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

Plastic scintillator tiles of 7 mm × 8 mm cross section with an embedded green wavelength shifting fiber form the elements of an x−y 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 Phillips 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 μm 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.