The Yakutsk extensive air shower array studies cosmic rays of extremely high energies above 10 PeV, i.e. in the field of cosmic ray astrophysics, an active area at the cutting edge of basic research. The main goals in the construction of this array were: i) the investigation of cascades of elementary particles in atmosphere initiated by primary cosmic rays (=particles); ii) reconstruction of astrophysical properties of the primaries – intensity, energy spectrum, mass composition and their origin.
Detection of Extensive Air Showers of Cosmic Rays
When a primary energetic particle reaches Earth’s atmosphere, it collides with a nucleus, producing secondary particles, which share the original primary particle's energy. These secondaries successively create new generations of particles, i.e. extensive air shower, which arrives at ground level as billions of energetic particles extending over tens of square kilometers (schematically illustrated in figure).
One method to detect such a shower is to create an array of particle detectors on the ground. That is the case of the Yakutsk array. Other methods are used by the Fly’s Eye detector group, Pierre Auger observatory, etc. In our case charged particles are detected by scintillators on the ground, muons are detected by scintillators shielded with soil layer, and Cherenkov light emitted in air by relativistic electrons is observed by photomultiplier tubes (PMT). Coincident signals from detectors are shower indicators.