Do PI coils.............

[Anonymous]

Have a cone shaped beam of detection or a soild beam?

 

[Anonymous]

On most targets, most metal detector coils have a response pattern that is somewhere between conical and hemispherical. The actual response pattern depends on what kind of target, its orientation, the type of searchcoil, etc.
No metal detector has a "solid beam" shaped detection zone. If you're thinking of a picture you may have seen in a Minelab advertisement, that's "artistic license" and not technical information.
--Dave J.