Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

Journal Article · 13 June 2017 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.4985320 · OSTI ID:1485499

Subramaniam, Vivek ^[1]; Raja, Laxminarayan L. ^[1]

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1. Univ. of Texas, Austin, TX (United States). Dept. of Aerospace Engineering and Engineering Mechanics

Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this paper, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and the resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the gener- ation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. Finally, this also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.

• Research Organization: Stanford Univ., CA (United States); Univ. of Texas, Austin, TX (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0002011
• OSTI ID: 1485499
• Alternate ID(s): OSTI ID: 1363706; OSTI ID: 1363884
• Journal Information: Physics of Plasmas, Vol. 24, Issue 6; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English