ИСТИНА

Despite the efforts of numerous experiments with different components of extensive air showers (EAS) in the last decades, the uncertainty in the all nuclei spectrum of primary cosmic rays is still high and the results on chemical composition of primary cosmic rays from different experiments contradict each other. This study presents the results of the baloon-borne SPHERE experiment on the energy spectrum and mass composition of primary cosmic rays in the 5-100 PeV energy range. The experiment is based on registration of Vavilov-Cherenkov radiation from EAS reflected from the snow surface and features a quasicontinuous sensitive area, absolute calibration of the detector and an event-by-event control of its sensitivity. The new approach to EAS measurements and data analysis allows to separate several groups of primary nuclei.