Simultaneous Air Shower and Deep Muon Observations at Soudan

Recently, a few groups1 have made attempts to simultaneously measure the electromagnetic and deep underground muon components of cosmic ray showers. This is one such experiment, using a small proportional tube surface air shower detector in coincidence with the Soudan 2 nucleon decay detector. It has run since June, 1991, and some 22 000 events which triggered both detectors have been recorded. This body of data may provide insight into the composition of cosmic rays in the “knee” area of the cosmic ray spectrum.