ИСТИНА

Here is presented the current state of the SPHERE-2 balloon-borne experiment. The detector is elevated up to 1 km above the snow surface and registers the rejected Vavilov-Cherenkov radiation from extensive air showers. This method has good sensitivity to the mass composition of the primary cosmic rays due to its high resolution near the shower axis. The detector consists of a 1500 mm spherical mirror with a 109 PMT cluster in its focus. The electronics record a signal pulse profile in each PMT. Measurements in 2012 showed high sensitivity of the method to chemical composition of primary cosmic rays. Characteristics for more than 300 events of EAS were reconstructed. For increase in quantity of events in March, 2013 an additional series of measurements for better reliability of results was carried out.