Linear analysis of outboard scrape-off layer instability in MAST-U

The ArbiTER¹ linear eigenvalue code is a useful tool for analyzing not only the sources of turbulence and filamentary structures in the scrape-off layer of tokamaks, but also their dynamics and spatial structure.  Past examples include penetration of filamentary structures into the divertor leg in single-null configuration, and analysis of instability in the private scrape-off layer in double-null configuration.

 

In the present work, this code is applied to plasma parameters and magnetic geometry from SOLPS simulations and available data of the scrape-off layer of MAST-U.  A question of particular importance is what effect advanced divertor configurations, such as the super-X, have on instability in the divertor leg.  Another is the role of midplane-localized instability, via penetration of filamentary structures into the divertor leg, as compared to locally-generated instability.  This in turn is affected by the relative role of drift vs. curvature drive.

 

These results will be informative to future divertor designs, particularly with regard to the question of whether magnetic path in the divertor can play a significant role in heat flux width.

 

 

1. D. A. Baver, J. R. Myra and M. V. Umansky, Comm. Comp. Phys. 20, 136 (2016).