Investigation of signal readout methods for the Hamamatsu R8500 flat panel PSPMT

Pulse processing efficiency is among the most important parameters to maximize when designing effective systems for positron emission tomography (PET) applications. As the activity of the positron source increases, the attainable processing efficiency is often limited by the increased probability of pulse pileup. Various techniques have been proposed to read out position-sensitive multiwire or multianode photomultiplier tubes (PSPMTs) that trade resistance to pulse-pileup against the simplicity (and cost) of the readout method. Light spreading onto the detector surface also affects the choice of readout method for multianode tubes. Four methods for readout of signals are compared for the H8500 Hamamatsu multianode PSPMT. The first combines signals from the entire device surface; the second scheme implements readout of signals from four separate quadrants. The third scheme, proposed by Majewski et al., is based on row and column readout. We propose a fourth, and new, readout scheme based on a geometrical arrangement of overlapping square sectors. We show that this solution reduces pulse pileup yet requires a relatively small number of output signal lines to determine the energy and position of each scintillation event.