A facility to validate photomultipliers for the upgrade of the Pierre Auger Observatory

The Pierre Auger Observatory is undergoing a major upgrade named AugerPrime with the primary aim to add sensitivity to the mass-composition discrimination of ultrahigh-energy cosmic rays. Two different photomultipliers will be added to each water-Cherenkov station of the surface detector of Observatory. To achieve the scientific goals of AugerPrime these photomultipliers have to ensure a linear response to input-light in a wide range. This paper describes a system developed for the validation of AugerPrime-photomultipliers.