Peculiarities of the FEhU-115 single-electron characteristics

Basic one-electron characteristics of FEhU-115 photomultiplier have been measured. Effects of anode and focusing voltages on them have been studied. The results obtained show that for reaching a maximum counting rate the photocathode-first dynode focusing voltage U1 must constitute 60-80% of intercascade voltage. To generate maximum anode current U1 value must be lower by 10%. Optimization with respect to counting rates of one-electron pulses resulted from a signal and dark-current noise and one-electron amplification factor is reached at UL1 values exceeding half of intercascade voltage. It is concluded that FEhU-115 photomultipliers are less critical with respect to supply regimes as compared with FEhU-100 photomultipliers, which have similar structure and some parameters. Standard working voltages of FEhU-115 supply are in the range of 1.4-1.8 keV, level of dark-current noises constitutes as a rule several hundred pulses per second at room temperature