DOCSLIB.ORG

Performance of ATLAS Muon Precision Drift Chambers in a High Radiation Environment

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Performance of ATLAS Muon Precision Drift Chambers in a High Radiation Environment Die approbierte Originalversion dieser Dissertation ist an der Hauptbibliothek der Technischen Universität Wien aufgestellt (http://www.ub.tuwien.ac.at). The approved original version of this thesis is available at the main library of the Vienna University of Technology (http://www.ub.tuwien.ac.at/englweb/). Dissertation Performance of ATLAS Muon Precision Drift Chambers in a High Radiation Environment ausgeführt zum Zwecke der Erlangung des Doktorgrades der technischen Wissenschaften unter der Leitung von Ao. Univ. Prof. Dr. Christian W. Fabjan Atominstitut der Österreichischen Universitäten (E141) eingereicht an der Technischen Universität Wien Technisch-Naturwissenschaftliche Fakultät von Dipl.-Ing. Claus Cernoch Matrikelnummer: 9325777 geboren am 4. April 1974 Wulzendorfstrasse 48, A-1220 Wien Genf, am 27. August 2003 Kurzfassung ATLAS ist ein Universalexperiment für den zukünftigen Large Hadron Collider (LHC) am CERN, welches es ermöglichen wird in neue Gebiete der elementaren Physik vorzudringen. Dabei wird ein Energiebereich erschlossen, welcher weit über jenen heutiger Experimente hinausreicht. Das Müonenspektrometer des ATLAS-Detektors benötigt Präzisionsdriftkammern mit einer Gesamtfläche von 5500 m2, mit welchen die Müonenbahnen in einem Magnetfeld von ~ 0.5 T rekonstruiert werden. Etwa 370000 Driftrohre, gefüllt mit 800m3 Driftgas (Ar-CG"2 Gasmischung), bilden an die 1200 dieser Driftkammern (Monitored Drift Tubes MDT), mit welchen eine Impulsauflösung von 10 % für Müonen mit einem Transversalimpuls von pr = 1 TeV erreicht werden soll, um das volle Entdeckungspotential des LHC auszuschöpfen. Dieses ambitionierte Ziel muss selbst bei dem auftretenden Photonen- und Neutronenhintergrund erfüllt werden, welcher zu Hintergrundzählraten von bis zu 300 kHz pro Driftrohr führt. Diese Hinter- grundstrahlung bewirkt einerseits eine Verschlechterung der Detektoreigenschaften und kann andererseits Alterungsprozesse an den Elektroden hervorrufen. In der vorliegenden Arbeit wurde zum ersten Mal ein Langzeittest einer M DT-Kammer in einer Hochratenumgebung durchgeführt, vergleichbar der im ATLAS-Betrieb. Auch die nötige Infrastruktur der Driftkammer wurde weitgehend dem Endsystem entsprechend realisiert: Eine Ausleseelektronik ähnlich der Endversion wurde zur Driftzeitdatennahme verwendet und ein Prototyp eines zirkulierenden Gassystems versorgte die Kammer. In dieser Arbeit wurde dieser hochreine Gassystemprototyp mit samt seiner Ansteuerung konzipiert, technisch realisiert und auf Stabilität und Verhalten im Dauerbetrieb getestet. Die gewonnenen Erfahrungen bestätigten die Umsetzbarkeit des Konzeptes fuer das entgültige MDT Gassystem. Weiters wurden die Auswirkungen der Gaszirkulation auf das Alterungsverhalten im Detail studiert, indem eine Hälfte der Kammer zirkulierend und die andere im Durch- fluss betrieben wurde. Im Laufe des Alterungstests wurde von den Driftrohren eine Ladung aufgenommen, welche jener entspricht, die während 4 Jahren ATLAS-Betrieb im schlimmst angenommenen Fall anfallen würden. Das Signal verhalten der Driftrohre wurde im Laufe des Langzeittests mit Refenzmessungen kosmischer Müonen verfolgt. Der Test zeigte keine Art von Alterung in den Rohren des offenen Gassytems bei der akkumulierten Strahlungsdosis. Die Driftrohre, welche vom zirkulierenden System ver- sorgt wurden, zeigten ein Sinken der Pulshöhen in den ersten ~ 30 cm der Seite des Gaseinlasses. Dieser Effekt wurde ausführlich untersucht und als Silikonpolymerisa- tion am Anodendraht identifiziert - ein Indiz dafür, dass die Alterung nicht durch das zirkulierende Driftgas selbst verursacht wurde, sondern durch Gas Verunreinigungen. Let- ztendlich wurde der Ursprung