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

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7 The Source Runs in CTF2 transparent, so that it doesn’t absorb the scintillation light, and has a refractive index similar to that of the scintillator. For the production of the sources (see fig. 7.1) a Rn-emanating Ra-source was used (emanation rate Bq). Special care was taken that the source never comes in direct contact with the scintillator to avoid a possible Ra contamination, as this would contaminate the CTF scintillator in the case of leaking or breaking of the quartz vial. The Ra source was placed in a small evacuated gas volume and left there for several days. 98 (a) (b) (c) (d) Ra-source Ra-source + Radon gas Ra-source + Radon gas to vacuum pump scintillator in gas volume evacuated gas volume Radon gas Rn-spiked scintillator Figure 7.1: Schematic drawing of the production of the sources: (a) all volumes are evacuated; (b) the Ra-source emanates Rn-atoms into the vacuum; (c) both volumes are connected, the Rnconcentration in both volumes equilibrates; (d) the flask containing the Ra-source is isolated, scintillator is sucked into the other flask due to low pressure.
7.2 Production of the Sources Then the gas volume was decoupled from the source and brought in contact with PXE scintillator (that had been bubbled with nitrogen first to remove dissolved oxygen). As the partition coefficient for Rn in liquid scintillator to Rn in gas is about 10:1, after a short contact time most of the Rn should have been transferred from the gas phase to the scintillator. The Rnloaded scintillator was finally filled into a small quartz vial and closed with teflon screw caps (see fig. 7.2). In the transfer of the radon-spiked scintillator to the source vial, it was necessary to minimize oxygen contamination, as oxygen causes quenching of the scintillation light. Hence all the work was carried out in a glove bag under nitrogen atmosphere. Anyhow, the sources showed some evidence of oxygen contamination, as the position of the Po peak was shifted to lower energies compared to its position during the ‘non-source’ runs. The spiked scintillator could not be sparged for oxygen removal, as this would also remove the Rn. The source test in the CTF2 was done with two different Rn-sources: - Source no. 1 consisted of a cylindrical quartz vial with a diameter of 1.7 cm, 9.5 cm length, filled with Rn-loaded scintillator and closed with teflon screw caps at both ends. This source had a rather low Rn-activity ( 0.06 Bq). The scintillator inside the source was quenched ( Po-peak at 200 pe). - Source no. 2 had a diameter of 1 cm, 5.5 cm length, and only one teflon screw cap at the top. The initial Rn-activity was 0.3 Bq. The scintillator was highly quenched ( Popeak at 100 pe). Figure 7.2: Two quartz vials filled with Rn-spiked scintillator, that were used for the calibration runs in CTF2. 99
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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
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1 Solar Neutrinos Figure 1.1: The p
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1 Solar Neutrinos 1.2 Detection of
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1 Solar Neutrinos With this detecti
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1 Solar Neutrinos 1.2.3 Future Expe
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1 Solar Neutrinos 1.3.2 Astrophysic
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1 Solar Neutrinos Using the unitari
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1 Solar Neutrinos km in the earth.
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1 Solar Neutrinos 16 Solution ¡Ñ
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2 The Borexino Experiment The relat
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2 The Borexino Experiment Figure 2.
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2 The Borexino Experiment 2.2 The D
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2 The Borexino Experiment 2.3 Detec
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2 The Borexino Experiment 2.3.2 Anc
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2 The Borexino Experiment which per
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2 The Borexino Experiment 2.4 Backg
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2 The Borexino Experiment ns; Rn-
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2 The Borexino Experiment volume wo
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3 The Counting Test Facility (CTF)
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4 Position Reconstruction of Scinti
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Page 72 and 73: 5 Particle Identification with a Ne
Page 86 and 87: 6 Test of a PXE based scintillator
Page 110 and 111: 7 The Source Runs in CTF2 7.3 The S
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Page 124 and 125: Summary and Outlook possible to dis
Page 126 and 127: Bibliography [Ade98] E. G. Adelberg
Page 128 and 129: Bibliography [Bra00] L. De Braeckel
Page 130 and 131: Bibliography [Lom97] P. Lombardi, D
Page 132 and 133: Bibliography [Vog96] R. B. Vogelaar
Page 134 and 135: Danksagung An dieser Stelle möchte
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Development of a Liquid Scintillator and of Data ... - Borexino - Infn

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