Characterization of a new multianode PMT for optical fiber readout at low-level light intensity

We have characterized the new Hamamatsu R5900-L16 multianode photomultiplier with regard to its suitability for charge division position-sensitive readout with just two analog channels for each 16-anode PMT. Because of the low capacitance of the anode structure of the PMT, we obtain an output pulse width of less than 20 ns in response to narrow LED input pulses. We were able to obtain position-sensitive readout of light pulses corresponding to a single photoelectron with a spatial width of less than 1 mm FWHM for a collimated light source and of about 2 mm FWHM for a single fiber. Combined with the good single photoelectron peak for the R5900-L16, this provides excellent performance at very low-level light intensity. We discuss application of this device to the precise determination of gamma-ray interaction position within thin crystal scintillators.