der Verunreinigung ausfindig gemacht. Die Ergebnisse dieses Tests haben einen wesentlichen Einfluß auf die Konstruktion des MDT Gassys- tems. Abstract ATLAS (A Large Toroidal LHC ApparatuS) is a general-purpose experiment for the future Large Hadron Collider (LHC) at CERN which will offer the opportunity to explore new aspects of fundamental physics by advancing to an energy scale well beyond that achieved by current experiments. The muon spectrometer of the ATLAS detector requires an area of around 5500 m2 of precision tracking chambers, which will reconstruct the muon tracks in a magnetic field of ~ 0.5 T. Approximately 370000 high pressure drift tubes 3 (MDTS), filled with 800m drift gas (Ar-CO2 gas mixture), form about 1200 of these tracking chambers, aiming to reach a momentum resolution of 10% for muons with a transverse momentum of pr = 1 TeV, to exploit the LHC physics discovery range. This demanding performance requirement has to be fulfilled in the presence of a very high particle background of photons and neutrons leading to background counting rates of up to 300 kHz per drift tube. This background irradiation deteriorates the detector performance and may induce ageing processes on the electrodes. In the presented work for the first time a long-term study with a MDT chamber in a high-background environment, similar to the ATLAS operational environment, has been performed. Also the required infrastructure of the drift chamber was to a large extend realised according to the final system: A front-end electronics close to the final version was utilised to take drift time data and a recirculating gas prototype was supplying the chamber. Within this work the high purity gas prototype and its control system was designed, realised and tested for stability and system behaviour in permanent operation. The gained experiences certified the feasibility of the final MDT gas system. Moreover the impact of gas recirculation on the ageing behaviour of the drift chamber was studied in detail, by operating half of the chamber in recirculated and the other half in flushed gas mode. In the course of the ageing test a charge corresponding to 4 years of ATLAS operation, assuming a conservative worst-case irradiation, were accumulated by the drift tubes. The signal pulseheight spectra of the MDTS were followed up with reference measurements of cosmic muons during this long-term test. The test proved that no ageing occurred in the drift tubes of the open gas system within the accumulated irradiation dose. The drift tubes connected to the circulated gas system showed a local pulseheight drop in the first ~ 30 cm on the gas inlet side. This effect was studied intensively and found to be caused by silicone polymerisation on the anode wire - an evidence that the ageing was not caused by the drift gas and gas circulation itself, but by accumulating gas impurities. The source of the contamination was found eventually. The results of this test has a significant influence on the construction of the MDT gas system. Acknowledgements First and foremost I am very grateful for all the support and motivation from my super- visor Chris Fabjan. I would like to thank him for giving me this unique possibility of working at CERN. I want to express my gratitude to Sandro Palestini who supervised my work so patiently with his fatherly charisma. Many thanks and a great respect to Stephanie Zimmermann, from whom I learned a lot and who never would give up fighting however hopeless a state of an experiment is. I want to thank my colleagues for all their generous countless help. In particular I want to thank Axl Schricker, Cedric Petitjean, Charles Gruhn, Christoph Amelung, Ferdinand Hahn, Isabel Trigger, Ivan Lehraus, Jean-Daniel Capt, Ludovico Pontecorvo, Manuela Cirilli, Raquel Avramidou, Rolf Stampfli, Rüdiger Voss, Silvia Schuh, Stefan Haider and William Andreazza. Many thanks appertain to Christoph and Agnes