Characterization and absolute calibration of R11265 multi-anode photomultiplier tubes for the JEM-EUSO space and balloon program, I: Methods and generic features

Abstract

Over the last decade, the Joint Exploratory Missions for an Extreme Universe Space Observatory (JEM-EUSO) collaboration has developed several balloon and space missions implementing different versions of a dedicated camera based on multi-anode photomultiplier tubes (MAPMTs) used in single photoelectron counting mode, in the near ultra-violet. In this paper, we present the experimental techniques developed to calibrate these MAPMTs and determine their main characteristics, relevant to the JEM-EUSO applications. Our results include the absolute calibration of the MAPMTs in both full illumination and localized illumination modes, the measurement of the so-called s-curves and their fitting with a newly developed fitting formula, the study of cross-talk and residual non-Poissonian behaviour, the determination of the physical size of the individual pixels, the wavelength dependence of the photodetection efficiency, the characterization of the pile-up effect and the determination of the corresponding double pulse resolution using a dedicated readout implementing the SPACIROC-3 Application-specific integrated circuit. These techniques allowed us to identify generic features of the MAPMTs of type R11265 from Hamamatsu, including the occasional occurrence of multiple counting of single photons, which the Hamamatsu company was then able to correct and eliminate. We find that the reliability, high-efficiency and homogeneity of these MAPMTs is well suited for the multi-disciplinary scientific objectives of the JEM-EUSO collaboration. The application of our techniques to the characterization and absolute calibration of the fluorescence camera of the EUSO-SPB2 mission is presented in an accompanying paper.