ИСТИНА

Some new developments in EAS method made in the framework of Pamir-XXI project are presented. First, primary energy and direction definition accuracies by an network of fast scintillators are considered, optimum network cell size is defined for 10 PeV showers. Second, the same accuracies for a network of fast optical (Cherenkov) detectors are considered for 30 TeV — 10 PeV showers. Third, the possibilities of separation of EAS initiated by protons, nitrogen and iron nuclei of 1 and 10 PeV using wide-angle Cherenkov telescope are discussed. At last, the results of the extraction of 30-50 TeV gamma showers from the proton shower background with the same telescope are presented. Presumably, our developments can help in the study of PCR mass composition and ultra high energy gamma ray astronomy in other projects.