who have been like a family for me here. Special thanks have to go to Bernhard for encouraging me so much and for sharing with me the first unforgettable emotions of discovering the region above 4000 m. A huge amount of thanks to Katharina for all the conversations and for persuading me to start and stop my Salsa career. A special thankyou must go to Zita for her sunshiny nature. Many thanks I owe my "Mukibuden"-friends Andy and Peter. Thanks to Walter for being such a warm-hearted neighbour. It is a pleasure to be able to thank Sophia, the best cook and sailor here around. I am very grateful to young Bernhard, for being the chief officer on our sailing trip and for his creative influence. Thanks Werner for standing my pessimism. A big "Prösterscheeees" goes to Jan with whom I discovered bravely the night life of Geneva. I'm very grateful to Adrian, who influenced strongly my decision to come to CERN and who managed a flat for me already before I was arriving. I never will forget the impressing, honest moments in the mountains with Thomas, who gave me an idea what being a real mountaineer means. Thanks also for your uncomplicated straightforwardness. I am very glad for being part of the high-class CERN volleyball team. A special thankyou has to go here to our coach Jan. A huge "Thank You" to my friends in Vienna - Tomek, Georg, Hoffi, Hanna, Wolfi, Blacko, Alex, Andy, Emi ... - for not forgetting me and for spending the short but intense moments with me at home or on common holidays. Vielen Dank Wolfi, Dich als einzigartigen Mensch und Freund kennengelernt zu haben - Dein Geist, Deine Ideen, Dein Stil, Dein Humor werden mir immer unvergesslich bleiben. Nicht zuletzt möchte ich mich bei meiner Familie herzlich für den Rückhalt bedanken, den sie mir während meiner gesamten Ausbildung so selbstlos schenkten und welcher mir erst dieses erfüllte Leben ermöglichte. Meinen Eltern in Dankbarkeit gewidmet Contents
Load more

Recommended publications
  • CERN Courier–Digital Edition
    CERNMarch/April 2021 cerncourier.com COURIERReporting on international high-energy physics WELCOME CERN Courier – digital edition Welcome to the digital edition of the March/April 2021 issue of CERN Courier. Hadron colliders have contributed to a golden era of discovery in high-energy physics, hosting experiments that have enabled physicists to unearth the cornerstones of the Standard Model. This success story began 50 years ago with CERN’s Intersecting Storage Rings (featured on the cover of this issue) and culminated in the Large Hadron Collider (p38) – which has spawned thousands of papers in its first 10 years of operations alone (p47). It also bodes well for a potential future circular collider at CERN operating at a centre-of-mass energy of at least 100 TeV, a feasibility study for which is now in full swing. Even hadron colliders have their limits, however. To explore possible new physics at the highest energy scales, physicists are mounting a series of experiments to search for very weakly interacting “slim” particles that arise from extensions in the Standard Model (p25). Also celebrating a golden anniversary this year is the Institute for Nuclear Research in Moscow (p33), while, elsewhere in this issue: quantum sensors HADRON COLLIDERS target gravitational waves (p10); X-rays go behind the scenes of supernova 50 years of discovery 1987A (p12); a high-performance computing collaboration forms to handle the big-physics data onslaught (p22); Steven Weinberg talks about his latest work (p51); and much more. To sign up to the new-issue alert, please visit: http://comms.iop.org/k/iop/cerncourier To subscribe to the magazine, please visit: https://cerncourier.com/p/about-cern-courier EDITOR: MATTHEW CHALMERS, CERN DIGITAL EDITION CREATED BY IOP PUBLISHING ATLAS spots rare Higgs decay Weinberg on effective field theory Hunting for WISPs CCMarApr21_Cover_v1.indd 1 12/02/2021 09:24 CERNCOURIER www.
