Abstract:
The origin and the underlying acceleration mechanisms of ultra high energy
cosmic rays (UHECR) are one of the topics of research in astroparticle physics.
To answer these questions, measurements with high statistics are needed of the
extensive air showers the UHECR produce in the earth’s atmosphere. By going
to space, the proposed Extreme Universe Space Observatory (EUSO) aims to
detect atmospheric showers over a large area using the fluorescence method,
which requires sensitive light detectors. Silicon photomultipliers (SiPM) have
emerged as promising alternatives to conventional photomultiplier tubes, with
various advantages such as lower weight and lower operating voltage. However,
the ability of SiPM to detect light in a near-space environment has yet to be
demonstrated, and the influence of the high rate of thermal noise and strong
dependence on ambient temperature has to be assessed.
This work is divided into two parts. First, the temperature dependence of
the SiPM gain is studied with an experimental setup. A novel algorithm is
presented to measure the SiPM gain in real-time, which allows the stabilization
of the gain without the need for external temperature measurements. In the
second part, data of a prototype SiPM camera, which was flown on a EUSO
super pressure balloon pathfinder in the spring of 2017, were analysed. This
includes a statistical analysis of the background for UHECR search, both from
thermal detector noise and from physical UV background in the atmosphere.
Furthermore, transient events were identified, which hint at moving clouds. In
the end, a brief comparison between the SiPM prototype and the main camera
using photomultiplier tubes is shown.