  COSINE is a dark matter search experiment based on an array of low background
NaI(Tl) crystals located at the Yangyang underground laboratory. The assembly
of COSINE-100 was completed in the summer of 2016 and the detector is currently
collecting physics quality data aimed at reproducing the DAMA/LIBRA experiment
that reported an annual modulation signal. Stable operation has been achieved
and will continue for at least two years. Here, we describe the design of
COSINE-100, including the shielding arrangement, the configuration of the
NaI(Tl) crystal detection elements, the veto systems, and the associated
operational systems, and we show the current performance of the experiment.
