Measurement of the energy spectrum of primary cosmic rays in the "knee" region (3x1014eV-2x1016eV):
We made a precise measurement of the energy spectrum of primary cosmic
rays in the "knee" region (Fig. 13).
On the other hand, the burst detectors and emulsion chambers set up at the
center of the air shower array preferentially detect high-energy
particles in an air shower event. We can classify primary
cosmic-ray nuclei into several groups according to the energy
and spatial distributions of the high-energy component of an air shower
event detected with the burst detectors and emulsion chambers.
We also measure the total energy of the
event by the air shower array. Therefore, simultaneous observation of
an air shower event by the burst detectors, emulsion chambers and air
shower array gives us the energy spectrum of each group
in primary cosmic rays (Fig. 13). The chemical composition in the ''knee''
region is a crucial key to clarify the mechanism how cosmic rays are
generated, accelerated and propagate to the Earth.
Fig. 13 Energy spectrum of primary cosmic rays in the ''knee'' region.