3mpl graduate school days presentation
TRANSCRIPT
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Some Results of the Codalema
Experiment at Nançay
Ahmed Rebai
Subatech Laboratory Nantes JED le Mans 30 June 2011
• Introduction
• North-South Asymmetry
• Energy Calibration
• Reconstruction of the radio wave emission center
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Auger data 2008
Many unanserewed questions about cosmic rays with
energies in the range of joule (~ 1019 eV )
Radio-detection as a complementary detection
technique ?Surface
Duty Cycle
Cost, simplicity
Angular resolution , Energetic resolution ?
Nature of the cosmic rays ?
Since 2003 installation of CODALEMA
experiment at Nançay: as demonstration of
the feasibility and potential of this method
Nature of those particles ?
Astrophysical Sources ?
A limit in their energies ?
Motivations
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CODALEMA energy
range
Motivations
Cosmic rays spectrum
Energy Threshold : 5.1015 eV
Trigger Rate : 1 evt/ 7 mn
Analysis Threshold : 5.1016 eV
Counting rate : 1 good evt/3 days
Detection surface : 0.25 km2
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Codalema actual setup
-21 dipole antennas E-W
- 3 dipole antennas N-S
Scintillator array
17 scintillator
=>Experiment Trigger
=> Energy Estimator
Array of short antennas
18 groups of 8 log-periodic
phased antennas
Decametric array
CODALEMA Experiment@Nançay
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10% e-,e+
Xmax
Maximum shower
development Nmax
maximum particles
number
Radio Emission
-+
e-/e+ deflection under the geomagnectic field
effect dipole emission, transverse
current, synchrotron radiation
Time variation of the negatif charge excess
monopole emission
Time variation of the charged particles
number
Frequency ~ 100 MHz
Amplitude ~ 100 µV.m-1
Duration ~ 1 ns – 100 ns
Radio Signal
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Detection methodNumeric filter in the 23-83
MHz band
1 event = 2 physical quantities / antenna ( amplitude Vi , time ti , … )
+ Corrections : time delay,
attenuation, antennas gainTime [s]
Am
plit
ude [V
]
FMAM
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ITrigger
IG11
ID98
ID32 IA1
Arrivals direction reconstruction
•Hypothesis: plane wave front Ux.x+Uy.y+Uz.z + cte =0
•Maximum amplitude time ti on antennas
Arrival direction
Θ : Zenithal angle
Φ : Azimuthal angle
σ = 1.6°
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CODALEMA Model
(also SELFAS2, ReAIRES)
Emission mechanism
Polarization E-O
North
confirmed at RAuger@Auger
Argentina (magnetic field
inversed in the southern
hemisphere)
D.Ardouin & al Astro.ph 31 2009
NorthSouth
Zenith
B
θ=27°
|VxB|E-W minimum |VxB|E-W maximum
B
Detection threshold correlated
with arrivals directions
Geomagnetic Effect
Radio Signal Amplitude ~ |VxB|E-W
South
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Radio signal lateral profil in the ground
=> Allan formula : E = E0.exp(-d/d0)
Use of E0 as an energy estimator of the primary particle
E0 on the shower axis
d0 distance of the shower decay
(X0, Y0) shower core
1 event = (E0, d0, X0, Y0)
Lateral Profil Distribution
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Energy Correlation
E0 =a Ep + b Radio calibration Egerbe =(1/a)*E0 – b/a
Calibration depends on :
E0 errors
Ep errors
Ep estimated with the CIC
method (Constant intensity Cut)
ΔEp/Ep ~ 30 %
ΔE0/E0 < 10 %
E0 ~ Epα avec α ~ 1.0
linear dependency
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Radius of Curvature
Approximation 0 a plane wave front
Approximation 1 Non planar wave front +
Emission center in a distance R
Time [s]
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Example of a simulation (spherical wave front):
Delay decrease R increase Far emission center
planewave front
Delay increase R decrease Near emission center
Curved front
cdt
UUU
yUxUyUxUd
zUyUxUzUyUxU
th
zyx
ftayftaxyx
ftazftayftaxzyx
222
)(
0)(
First tagged antenna t0 .
tth – t0 = Expected delay
tps – t0 = Experimental delay
Simulation
Data
Systematic gap / planewave front Non planar
wavefront
Radius of Curvature
σt= 10 ns
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Radius of curvature Estimation : Fitting of the
waveplan front gap•Hypothesis = parabolic gap
5 free parameter model :
Shower Core coordinate xc, yc et zc
Radius of curvature Rc Emission center
Radius of Curvature distribution
maximum ~ 4 km …
… But interpretations difficulties
(Very large Radius observed)
222max ..2
1. r
c
r
i
r
c
r
i
r
c
r
i
c
pred
ii zzyyxxR
attc
?
4 km
σ = 3m
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Towards a direct shower energy estimator
Greisen Model Shower of only e-/e+
Xmax = X0ln (Ep/E0) Ep
X0 = 36.7 g.cm-2
E0 = 83 MeV
θ Rc
sol
radioX maxHypothesis : Emission Center = Xmax
)cos(
))cos(.(max
c
Linsley RfX
z
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60 automous stations to be installed at Nançay during 2011
Array with 1 km2 of surface
Exploration in continuity of the Codalema physic
programme
Towards a autonomous radiodetection array : CODALEMA3
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Conclusions
Faisability of radiodedection with CODALEMA 2:
Detection of the radio signal induced by the shower
developpement
Emission mechanism : geomagnetic effect
Energie Correlation
New analysis method : Rc
Exploration of CODALEMA 3 (autonomous station)
Thank you