Low power high dynamic range photomultiplier bases for the surface detectors of the Pierre Auger observatory

Abstract Design, tests and production methods of the photomultiplier bases for the surface detectors of the Pierre Auger Observatory are presented. The voltage divider is a purely resistive chain including a low consumption high voltage power supply. Two different output sensitivities have been obtained by using the anode and the last amplified dynode outputs. The charge ratio between the anode and the amplified dynode is around 32. The design ensures the stability of the gain and of the base line for events made of several pulses over a long time duration (up to 20 μs) and a total charge ranging from a few to 6×10 5 photoelectrons (typical value: a few thousands) with a peak photocathode current of up to 200 nA. The pre-production, test and mounting on photomultipliers of 200 bases has been carried out. The total production is 5000 pieces.