Design studies and sensor tests for the beam calorimeter of the ILC detector [Elektronische Ressource] / von Ekaterina Kuznetsova

Kuznetsova Ekaterina

Sujets

• Physik

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2006
• Nombre de lectures: 9
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Design Studies and Sensor Tests for the Beam
Calorimeter of the ILC Detector
DISSERTATION
zur Erlangung des akademischen Grades
doctor rerum naturalium
(Dr. rer. nat.)
im Fach Physik
eingereicht an der
Mathematisch-Naturwissenschaftlichen Fakultät I
Humboldt-Universität zu Berlin
von
Frau Magister Ekaterina Kuznetsova
geboren am 10.08.1976 in Leningrad, USSR
Präsident der Humboldt-Universität zu Berlin:
Prof. Dr. Hans Jürgen Prömel
Dekan der Mathematisch-Naturwissenschaftlichen Fakultät I:
Prof. Thomas Buckhout, PhD
Gutachter:
1. Prof. Dr. Hermann Kolanoski
2. Prof. Dr. Thomas Lohse
3. Prof. Dr. Achim Stahl
eingereicht am: 30. November 2005
Tag der mündlichen Prüfung: 20. April 2006Abstract
The International Linear Collider (ILC) is being designed to explore particle
physics at the TeV scale. The design of the Very Forward Region of the ILC
detector is considered in the presented work. The Beam Calorimeter - one of
two electromagnetic calorimeters situated there - is the subject of this thesis.
The Beam Calorimeter has to provide a good hermeticity for high energy
electrons, positrons and photons down to very low polar angles, serve for fast
beamdiagnosticsandshieldtheinnerpartofthedetectorfrombackscattered
beamstrahlung remnants and synchrotron radiation.
As a possible technology for the Beam Calorimeter a diamond-tungsten
sandwich calorimeter is considered. Detailed simulation studies are done
in order to explore the suitability of the considered design for the Beam
Calorimeter objectives. Detection efficiency, energy and angular resolution
forelectromagneticshowersarestudied. Atthesimulationlevelthediamond-
tungstendesignisshowntomatchtherequirementsontheBeamCalorimeter
performance.
Studiesofpolycrystallinechemicalvapourdeposition(pCVD)diamondas
asensormaterialfortheBeamCalorimeteraredonetoexploretheproperties
ofthel. ResultsofthemeasurementsperformedwithpCVDdiamond
samples produced by different manufacturers are presented.
Keywords:
ILC, Beam Calorimeter, diamond, electromagnetic calorimeterZusammenfassung
Der zukünftige Linearbeschleuniger (International Linear Collider - ILC)
wird für die Teilchenforschung im Energiebereich bis zu einem Tera-Elek-
tronenvolt (TeV scale) entwickelt. In dieser Arbeit wird der Entwurf des
inneren Vorwärtsbereichs (Very Forward Region) eines Detektors für diesen
Beschleuniger beschrieben. Das Beam-Kalorimeter - eines der zwei elektro-
magnetischen Kalorimeter, die hier angeordnet sind - ist Gegenstand dieser
Arbeit.
Das Beam-Kalorimeter muß eine gute Hermetizität für hochenergetische
Elektronen,PositronenundPhotonenbishinabzusehrkleinenPolarwinkeln
gewährleisten. Es dient für die schnelle Strahldiagnose und als Abschirmung
des inneren Detektors gegen rückgestreute Beamstrahlungsreste und Syn-
chrotronstrahlung.
Als eine mögliche Technologie für das Beam-Kalorimeter wird eine Sand-
wich-AnordnungausDiamantsensorenundWolfram-Absorberplattenbetrach-
tet. Es werden detaillierte Simulationen einer solchen Anordnung durchge-
führt. Die Nachweiseffektivität und die Energie- sowie Winkelauflösung für
elektromagnetische Schauer werden untersucht. Im Ergebnis der Simulati-
onsrechnungen wird nachgewiesen, dass die vorgeschlagene Anordnung die
Anforderungen an ein Beam-Kalorimeter erfüllt.
Zusätzlich werden Untersuchungen an polykristallinem Diamantmaterial,
hergestellt mittels Abscheidung aus der Dampfphase (Chemical Vapour De-
position - CVD), durchgeführt, um dessen Eigenschaften als Sensormaterial
für ein Beam-Kalorimeter zu ermitteln. Die Ergebnisse der Messungen von
Mustern verschiedener Hersteller werden dargestellt diskutiert.
Schlagwörter:
ILC, Beam-Kalorimeter, Diamant, elektromagnetisches KalorimeterContents
1 Introduction 1
2 Physics case of the ILC 3
2.1 The ILC parameters . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 The requirements on the ILC detector . . . . . . . . . . . . . 6
2.3 The ILC detector . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Very Forward Region 13
3.1 Luminosity Calorimeter . . . . . . . . . . . . . . . . . . . . . 14
3.2 Beam Calorimeter . . . . . . . . . . . . . . . . . . . . . . . . . 18
4 Simulation studiesofthediamond-tungstenBeamCalorime-
ter 27
4.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2 Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3 Fake rate and detection efficiency . . . . . . . . . . . . . . . . 30
