A Three-Class Imaging Atmospheric Cherenkov Array: Threshold, Effective Area and Sensitivity Computed from Photon Statistics

A computed design is presented for a ground-based gamma-ray observatory of 99 imaging atmospheric Cherenkov telescopes in three size classes. Energy thresholds follow from the fluctuation of night-sky background light inside one camera pixel during the trigger gate, scaled by mirror area and pixel size: 25 GeV for the four 23 m telescopes, 86 GeV for the twenty-five 12 m telescopes and 334 GeV for the seventy 4.3 m telescopes. Near 1 TeV the array effective area is 1.20e+06 square metres, and a counting model with 9,000 residual background events in a 50-hour exposure gives a differential sensitivity of 0.94 percent of the Crab Nebula flux, or 2.82e-13 per square centimetre per second per TeV, with 0.06 degree angular resolution. The installation totals 2,022 tonnes and 0.71 MW. Every figure is computed from the stated photon-statistics model; the design is simulated, not measured.