Preliminary study of a topological trigger device for cosmic-ray detectors

In view of implementing a topological trigger criterion in cosmic-ray detectors for efficient selection of required events a preliminary test has been done with a scintillating-fibre hodoscope using a position-sensitive photomultiplier. A space resolution of ∼0.6 mm in σ with a detection efficiency >97% has been obtained for charged particles of 5 GeV/c passing through 2×2 mm squared fibres. A custom-made discriminator, suppressing the cross-talk between adjacent fibres, allowed a better definition of track position even at high incident angles compared to the simple threshold discriminators. Simplicity as well as reliability of the prototype allow us to foresee a topological trigger device incorporated in different type of detectors, such as cosmic gamma or electron telescopes, solar neutron detectors and so on.