Fine vacuum gridding leads to numerical instability

[matt-pharr]

Vacuum does not automatically adjust the number of grid points it counts as "near the singularity" for the purpose of separating the singularity into a non-singular and an analytic term. This means that when the number of poloidal grid points gets sufficiently high, we start getting points close enough to the singularity that they start blowing up and the accuracy starts to suffer. This was originally noticed by Stuart Benjamin, I believe. A solution to this may be to adjust the number of designated singular points based on the number of poloidal grid points.

[jhalpern30]

@matt-pharr is there a known equilibrium/resolution where this bug appears and/or a script that reproduces and plots it? i.e. "Solovev ideal example when mtheta > 2048". Ok if not, but don't want to repeat work tracking one down