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Dissertation Zur Erlangung Des Akademischen Grades Eines Doktors Der Naturwissenschaften System Tests, Initial Operation and First Data of the AMIGA Muon Detector for the Pierre Auger Observatory Dissertation zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften vorgelegt von Master of Science Michael Pontz, geboren am 17. September 1982 in Mainz, dem Department Physik der Naturwissenschaftlich-Technischen Fakultät der Universität Siegen Siegen, Dezember 2012 Berichte aus der Physik Michael Pontz System Tests, Initial Operation and First Data of the AMIGA Muon Detector for the Pierre Auger Observatory Shaker Verlag Aachen 2013 Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available in the Internet at http://dnb.d-nb.de. Zugl.: Siegen, Univ., Diss., 2013 Copyright Shaker Verlag 2013 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers. Printed in Germany. ISBN 978-3-8440-1758-8 ISSN 0945-0963 Shaker Verlag GmbH • P.O. BOX 101818 • D-52018 Aachen Phone: 0049/2407/9596-0 • Telefax: 0049/2407/9596-9 Internet: www.shaker.de • e-mail: [email protected] Abstract Investigating the energy region between 1017 eV and 4 1018 eV for primary cosmic particles will lead to a deeper understanding of the origin× of cosmic rays. Effects of the transition from galactic to extragalactic origin are expected to be visible in this region. The knowledge of the composition of cosmic rays strongly depends on the hadronic interaction models, which are applied in the air shower reconstruction. Directly determining the number of muons from an air shower on ground level will improve the precision of the composition measurements by reducing the dependence on the models. The Pierre Auger Observatory is facing these challenges with an upgrade of the original detector setup. A denser sub-array of water Cherenkov detectors and a dedicated muon detector (MD) array constitute the AMIGA enhancement (Auger Muon and Infill for the Ground Array). Additional fluorescence telescopes constitute HEAT (High Elevation Auger Telescopes). Seven MD modules have been installed until mid 2012 in a first hexagon at the site of the Pierre Auger Observatory in Malargüe, Argentina. The corresponding readout electronics, and 19 more of these setups, were assembled and tested in Siegen to assure correct functionality. The detectors were incorporated in the trigger structure of the original surface detector (SD) array of the Pierre Auger Observatory and are now taking data synchronously. In the framework of this thesis, system tests have been developed, a pre-unitary cell (PUC) of seven modules has been successfully operated and their trigger has been synchronised with the SD trigger. First data from the MD have been analysed and have been combined with data from the SD. Zusammenfassung Die Erforschung der primären kosmischen Strahlung im Energiebereich von 1017 eV bis 4 1018 eV wird zu einem tieferen Verständnis ihrer Herkunft führen. Effekte, verursacht× durch den Übergang von galaktischem zu extragalaktischem Ursprung der Strahlung, werden in diesem Bereich als beobachtbar erwartet. Die Erkenntnisse über die Zusammensetzung der kosmischen Strahlung hängen dabei stark vom hadronischen Interaktionsmodell ab, welches in der Luftschauerrekonstruktion verwendet wird. Ein direkter Nachweis der Anzahl der Myonen auf Bodenniveau in einem solchen Luftschauer wird die Präzision der Messungen zur Zusammensetzung der Strahlung verbessern, da er die bestehenden Abhängigkeiten von den Modellen reduzieren wird. Das Pierre Auger Observatorium begegnet diesen Herausforderungen mit einer Erweiterung des ursprünglichen Detektoraufbaus. Ein dichter gesetztes Detektorfeld von Wasser-Cherenkov-Detektoren und zusätzliche, spezielle Myon-Detektoren bilden die AMIGA Erweiterung (Auger Muon and Infill for the Ground Array). Zusätzliche Fluoreszenz-Teleskope bilden HEAT (High Elevation Auger Telescopes). Sieben Module des Myon-Detektors wurden bis Mitte 2012 in einem ersten Hexagon am Pierre Auger Observatorium in Malargüe in Argentinien installiert. Die dazugehö- rige Ausleseelektronik, und 19 weitere dieser Systeme, wurden in Siegen zusammen- gesetzt und getestet um korrekte Funktionalität zu garantieren. Die Module wurden in die Trigger-Struktur des bestehenden Oberflächen-Detektorfeldes eingebunden und nehmen nun Daten in einem synchronisierten Modus. Im Rahmen dieser Arbeit wurden Systemtests entwickelt, die ersten Module des Myon- Detektors erfolgreich in Betrieb genommen und ihr Trigger mit dem bestehenden Triggersystem synchronisiert. Erste resultierende Daten wurden mit den Daten des Oberflächen-Detektors kombiniert und analysiert. III Gutachter der Dissertation: Prof. Dr. Peter Buchholz Prof. Dr. Markus Risse Datum der Disputation: 01. Februar 2013 IV Contents 1 Introduction 1 2 Astroparticle Physics 3 2.1 Historical Remarks .................................... 