It is the aim of this experiment to reach a sensitivity for 
oscillation which is at least an order of magnitude better than that
achieved in present experiments.
Therefore,
an increase of the event rate by a similar factor must be achieved
while retaining a negligible background.
As a consequence, the background rejection must also improve by an
order of magnitude.
A baseline design will be described for a detector capable of reaching the above goals. This design adopts a conservative approach implementing well known and proven techniques. The design is based on the experience accumulated in the CHORUS and NOMAD experiments. It exploits the basic ideas described in the introduction, as derived from studies as in [33] and [34] and discussed in the recent Workshops at CERN.
This design calls for a hybrid detector with a massive target composed of nuclear emulsion followed by high precision silicon microstrip detectors, both placed in a magnetic field and surrounded by an efficient muon detection system. These choices will be justified below.
Optional optimizations will also be explored. It is expected that these will make it possible to enhance the sensitivity of the experiment by increasing the efficiency or the ability to implement more target mass. Some of the features adopted in these approaches need to be supported by results of test experiments, planned to be performed at the CERN PS in September 1997.