Solid Light Concentrators for Cherenkov Astronomy

Pixelized cameras of Imaging Atmospheric Cherenkov Telescopes use hollow light guides with reflective surfaces that are based on the Winston cone design. These cones minimize insensitive spaces between the photo sensors and shield the camera from stray background light by limiting the angular acceptance to the primary reflector area. Raytracing simulations comparing different geometries and materials were performed. Especially in combination with the favourable angular acceptance properties of Geiger-mode Avalanche Photodiodes as used in the FACT Project, these simulations show that solid cones based on total reflection allow larger concentration ratios than the classical hollow cones for the price of additional background light. Simulation results for different geometries and test measurements with hollow and glass cones will be presented.