JEM-EUSO prototypes for the detection of ultra-high-energy cosmic rays (UHECRs) : from the electronics of the photo-detection module (PDM) to the operation and data analysis of two pathnders

The JEM-EUSO (Extreme Universe Space Observatory on-board the Japanese Experiment Module) international space mission is designed to observe UHECRs by detecting the UV fluorescence light emitted by the so-called Extensive Air Shower (EAS) which develop when UHECRs interact with the Earth’s atmosphere. The showers consist of tens of billions or more secondary particles crossing the atmosphere at nearly the speed of light, which excite nitrogen molecules which then emit light in the UV range. While this so-called “fluorescence technique'” is routinely used from the ground, by operating from space, JEM-EUSO will, for the first time, provide high-statistics on these events. Operating from space, with a large Field-of-View of ±30 °, allows JEM-EUSO to observe a much larger volume of atmosphere, than possible from the ground, collecting an unprecedented number of UHECR events at the highest energies.For the four pathfinder experiments built within the collaboration, we have been developing a common set of electronics, in particular the central data acquisition system, capable of operating from the ground, high altitude balloons, and space.These pathfinder experiments all use a detector consisting of one Photo-detection Modules (PDMs) identical to the 137 that will be present on the JEM-EUSO focal surface. UV light generated by high-energy particle air showers passes the UV filter and impacts the Multi-anode Photomultiplier Tubes (MAPMT). Here UV photons are converted into electrons, which are multiplied by the MAPMTs and fed into Elementary Cell Application-Specific Integrated Circuit (EC-ASIC) boards, which perform the photon counting and charge estimation. The PDM control board interfaces with these ASIC boards, providing power and configuration parameters, collecting data and performing the level 1 trigger. I was in charge of designing, developing, integrating, and testing the PDM control board for the EUSO-TA and EUSO-Balloon missions as well as the autonomous trigger algorithm testing and I also performed some analysis of the EUSO-Balloon flight data and data from the EUSO-TA October 2015 run.In this thesis, I will give a short overview of high-energy cosmic rays, including their detection technique and the leading experiments (Chapter 1), describe JEM-EUSO and its pathfinders including a description of each instrument (Chapter 2), present the details of the design and the fabrication of the PDM (Chapter 3) and PDM control board (Chapter 4), as well as the EUSO-TA and EUSO-Balloon integration tests (Chapter 5). I will report on the EUSO-Balloon campaign (Chapter 6) and results (Chapter 7), including a specific analysis developed to search for global variations of the ground UV emissivity, and apply a similar analysis to data collected at the site of Telescope Array (Chapter 8). Finally, I will present the implementation and testing of the first-level trigger (L1) within the FPGA of the PDM control board (Chapter 9). A short summary of the thesis will be given in Chapter 10.