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The Hall Term and Anomalous Resistivity Effects in Neon Gas-Puff Z-Pinches

A. Rososhek, C. E. Seyler, E. S. Lavine, D. A. Hammer

Abstract

In this paper, we compare experimental and numerical simulation results to benchmark the PERSEUS code against gas-puff $Z$-pinch implosions on COBRA. We then use the code to investigate the structure of the plasma sheath. To this end, we study the morphology of the implosion, focusing on non-magnetohydrodynamical (MHD) effects such as electron drifts governed by the Hall term within the growing magneto-Rayleigh-Taylor instability (MRTI). The spatial wavelength of MRTI is better reproduced when both the Hall term and an anomalous resistivity driven by the electron drift are included. Additionally, cathode-anode gap polarity effects are more accurately captured when the Hall term is turned on. The plasma sheath structure, which includes both the accelerating piston driven by the magnetic pressure and the shockwave ahead of it, matches interferometric measurements in width only when a current-driven anomalous resistivity model is used. This anomalous resistivity is assumed to be driven by the lower-hybrid-drift instability, which generates small-scale turbulence with typical wavelengths < 30μm.

The Hall Term and Anomalous Resistivity Effects in Neon Gas-Puff Z-Pinches

Abstract

In this paper, we compare experimental and numerical simulation results to benchmark the PERSEUS code against gas-puff -pinch implosions on COBRA. We then use the code to investigate the structure of the plasma sheath. To this end, we study the morphology of the implosion, focusing on non-magnetohydrodynamical (MHD) effects such as electron drifts governed by the Hall term within the growing magneto-Rayleigh-Taylor instability (MRTI). The spatial wavelength of MRTI is better reproduced when both the Hall term and an anomalous resistivity driven by the electron drift are included. Additionally, cathode-anode gap polarity effects are more accurately captured when the Hall term is turned on. The plasma sheath structure, which includes both the accelerating piston driven by the magnetic pressure and the shockwave ahead of it, matches interferometric measurements in width only when a current-driven anomalous resistivity model is used. This anomalous resistivity is assumed to be driven by the lower-hybrid-drift instability, which generates small-scale turbulence with typical wavelengths < 30μm.
Paper Structure (5 sections, 1 equation, 5 figures)

This paper contains 5 sections, 1 equation, 5 figures.

Table of Contents

  1. Introduction
  2. Experimental setup
  3. Gas-Puff Z-pinch on COBRA
  4. PERSEUS simulation
  5. Results and Discussion

Figures (5)

  • Figure 1: The measured COBRA current during one experimental compaign along with the current form used in the PERSEUS code run.
  • Figure 2: The typical XUV images representing key morphology features of the Ne GZP experiment on COBRA
  • Figure 3: The PERSEUS simulated density profile cut at the $x=0$ plane, where clockwise starting top left (a) - is the Hall MHD model with anomalous resistivity; (b) - the Hall MHD model with Spitzer resistivity; (c) - the pure MHD model with Spitzer resistivity; (d) - the pure MHD model with anomalous resistivity.
  • Figure 4: The plasma number density distribution cross-section through the plasma column center on a log scale obtained from the same PERSEUS code run. Timings in the top right of each figure indicate the time relative to the stagnation stage onset.
  • Figure 5: The plasma sheath width as a function of time.