Measurement of the Fluorescence Yield for UHECR study
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Measurement of the Fluorescence Yield for
UHECR study
Gwenaëlle LEFEUVREAPC – Collège de France
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2
1. Cosmic Rays2. Fluorescence3. Yield Measurements
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Ultra-High Energy Cosmic Rays
Energy max. ?Nature ?Origin ?Processes ?
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The need of an accurate energy
15 % in energy almost 40 % in flux * E3 !
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Air shower
•some 103 hadrons•some 109 electrons
Electromagnetic part : 90 % of total energy !
Cosmic ray
Nuclei
Cosmic ray
Fluorescence(isotropic)
Cerenkov cone
Charged particles
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Detecting the UHECR
Sampling• extrapolation of cross sections• AGASA, Auger
Fluorescence• development of the shower• HiRes, Auger, EUSO
Today : Augercalibration of surface detectorby fluorescence
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What is the fluorescence ?
e-sh + N2 e- + N2
+* + e-sh
Excitation
e- + N2+ N2*
e- + N2 e- + N2*
Bunner, PhD thesis, 1967
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Fluorescence spectrum
(Ulrich, Airlight workshop, 2003)
• « Dry air » (80 % N2, 20% O2), 1 barafter correction of spectrometer response• electron gun, 1013 e-/s
Wavelength
Inte
nsit
y (
rel.
un
it.)
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De-excitation of nitrogen
• Radiation • Internal
• Collision• Recombination : O2
Null pressure
f(P, T)
Yie
ld (
ph
oto
ns /
m
)
Pressure (hPa)
photons / e- / meter
dX
dE
hTPTPY
1),(),(
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US-Standard 76 atmosphere
Density Pressure Temperature
)(),( zYTPY
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2,7
2,9
3,1
3,3
3,5
3,7
3,9
4,1
4,3
0 2 4 6 8 10 12 14 16 18 20
altitude (km a.s.l.)
flu
ore
scen
ce y
ield
(p
ho
ton
s/m
)
Keilhauer with Ulrich cross sections, only 10wavelengths as for NaganoKeilhauer with Ulrich cross sections, all 19wavelengthsNagano (2004)
Kakimoto (1996)
Yield variation with altitude
ModelsMeasurements
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2,7
2,9
3,1
3,3
3,5
3,7
3,9
4,1
4,3
0 2 4 6 8 10 12 14 16 18 20
altitude (km a.s.l.)
flu
ore
scen
ce y
ield
(p
ho
ton
s/m
)
Keilhauer with Ulrich cross sections, only 10wavelengths as for NaganoKeilhauer with Ulrich cross sections, all 19wavelengthsNagano (2004)
Kakimoto (1996)
Yield variation with altitude
13.5 %
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Already, my result...
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Objectives
• Absolute yield in [300, 430] nm with the best accuracy possible
• Absolute fluorescence spectrum
To achieve this : need an accurate and absolute
calibration of the detectors
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the setup
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the setup370 MBq
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the setup
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the setup
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the setup
BG3 (Schott)
wavelength (nm)
Tra
nsm
issio
n (
%)
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the setup
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the setup
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the setup
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the setup
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the setup
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the setup
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