We are adding a prototype detector module to the emulsion hybrid detector set-up to obtain experience with this novel technique. This module will be composed of 20 um diameter fibres oriented transverse or parallel to the incident beam, see figure 15a,b.
Figure 15: Transverse and parallel orientations of the fibre target.
Our specifications require a minimum of 4 detectable hits/mm on tracks crossing the far end of the fibre target. This requirement is based on a study of pattern recognition using Monte Carlo methods, which indicates that a vertex resolution of about 10 um and a reconstruction probability of tau-decay kinks of about 20% are possible, using fibres of 20 um diameter [12, 13].
The mass of the 150 cm long prototype module is ~ 1 kg and should be sufficient to collect a sample of neutrino interactions which will enable us to test the analysis chain, including pattern recognition and kink detection efficiency.
We envisage using blocks of glass capillaries filled with liquid scintillator [12, 13]. Our investigations show that in capillaries filled with liquid scintillator reflection loss give attenuation lengths larger than 1 m. The presently developed technology allows to produce submodules with sizeable dimensions (2 x 2 x 150 cm3). Suitable liquid scintillators with high refractive index have been optimised for small self absorption and high light output.