In order to provide a precise track extrapolation from the drift chamber target to the calorimeter, five drift chambers were embedded in the TRD, one after each TRD doublet and one after the last module.
The active target was a set of drift chambers with a fiducial mass of about 2.7 tons and a low average density (99 kg/[m.sup.3]) comparable to liquid hydrogen.
Moving downstream along the beam direction came a veto counter, a front calorimeter, a large active target consisting of drift chambers, a transition radiation detector, a preshower, an electromagnetic calorimeter, a hadron calorimeter, and an iron filter consisting in the return-yoke of the magnet followed by a set of large drift chambers used for muon identification.
The momentum resolution provided by the drift chambers was a function of momentum and track length.
In this case the resolution was worse and electron energies were measured by combining information from the drift chambers and the electromagnetic calorimeter.
Most neutrino interactions in the NOMAD active target occurred in the passive panels of the drift chambers. Interaction vertices were reconstructed by extrapolating the tracks of charged secondary interaction products.
The NOMAD muon detector consisted of 10 drift chambers previously used in the UA1 experiment.
The ions are gated into a drift chamber where they are accelerated toward a collector electrode.
Different ion species are identified by measuring the time for them to reach the collector electrode at the end of the drift chamber. When each group of identical ions reach the end of the chamber they register on a plasmagram that measures their number as well as the retention time in milliseconds that they took to travel through the chamber.