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

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3 The Counting Test Facility (CTF) of Borexino 38 ADC 1 150 ns gate g a TTR 1 ADC 1 e t stop TDC 1 ECL --- NIM gate 500 ns out α−β common start s t o p 0 2 4 6 48 ns NEW 1 150 ns common stop i n p u t i n p u t 32 ns FI -- FO 11/1 16 ns att 3/1 gate 150 ns L E D & 3/2 A FI/FO 2/1 em FI/FO FI/FO 4/1 veto S U M 1/1 PMT common LONG RANGE input 1 FI -- FO TDC 10/2 input 5 P D U 150 ns 1 10/1 FI -- FO Trigger Selection 8.3 ms gate c l e a r 2 A & 3/1 MAIN C F D FI -- FO Ampl 150 ns 3 LASER B 10/4 FI -- FO 4 FI -- FO veto m e em o u t PULSER C STATUS A gate 1.0 ms veto & A 6/1 M L U FI -- FO 1/2 FI/FO veto L E D em 150 ns gate 4/2 L E D B veto FI/FO & A A & ECL --- NIM Figure 3.2: Block diagram of read out electronics of the CTF. 10/3 11/3 FI/FO 2/2 3/2 3/3 6/3 common stop att common start i n p u t s t o p 2 ADC α−β g a t e TDC 2 stop ECL --- NIM i n p u t TTR 2 gate 500 ns 6 4 2 0 16 ns out 32 ns 150 ns gate 48 ns 11/2 FI -- FO MUON VETO NEW 2 DEAD TIME ADC 2 150 ns
3.3 Results from the CTF1 All the structure is immersed in 1000 tons of deionized water contained within a carbon steel tank (11 m diameter, 10 m high), whose inside walls are coated with a black epoxy resin in order to minimize light reflections from the tank walls. The water provides shielding from the external -ray background coming from the PMTs, the steel, and the surrounding rocks. Fig. 3.2 shows the data acquisition logic. The 100 photomultiplier outputs are processed in 64 electronic channels, 72 PMTs are fanned together in pairs into 36 channels, and 28 PMTs are read as single channels. Each electronic channel has a time-to-digital-converter (TDC) and an analog-to-digital-converter (ADC). The trigger is provided by a Majority Logic Unit. The trigger condition is set so that a certain number of PMTs (usually 6) must receive a photon within a time window of 30 ns. This trigger condition is necessary because each PMT has a dark noise of approximately 1 kHz. For each event the charge and timing of the hit phototubes are recorded. To avoid missing fast time correlated events, each processing channel is doubled by a second channel to record events coming within a time window of 8 ms after the first event. The delay time is measured with a precision of 1 ns. For longer correlation times, the internal clock of the computer is used (with a resolution of s). The PMT analog signals are also summed up to provide the total charge and the charge integrated over the pulse tail (with a delay of 32 ns and 48 ns), to discriminate between alpha and beta events, and to record the pulse shape of each event by a waveform digitizer. The time calibration of the PMT signals is done with a pulsed laser (pulse width 50 ps) with a wavelength of 410 nm, which is coupled to a bunch of 100 optical fibers leading to each PMT. The intensity of the laser signal is attenuated so that each PMTs receives photoelectron from each laser pulse. 3.3 Results from the CTF1 From March 1995 until August 1996 the scintillator È ÈÈÇ Ð was tested in the CTF. With the CTF the scintillator radiopurity was measured at previously unachieved levels. It is the largest nuclear detector ever built with sensitivity down to the sub 100 keV spectral regime; and with a background of 0.03 events kg keV yr in the 0.25 - 2.5 MeV energy window [Ali98c] it is the detector with the lowest background activity in this regime, even better than detectors searching for neutrino-less double beta decay. The C content in the scintillator was determined by normalizing the CTF low energy spectrum (50 - 150 keV) to the spectral shape expected from the decay of C (see fig. 3.3), giving a value of ¦ Ali98b℄ The concentration of Rn and Th in the scintillator was determined by tagging the correlated decays of their short-lived daughters Po (Ø ×) and Po (Ø Ò×). Assuming secular equilibrium in the decay chains, this activity can be ex- 39
Page 1: Fakultät für Physik der Technisch
Page 4 and 5: Abstract The first chapter contains
Page 6 and 7: Übersicht an Radionukliden in BORE
Page 8 and 9: Contents 3 The Counting Test Facili
Page 10 and 11: 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
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6 Test of a PXE based scintillator
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7 The Source Runs in CTF2 transpare
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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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