Air Fluorescence Light Yield Measurements

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Air Fluorescence Light Yield Measurements

• Summary of the
• IWFM05 Workshop
• http//lappweb.in2p3.fr/IWFM05/

Thanks to IWFM05 speakers
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Purpose

• Understand (better) and Calibrate the Air
  Fluorescence Light Yield (FLY)
• Estimate the quality of the air as a
  scintillator
• Understand experimental uncertainties

• Hires Agasa controversy

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Who is interested?

• HiRes (and AGASA)
• Auger
• EUSO, TUS, KLYPVE, OWL,
• Telescope Array

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Interaction UHECR/atmosphere
Air Fluorescence (HiRes, AUGER,TA,
EUSO,TUS,) Cerenkov
Extensive Air Shower
Charged tracks on groung (AGASA, AUGER,TA,)
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Shower Atmosphere properties

• FLY should varies with
• Pressure
• Temperature
• Components (H2O,)

0.2 1 atm
-50 20 oC
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Electron induced Air excitation
e-(high energy)
?
Bremsstrahlung
Ar
N2 and N2 excitation
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Air De-excitation
Fluorescence
UV
UV light emission
UV
Collision
Increase of temperature
No UV light produced
Competition between different processes Decay
Time / Collision Time
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Fluorescence Light Yield Spectrum
Between 300 et 400 nm The Space Window
Davidson et ONeil (1964) Bunner (1967)
Incertainties on FLY measurements 30
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What to measure?
Reproduce study in laboratory the light induced
by an atmospheric shower
Air N2 FLY as a function of
N2 for ref. comparison

• Pression (0 to 1 atm )
• Temperature (-50 ? 20 oC)
• Air composition (O2, Ar)
• Impurities (humidity, aerosol)
• Particule energy
• Particule density
• Particule nature (e-,,?, m, p)
• Shower age (X0)
• Cherenkov contribution
• Lifetimes

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History - References

• A.N. Bunner, PhD thesis, Cornell, 1967
• Cosmic Rays detection by Atmospheric .
  Fluorescence
• Nitrogen fluorescence spectrum between 300 and
  400nm
• Compilation
• Error 30 on yield at each l
• H. Brunet, PhD thesis, Toulouse,1973
• Destruction des états C3Pu de N2 dans lazote
  pur et mélange avec O2, H2O, CO2,CH4
• Rediscovered at Bad Liebenzell (second workshop)
• Kakimoto et al. (1995)
• measurement of total yield between 300 and 400 nm
• three lines (337 nm, 357 nm, 391 nm)
• Error gt 10

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A New Field emerged
Goal understand the fluorescence yield to
better than 10
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• Experimental approach
• Spectroscopy Dl 1 nm
• Narrow band filters Dl 10 nm
• Large band filters Dl 100 nm

published paper(s)
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Published Nagano Results(reference)
15 wave bands measured with a 13
systematic uncertainty using narrow Band filter
(Astropart. Phys. 22 (2004) 235)
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Nagano(cont.)
FLY 3.3 3.9 photons/m/e- _at_ 1atm
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Experimental Setup

• 90Sr Electron Source
• Endpoint Energy 2.3 MeV
• Activity 37 MBq
• Rate _at_ Scintillator 10 20 kHz
• 7 Photon Detectors
• Electrostatic magnetic shielding
• ? low dark rates, stable operation
• Dark rates 400 500 Hz over thr.
• 1 MUG-6 filter
• 6 narrow band filters (FWHW 10 nm)
• _at_ 317, 360, 380, 337, 391, 427 nm
• Gas
• N2, Air
• Pressure range 1 hPa 1000 hPa
• Temperature 16 C

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MF1 Air pressure dependence
DL In Air for 50GeV e- at 28C
DL FLY x eMF1 CDL Cst
Fluorescence FLY Edep . C/(1P/P)
DL (mpe)
Cerenkov CDL a P/Patm , a 0.6 mpe
Background Cst 1.6 mpe
G4 simu
Vacuum measurement
measurement
G4 simu calibration
Fly/Edep in photon/keV
G4 simu
Fit with 2 free parameters C and P

• Results
• C 0.760.1 photon/keV
• P 23.5 5 hpa

Preliminary results
FLYair (Patm) 0.0172 ph/keV
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MF1 vs other experiments
Air Fly in photon/meter for 50GeV e- at 28C
Nagano et al (04) (300 to 406 nm)
Kakimoto et al (96)
Bunner (300 to 406)
Macfly air FLY 9 less than Nagano 8 more
than Kakimoto 6 more than Bunner
Preliminary results
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Shower age dependence
Detected light in air for primary 50GeV e- at
25C
Blue 500 hpa Red 100 hpa ------ GIL model
(50 GeV e- in Cu)
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MF1 Energy Dependence
Air Fluorescence Light Yield
Preliminary results
FLY (ph/m)
Kinetic Energy (MeV)
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Experimental set-up July 2004
Cooling unit
PM3
scintillator
PM1, PM2 - XP2020Q PM3 R1166
Cooling Box
to vacuum pump
Pressure sensor
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Raw data (a particle excitation)
P0 600 hPa r 0,59 ro
P0818 hPa r 0,80 ro
P0688 hPa r 0,68 ro
P0 520 hPa r 0,51 ro
P0434 hPa r 0,43 ro
Temperature dependance
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Outlook

• Delicate measurements Goal 10 syst.
• All the projects are Running Experiments
• Lines Filters measurements performed
• Pressure dependence (all)
• Temperature (Coimbra, AirFly)
• First Shower age FLY measurements
• MacFly, FLASH
• Simulation G4
• Needed, mature
• Absolute calibration
• Cerenkov, Rayleigh,
• Difficult, needed
• Theory/Models
• improving

Where the FLY story ends?
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