  EXO-200 is an experiment designed to search for double beta decay of
$^{136}$Xe with a single-phase, liquid xenon detector. It uses an active mass
of 110 kg of xenon enriched to 80.6% in the isotope 136 in an ultra-low
background time projection chamber capable of simultaneous detection of
ionization and scintillation. This paper describes the EXO-200 detector with
particular attention to the most innovative aspects of the design that revolve
around the reduction of backgrounds, the efficient use of the expensive
isotopically enriched xenon, and the optimization of the energy resolution in a
relatively large volume.
