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Measurement of the Fluorescence Yield for UHECR study. Gwenaëlle LEFEUVRE APC – Collège de France. Cosmic Rays Fluorescence Yield Measurements. Ultra-High Energy Cosmic Rays. Energy max. ? Nature ? Origin ? Processes ?. The need of an accurate energy. - PowerPoint PPT Presentation
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Measurement of the Fluorescence Yield for
UHECR study
Gwenaëlle LEFEUVREAPC – Collège de France
2
1. Cosmic Rays2. Fluorescence3. Yield Measurements
Ultra-High Energy Cosmic Rays
Energy max. ?Nature ?Origin ?Processes ?
The need of an accurate energy
15 % in energy almost 40 % in flux * E3 !
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
Detecting the UHECR
Sampling• extrapolation of cross sections• AGASA, Auger
Fluorescence• development of the shower• HiRes, Auger, EUSO
Today : Augercalibration of surface detectorby fluorescence
What is the fluorescence ?
e-sh + N2 e- + N2
+* + e-sh
Excitation
e- + N2+ N2*
e- + N2 e- + N2*
Bunner, PhD thesis, 1967
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.)
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),(),(
US-Standard 76 atmosphere
Density Pressure Temperature
)(),( zYTPY
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
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 %
Already, my result...
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
the setup
the setup370 MBq
the setup
the setup
the setup
BG3 (Schott)
wavelength (nm)
Tra
nsm
issio
n (
%)
the setup
the setup
the setup
the setup
the setup
the setup
