In contrast to the muon detectors of the KASCADE array that count muons by measuring their energy deposit of the muons, the MTD measures muon tracks through a position-resolving detector.
A tunnel of size 5.5m x 48m houses a detector consisting of 3
horizontal layers of limited streamer
tubes where each layer covers an area of 128 mē. Additional
vertical detector-modules along the sides of the setup increase the
solidangle for the detection of inclined tracks.
The background of electrons and gammas is reduced by an absorber of about 18 radiation lengths concrete, iron and soil.
By measuring the coordinates in 3 layers, it is possible to reconstruct the tracks of (mostly charged) particles that cross the detector. As the detector is placed under the absorber, those particles are mostly muons and low-energetic electrons and gammas produced in the absorber. Particles whose tracks lead straight through the detector and have a direction similiar to that of the airshower (as determined by the array detectors of KASCADE) are identified as muons.
The following 2 pictures show the active detectors within the MTD tunnel. To increase the numbers of particles that can be reconstructed the whole detector is divided into separate modules of 2 m by 4 m size:
KASCADE - MTD Interna