  The COBRA demonstrator, a prototype for a large-scale experiment searching
for neutrinoless double beta-decay, was built at the underground laboratory
Laboratori Nazionali del Gran Sasso (LNGS) in Italy. It consists of an array of
64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid
design and a total mass of 380g. It is used to investigate the experimental
challenges faced when operating CdZnTe detectors in low-background mode, to
identify potential background sources and to show the long-term stability of
the detectors. The first data-taking period started in 2011 with a subset of
the detectors, while the demonstrator was completed in November 2013. To date,
more than 250kg d of data have been collected. This paper describes technical
details of the experimental setup and the hardware components.
