EMMA – a new underground cosmic-ray experiment

A new cosmic-ray experiment is under construction in the Pyhäsalmi mine, Finland. It aims to study the (mass) composition of cosmic rays at and above the knee region. The array, called EMMA, will cover approximately 150 m2 of detector area at a depth of 85 metres (∼240 mwe). It is capable of measuring the multiplicity and the lateral distribution of underground muons and the arrival direction of the air shower. The full-size array is expected to be ready by the end of 2007. A partial-size array (one third of the full size) is planned to record data already at the first quarter of 2007. It is also expected that the array is capable of measuring such high-multiplicity muon bundles that were observed at the cosmic-ray experiments at the LEP detectors.