Characterization of multi-pixel PMTs

The MINOS experiment is a long baseline neutrino oscillation experiment (~730 km), designed to search for neutrino oscillations down to 1.5×10^-3 eV² and measure oscillation parameters. It will employ two detectors, one at Fermilab, and a second one in the Soudan Mine in Minnesota. Both detectors will be constructed with alternating planes of iron and scintillator. The scintillator planes will be made of extruded plastic scintillator strips with wavelength-shifting fibers which are read out by multi-anode photomultipliers. The near detector will use 64-pixel R5900-00-M64 tubes while the (5.4 kton) far detector will use 16-pixel R5900-00-M16 tubes, both manufactured by Hamamatsu Photonics K.K. Each M16 tube will read out 8 optically multiplexed fibers per pixel. We have performed a series of comprehensive tests of these photomultipliers specially optimized for MINOS. We report on results of our studies of main characteristics of M64 and M16 tubes with an emphasis on gain, linearity, uniformity, and cross-talk, for a range of average light fluxes varying from a fraction of a photoelectron to hundreds of photoelectrons, correspondingly