  We study theoretically the lifetime of magnetically trapped atoms in the
close vicinity of a type-II superconducting surface, in the context of
superconducting atom-chips. We account for the magnetic noise created at the
cloud position by the vortices present in the superconductor and give specific
results for our experiment which uses a niobium film. Our main result is that
atom losses are dominated by the presence of vortices. They remain however
dramatically smaller than in equivalent room-temperature atom-chip setups using
normal metals.
