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Rencontres de Moriond 2009. Very High Energy Phenomena in the Universe. RADIODETECTION AND CHARACTERIZATION OF THE COSMIC RAYS AIR SHOWER RADIO EMISSION FOR ENERGIES HIGHER THAN 10 16 eV WITH THE CODALEMA EXPERIMENT. Thomas SAUGRIN. for the CODALEMA collaboration. WHY RADIODETECTION ?. - PowerPoint PPT Presentation
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RADIODETECTION AND CHARACTERIZATION OF THE COSMIC RAYS AIR SHOWER RADIO EMISSION FOR ENERGIES HIGHER THAN 1016 eV WITH THE CODALEMA EXPERIMENT
Thomas SAUGRIN
1
Rencontres de Moriond 2009
Very High Energy Phenomena in the Universe
for the CODALEMA collaboration
WHY RADIODETECTION ?
Advantages Disadvantages
Surface detectors
- Duty cycle of 100% - Shower model dependence (sensibility to lateral distribution)- Large covered area is needed
Fluorescence detectors
- Shower model independence (sensibility to longitudinal distribution)- Large detection volume
- Duty cycle of 10%
04/02/2009 2Thomas SAUGRIN
Features of « classical » EAS detection methods:
EAS electric field creation mechanisms:
- negative charge excess (Askar’yan, 1962) - geomagnetic mechanism (Kahn and Lerche, 1965):
- geosynchrotron model (Huege and Falcke, 2000)- transversal current model (Lasty, Scholten and Werner, 2005)
Present experiments on radiodetection: - the LOPES experiment (Germany) - the CODALEMA experiment (France)
But… first experiments (1963-1980) failed to prove EAS radiodetection efficiency
WHY RADIODETECTION ?
04/02/2009 3Thomas SAUGRIN
WHY RADIODETECTION ?
04/02/2009 3Thomas SAUGRIN
Theorical features of EAS radiodetection:
EAS electric field creation mechanisms:
- negative charge excess (Askar’yan, 1962) - geomagnetic mechanism (Kahn and Lerche, 1965):
- geosynchrotron model (Huege and Falcke, 2000)- transversal current model (Lasty, Scholten and Werner, 2005)
Present experiments on radiodetection: - the LOPES experiment (Germany) - the CODALEMA experiment (France)
But… first experiments (1963-1980) failed to prove EAS radiodetection efficiency
EXPERIMENTAL CONFIGURATION (2008)
21 antennaswith EW polarization
3 antennaswith NS polarization
17 scintillatorstrigger of the antenna array
2 overlapping arrays:
Antenna array:
Scintillator array:
04/02/2009 4Thomas SAUGRIN
ACTIVE DIPOLAR ANTENNAS
Gain 30 dB
Frequency bandwith 80 kHz à 230 MHz
Input impedance 10 pF
Input noise 19 µV
Length 1,2 m
Width 10 cm
Height 1,2 m
Sensible to the galactic noise
Antenna lobe obtained by simulation (EZNEC software)
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LST time
Mea
n si
gnal
(V)
Equivalence voltage – electric field obtained by the simulated antenna response
SCINTILLATOR ARRAY
Trigger rate: 1 evt/ 7 mins
Energy threshold: 1.1015 eV
Zenithal acceptanceZenithal acceptance: : 0° < <60°
Informations on EAS:- Arrival direction- Shower core position- Energy estimate (CIC method)
2 different classes of trigger events (5 central stations in coincidence) :
- Internal events: Station with the maximum signal is not on the border of the array. Correct estimate of shower energy and core position.
- External events: Unreliable estimate of shower energy and core position.
04/02/2009 6Thomas SAUGRIN
DETECTION EFFICIENCY
Radiodetection threshold (~5.1016 eV) > Trigger threshold (1015 eV)
Maximal detection efficiency of 50% for an energy of 7.1017 eV
Source of event deficit ?
04/02/2009 7Thomas SAUGRIN
scintillators
antennas
Only a few events can be detected by CODALEMA
CODALEMA can only access to a restricted energy bandwith
ARRIVAL DETECTION
Geomagneticaxis
- Deficit of events in the geomagnetic axis area- Uniform azimutal acceptance for the scintillator array:
Evidence for a geomagnetic effect in the electric field creation mechanism?
Strictly a radio effect
04/02/2009 8Thomas SAUGRIN
North
South
EastWest
North
South
EastWest
Sky map Covering map
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Predicted covering map:Predicted covering map:
Total Lorentz force (sin α)
Toy model:
04/02/2009 9Thomas SAUGRIN
North
South
EastWest
u. a.
