Development of a Liquid Scintillator and of Data ... - Borexino - Infn

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4 Position Reconstruction of Scintillation Events 52 Figure 4.5: Quantum efficiency of the 8” Thorn EMI 9351 photomultiplier used in BOREXINO. Figure 4.6: Pulse height distribution of the single photoelectron pulse and transit time distribution measured with one of the 8” Thorn EMI 9351 photomultipliers used in BOREXINO. Ü. It is assigned a wavelength , a scintillation delay time Ø×, and a direction Ù. The refractive index Ò is calculated depending on the medium and wavelength. 2. Calculate the distance to the next border and the free path lengths for absorption and scattering on PC and PPO. The process with the minimum distance ÖÑÒ occurs. The photon proceeds to this point (Ø Ø ÖÑÒÒ , Ü Ü ÖÑÒÙ). 3. If an interaction occurs: - Scattering: new direction of the photon Ù Ù , continue with 2. - Absorption: calculate the probability for reemission. If reemission occurs, go to 1.
4. If the photon reaches a surface: 4.2 The Tracking of the Scintillation Photons - Inner Vessel Radius, 425 cm (only for water buffer): Reflection? Refraction? Calculate new direction (Ù Ù ), index of refraction in the new medium, and continue with 2. - Radius of PMTs with cones, 635 cm: Cone aperture hit? Is it reflected by the cone? If it is accepted, proceed to the PMT. Is it reflected on the surface? If not, go to 5, otherwise continue with 2. - Radius of PMTs without cones, 655 cm: PMT hit? If yes, is it reflected? If not, goto 5, otherwise calculate reflection angle and continue with 2. - Stainless Steel Sphere, 685 cm: absorption or reflection on stainless steel? 5. PMT hit: the photon is converted into a photoelectron according to the photocathode efficiency. Calculate the time jitter and the pulse height signal. If the pulse height is above the threshold, store the time of the signal. When the grid for the reconstruction is computed, the program loops over a spatial grid, where a fixed number of photons starts from each grid point. In the end, only the time of the first photoelectron of each PMT is stored for each grid point. This simulation has to be done with a very high statistics, in order to get the earliest possible arrival time of a photon at each PMT Ø min Ü Ý Þ . The probability density function for a single photoelectron Ø is derived from a Monte Carlo simulation, where a number of photons starts from the center of the detector (so that the distance to all PMTs is the same) and is stored in a separate file. This probability density function reflects the decay time of the primary scintillation light emission, additional delays introduced through absorption and reemission, scattering, reflection, etc. of the photon on its way to the PMT, and the time jitter of the PMT. In principle, this distribution also depends on the distance between the primary emission point and each individual PMT, but in the first order it is the same for all positions inside the scintillator. Fig. 4.7 shows the averaged probability density function for the CTF for two different positions, in the center and in a distance of 94 cm from the center (corrected for the time of flight to the PMTs). There are notable differences only for late arrival times, which do not provide good information for the position reconstruction, anyway. 53
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Fakultät für Physik der Technisch
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Abstract The first chapter contains
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Übersicht an Radionukliden in BORE
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Contents 3 The Counting Test Facili
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Contents viii
Page 12 and 13: 1 Solar Neutrinos Figure 1.1: The p
Page 14 and 15: 1 Solar Neutrinos 1.2 Detection of
Page 16 and 17: 1 Solar Neutrinos With this detecti
Page 18 and 19: 1 Solar Neutrinos 1.2.3 Future Expe
Page 20 and 21: 1 Solar Neutrinos 1.3.2 Astrophysic
Page 22 and 23: 1 Solar Neutrinos Using the unitari
Page 24 and 25: 1 Solar Neutrinos km in the earth.
Page 26 and 27: 1 Solar Neutrinos 16 Solution ¡Ñ
Page 28 and 29: 2 The Borexino Experiment The relat
Page 30 and 31: 2 The Borexino Experiment Figure 2.
Page 32 and 33: 2 The Borexino Experiment 2.2 The D
Page 34 and 35: 2 The Borexino Experiment 2.3 Detec
Page 36 and 37: 2 The Borexino Experiment 2.3.2 Anc
Page 38 and 39: 2 The Borexino Experiment which per
Page 40 and 41: 2 The Borexino Experiment 2.4 Backg
Page 42 and 43: 2 The Borexino Experiment ns; Rn-
Page 44 and 45: 2 The Borexino Experiment volume wo
Page 46 and 47: 3 The Counting Test Facility (CTF)
Page 56 and 57: 4 Position Reconstruction of Scinti
Page 72 and 73: 5 Particle Identification with a Ne
Page 86 and 87: 6 Test of a PXE based scintillator
Page 108 and 109: 7 The Source Runs in CTF2 transpare
Page 110 and 111: 7 The Source Runs in CTF2 7.3 The S
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7 The Source Runs in CTF2 102 of th
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7 The Source Runs in CTF2 7.4 Analy
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7 The Source Runs in CTF2 7.4.2 Rec
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7 The Source Runs in CTF2 7.4.3 Ene
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7 The Source Runs in CTF2 45 40 35
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7 The Source Runs in CTF2 112 reemi
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Summary and Outlook possible to dis
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Bibliography [Ade98] E. G. Adelberg
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Bibliography [Bra00] L. De Braeckel
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Bibliography [Lom97] P. Lombardi, D
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Bibliography [Vog96] R. B. Vogelaar
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Danksagung An dieser Stelle möchte
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Development of a Liquid Scintillator and of Data ... - Borexino - Infn

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