Crystal Array

CALO is made of about 7500 LYSO cubes arranged into an octagonal prism, which corresponds to from all directions 55 radiation lengths and 3 Nuclear Interaction Lengths. Large statistics of cosmic rays up to PeV energy is then feasible, and high energy resolution of high energy particles is also guaranteed. Each crystal has a side length of 3 cm and the space in between crystals is strictly limited for a better energy reconstruction.

Each crystal is readout by two wavelength shifting fibers on both ends. The four fiber ends, acting as a low range fiber, a high range fiber and two trigger fibers, are routed to a low range Intensified sCMOS (IsCMOS) camera, a high range IsCMOS camera, and two trigger systems, respectively.