  With the development of the Imaging Atmospheric Cherenkov Technique (IACT),
Gamma-ray astronomy has become one of the most interesting and productive
fields of astrophysics. Current IACT telescope arrays (MAGIC, H.E.S.S, VERITAS)
use photomultiplier tubes (PMTs) to detect the optical/near-UV Cherenkov
radiation emitted due to the interaction of gamma rays with the atmosphere. For
the next generation of IACT experiments, the possibility of replacing the PMTs
with Silicon photomultipliers (SiPMs) is being studied. Among the main
drawbacks of SiPMs are their limited active area (leading to an increase in the
cost and complexity of the camera readout) and their sensitivity to unwanted
wavelengths. Here we propose a novel method to build a relatively low-cost
pixel consisting of a SiPM attached to a PMMA disc doped with a wavelength
shifter. This pixel collects light over a much larger area than a single
standard SiPM and improves sensitivity to near-UV light while simultaneously
rejecting background. We describe the design of a detector that could also have
applications in other fields where detection area and cost are crucial. We
present results of simulations and laboratory measurements of a pixel prototype
and from field tests performed with a 7-pixel cluster installed in a MAGIC
telescope camera.
