  The dynamics of vortex lattices in stirred Bose-Einstein condensates have
been studied at finite temperatures. The decay of the vortex lattice was
observed non-destructively by monitoring the centrifugal distortions of the
rotating condensate. The formation of the vortex lattice could be deduced from
the increasing contrast of the vortex cores observed in ballistic expansion. In
contrast to the decay, the formation of the vortex lattice is insensitive to
temperature change.
