A high efficiency tile-fiber hodoscope read out by multichannel phototubes

Plastic scintillator tiles of 7 mm x 8 mm cross section with an embedded green wavelength shifting fiber form the elements of an x-v hodoscope to be used in the g-2 experiment at Brookhaven. The fibers are read out through 1.5 m clear fibers by a new ''low crosstalk'' design of the Philips multi-channel photomultiplier tube XP1723/D1. An average light yield of 30 photoelectrons are produced in a standard bialkali tube per minimum ionizing particle. Detection efficiencies of 98.6% averaged across an assembled plane can be completely accounted for by the measured 110 mu m of paint thickness between elements. Data is presented on the light yield and attenuation of the hodoscope elements; the crosstalk, uniformity, and fast gating of the multichannel tubes; and the overall performance of the device in a test beam.