A new experiment to observe gamma rays around 100 TeV at Yanbajing (4300 m) in Tibet, China is planned by a collaboration between China and Japan. To study the feasibility of this experiment a test array was built at Mt. Norikura in Japan. Preliminary results from a search for gamma rays from Cyg X-3 and Her X-1 observed by this air shower array showed the upper limit fluxes of 5.6 × 10-13cm-2s-1 and 3.0 × 10-13cm-2s-1 with a 95% confidence level above TeV, respectively. At the first step experiment we will set up 65 scintillation counters in Tibet. An angular resolution of the apparatus will be better than 1° at an energy of 100 TeV. The detectors are monitored by a nitrogen laser system automatically which guarantees a long term quality of the data.
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