  A fusion boundary-plasma domain is defined by axisymmetric magnetic surfaces
where the geometry is often complicated by the presence of one or more
X-points; and modeling boundary plasmas usually relies on computational grids
that account for the magnetic field geometry. The new grid generator INGRID
(Interactive Grid Generator) presented here is a Python-based code for
calculating grids for fusion boundary plasma modeling, for a variety of
configurations with one or two X-points in the domain. Based on a given
geometry of the magnetic field, INGRID first calculates a skeleton grid which
consists of a small number of quadrilateral patches; then it puts a subgrid on
each of the patches, and joins them in a global grid. This domain partitioning
strategy makes possible a uniform treatment of various configurations with one
or two X-points in the domain. This includes single-null, double-null, and
other configurations with two X-points in the domain. The INGRID design allows
generating grids either interactively, via a parameter-file driven GUI, or
using a non-interactive script-controlled workflow. Results of testing
demonstrate that INGRID is a flexible, robust, and user-friendly
grid-generation tool for fusion boundary-plasma modeling.
