Determination of the single photo-electron spectrum and gain measurement for the Cherenkov Telescope Array camera NectarCAM
Résumé
The measurement of the photomultiplier gain is a crucial step for Imaging Atmospheric Cherenkov Telescopes in order to translate the measured charge to a number of photons. For that, one of the possibility is to perform measurements with a flashing light source at a low intensity level, in order to reconstruct the charge distribution of a single photon. In this contribution, we will present a method to reconstruct the single photo electron spectrum using low intensity charge distribution. We will show that the usually adopted Gaussian assumption does not reproduce well this data, and will present a new model which explains the data behavior. The impact of this measurement on the gain determination will be presented, and the associated uncertainty will be discussed.