Characterizing the Plasmas of Dense $Z$ -Pinches

Ryutov, D. D.

doi:10.1109/tps.2015.2453265

Cited by 39 publications

(14 citation statements)

References 89 publications

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“…Magnetic reconnection is the rapid change of magnetic field topology in a plasma, accompanied by bulk heating and particle acceleration [1,2]. Reconnection is a ubiquitous process which occurs across a vast region of parameter space, including the collisionless plasmas at the heliopause [3] and the dense, hot plasmas deep in the solar convection zone [4,5]. Understanding of magnetic reconnection has improved over the years thanks to dedicated laboratory experiments.…”

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confidence: 99%

Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

et al. 2017

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We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields (B ¼ 3 T), advected by supersonic, subAlfvénic carbon plasma flows (V in ¼ 50 km=s), are brought together and mutually annihilate inside a thin current layer (δ ¼ 0.6 mm). Temporally and spatially resolved optical diagnostics, including interferometry, Faraday rotation imaging, and Thomson scattering, allow us to determine the structure and dynamics of this layer, the nature of the inflows and outflows, and the detailed energy partition during the reconnection process. We measure high electron and ion temperatures (T e ¼ 100 eV, T i ¼ 600 eV), far in excess of what can be attributed to classical (Spitzer) resistive and viscous dissipation. We observe the repeated formation and ejection of plasmoids, consistent with the predictions from semicollisional plasmoid theory. DOI: 10.1103/PhysRevLett.118.085001 Magnetic reconnection is the rapid change of magnetic field topology in a plasma, accompanied by bulk heating and particle acceleration [1,2]. Reconnection is a ubiquitous process that occurs across a vast region of parameter space, including the collisionless plasmas at the heliopause [3] and the dense, hot plasmas deep in the solar convection zone [4,5]. Our understanding of magnetic reconnection has improved over the years thanks to dedicated laboratory experiments. In facilities like MRX [6][7][8] and TREX [9] the magnetic energy is much larger than the other plasma energy components. In contrast, laser-driven high energy density experiments are strongly driven-the kinetic and thermal energies are much larger than the magnetic energy [10,11], and reconnection heating is small [12].In this Letter we present experimental studies of high energy density magnetic reconnection driven by a new pulsed-power platform. The reconnection layer was created by the interaction of magnetized plasma flows in a quasi-2D geometry, which we studied using high resolution, nonperturbative measurements of the temperature, flow velocity, electron density, and magnetic field in the reconnection layer. The colliding plasma flows were supersonic (M s ∼ 1.6) but sub-Alfvénic (M A ∼ 0.7), and therefore the thermal and dynamic plasma betas (ratio of the thermal or ram pressure to the magnetic pressure) are close to unity (β th ∼ 0.7, β dyn ∼ 0.9). These parameters are significantly different from those found both in magnetically driven experiments, such as MRX, and in laser driven experiments, and we believe our experiments are the first to make a detailed study of this regime. We observed the formation of a reconnection layer with an aspect ratio of L=δ > 10, which existed for at least ten hydrodynamic flow times δ=V in , where L is the layer half length and δ is the layer half width [ Fig. 1(a)]. The annihilation of the magnetic flux caused strong plasma heating in the reconnection layer (T i ≈ 600 eV,ZT e ≈ 600 with T e ≈ 100 eV in a carbon plasma with average ionizationZ ≈ 6)...

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Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

et al. 2017

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“…Note that if impurities from the liner are magnetized, they will be similarly expelled from the hotspot by the same mechanisms as the ash. This tendency was observed in mixed-magnetization impurity transport simulations for a non-compressing, wall-confined plasma, where the impurity distribution was found to peak near the point of marginal magnetization Ω I τ IH ∼ 1 [20,23]. The peaking occurs because near the wall, where the impurities are not magnetized, the thermal forces act oppositely.…”

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confidence: 81%

“…For this choice of parameters, D 0a = 0.68 and S 0a σv 0a = 0.087, while at the core D 0h = 0.1 and S 0h σv 0h = 0.24. This is on the slower and higher-field end for MagLIF stagnation parameters [20], which we adopt to make sure that our orderings Ω I τ IH > 1 and ρ I /a 1 remain valid throughout most of the plasma for the duration of the simulation; at t = 0, r = a, we have Ω I τ IH = 2.1 and ρ I /a = 0.012. The brief periods at the beginning and end during which the edge plasma is unmagnetized should not have a substantial impact on the results, since (a) the majority of the plasma is more magnetized than the edge, and (b) most reactions occur near maximal compression, when the edge plasma is magnetized.…”

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Favorable Collisional Demixing of Ash and Fuel in Magnetized Inertial Fusion

Ochs

Fisch

2018

Phys. Rev. Lett.

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Magnetized inertial fusion experiments are approaching regimes where the radial transport is dominated by collisions between magnetized ions, providing an opportunity to exploit effects usually associated with steady-state magnetic fusion. In particular, the low-density hotspot characteristic of magnetized liner inertial fusion results in diamagnetic and thermal frictions which can demix thermalized ash from fuel, accelerating the fusion reaction. For reactor regimes in which there is substantial burnup of the fuel, increases in the fusion energy yield on the order of 5% are possible. PACS numbers:

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“…The atomic mass was equal to 2. Hence, the temperature equilibration time of electrons and ions was approximately 10 ns, according to the known relation given in [4]. Consequently, at this temperature, density, and dimensions of the structure, we could assume the temperature equilibrium inside the ball-like structures.…”

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Evolution of the small ball-like structures in the plasma focus discharge

et al. 2016

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Abstract. The experiments were carried out in the PF-1000 plasma-focus device at the maximum current reaching about 2 MA, at the deuterium or neon fi lling and with deuterium injected from a gas-puff nozzle placed on the axis of the anode face. Ball-like structures of diameters of 1-12 mm were identifi ed in interferometric and XUV pinhole camera frames. We made the statistical description of their parameters. A lifetime of the ball--like structures was in the range from 30 to 210 ns, and in some cases even more. These structures appeared mostly at the surface of the imploding plasma shell and they did not change their position in relation to the anode end. During the evolution of these structures, interferometric fringes were observed near the surfaces of the structures only, and their internal parts were initially chaotic (without noticeable) fringes. Subsequently the number of interferometric fringes increased (the internal 'chaotic' area was fi lled with fringes too) and later on it decreased. The radii of the ball-like structures were mostly increasing during their existence. The maximum electron density reached the value of 10 24 to 10 25 m -3. The ball-like structures decayed by absorption inside the expanded pinch column and/or gradually expired in rare plasma outside of the dense plasma column.

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Characterizing the Plasmas of Dense $Z$ -Pinches

Cited by 39 publications

References 89 publications

Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

Favorable Collisional Demixing of Ash and Fuel in Magnetized Inertial Fusion

Evolution of the small ball-like structures in the plasma focus discharge

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