Gwena

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1) Production of secondary electrons
Widening of the fluorescence volume 2 mm
Atm. pressure 99 of electrons have E 5 keV
Negligible impact on electron length
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2) Diffusion on the lead
Influence on the electron spectrum simulated
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3) Retro-diffusion on the scintillator
Only 10-9 effect negligible
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Gas circulation
Switch
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Principle of the DAQ
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Calibration how do the PMTs work ?
Poisson law
electron-PMT µ 2 000 pe
integral spectro PMT µ 0.02 pe

• P(0) 0.98, P(1) 0.02
• single photoelectron mode

• P(0) 0
• Efficiency 1

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Pure single pe in PMTs
Analog signal
Photonis XP2020Q  0  /   1  50
ADC channel
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Pure single pe in PMTs
Analog signal
ADC channel
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Pure single pe in PMTs
Analog signal
Detection inefficiency
integral-PMT 3.76 spectro-PMT 3.85
ADC channel
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Efficiency measurement process
New method in 3 steps uncertainty lt 2 CNRS
patent application

1. X-Y mapping
2. Absolute efficiency in (x0, y0)
3. Normalization of the map

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1) Mapping
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1) Mapping
integral-PMT
spectro-PMT
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1) Mapping
spectro-PMT
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2) Absolute efficiency

• Absolute comparison with something known
• calibrated source or photodetector

spatial distribution of light 10 accuracy NO
gain 1 when PMT have gain 107
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2) Absolute efficiency
Integrating spheres AND diaphragms
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2) Absolute efficiency
Integrating Sphere
NIST photodiode
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2) Absolute efficiency
everything stays the same but the PMT
2 Spheres 3 diaphragms Flux reduction 2.42
106
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3) Normalization of the map
integral-PMT
18.5 1.7 uncertainty
Efficiency ()
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Result for integral-PMT
0.178 0.004 Uncertainty 2.2
Efficiency
wavelength (nm)
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Integral measurement
Quantity Uncertainty
Detection inefficiency, scaler dead time negligible
geometry (Le and solid angles) 1.5
Transmission of the quartz window 1
Efficiency of the PMT 2.2
TDC 4
Statistics 0.2
TOTAL 4.91
After normalizations (P, T, E) 5
4.23 0.22 photons / m
G. Lefeuvre et al, to be published (NIM A)
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Spectral measurement
(Ulrich, Airlight workshop, 2003)
3.9 0.8 ph/m
yield (photons / m)
wavelength (nm)
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Spectral measurement
Our results
Ulrichs spectrum, convoluted with our 3 nm
resolution
yield (photons / m)
wavelength (nm)
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Conclusion
Flys Eye
J x E2,61 (eV1,61/m2 . sr . s)
Extra-Galactic Galactic
Galactic
No GZK
HiRes
FlyEyes
Yakutsk
AGASA
1020
1019
1018
E (eV)
Bahcall Waxman hep-ph/0206217 v5
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Still much to measure...

• Pressure Temperature dependences
• Impurities
• Spectrometer CCD light intensifier
• Reduction of the TDC uncertainty
• Flash-ADC

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Thank you