4.4 Energy resolution . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.5 Angular resolution . . . . . . . . . . . . . . . . . . . . . . . . 41
5 CVD diamond 45
5.1 CVD diamond growth . . . . . . . . . . . . . . . . . . . . . . 47
5.2 Electrical properties of pCVD diamond . . . . . . . . . . . . . 54
5.3 Signals from ionizing particles in a CVD diamond detector . . 61
6 CVD diamond measurements 67
6.1 Capacitance measurements . . . . . . . . . . . . . . . . . . . . 69
6.2 Current-voltage characteristics . . . . . . . . . . . . . . . . . . 71
6.3 Measurements of the Charge Collection Distance . . . . . . . . 80
6.4 MeasurementsoftheChargeCollectionDistanceasafunction
of the absorbed dose. . . . . . . . . . . . . . . . . . . . . . . . 85
6.5 Further studies . . . . . . . . . . . . . . . . . . . . . . . . . . 92
iv6.6 Linearity of diamond response . . . . . . . . . . . . . . . . . . 100
7 Summary 109
7.1 Simulation studies . . . . . . . . . . . . . . . . . . . . . . . . 110
7.2 pCVD diamond sensor tests . . . . . . . . . . . . . . . . . . . 110
7.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
A Fast Beam Diagnostics 113
B Material analysis 115
B.1 Raman spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 115
B.2 Photo-induced luminescence . . . . . . . . . . . . . . . . . . . 117
C Correction for a geometry effect of the LED light intensity 118
vChapter 1
Introduction
+ −The International Linear Collider (ILC) is an e e collider proposed for
precise physics studies at the TeV-scale. The ILC would allow to explore the
mechanism of the electroweak symmetry breaking, to probe physics beyond
the Standard Model via precision measurements on basic physics processes
and to make discoveries.
A precise luminosity measurement and an excellent hermeticity of the
ILC detector are required for the physics program foreseen at the ILC and
will be provided by the instrumentation of the Very Forward Region of the
detector.
The design of the Very Forward Region of the ILC detector is consid-
ered in the presented work. Two electromagnetic calorimeters are located
there. The Luminosity Calorimeter is purposed for the luminosity measure-
ment based on the small-angle Bhabha scattering. The Beam Calorimeter
will be positioned just adjacent to the beampipe covering the lowest pos-
sible polar angles. This calorimeter improves the hermeticity of the whole
detector measuring high energy electrons, positrons and photons down to
polar angle of about 6mrad. Another purpose of the Beam Calorimeter is to
+ −serve for a fast beam diagnostics detecting e e pairs originating from the
beamstrahlung photon conversion. In addition, the calorimeter shields the
inner part of the detector from backscattered beamstrahlung remnants and
synchrotron radiation.
The design of the Beam Calorimeter is the subject of this thesis. The
+ −calorimeter is exposed to e e pairs originating from beamstrahlung which
cause a huge energy deposition for each bunch crossing. This deposition is
used for the fast beam diagnostics, but forms a background for the detection
of a single high energy electron or photon. Moreover, due to these harsh
radiation condition the active material of the Beam Calorimeter must be
ran hard.
1As a possible technology for the Beam Calorimeter, a diamond-tungsten
sampling calorimeter is considered in this work. The performance for detec-
tion of a single high energy electron determined from full simulation of signal
and background events. Detection efficiency, energy and angular resolution
for electromagnetic showers in the Beam Calorimeter are studied. The re-
sults of the studies indicate requirements to the calorimeter segmentation,
diamondsensorpropertiesandreadoutelectronicsforthediamond-tungsten
Beam Calorimeter.
The measurements of polycrystalline diamond sensors done to explore
their performance for the detection of ionizing particles in a calorimeter are
discussed in this work as well. The electrical properties, signal size and
stability of the response under electromagnetic radiation are studied for di-
amond samples produced by different manufacturers. Results of beam test
measurements done to examine a linearity of the diamond response over a
large dynamic range are presented.
Chapter 2 briefly describes the physics goals at the ILC. The correspond-
ing technical requirements on the ILC detector are discussed as well. The
main accelerator and beam parameters and the detector design are reviewed.
A detailed description of the Very Forward Region is done in Chapter 3.
The tasks, requirements and possible designs of the Luminosity and Beam
Calorimeter