Structure and dynamics of magneto-inertial, differentially rotating laboratory plasmas

Journal Article · 08 October 2024 · Journal of Plasma Physics

DOI: https://doi.org/10.1017/S0022377824000710 · OSTI ID:2460579

Valenzuela-Villaseca, V. ; Suttle, L. G. ; Suzuki-Vidal, F. ; Halliday, J. W. D. ; Russell, D. R. ; Merlini, S. ; Tubman, E. R. ; Hare, J. D. ; Chittenden, J. P. ; Koepke, M. E. ; Blackman, E. G. ; Lebedev, S. V.

We present a detailed characterization of the structure and evolution of differentially rotating plasmas driven on the MAGPIE pulsed-power generator (1.4 MA peak current, 240 ns rise time). The experiments were designed to simulate physics relevant to accretion discs and jets on laboratory scales. A cylindrical aluminium wire array Z pinch enclosed by return posts with an overall azimuthal off-set angle was driven to produce ablation plasma flows that propagate inwards in a slightly off-radial trajectory, injecting mass, angular momentum and confining ram pressure to a rotating plasma column on the axis. However, the plasma is free to expand axially, forming a collimated, differentially rotating axial jet that propagates at $${\approx }100\,{\rm km}\,{\rm s}^{-1}$$ . The density profile of the jet corresponds to a dense shell surrounding a low-density core, which is consistent with the centrifugal barrier effect being sustained along the jet's propagation. We show analytically that, as the rotating plasma accretes mass, conservation of mass and momentum implies plasma radial growth scaling as $$r \propto t^{1/3}$$ . As the characteristic moment of inertia increases, the rotation velocity is predicted to decrease and settle on a characteristic value $${\approx }20\,{\rm km}\,{\rm s}^{-1}$$ . We find that both predictions are in agreement with Thomson scattering and optical self-emission imaging measurements.

• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0003764; SC0020434
• OSTI ID: 2460579
• Journal Information: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 4 Vol. 90; ISSN 0022-3778
• Publisher: Cambridge University Press (CUP)Copyright Statement
• Country of Publication: United Kingdom
• Language: English