Cosmic rays, which we cannot see or feel, are constantly bombarding Earth without us noticing. A tube filled with Helium gas is biased by axial and coaxial electrodes. When the Muon collides with the gas, it will locally ionize the Helium. The free charges will rush to the surface, due to the electric field, ionizing more Helium along the way. From this ionization we are able to read out a signal whenever a muon strikes the detector.