Anisotropic mesh for spheres

I am working on a project where I would like to have greater refinement in a tight shell about an interface between two concentric spheres. (say, for example, a metal sphere suspended in a spherical vacuum) I thought a sensible approach might be to create the shell using the constructive geometry, and then use an anisotropic mesh to avoid the issue of sharp angles in the narrow shell, but the implementation is not obvious to me. In particular, using CloseSurfaces seems to immediately brick my kernel when I start trying to construct the mesh. Does anyone have any advice for this approach?

Ben Latham

I’m also interested in the problem. Did you manage to solve it?