|Location||Call number||Copy number||Status||Date due|
|Sala B : Armadio Tesi||THS_2017 539.7 A534 (Browse shelf)||1||Available|
|Sala B : Armadio Tesi||THS_2017 539.7 A534 (Browse shelf)||2||Available|
Tesi di diploma di 2° livello per la Classe delle Scienze Sperimentali Diploma di 2° livello Scuola Superiore di Catania, Catania, Italy 2017 A.A. 2016/2017
Includes bibliographical references (p. 83-87).
Introduction -- The cosmic rays and the techniques for the detection of the ultra high energy component -- The JEM-EUSO mission -- The diffuse night sky brightness -- Simulation of the night sky background in the JEM-EUSO mission -- Conclusion -- Bibliography.
Tesi discussa il 13/01/2017.
The main goal of the present thesis is to provide a simulation of the diffuse night sky brightness that will constitute the background signal for the data collected during the JEM-EUSO space mission, starting from a preliminary analysis of the night sky background data collected by its EUSO-Balloon pathnder detector. The JEM-EUSO mission will be an observatory for the detection of ultra-high energy cosmic rays, extragalactic messengers of information about the Universe and its history. The ultra-high energy cosmic rays can be studied only through the observation of particle showers produce in their interaction with the Earth's atmosphere, using the fluorescence detection technique. In the first chapter the basics of the cosmic ray physics are addressed, describing shortly their propagation and acceleration from astrophysical sources to Earth and then focusing on the fluorescence technique used to reconstruct their characteristics from the detection of Extensive Air Showers. The second chapter deals with the description of the JEM-EUSO mission, introducing its scientic goals and its instruments, including three underway pathfinder experiments. In the third chapter the diffuse night sky brightness, the main background signal for the detection of fluorescence light from cosmic ray showers, is described. Despite the importance of this background, its implementation in the simulation of the JEM-EUSO experiment is still preliminary. Furthermore, the data already collected by the pathfinders are poorly exploited for this goal. Therefore the rst aim of the present thesis was to include a simulation of the night sky background in the JEM-EUSO software package. For this purpose I had to to study this software framework, briefly illustrated in the fourth chapter. The algorithm for the night sky background simulation has been successfully implemented and added to the software package. Although the operation is technically correct inside the JEM-EUSO software environment, it is not realistic: the outcome is what expected for a uniform flux of radiation (a good approximation for the night sky background) observed by an ideal detector with equal sensitivity for each pixel. That is not the case of the EUSO-Balloon instrument, as the detector presents a noticeable spread in the pixel response. Therefore a second issue arose: the requirement of taking into account for non homogeneous behaviour of pixels. The idea was to generate an algorithm for the determination of the pixel sensitivity on an event-by-event basis, through a statistical analysis of the temporal sequence of the FADC counts detected by each pixel. In this way each measurement of the diffuse night sky brightness could be used for an artificial "flat-fielding" of the detector. The developed algorithm was used on several events collected during the first EUSO-Balloon flight, to obtain the maps of pixel response shown in the forth chapter of the present thesis. In a first approximation, these results are in agreement with the measured maps of efficiency and of electronic noise presented at the last International Cosmic Ray Conference (2015) by the JEM-EUSO Collaboration. The success of this comparison represents a first validity check for the algorithm produced. The future goals are twofold. On the one hand, the implementation of the developed code inside the ocial release of the JEM-EUSO software package. On the other hand, it is foreseen an improvement of the algorithm for the pixel response and then proper validation tests. Indeed, it is forthcoming a proposal of this method to the JEM-EUSO Collaboration as a possible alternative for monitoring the detector performances when the normal calibration or "flat-fielding" methods are not available or can not be performed.