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IACT stands for Imaging Atmospheric (or Air) Cherenkov Telescope  or Technique.   It is a device or method to detect very high energy gamma-ray photons in...
Official Full-Text Publication: Imaging Atmospheric Cherenkov Telescope on ResearchGate, the professional network for scientists.
arXiv:0907.4975. The reflector used by an imaging atmospheric Cherenkov telescope (IACT) consists of a tessellated array of mirrors mounted on a large frame.
Frascati Physics Series Vol. nnn (2001), pp. 000-000 IX Int. Conf. on Calorimetry in Part. Phys. - Annecy, Oct. 9-14, 2000 IMAGING ATMOSPHERIC CHERENKOV TELESCOPE