PMT measurements in Antares

The comparison of simulated and real data in the Antares experiment shows some discrepancies. Differences are observed in the charge distribution of background hits, in the trigger efficiency, and in the counting rate of 40K decay induced events. These discrepancies must be understood to improve data analysis. It turns out that most of the simulated/real data mismatch can be explained by a undetailed description of the PMT response in the simulations. PMT parameters such as late pulses, afterpulses and angular acceptance have been reviewed and when necessary measurements of these parameters have been carried out using Antares PMTs and optical modules. In addition a more detailed simulation of the angular acceptance of the Antares optical module has been performed. Results of these studies are presented.