April 15-17

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Abstracts

Author: Mike F Martin
Requested Type: Poster
Submitted: 2019-02-22 16:02:30

Co-authors: Matt Landreman

Contact Info:
University of Maryland
A.V. Williams Bldg. Rm. 3324
College Park, Maryland   20742
United States

Abstract Text:
Quasisymmetric stellarator configurations aim to combine the stability of stellarators with the confinement of tokamaks. However, perfect quasisymmetry can only be achieved on a single flux surface at best. It is therefore useful to study configurations with small deviations from perfect quasisymmetry. A particular phenomenon that occurs in tokamaks, which are naturally quasisymmetric, is a favorable outward radial flux of highly charged impurity ions, commonly referred to as impurity temperature screening. Conversely, stellarators generally display an inward impurity flux, causing an impurity accumulation in the core that can be detrimental to performance. In this work, we use the SFINCS drift-kinetic solver to explore how the impurity particle flux is influenced as the degree of symmetry-breaking is varied between realistic levels and perfect quasisymmetry, over various parameter regimes and configurations. We aim to answer the question of exactly how much symmetry-breaking a particular configuration can tolerate before impurity temperature screening is lost.

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