Studies with a Liquid Argon Time Projection Chamber: Addressing Technological Challenges of Large-Scale Detectors

158 Pages·2015·5.07 MB·English

by  Michael Schenk (auth.)

BestMasters
Springer awards „BestMasters“ to the best master’s theses which have been com-
pleted at renowned universities in Germany, Austria, and Switzerland.
Th e studies received highest marks and were recommended for publication by
supervisors. Th ey address current issues from various fi elds of research in natural
sciences, psychology, technology, and economics.
Th e series addresses practitioners as well as scientists and, in particular, off ers guid-
ance for early stage researchers.
Michael Schenk
Studies with a Liquid
Argon Time Projection
Chamber
Addressing Technological Challenges
of Large-Scale Detectors
Michael Schenk
Bern, Switzerland
BestMasters
ISBN 978-3-658-09429-4 ISBN 978-3-658-09430-0 (eBook)
DOI 10.1007/978-3-658-09430-0
Library of Congress Control Number: 2015935658
Springer Spektrum
© Springer Fachmedien Wiesbaden 2015
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or
part of the material is concerned, speci(cid:191) cally the rights of translation, reprinting, reuse of illus-
trations, recitation, broadcasting, reproduction on micro(cid:191) lms or in any other physical way, and
transmission or information storage and retrieval, electronic adaptation, computer software, or by
similar or dissimilar methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publication does not imply, even in the absence of a speci(cid:191) c statement, that such names are
exempt from the relevant protective laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this
book are believed to be true and accurate at the date of publication. Neither the publisher nor the
authors or the editors give a warranty, express or implied, with respect to the material contained
herein or for any errors or omissions that may have been made.
Printed on acid-free paper
Springer Spektrum is a brand of Springer Fachmedien Wiesbaden
Springer Fachmedien Wiesbaden is part of Springer Science+Business Media
(www.springer.com)
Preface
This master thesis is the outcome of 16 months of research and devel-
opment work on the Argontube project at the Laboratory for High
Energy Physics and Albert Einstein Center for Fundamental Physics
(LHEP-AEC) of the University of Bern. This project has been initi-
ated specifically to evaluate certain aspects of the feasibility of large
and massive, i.e. kiloton-scale, liquid argon time projection chambers
(LArTPC) and to address the associated technological challenges.
LArTPCs are a promising particle detector type offering the detection
capabilities required amongst others by neutrino and astrophysics
experiments.
Formymasterthesis,Ihavebecomefullyinvolvedintothisfascinating
project and have taken the opportunity to make my own contribu-
tions to the development of this particle detector technology. I have
participated in five measurement campaigns where a large number
of UV laser induced events as well as cosmic muon tracks have been
acquired with a novel cryogenic read-out. These data allowed the
extraction of interesting results, relevant for the Argontube project
as well as for future large LArTPCs in general. In between the runs,
I was involved in doing technical work, modified and prepared the
detector and associated systems. I have gained experience in the fields
of vacuum technique, cryogenics, electronics and programming.
Apart from a general introduction to the LArTPC technology, this
master thesis reports on the Argontube detector upgrades that have
been realized as well as the measurements and studies that have been
carried out.
VI Preface
During my work on the Argontube project, I have been supported
by a number of persons to whom I wish to express my sincere gratit-
ude.
First of all, Prof. Dr. Antonio Ereditato who initiated this master
thesis and allowed me to be part of such an interesting research pro-
ject.
PD Dr. Igor Kreslo and Prof. Dr. Michele Weber, who have been
excellent mentors and advisors during my involvement in the Argon-
tube project. I thank you for sharing your valuable knowledge and
experience with me. I enjoyed the freedom and responsibility I was
given to carry out my studies.
Dr. Marcel Zeller and Christoph Rudolf von Rohr for teaching me
everythingaboutArgontube. Ihavehighlyappreciatedyoursupport
