An optical readout for a fiber tracker

The performance of 16 and 64 channel photomultipliers coupled to scintillating fibers has been tested. The devices are sensitive to single photoelectrons, show little gain losses for magnetic fields up to 100 G and have moderate optical cross-talk. The maximum channel-to-channel gain variations reach a factor two for the 16 channel version and a factor of four for the 64 channel PM. The measurements and simulations indicate that the photomultipliers are well suited for the light detection in fiber trackers.