Title: Kinetic simulations of sheared flow stabilization in high-temperature Z-pinch plasmas

Abstract

We present that the first fully kinetic particle-in-cell (PIC) simulations of sheared flow stabilized Z-pinch plasmas show the suppression of the sausage instability by shear, ∂_rv_z ≠ 0, with flow Mach numbers ≲1, consistent with experimental observations. Experimental investigations of sheared-flow stabilized Z-pinches demonstrated stability for 10 s of microseconds, over 1000 Alfvén radial transit times, in quasi steady-state plasmas that are an intermediate between conventional inertial and magnetic confinement systems. The observed stability coincides with the presence of radial shear in axial flow profiles with peak speeds less than Mach 1, and experiments are underway to validate scaling this design to fusion conditions. The experimentally observed stability agrees with models of m = 1 kink mode suppression by sheared flows, but existing models of the m = 0 sausage mode underestimate the efficacy of sheared flow stabilization. These models rely on fluid approximations and find that stabilization requires flows ranging from Mach 1.7 to 4.3, and in some cases, stabilization is not reproduced in the models. This is faster than the measured flows in long-lived plasmas and would necessitate substantial energy convection out of the Z-pinch and the need to drive and sustain supersonic flows in future devices. Themore » MHD models typically used in the literature are invalid in the high-temperature, high-current environments desirable for many Z-pinch applications, and they ignore large Larmor radius effects and viscous dissipation which are known to impact Z-pinch stability. PIC simulations can capture all these effects as well as kinetic instabilities that could influence the performance of high-temperature sheared flow stabilized Z-pinch plasmas. The PIC simulations presented here show the suppression and damping of m = 0 modes by sheared flows ∂_rv_z = 0.75v_A/r₀ with flow Mach numbers ≲1. Lastlyl, equivalent stability occurs under plasma conditions ranging from the limits of present-day experimental capabilities to the projected conditions of a sheared flow stabilized Z-pinch reactor.« less

Authors:

Tummel, K. ^[1]; Higginson, D. P.  ^[1];

• Search DOE PAGES for author "Higginson, D. P."
• Search DOE PAGES for ORCID "0000-0002-7699-3788"

Link, A. J. ^[1]; Schmidt, A. E. W. ^[1]; Offermann, D. T.  ^[2];

• Search DOE PAGES for author "Offermann, D. T."
• Search DOE PAGES for ORCID "0000-0002-6033-4905"

Welch, D. R. ^[2]; Clark, R. E. ^[2]; Shumlak, U.  ^[3];

• Search DOE PAGES for author "Shumlak, U."
• Search DOE PAGES for ORCID "0000-0002-2918-5446"

Nelson, B. A. ^[3]; Golingo, R. P. ^[3]; McLean, H. S.  ^[1]

• Search DOE PAGES for author "McLean, H. S."
• Search DOE PAGES for ORCID "0000-0002-1884-9980"

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+ Show Author Affiliations

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Voss Scientific, LLC, Albuquerque, NM (United States)
3. Univ. of Washington, Seattle, WA (United States)

Publication Date:

Thu Jun 13 00:00:00 EDT 2019

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE Advanced Research Projects Agency - Energy (ARPA-E)

OSTI Identifier:

1544963

Alternate Identifier(s):

OSTI ID: 1526092

Report Number(s):

LLNL-JRNL-767536
Journal ID: ISSN 1070-664X; 957144

Grant/Contract Number:  

AC52-07NA27344; AR0000571

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 26; Journal Issue: 6; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY