Layout of the HAWC Observatory
The HAWC observatory uses water Cherenkov detectors (or "tanks") to observe particles from air showers. The detector contains 300 tanks in total, with 3 peripheral and 1 central photomultiplier tube (PMT) per tank. Hence, the observatory's main array comprises 1200 PMTs in total. The optical isolation of the PMTs between tanks reduces the noise rate in the detector. This is an important consideration at high altitude, where the flux of low-energy cosmic rays is quite large.
The layout of the HAWC detector is shown in the figure above. The building in the center of the array is the Counting House, which contains the data acquisition system, online computing farm, and laser calibration system of the detector. Buried coaxial cables run from the Counting House to each tank, providing high voltage and receiving signal from the photomultipliers. The large white rectangle on the right side of the image is the HAWC Utility Building (HUB), which contains the water filtration plant for the Cherenkov detectors.
The ground under the HAWC array has been graded with an excavator to ensure that the detector is level. Once the HAWC since program is complete (approximately 10 years after commissioning) the site will be returned to its natural state.