and ideas. Furthermore, Prof. Dr. S˘tefan J´ano˘s, S´ebastien Delaquis
and Dr. Akitaka Ariga for their precious technical advice on related
topics.
Igor Kreslo, Michele Weber and Thomas Strauss for proof-reading
this document and giving numerous valuable inputs to my thesis.
My fellow students and friends Sabina Joos, Matthias Lu¨thi and Mar-
cel H¨aberli with whom I spent most of the time during my master
studies. A big thank you to all of you.
Finally, my dear family and friends for supporting me in all the ways
possible throughout my studies at the University of Bern.
Michael Schenk
Contents
Introduction 1
1 The liquid argon time projection chamber 5
1.1 Working principle . . . . . . . . . . . . . . . . . . . . . 5
1.2 Liquefied argon as a detection medium . . . . . . . . . 8
1.3 Energy dissipation in liquefied argon . . . . . . . . . . 11
1.4 Recombination mechanisms . . . . . . . . . . . . . . . 16
1.5 Scintillation mechanisms . . . . . . . . . . . . . . . . . 21
1.6 Charge carrier transport . . . . . . . . . . . . . . . . . 22
1.7 Electron attachment losses . . . . . . . . . . . . . . . . 25
1.8 Wireplane read-out and signal formation . . . . . . . . 27
2 The ARGONTUBE detector 29
2.1 Cryostat design . . . . . . . . . . . . . . . . . . . . . . 30
2.2 Field cage design and high voltage generation . . . . . 31
2.3 Liquid argon purification . . . . . . . . . . . . . . . . . 35
2.4 UV laser system . . . . . . . . . . . . . . . . . . . . . 39
2.5 Read-out, data-acquisition and triggering systems . . . 41
2.6 Detector operation . . . . . . . . . . . . . . . . . . . . 45
2.7 Event gallery . . . . . . . . . . . . . . . . . . . . . . . 47
3 Regeneration system for argon purifiers 51
3.1 Working principle of argon purifiers. . . . . . . . . . . 52
3.2 The regeneration system . . . . . . . . . . . . . . . . . 53
3.3 Measurements and observations . . . . . . . . . . . . . 57
4 The Greinacher high-voltage generator 67
4.1 Model for the Greinacher circuit . . . . . . . . . . . . 69
VIII Contents
4.2 The electric field in ARGONTUBE . . . . . . . . . . . 73
4.3 Cathode voltage measurements . . . . . . . . . . . . . 80
5 Realization of a GPU-based track finder 85
5.1 The Hough transform . . . . . . . . . . . . . . . . . . 85
5.2 Brief introduction to CUDA GPGPU programming . . 91
5.3 The GPU-based track finder for ARGONTUBE . . . . 93
5.4 Computational speed-up of the Hough transform . . . 99
6 Study of cosmic muon events 105
6.1 Linear energy transfer of muons in liquid argon . . . . 106
6.2 Momentum measurement by analysis of MCS . . . . . 112
7 UV laser methods and measurements 121
7.1 Liquid argon purity measurements . . . . . . . . . . . 121
7.2 Measurement of the longitudinal diffusion coefficient . 129
Conclusions 137
Bibliography 143
List of Figures
1.1 CAD drawing of a TPC and illustrations of the electric
field lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Working principle of a liquid argon TPC. . . . . . . . . . 9
1.3 Illustration of multiple Coulomb scattering. . . . . . . . . 14
1.4 Recombination factors for charge and light in liquid argon
as functions of the electric field strength and the ionization
density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.5 Main scintillation mechanisms in liquid argon.. . . . . . . 22
1.6 Measurements of the electron drift velocity in liquid argon
as a function of the electric field strength. . . . . . . . . . 24
1.7 Electric field lines and signal pulse shapes at the wireplane
read-out. . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.1 CAD drawings of the laboratory and of Argontube. . . 31
2.2 Photographs of the Argontube top flange. . . . . . . . . 32
2.3 Photographs and a CAD drawing of the Argontube field
cage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.4 Wiring diagram of the Greinacher circuit. . . . . . . . . . 35
2.5 Photographs of the Argontube recirculation system. . . 37
2.6 Photographs of the Argontube UV laser system. . . . . 39
2.7 Photographs of the Argontube read-out section and of
the PMTs. . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.8 Schematic of the Argontube read-out chain. . . . . . . . 43
2.9 Argontube events. . . . . . . . . . . . . . . . . . . . . . 48
3.1 Photograph of the Argontube purifier cartridge. . . . . 52
3.2 The regeneration system for argon purifiers. . . . . . . . . 54