  Conceived to host 5 kg of xenon at a pressure of 15 bar in the fiducial
volume, the NEXT- White (NEW) apparatus is currently the largest high pressure
xenon gas TPC using electroluminescent amplification in the world. It is also a
1:2 scale model of the NEXT-100 detector scheduled to start searching for
$\beta\beta 0\nu$ decays in 136Xe in 2019. Both detectors measure the energy of
the event using a plane of photomultipliers located behind a transparent
cathode. They can also reconstruct the trajectories of charged tracks in the
dense gas of the TPC with the help of a plane of silicon photomultipliers
located behind the anode. A sophisticated gas system, common to both detectors,
allows the high gas purity needed to guarantee a long electron lifetime.
NEXT-White has been operating since October 2017 at the Canfranc Underground
Laboratory (LSC), in Spain. This paper describes the detector and associated
infrastructures.
