Would the 'Ion implant' be that accurate since the hydrogen diffuses so rapidly through the target material?
Details, details.
Assuming a circular beam, you might get a central uniform spot, with a radial fall-off.
Of course, all this looks as though it's exploring bulk effects, rather than a cruddy surface/crack effect.
If the beam is narrow enough you could steer it in a raster pattern to get a map of activity vs surface SEM structures before and after.
