A SCINTILLATING TILE HODOSCOPE WITH WLS FIBER READOUT

We describe the construction and performance of a hodoscope consisting of 127 hexagonal scintillating tiles covering hermetically a surface of about 1 m diameter. Each tile is read out on one face by five wavel ength-shifting (WLS) fibres that are embedded and glued into the surfa ce of the scintillator. The fibres serve the double purpose of primary light collection and subsequent light transmission to high gain photo multipliers located outside the active hodoscope area. Each individual tile detects the passage of a minimum ionizing particle with an effic iency > 99%. Taking into account the small gaps due to the light-light wrapping of each tile, the global efficiency of the hodoscope is grea ter than or equal to 98%. As a test beam application of this detector, we present measurements of the albedo from a compensating lead/scinti llating fibre calorimeter which was installed behind the scintillating tile hodoscope.