Treating the Gain Non-Uniformity of Multi Channel PMTs by Channel-Specific Trigger Levels

This paper presents a readout method for multi channel PMTs in scintillation detectors. Especially in larger systems the complete readout of each individual channel signal is not feasible. Often it is sufficient to generate binary position information indicating the channel that delivered the signal. The analog pulse is still provided by the PMT's last dynode and requires only one processing channel per PMT. If a general trigger threshold is used for all anodes of the PMT, the typically strong variations in the channel gains may cause problems because channels will differ strongly in their sensitivity. An individual adjustment of the trigger levels solves this problem and can completely equalize the sensitivities.