  The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a
ground-based instrument designed to study astrophysical sources of gamma
radiation in the energy range of 50 to 500 GeV. STACEE uses an array of large
heliostat mirrors at the National Solar Thermal Test Facility in Albuquerque,
New Mexico, USA. The heliostats are used to collect Cherenkov light produced in
gamma-ray air showers. The light is concentrated onto an array of
photomultiplier tubes located near the top of a tower. The construction of
STACEE started in 1997 and has been completed in 2001. During the 1998-99
observing season, we used a portion of the experiment, STACEE-32, to detect
gamma-rays from the Crab Nebula. The completed version of STACEE uses 64
heliostat mirrors, having a total collection area of 2300 m^2. During the last
year, we have also installed custom electronics for pulse delay and triggering,
and 1 GHz Flash ADCs to read out the photomultiplier tubes. The commissioning
of the full STACEE instrument is underway. Preliminary observations and
simulation work indicate that STACEE will have an energy threshold below 70 GeV
and a reach for extragalactic gamma-ray sources out to redshift of ~1.0. In
this paper we describe the design and performance of STACEE.