3 2.2 Cosmic Rays ........................................ 4 2.2.1 The Energy Spectrum of Cosmic Rays ................... 4 2.2.2 The Knees in the Spectrum .......................... 5 2.2.3 The Ankle in the Spectrum ........................... 7 2.2.4 The GZK Suppression .............................. 8 2.2.5 Composition of Primary Cosmic Rays .................... 8 2.3 Extensive Air Showers .................................. 10 2.3.1 A simple Model for Electromagnetic Cascades .............. 10 2.3.2 A simple Model for Hadronic Cascades ................... 11 2.4 Detection Techniques in Astroparticle Physics .................. 13 2.4.1 Array Detectors.................................. 13 2.4.2 Cherenkov Detectors .............................. 13 2.4.3 Fluorescence Detectors ............................. 14 2.4.4 Radio Detectors .................................. 14 3 The Pierre Auger Observatory 17 3.1 Introduction ........................................ 17 3.2 Physics Aims ........................................ 19 3.3 The Surface Detector Array .............................. 20 3.4 The Fluorescence Detectors .............................. 22 3.5 The Trigger System .................................... 23 3.5.1 SD Trigger ..................................... 23 3.5.2 FD Trigger ..................................... 26 3.6 Enhancements of the Pierre Auger Observatory ................. 27 3.7 Results of the Pierre Auger Observatory ...................... 32 4 The Muon Detector of the AMIGA Enhancement 43 4.1 Physics Aims of the AMIGA Enhancement ..................... 43 4.2 The Muon Detector Array ................................ 45 4.2.1 Deployment of the Muon Detector Array .................. 46 4.3 The Muon Detector Modules .............................. 47 4.3.1 Scintillator Unit .................................. 47 4.3.2 The Photomultiplier Tube ........................... 49 V Contents 4.4 The Muon Detector Electronics ............................ 50 4.4.1 The Underground Electronics ......................... 50 4.4.2 The Surface Electronics ............................. 54 5 System Tests 57 5.1 Test Stand Setup ..................................... 58 5.2 Configuration of the Microcontroller ......................... 61 5.3 Communication via CAN ................................ 61 5.4 Configuration of the FPGA ............................... 62 5.5 Read and Write Access to Registers of the FPGA ................. 63 5.6 Channeltest ........................................ 63 5.7 Crosstalk Test ....................................... 65 5.8 External Trigger Acceptance .............................. 66 5.9 Threshold Scan ...................................... 68 5.10High Voltage Characterisation ............................. 72 5.11Monitoring Voltages and Temperatures ....................... 74 5.12Temperature Dependence ............................... 77 5.13Triggers to the AMIGA MD Modules .......................... 77 5.13.1Internal Trigger .................................. 77 5.13.2External Trigger .................................. 78 5.14Detector Calibration ................................... 82 6 Results 85 6.1 Test Stand .......................................... 86 6.2 Results of the Full System Tests ............................ 88 6.2.1 Channeltest and Crosstalk Test ........................ 88 6.2.2 Threshold Scans ................................. 89 6.2.3 Monitoring Voltages and Temperatures ................... 92 6.2.4 High Voltage Characterisation ........................ 94 6.2.5 Power Consumption of the Electronics ................... 95 6.2.6 Addressing of Individual Channels ...................... 96 6.3 Advanced Trigger Tests ................................. 97 6.3.1 Event Request Efficiency ............................ 97 6.3.2 Local Timestamp Identity in the Trigger Signals ............. 100 6.4 Results of the Detector Calibration .......................... 104 6.5 Temperature Dependence of the High Voltage .................. 110 6.6 Combined Analysis of SD and MD Data ....................... 113 6.6.1 Datasets and Event Selection for the SD .................. 113 6.6.2 Reconstructed Energy and Arrival Direction of the SD Events .... 113 6.6.3 Reconstructed Signal Strength in the SD Stations ............ 114 6.6.4 Data Taking Periods of the MD ........................ 114 6.6.5 Analysis of the MD Data ............................ 115
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