April 4-6

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Author: Eric Held
Requested Type: Poster
Submitted: 2022-03-04 11:46:06

Co-authors: J. Andrew Spencer, Tyler Markham, Joseph Jepson

Contact Info:
Utah State University
4415 Old Main Hill
Logan,   84322-4

Abstract Text:
Recent work has led to improvements to NIMROD's implementation of continuum drift kinetic closures for extended MHD simulations of magnetically confined plasmas. Enhanced efficiency and accuracy of the collision operator[1] and the use of finite elements in pitch-angle with vertex nodes at the trapped-passing boundary[2] have made 4D (2 space, 2 velocity space), hybrid fluid/kinetic simulations with NIMROD fairly routine. Testing of the kinetic fluid coupling in axisymmetric geometry is underway both for bulk electrons and relativistic sub-populations of runaway electrons (REs). In this work we compare and contrast the bulk versus RE models both in terms of their kinetic treatments and their coupling to NIMROD's evolving fluid model. Axisymmetric results for the bootstrap current tied to the bulk electron closures and preliminary 4D simulations of a low-density RE population are presented.

This research is supported by the U.S. Department of Energy grant nos. DE-FG02-04ER54746 and DE-SC0018146.

[1] J. A. Spencer, et. al., J. Comput. Phys., 450, 110862 (2022).
[2] J. R. Jepson, et. al., Phys. Plasmas, 28, 082503 (2021).