The Imaging Air Cherenkov Telescopes (IACTs), like, HESS, MAGIC and VERITAS well demonstrated their performances by showing many exciting results at very high energy gamma ray domain, mainly between 100 GeV and 10 TeV. It is important to investigate
how much we can improve the sensitivity in this energy range, but it is also important to expand the energy coverage and sensitivity towards new domains, the lower and higher energies, by extending this IACT techniques. For this purpose, we have carried out the optimization of the array of large IACTs assuming with new technologies, advanced photodetectors, and Ultra Fast readout system by Monte Carlo simulation, especially to obtain the best sensitivity in the energy range between 10 GeV and 100 GeV. We will report the performance of the array of Large IACTs with advanced technologies and its limitation.