    [Show full text]
  • A Gas Monitoring Chamber for ATLAS Mdts
    A Gas Monitoring Chamber for ATLAS MDTs Dissertation zur Erlangung der Doktorwürde Vorgelegt von Song Xie November 2011 Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Dekan: Prof. Dr. Kay Königsmann Referent: Prof. Dr. Ulrich Landgraf Koreferent: Prof. Dr. Karl Jakobs Tag der Verkündigung des Prüfungsergebnisses: 29. November 2011 Abstract As one of the four experiments at the Large Hadron Collider (LHC), the ATLAS experiment features the largest muon tracker in terms of volume. The main detecting elements of the muon tracker are Monitored Drift Tubes (MDTs) which measure the drift times of the electrons created by a traversing muon ionizing the operating gas. The trajectory of the muon is reconstructed from the drift times according to the so-called space-to-drift time relation (rt-relation). The design goal of the performance of the muon tracker is a stand-alone transverse momentum resolution of approximately 10 % for tracks of 1 TeV particles. This requires the MDT detector to have a spacial resolution better than 50 µm within a volume of a length of 40 m and a diameter of 25 m. The ATLAS MDTs use Ar:CO2 93:7 plus a few hundred ppm water vapour as the operating gas. The types of the gas components and their ratios should be kept very steady in order to have a stable rt-relation. In this thesis, the influences of the fluctuations of the mixture ratio on the elec- tron velocity are discussed. Gas Monitoring Chambers (GMCs) have been designed and implemented to monitor the gas of the ATLAS MDTs by measuring the electron drift velocity in the operating gas as a function of the reduced electric field (v-r.e.f relation).
    [Show full text]
  • Impact of Humidity on Deformations Offr-4 Based Detector
    Impact of Humidity on Deformations of FR-4 Based Detector Elements in the ATLAS New Small Wheel Yanwen Hong Supervisor: Prof. Dr. Ulrich Landgraf Dr. Stephanie Zimmermann Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg This dissertation is submitted for the degree of Master of Science Abteilung Prof. Dr Gregor Herten July 2019 Abstract The discovery of the Higgs boson in the ATLAS and CMS experiments showed the necessity of high luminosity in discovering new physics. The LHC is undergoing upgrades of the collider, accelerator chain and detectors for the High-Luminosity LHC project in several phases. The inner endcap of the muon spectrometer in the ATLAS detector will be replaced by the New Small Wheel. The two technologies used in the NSW are sTGC and MicroMegas, which can achieve a high spatial resolution in muon tracking and better angular resolution in trigger performance by implementing strip-structured detector modules. FR-4 grade PCBs are one of the crucial components of the detectors. Mechanical deformations caused by a humid environment were observed during the single layer detector element machining and detector module assembly processes. These deformations will lead to strips misalignment and furthermore have a direct impact on resolution of the detectors. In order to evaluate the impact of these deformations on the performance of the detector, a designed humidity study is conducted in this thesis. The maximum and residual strip misalignment of three detector elements at an extremely humid environment and after the air-drying process is determined by measurement data. Considering the machining and manufacturing process, the values of mechanical tolerances of the detector modules are compared to the maximum and residual strip misalignment.
    [Show full text]
  • Freiburg Institute of Physics Activity Report 2011-2013
    Freiburg Institute of Physics Activity Report 2011-2013 Albert-Ludwigs-Universität Freiburg INSTITUTE OF PHYSICS UNIVERSITY OF FREIBURG ACTIVITY REPORT 2011 - 2013 Institute of Physics Albert-Ludwigs-Universität Freiburg Hermann-Herder-Str. 3 79104 Freiburg Front cover Measured angular distribution of photoelectrons emitted from a Na55− cluster, scanning tunneling microscope image showing chains of oligomeric molecules, and a candidate event for a Higgs boson produced in the ATLAS experiment, symbolising the three research areas of the Institute of Physics. IMPRESSUM Published January 2014 by the Freiburg Institute of Physics Editorial Team K. Jakobs T. Schaetz O. Waldmann Design Christina Skorek Tamara Klaas Printed by University of Freiburg All rights reserved. ii The Institute of Physics of the University of Freiburg, with the explicit support of the Rectorate of the University, has decided to install an international Scientific Advisory Board (SAB), to consult and advise the institute in all aspects of its academic research and education, on a regular basis. The present activity report provides a concise description of the scientific activities of the research groups during the years 2011 to 2013, of the teaching and outreach programme, and of the available infrastructure. The part of the scientific activities is divided into three main chapters dedicated to the three main research areas of the institute. The variable structure of these chapters reflects the diverse and lively scientific cultures of the different areas which meet under the roof of this institute. The inaugural meeting of the Scientific Advisory Board is scheduled for 17 and 18 February 2014, and will be embedded into a public workshop programme, where cutting edge research on a broad selection of topics will be presented by members of the institute.
