Abstract
As muons which are a major component of cosmic rays at the ground level have strong penetrating ability, they are possibly utilized as a radiation source for non-destructive inspection of large materials or geological survey.
To examine the feasibilities of them, we developed a cosmic ray measuring system using the coincidence counting method with two largearea plastic scintillators. After some fundamental tests, cosmic ray angular distribution (for zenith angle) measurement was made in an underground tunnel. The data obtained well represented the topography above the tunnel.
