The time synchronization system of JEM-EUSO and JEM-EUSO
pathfinders
Creators: name: Scotti, Valentina
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2015

description: In this thesis I present the Time and Synchronization System for the JEM-EUSO pathfinder, which I designed and developed as main part of my PhD work.

JEM-EUSO has been designed to address basic problems of fundamental physics and high-energy astrophysics investigating the nature of the Extreme Energy Cosmic Rays, EECRs (E$&gt;\SI{5 e19}{\electronvolt}$), which constitute the most energetic component of the cosmic radiation. 

Cosmic rays are highly penetrating ionizing radiation arriving at the Earth isotropically from outer space. The phenomenon of cosmic rays has been discussed since the beginning of last century, although the study of EECR has progressed considerably over the last decade, any astrophysical accelerators able to produce such extreme events has been identified so far. These high energy particles can also shed light about the regions in which they were accelerated and the vast spaces through which they passed on their way to Earth. However, there are still a lot of unanswered question about their energy spectrum, their composition and their origin. Current data indicates that only a significant increase in the exposure at the highest energies will allow to answer all the questions concerning the particles which strike the Earth with such enormous energies. 

JEM-EUSO will pioneer the investigation from Space of EECR-induced Extensive Air Showers, making accurate measurements of the primary energy, arrival direction and composition of EECRs, using a target volume far greater than is possible from the ground. While the research and development work for JEM-EUSO is ongoing, the JEM-EUSO collaboration is completing several pathfinder experiments: EUSO-TA, EUSO-Balloon, and Mini-EUSO. 

The first chapter gives a general introduction to cosmic ray physics and detectors. It also summarizes experimental results above the ankle of the spectrum with particular emphasis on those obtained above \SI{e19}{\electronvolt}.

The first chapter will give a brief summary of the field of cosmic ray physics, focusing on EECR. As at very high energies cosmic rays can be studied only by measuring the secondary radiation they generate in the Earth's atmosphere, also the mechanisms which originate these particle shower and the most common techniques employed their detection are exploited. In the chapter there is also a short summary of the experimental results obtained by the two main experiments which observe EECR, the Pierre Auger Observatory (PAO) and Telescope Array (TA) project, on spectrum, mass and arrival directions of cosmic rays in the energy region in the top end of the spectrum (above \SI{e19,5}{\electronvolt}). 

The second chapter is devoted to an analysis of the scientific goals of JEM-EUSO and its innovations compared to the other observatory of EECR. Then a detailed description of the operating principles of the telescope and its main components will be presented, paying particular attention to the timing and synchronization system and to its links with the electronics of the focal surface. The EUSO-Balloon mission and instrument will be described in the following chapter.

The forth chapter describes the first part of my thesis work, which consisted in the design of the timing and synchronization system for the JEM-EUSO pathfinders. The system will be described together with the design strategy and the implementation.

In the following chapter every phase of the integration and assembly of the EUSO-Balloon pathfinder which involved the Time and Synchronization System will be shortly reviewed. Then, in the sixth chapter I will describe the EUSO-Balloon launch campaign, which was held in Timmins (Canada) in August 2014.

The last chapter is devoted to show preliminary results of the analysis of data taken during the first EUSO-Balloon flight.