Statistical current monitor for the cosmic ray experiment Pierre Auger

The air fluorescence telescopes are one essential part of the Pierre Auger Project, currently under construction in Argentina. They observe fluorescence light induced by cosmic ray extensive air showers passing through the atmosphere with a pixel camera of 440 photomultiplier tubes (PMT). In this paper we report on a method to monitor the DC anode current in each PMT by statistical analysis of the signal fluctuations. The method has the advantage that no extra components are required and there is no distortion of the PMT signal induced. We present details of the design of the current monitor and results on the performance gained by measurements in the prototype phase.