    [Show full text]
  • Construction and Calibration of a Setup for Micro-Pattern Gaseous Detectors Using UV Laser Photoelectrons
    Construction and Calibration of a Setup for Micro-Pattern Gaseous Detectors Using UV Laser Photoelectrons Dissertation zur Erlangung der Doktorwürde Vorgelegt von Kim Temming Dezember 2013 Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg im Breisgau After the discovery of the Higgs boson at the Large Hadron Collider (LHC) in summer 2012, the properties and couplings of the newly found particle need to be determined. To deliver the necessary amount of data, the LHC will raise its luminosity significantly and new detector technologies are needed that can withstand the demands due to the increased particle flux. New types of gaseous detectors like Micro Pattern Gaseous Detectors (MPGD) and especially the Micromegas that are foreseen for the ATLAS Muon New Small Wheel upgrade, show very good rate capabilities so far. A test setup to investigate the properties of Micromegas has been designed and built. The setup uses photoelectrons created by a UV laser in the drift volume as the primary charge to probe the detector. The creation points and times are precisely known and the setup is independent of test beams. It includes a reference measurement system based on multi-wire technology and has been commissioned and fully calibrated. A Micromegas test candidate unit with 8 different readout geometry zones and an additional cathode layer has been designed and the performance of a prototype was intensively investigated. Gain studies as well as drift and diffusion studies have been carried out successfully. Studies and Garfield simulations regarding the discharge behavior of the Micromegas test can- didate and the supplementary cathode on the bottom of the detector have been carried out and indicate a controllable influence on the electric field configuration in the amplification area by the additional potential.
    [Show full text]
  • Study of the Z+Bb Production with the ATLAS Detector at The
    Study of the Z + bb¯ Production with the ATLAS Detector at the LHC Dissertation der Fakultat¨ fur¨ Physik der Ludwig-Maximilians-Universitat¨ Munchen¨ vorgelegt von Dan Nicolae Vladoiu˘ geboren in Bukarest Munchen,¨ Juli 2013 Study of the Z + bb¯ Production with the ATLAS Detector at the LHC Dissertation der Fakultat¨ fur¨ Physik der Ludwig-Maximilians-Universitat¨ Munchen¨ vorgelegt von Dan Nicolae Vladoiu˘ geboren in Bukarest Munchen,¨ Juli 2013 Erstgutachterin: Prof. Dr. Dorothee Schaile Zweitgutachter: Prof. Dr. Martin Faessler Tag der mundlichen¨ Prufung:¨ 01. Oktober 2013 Abstract A first inclusive measurement of the productionp cross-section for a Z boson in associa- tion with a bottom-antibottom quark pair at s = 7 TeV at the Large Hadron Collider is presented, using the full dataset of R L(t)dt = 4:64 pb−1 collected by the ATLAS detector during the year 2011. Such a measurement provides a direct test of perturbative quantum chromodynamics pre- dictions, and, for production of a Higgs boson in association with a Z boson, Z + bb¯ represents the highest irreducible background. The decay channels of the Z boson considered are: Z ! e+e− and Z ! µ+µ−. For the reconstruction of the Z boson candidate, exactly two leptons with opposite charge and of the same-flavor are required to have an invariant mass within 76 GeV - 106 GeV. Jets with weakly decaying b-hadrons are selected with a b-tagging algorithm at 75% efficiency. For the reduction of the top-antitop background, events are required to have a missing transverse energy of less than 30 GeV. The extraction of the signal cross-section from the data sample was realized with a binned likelihood template fit method, using as template fit a strong discriminant between heavy- flavor and charm=light-flavor jets.
    [Show full text]