Analysis of Signal Spectra of Multianode Photo Multiplier Tubes

The signal response of Multianode Photo Multiplier Tubes (MaPMT) is studied. The pulse height spectra of MaPMT are fitted with three different methods. The first method is based on Gaussian distributions for the signal, the second method is based on Poissonian signal distributions and the third approach includes a possible production of photoelectrons at the first dynode. The simulation of MaPMT pulse height spectra is discussed with the additional feature of a possible inhomogeneity in the electron multiplication probability across the surface of the first dynode. The signal loss below a threshold cut is measured with three methods.