Reduced domain studies of divertor-localized modes in spherical tokamaks*

Instabilities in the divertor legs of spherical tokamaks are of interest for a number of reasons, such as determining the width of the plasma at the divertor plate.  However, such instabilities are challenging to model due to high levels of magnetic shear in this region.  This in turn results in instabilities with fine structures requiring high resolution to model accurately.  One solution to this problem is to construct grids localized to the region of interest.  By modeling such domains using the ArbiTER eigenvalue code, we can determine the structure and mechanism of these instabilities.