when is Fam (E) a topos?

A couple of days ago I made the wrong claim that

If BB is a topos and P : XX -> BB is a fibration then P is a fibration of toposes iff XX is a topos and P is a logical functor.

The following shows how wrong this claim is. Let E be a topos then Fam(E) -> Set is certainly a fibered topos but by Th.6.2.3 of Pieter Hofstra's Thesis Fam(E) is a topos iff E is an atomic category (in the sense of Johnstone's 1977 book on Topos Theory, exercise 12 on p. 257). But in atomic categories all morphisms are epic and thus Fam(E) is a topos only if E is trivial. Thus, for the motivating examples of fibred toposes the total category is a topos only in the trivial case! Thomas [For admin and other information see: http://www.mta.ca/~cat-dist/ ]