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Title: Understanding the impact of insulating and conducting endplate boundary conditions on turbulence in CSDX through nonlocal simulations

The Controlled Shear Decorrelation Experiment (CSDX) linear plasma device provides a unique platform for investigating the underlying physics of self-regulating drift-wave turbulence/zonal flow dynamics. A minimal model of 3D drift-reduced nonlocal cold ion fluid equations which evolves density, vorticity, and electron temperature fluctuations, with proper sheath boundary conditions, is used to simulate dynamics of the turbulence in CSDX and its response to changes in parallel boundary conditions. These simulations are then carried out using the BOUndary Turbulence (BOUT++) framework and use equilibrium electron density and temperature profiles taken from experimental measurements. The results show that density gradient-driven drift-waves are the dominant instability in CSDX. However, the choice of insulating or conducting endplate boundary conditions affects the linear growth rates and energy balance of the system due to the absence or addition of Kelvin-Helmholtz modes generated by the sheath-driven equilibrium E × B shear and sheath-driven temperature gradient instability. Moreover, nonlinear simulation results show that the boundary conditions impact the turbulence structure and zonal flow formation, resulting in less broadband (more quasi-coherent) turbulence and weaker zonal flow in conducting boundary condition case. These results are qualitatively consistent with earlier experimental observations.
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [1] ;  [1]
  1. Univ. of California, San Diego, CA (United States). Center for Energy Research
Publication Date:
Grant/Contract Number:
FG02-06ER54871
Type:
Published Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 4; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of California, San Diego, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; turbulent flows; plasma temperature; kelvin helmholtz instability; plasma turbulence; boundary value problems; Newtonian mechanics; ionospheric physics; ionospheric dynamics; magnetospheric dynamics; drift wave instabilities; differential equations; plasma instabilities; plasma interactions; flow instabilities
OSTI Identifier:
1361823
Alternate Identifier(s):
OSTI ID: 1420617; OSTI ID: 1423559