Methods for accurate measurement of the response of photomultiplier tubes and intensity of light pulses

Three different methods to determine accurately the intensity of weak light pulses measured with various photo-multiplier tubes are presented. The methods rely on a precise determination of the response of the PMTs to the detection of a single photon. 10 kHz LED pulses attenuated to a level where on average μ = 0.02 to 30 photons are detected per pulse were used. For weak intensity light pulses with μ <; 8, the unknown value of μ can be obtained by fitting measured pulse height spectra employing these single photon response spectra. For higher intensity pulses methods based on the position and/or the fractional variance of the recorded pulse height spectra will be used. The single photon response spectra provides information on the performance of the tested PMTs.