birth to large-scale plasmoids, originating from the solar atmosphere and expanding and propagating into the heliosphere [1] [2]. The occurrence rate of CMEs is about 4-5 CMEs per day at solar maximum [3], so that encounters and interactions between plasmoids are unavoidable. Nevertheless, inter-plasmoid collisions are far from understood. While collisions between blobs of ordinary gases are heavily affected by mixing, cross-field diffusion is effectively prohibited by sufficiently strong magnetic field.Experiments show that initially well-distinct plasmoids preserve their identity after a collision; historically, these experiments led to the very definition of 'plasmoid' as a 'plasma magnetic entity' with well-distinguished identity and geometrical structure [4]. In the lab, conventional magnetohydrodynamics fails to provide adequate macroscopic description of isolated plasmoids [5] -let alone their mutual interaction. In space, such description requires detailed knowledge of energy balance and state equation [2].Recent observation of a collision between plasmoids [1] suggests that such collisions may be superelastic, i.e. the total linear kinetic energy of the colliding plasmoids after the collision is larger than before the collision. A similar phenomenon is observed in collisions of spheres with elastoplastic plates, where rotational kinetic energy may be transferred into linear kinetic energy [6]. This analogy suggests that the linear kinetic energy in collisions between plasmoids may increase at the expense of the energy of some other degree of freedom, and magnetic energy is an obvious candidate. A preliminary investigation of energy balance supports this point of view; moreover, it has been suggested that the lower the impact velocity, the larger the relative increase of the linear kinetic energy [1]; in contrast, if the relative velocity of colliding plasmoids is too large, then no elastic scattering occurs [7], and the plasmoids may merge into each other.The aim of this work is to investigate this suggestion. We invoke the analogy [8] between plasmoids in the lab and space plasmoids and show how recent progress [5] [9] in the analytical description of the former provide information on the latter. In particular, we show that quantities usually invoked in Hall MHD [10] lead to a simple macroscopic description of interacting plasmoids. Some relevant properties of our plasmoids are discussed in Sec. 2. Secs. 3 and 4 discuss the structure...

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Introduction

2011

High‐Intensity X‐Rays – Interaction With Matter

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Ion Viscous Heating in a Magnetohydrodynamically UnstableZPinch at Over2×109Kelvin

Cited by 87 publications

References 15 publications

Planar wire array performance scaling at multi-MA levels on the Saturn generator.

Planar wire array performance scaling at multi-MA levels on the Saturn generator.

On super-elastic collisions between magnetized plasmoids in the heliosphere

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