  Ground-level particle detection is now a well-established approach to TeV
gamma-ray astronomy. Detection of Cherenkov light produced in water-filled
detection units is a proven and cost-effective method. Here we discuss the
optimization of the units towards the future Southern Wide-field Gamma-ray
Observatory (SWGO). In this context, we investigate a new type of configuration
in which each water Cherenkov detector (WCD) unit in the array comprises two
chambers with black or reflective walls and a single photomultiplier tube (PMT)
in each chamber. We find that this is a cost-effective approach that improves
the performance of the WCD array with respect to current approaches. A shallow
lower chamber with a PMT facing downwards enables muon tagging and the
identification of hadron-induced air showers, which are the primary source of
background in gamma-ray astronomy. We investigate how gamma/hadron separation
power and achievable angular resolution depend on the geometry and wall
reflectivity of the detector units in this configuration. We find that
excellent angular resolution, background rejection power and low-energy
response are achievable in this double-layer configuration, with the aid of
reflective surfaces in both chambers.