INTERPRETATION
XTrigger acceptance(zenithal angle distribution)
04/02/2009 10Thomas SAUGRIN
INTERPRETATION
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Predicted covering map:Predicted covering map:
Total Lorentz force (sin α)
Toy model:
North
South
EastWest
04/02/2009 11Thomas SAUGRIN
Carte de couverture prédite:Carte de couverture prédite:
Force de Lorentz totale (sin α)
Antenna lobe
INTERPRETATION
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Toy model:
North
South
EastWest
X
XAntenna lobe(EZNEC simulation)
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INTERPRETATION
Trigger acceptance(zenithal angle distribution)
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Predicted covering map:Predicted covering map:
Total Lorentz force (sin α)
Toy model:
North
South
EastWest
Projection on East-West axis(CODALEMA antenna polarization)
X
XAntenna lobe(EZNEC simulation)
X
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INTERPRETATION
Trigger acceptance(zenithal angle distribution)
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Predicted covering map:Predicted covering map:
Total Lorentz force (sin α)
Toy model:
North
South
EastWest
04/02/2009 14Thomas SAUGRIN
Carte de couverture prédite:Carte de couverture prédite:
Force de Lorentz totale (sin α)X
XLobe de l’antenne dipolaire(logiciel EZNEC)
Acceptance du trigger particules(paramétrisation de la distribution en angle zénithal)
X
SIMULATION DATANorth
South
EastWest
North
South
EastWest
INTERPRETATION
Hypothesis:Hypothesis:- Electric field proportional to the Lorentz force- Electric field polarization in the direction of the Lorentz force (linear polarization)
Toy model:
Simulated covering map only relevant for radiodetection at energy threshold
MODEL – DATA COMPARISON
Geomagnetic toy model fits correctly experimental data:- in zenithal angle- in azimuthal angle (notably the local maximum in the South direction)
Relevant experimental evidence for a geomagnetic effect in the electric field creation mechanism
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datatoy model
datatoy model
NORTH-SOUTH POLARIZATION
Only 3 antennas with North-South polarization: low statistic (90 events)
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North
South
WestEast
North
South
East West
Preliminary results show good agreement with simulation
NORTH-SOUTH POLARIZATION
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PRELIMINARY
Only 3 antennas with North-South polarization: low statistic (90 events)
Preliminary results show good agreement with simulation
ELECTRIC FIELD LATERAL DISTRIBUTION
Electric field exponential parameterization (Allan):
E(d) α EP . sin α . cos θ. exp(-d/d0)
E0
E0 radio estimator of shower energy ?
04/02/2009 18Thomas SAUGRIN
E0E0
E0/e E0/e
d0 d0
Elec
tric
fiel
d (µ
V/m
)
Elec
tric
fiel
d (µ
V/m
)
Distance to the shower axis (m) Distance to the shower axis (m)
ELECTRIC FIELD LATERAL DISTRIBUTION
Only 25% of the total events allow a relevant estimate of the E0 parameter
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Experimental limitations ?
Physical limitations ?
Near threshold detection, size of the antenna array, one polarization measurement
Incomplete parameterization of the electric field ?
ENERGY CORRELATION
For the 44 internal events with a For the 44 internal events with a relevant estimate of the Erelevant estimate of the E00 parameter: parameter:
E0corr (µV/m) = 95,7. (ECIC /1017 eV ) 1,04
σres = 34% σmin radio ~ 16%
- Linear relation between E0corr and ECIC
- Radio detector resolution seems to be better than particle detector resolution
In case of exponential lateral distribution, E0 is a relevant estimator of the shower energy
04/02/2009 20Thomas SAUGRIN
Log 10
(E0c
orr)
Log10(ECIC)
(E-E0)/E0
Event by event: E0corr= E0 /(cos θ . )
PRELIMINARY
SUMMARY/OUTLOOK
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Experimental evidence for a geomagnetic origin of the electric fieldExperimental evidence for a geomagnetic origin of the electric field
Energy calibration promising for the future of the methodEnergy calibration promising for the future of the method
Drawback of CODALEMA present experimental set-up:Drawback of CODALEMA present experimental set-up:
Small detection surface
Radiodetection energy threshold of ~5.1016 eV
Work near the detection threshold
Restricted energy bandwith
May explain difficulties of results interpretation
Creation of a dense array
Extension at largest area and to higher energies
NEXT STEPS
Autonomous stations :- self-triggered- measurement of the E-W and N-S polarizations
In 2009:
- 20 stations at Nançaydense array of 600m x
600m with 44 antennas
- Available for the radio@Auger project
large array with a step of ~300m
In 2010:
Extension of CODALEMA with 100 stations (1 km2)
04/02/2009 22Thomas SAUGRIN
STATISTICS
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