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66 5 Scintillator upgrade Figure 5.4: Planned scintillator assembly with delrin Nest, containing 64 CZT detectors. a) Twelve CsI:Tl blocks, surrounding the delrin Nest, can be seen, with the upper four scintillators lying on a delrin plate. b) Planned delrin Nest, with cable feed through at the front side and CZTs visible inside the Nest on delrin holders. c) Five Teflon tubes for calibration and nitrogen flushing will feed into the Nest. Drawings from Ebert [51]
5.3 Monte Carlo studies of the designed upgrade 67 tative. 5.3.1 Implementation of CsI detectors in Venom VENOM is the Cobra simulation framework, first developed by H. Kiel [8] and redesigned by J. Wilson and B. Morgan [53]. It is a Geant4 application, enabling reproducible simulations of signal and background physics processes in the detector for all COBRA collaborators. Venom contains packages, which can be added and extended by the user. All packages use the same physics class (VXPhysicsList) and material class (VXMaterials). Geometry, action, readout and generator classes can be added by writing new packages. THE SCINT64 PACKAGE was written as part of this diploma thesis. It is a new Venom package, constructing a simplified scintillator upgrade design. The simulated construction does not consider the cable and Teflon tubes, neglects the delrin layers, that hold the upper CsI crystals and simplifies the read out electronics of the scintillators. In the Geant4 simulation, twelve scintillator blocks of 5×5×20 cm 3 and eight cubes of 5×5×5 cm 3 surround a delrin Nest. These are attached to one (for cubes) or two (blocks) borosilicate glass, representing the PMT window. The other four or five sides of the scintillator are painted with a 0.5 mm thick MgO layer. Only a preliminary Nest-design, instead of the current design is implemented. It consists of 2 mm delrin plates and has an open front side. A visualisation of the constructed assembly is shown in figure 5.5. The Scint64 package uses the PhysicsList of Venom. It considers therewith a wide range of physical processes [53], without considering optical photons. The simulations of the previous section showed, that simulations of a few 10000 optical photons per deposited MeV particle energy, do enhance the simulation time significantly. As the background estimations for rare processes can require the simulation of several hundred million of events, a description without optical photons was preferred. The energy deposition in each crystal is recorded separately. This data is called raw Venom data and provides no energy resolution. In this package, the quenching of the scintillation light output for alpha particles is also considered and used a Birks factor of kB = 2.3 · 10 −3 gMeV −1 cm −2 for CsI:Tl as reported by Tretyak [31]. At run time, a reduced energy of the alpha particles, according to their
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A DESIGN STUDY FOR A COBRA UPGRADE
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I hereby declare that I have create
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vi Abstract
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viii Überblick
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x Contents 4.1.2 Scintillation proc
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xii Contents
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2 1 Introduction The CdZnTe detecto
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4 2 Neutrino physics mass scales no
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6 2 Neutrino physics Ground states
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8 2 Neutrino physics mi: 〈mνe〉
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10 2 Neutrino physics
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12 3 The COBRA experiment CdZnTe (C
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14 3 The COBRA experiment 1420:480:
Page 28 and 29: 16 3 The COBRA experiment Figure 3.
Page 30 and 31: 18 3 The COBRA experiment They are
Page 32 and 33: 20 3 The COBRA experiment Therefore
Page 34 and 35: 22 4 Scintillation detectors search
Page 36 and 37: 24 4 Scintillation detectors Figure
Page 38 and 39: 26 4 Scintillation detectors spectr
Page 40 and 41: 28 4 Scintillation detectors SCINTI
Page 42 and 43: 30 4 Scintillation detectors emissi
Page 44 and 45: 32 4 Scintillation detectors activa
Page 46 and 47: 34 4 Scintillation detectors descri
Page 50 and 51: 38 4 Scintillation detectors group
Page 56 and 57: 44 4 Scintillation detectors AVALAN
Page 60 and 61: 48 4 Scintillation detectors gap. T
Page 62 and 63: 50 4 Scintillation detectors photoc
Page 64 and 65: 52 5 Scintillator upgrade ergy phys
Page 66 and 67: 54 5 Scintillator upgrade event ID
Page 68 and 69: 56 5 Scintillator upgrade Ephoton (
Page 70 and 71: 58 5 Scintillator upgrade back side
Page 72 and 73: 60 5 Scintillator upgrade three dif
Page 74 and 75: 62 5 Scintillator upgrade vice. The
Page 76 and 77: 64 5 Scintillator upgrade lecting e
Page 80 and 81: 68 5 Scintillator upgrade Figure 5.
Page 84 and 85: 72 5 Scintillator upgrade In 3.1 %
Page 86 and 87: 74 5 Scintillator upgrade were repo
Page 90 and 91: 78 5 Scintillator upgrade crystal p
Page 92 and 93: 80 5 Scintillator upgrade and gamma
Page 94 and 95: 82 5 Scintillator upgrade Backgroun
Page 96 and 97: 84 5 Scintillator upgrade source of
Page 98 and 99: 86 6 Summary and future work dimens
Page 100 and 101: 88 A FIRST APPENDIX Scintillator De
Page 102 and 103: 90 A FIRST APPENDIX A.2 Reports abo
Page 104 and 105: 92 A FIRST APPENDIX trons than a st
Page 106 and 107: 94 B SECOND APPENDIX Figure B.1: Am
Page 108 and 109: 96 B SECOND APPENDIX Figure B.5: Am
Page 110 and 111: 98 B SECOND APPENDIX B.2 Geant4 Gea
Page 112 and 113: 100 B SECOND APPENDIX Cube, scint64
Page 114 and 115: 102 B SECOND APPENDIX
Page 116 and 117: 104 Bibliography [13] H. V. Klapdor
Page 118 and 119: 106 Bibliography [43] T. Y. Kim et
Page 120: Typeset September 29, 2010
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