WILLI-EAS, a detector for observing atmospheric and EAS muons

Abstract

The central part of WILLI - EAS is a compact calorimeter type detector set up for measuring the inclusive flux and the charge ratio of atmospheric muons in various directions of muon incidence. A mini array EAS is added and going to be operated for registering extensive air showers in order to study the muon charge ratio in EAS as affected by the geomagnetic field. The observed muon charge ratio measured for incident muons with energy 0.4 GeV, show a diurnal modulation of the muon flux. The analysis of the muon events for energies < 0.6 GeV reveals an aperiodic variation of the muon flux. The WILLI detector has been extended to WILLI-EAS with 12 detector stations arranged as an rray. Simulations studies of the muon charge ratio for the correlated EAS, (initiated by H and Fe primaries, with energies in a range 10 13 eV - 10 15 eV), show detailed effects of the direction of EAS incidence relative to the geomagnetic field, depending, in particular, of the primary mass.