A nuclear emulsion stack, made up of plates, can provide an efficient and background-free detection of the decay topology as well as a large target mass. With this technique, the decay can be visualized and the details of the decay topology (``kink'' in the track) can be studied. A unique feature is the three-dimensional nature of the information provided. Also the availability of extremely fine detail gives full efficiency for the detection of all charged tracks emerging from the reaction, and the possibility of electron identification. This provides a strong rejection of kinks produced in nuclear interactions by hadrons. Nuclear emulsion is the only known technique which can also provide a measurement of the direction and track length of the parent particle. The design follows the methods developed in CHORUS [20].
The emulsion will be scanned by fully automatic microscopes.
The method is to use high precision predictions onto the downstream face of the
emulsion, and to scan back plate by plate.
This method is being used in the CHORUS experiment.
Recent advances in the fast microscope technology have made it possible
to increase the scanning speed to the level that all events can be searched for kinks.
No kinematical preselection of events is necessary, thereby avoiding losses in the
selection process, thus keeping high efficiency for 
events.
A tracker composed of silicon microstrip detectors allows for a high-precision prediction of the event location in the emulsion. In combination with other tracking detectors, they are a powerful ingredient in the event reconstruction and charge and momentum measurement of charged particles. Silicon microstrip detectors combine good time resolution with excellent position and two-track resolution. The high resolution track extrapolation from the silicon detectors to the emulsion target allows to scan a smaller emulsion surface, contributing to effectively reduce the scanning time per event as compared to CHORUS. This experiment uses a configuration similar to the one presently being constructed for the NOMAD-STAR project [40].
The magnetic field, necessary for the determination of the charge of the decay daughter and for momentum analysis of all charged particles, is provided by the UA1 magnet, presently in use in the NOMAD experiment [21].
The large surface tracking detection inside the magnetic field is provided by honeycomb chambers, with a design similar to the tracking planes recently installed in the CHORUS apparatus [51]. These detectors are needed for pattern recognition, charge and momentum determination and muon identification.
Part of the present instrumentation of the NOMAD experiment, such as the electromagnetic calorimeter, external muon identification and hadron calorimeter will be reused. Additional chambers inside the magnet yoke extend the identification of muons to the large-angle region.