This system consists of the one presently used in NOMAD and located at the
end of its apparatus, complemented by an additional muon detector to provide
coverage at large angles.
The latter is necessary to enhance the identification of positive muons
accompanying negative charmed particles produced by 
.
The present system consists of 
drift chambers each made
of two planes of vertical and two planes of horizontal drift tubes.
The detectors are assembled in modules of two chambers.
The first muon detection station consists of three modules and
is placed behind the hadron calorimeter.
It is followed by an 80 cm thick iron absorber and a second muon station of two modules.
The chambers are operated with a 40-60 Argon-Ethane mixture and have a position
resolution of 450 
.
The magnet return yoke, described above, consists of 8 C's on each side of the magnet each 87.5 cm long along the beam (Fig. 10). Planes of streamer tubes are inserted in the 80 mm gaps between successive C's. These provides muon identification after they traverse part of the iron of the C's. In order to be detected in two successive planes of streamer tubes, a muon must have a momentum of at least 1.4 GeV/c. In the subsequent discussion on the background it has been assumed that muons with momenta greater than 2 GeV/c are identified. Fitting the 7 gaps with single planes of streamer tubes would result in a 5152 channel system of standard technology. A similar system would be designed to instrument the downstream end of the magnet just behind the hadron calorimeter.