A 16 channels NIM module for pure LaBr3 and LaBr3-NaI phoswich detectors

Fast scintillation detectors based on Lanthanum Bromide (LaBr3) crystals are nowadays used in nuclear physics experiments, mainly to measure γ-ray energy and time information. The Milano group has developed a 10 large volume (3.5″×8″) LaBr3 detector array (HECTOR+) and collaborates to a a γ-calorimeter based on tens of LaBr3-NaI phoswich detectors (PARIS). A dedicated 16 channels NIM analog module handling these photomultiplier detector signals has been developed in order to satisfy the experimental requests of both detector arrays. Each channel of the module provides two shaped signals, the 'Slow Out' proportional to the total energy of the γ ray and the 'Fast Out' proportional to the fast negative peak of the signal. For phoswich (LaBr3-NaI) detectors, the analysis of the two dimensional spectrum (fast versus slow) allows to disentangle the interactions in different part of the detector. If used with a pure LaBr3 detector, the Fast output can be switched as a second energy output. An independent gain control of this second output allows to have a wide energy range. For each channel there is also a constant fraction discriminator (CFD) which generates the time information. Slow control of the module parameters such as gain, CFD thresholds, width of logic signals, etc. is possible through a RS485 serial line.