A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

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38 experimental setup and data acquisition Counts 300 250 200 150 100 50 0 600 800 1000 1200 1400 1600 ADC (chn) (a) counts 80 70 60 50 40 30 20 10 0 0 200 400 600 800 1000 ADC (chn) Figure 19: (a) Calibration ADC spectrum of a sample paddle (G-21 top) excited at its centre with monoenergetic electrons from a 207 83 Bi radioactive source. Two peaks, corresponding to 0.481 MeV and the superposition of the 0.975 and 1.047 MeV lines, are clearly visible. 120 histograms for each of the seven HV values used in the calibration were fitted automatically by two Gaussians plus an exponential background. (b) Calibration ADC spectrum of F sample paddle excited with beam electrons going through Kaos working in reverse polarity. A single Gaussian with an exponential tail is fitted to the m.i.p energy histogram. with an accuracy of 1 cm. The study showed a clear deterioration of the optical properties of the plastic material, resulting in absorption lengths almost one order of magnitude smaller than expected. Time resolution was also affected as it scales with the square root of the number of detected photons (the resulting value was FWHM=200 ps). This reduced resolution was still sufficient for the time of flight PID needed at Kaos. The decision was taken of maintaining the existing paddles for the first physical measurements of the spectrometer. A first calibration of the walls was performed with a 207 83 (b) Bi source. Fig. 19(a) shows the clear double peak structure obtained by exciting the paddles at their center with the internal conversion electrons of energies 0.481, 0.975 and 1.047 MeV. A dedicated hardware trigger, consisting of the oring of the 60 top and bottom signal coincidences, was arranged for this purpose. The source was displaced from scintillator to scintillator for each of the seven calibration voltages between 1800 V and 2400 V. The automatized analysis of these 840 histograms was performed by a dedicated software. A pedestal localization and elimination was followed by a peak finding algorithm, complemented with a fitting routine where a model based on the sum of two Gaussian peaks and an exponential background was assumed. The set of seven ADC values obtained for each PMT was assumed to follow a relation of the type: chn = aV b . A linear fit in a log-log plot was used to extract the calibration parameters a and b. Unfortunately, the bad condition of many of the scintillator paddles did not allow a convergence of the peak finding algorithm for all
2.4 kaos spectrometer 39 channels. This calibration was thus considered provisional and used for testing purposes in the first Kaos runs. Final calibration was performed during beam time working Kaos dipole in reverse polarity and detecting the minimum ionizing electrons. A cut in the MWPCs measured position allowed a selection of electrons going through a narrow band in the center of the paddles, providing a clear energy signal (see Fig. 19 (b)). 2.4.5.3 Absorption Absorption coefficients for F and G paddles were obtained by fitting an exponential function Q(y) = Ce −y/L to the -corrected for path length- ADC histograms. Values of the order of 1 m were found for G wall. F paddles showed a much poorer performance being the average absorption length 25 cm. For data analysis, the most convenient method to correct light absorption was proved to be the use of geometrical average of top and bottom charge values ( � QtopQbottom), as this quantity does not depend of the vertical coordinate due to the cancelation of the two exponentials. ADC (a.u.) 900 800 700 600 500 400 300 200 100 -150 -100 -50 0 50 100 150 Fy (mm) F Absorption Length (mm) 500 450 400 350 300 250 200 150 100 50 0 Top PMT Bottom PMT ADC (a.u.) 200 -150 -100 -50 0 50 100 150 Fy (mm) 6 8 10 12 14 16 18 20 22 24 26 F Paddle Figure 20: Top: Absorption fits for top and bottom PMTs for a representative F paddle. Bottom: Absorption lengths obtained from the fits to all F paddles. Dotted black line shows the low average value resulting for these aged paddles. 800 700 600 500 400 300
Page 1: M E A S U R E M E N T O F T H E U N
Page 5: A B S T R A C T The new stage of th
Page 9 and 10: C O N T E N T S i kaon electroprodu
Page 11: Part I K A O N E L E C T R O P R O
Page 14 and 15: 4 introduction Lorentz invariance.
Page 16 and 17: 6 introduction appear in the K + Λ
Page 18 and 19: 8 introduction there was almost no
Page 20 and 21: 10 introduction This allows us to w
Page 22 and 23: 12 introduction K ¡p γ ∗ Λ(Σ
Page 24 and 25: 14 introduction means of the isobar
Page 26 and 27: 16 introduction amount of resonance
Page 28 and 29: 18 introduction photo and electropr
Page 30 and 31: 20 introduction 1.6 previous experi
Page 32 and 33: 22 introduction Figure 9: Total cro
Page 35 and 36: E X P E R I M E N TA L S E T U P A
Page 37 and 38: 2.3 target 27 Figure 11: Schematic
Page 39 and 40: 2.4 kaos spectrometer 2.4 kaos spec
Page 41 and 42: M MWPC L F 2.4 kaos spectrometer 31
Page 43 and 44: Table 3: Spectrometers properties 2
Page 45 and 46: 2.4 kaos spectrometer 35 Figure 16:
Page 47: 2.4.5.1 Read out electronics 2.4 ka
Page 51 and 52: 2.5 kaos single arm trigger 41 64MB
Page 53 and 54: 2.6 spectrometer b 43 Figure 23: Sc
Page 55 and 56: 2.7 coincidence setting 45 to be im
Page 57 and 58: 2.8 data acquisition and analysis s
Page 59: 2.9 kinematical setting 49 (GeV/c)
Page 62 and 63: 52 detection efficiencies and data
Page 91 and 92: C O N C L U S I O N S The effort to
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Page 95 and 96: cm [nb/sr] dσ / dΩ K 500 400 300
Page 97: Part II F E A S I B I L I T Y S T U
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90 conclusions Figure 55: Emission
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92 prototyping and efficiency measu
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100 prototyping and efficiency meas
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102 prototyping and efficiency meas
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104 noise and radiation damage Figu
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106 noise and radiation damage Prob
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110 noise and radiation damage Figu
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112 noise and radiation damage Puls
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114 noise and radiation damage Tabl
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118 conclusions been tested and fou
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120 theoretical background photopro
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122 theoretical background effect o
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124 theoretical background A physic
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126 theoretical background taken in
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128 theoretical background for the
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130 theoretical background a.8 φ d
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132 theoretical background where σ
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134 theoretical background by showi
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136 theoretical background With thi
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138 bibliography [16] J. C. David,
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140 bibliography [44] M. Bockhorst
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142 bibliography [71] P. Achenbach
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144 bibliography [98] S. Nozawa and
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146 bibliography Figure 24 Spek B d
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Figure 73 Annealing at 80° of the
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A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

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