Measurement of the Fluorescence Yield for UHECR study

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