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Main features of cosmic ray induced air showers measured by the CODALEMA experiment Lilian MARTIN 1,3 , R. Dallier 1,3 , A. Escudie 1 , D. Garca-Fernndez 1 , F. Gat 1* , A. Lecacheux 2 and B. Revenu 1,3 . 1 SUBATECH, Nantes 2 LESIA,

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Main features of cosmic ray induced air showers measured by the CODALEMA experiment

Lilian MARTIN1,3 , R. Dallier1,3 , A. Escudie1,

  • D. García-Fernández1, F. Gaté1*,
  • A. Lecacheux2 and B. Revenu1,3.

1SUBATECH, Nantes 2LESIA, Paris-Meudon 3USN, Nançay

*now at LAPP, Annecy

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SLIDE 2

L.M. ICRC July 2017 2

Motjvatjons of CODALEMA

  • Goals:

–

Study the propertjes of the radio electric fjeld produced in extensive air showers

–

Promote the radio detectjon technique as an competjtjve alternatjve to SD and FD techniques

–

Contribute to cosmic ray physics within the CODALEMA energy range

  • Context:

–

Installed since 2002 at the Nançay radio astronomy observatory

–

Several generatjons of antennas, LNA, triggers, daq and arrays developed...

Radio electric transients produced by the geomagnetjc and charge excess mechanisms

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SLIDE 3

L.M. ICRC July 2017 3

The CODALEMA instruments

57 autonomous statjons (B.Revenu et al. [CRI109]) 13 scintjllators 10+5 cabled antennas (A.Lecacheux et al. [CRI103]) 1 tripole antenna (R.Dallier et al. [CRI104]) 7 LF antennas (A.Escudie et al. [CRI102], D.García-

Fernández et al. [CRI118])

0 500 m

Surface: ~ 1 km2

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SLIDE 4

L.M. ICRC July 2017 4

The autonomous statjon

EW and NS horizontal polarizatjons Wide band – [20 – 200] MHz LONAMOS LNA 1 Gs/s – 2.5 μs Self triggering – On board processing GPS tjming

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SLIDE 5

L.M. ICRC July 2017 5

Event reconstructjon in the arrays

  • Typical rates (in a month) :

–

SC : 40 000 evts

–

SA : 1 200 000 evts (loose trigger)

–

Coincidences : 60 evts !

  • Arbitrary small sample of events for this

preliminary analysis :

–

Refmect roughly the observed variety in multjplicitjes, signal amplitudes, shower axis and locatjons

–

Not representatjve of the array acceptances

–

SA and SC arrival directjons agree

SA SC

Blue: early tjmes Red/Green: late tjmes

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SLIDE 6

L.M. ICRC July 2017 6

Convolutjon of the antenna response

  • Systematjc comparisons with model predictjons : SELFAS*
  • Convolutjon : ( Model predictjons → ADC values ) vs Data
  • Calculated/measured global transfer functjon of the detectjon chain

(including the antenna response)

NS signal EW signal Convolutjon + noise *V.Marin et al., Astropartjcle Physics, Elsevier, 2012, 35, pp.733-741.

SELFAS* simulatjon

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SLIDE 7

L.M. ICRC July 2017 7

Is the sensitjvity preserved ?

Model : SELFAS ADC : SELFAS convol. Spectrum and amplitude variatjons are preserved !

FM notch Sorted by distance to core Sorted by distance to core Sorted by arrival tjme

DATA

FM notch

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SLIDE 8

L.M. ICRC July 2017 8

Extractjng cosmic ray features

  • SELFAS+CONEX simulatjon

with a virtual antenna array using E=1017eV and (θ,φ)exp

  • Interpolate amplitudes

F(x,y)

  • Calculate χ2 from amplitude

difgerences

  • Convolutjon with

the antenna response H(f,θ,φ)

  • Loop over a range of core

locatjon (Xcore,Ycore) and scaling energy factor α χ2 map

+

χ

2=∑ ant

(Aant−α F(xant−Xcore, yant−Y core))2 σant

2

Inspired by the method used on AERA data by F.Gaté et al., ARENA 2016, Groningen, June 7-10, 2016.

  • Combinatjon of (Xcore,Ycore) and α

with the lowest χ2 (= χ2

min) is the

most probable set of values.

  • Process a set of SELFAS simulatjons (typ. 50 p, 10 Fe)

per event to sample the Xmax range

  • Compare the χ2

min values versus Xmax

  • The lowest χ2 determines the overall most probable

(Xcore,Ycore), E=α x1017 eV and Xmax

χ2

min vs Xmax

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SLIDE 9

L.M. ICRC July 2017 9

Some examples

+ + + + + + + +

Amplitude footprint χ2 vs core locatjon χ2 vs Xmax Lateral distributjon functjon

  • Data

+SELFAS

Few antennas give access to the CR propertjes !

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SLIDE 10

L.M. ICRC July 2017 10

Polarization patuerns solve ambiguitjes

Local minimum in the χ2

min values versus Xmax distributjon. Polarizatjon patuerns support only one solutjon.

Both EW and NS amplitudes must be matched separately !

Data SELFAS

EW signal NS signal Polarizatjon patuern footprint

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SLIDE 11

L.M. ICRC July 2017 11

Comparison with the scintjllators

+ Preliminary analysis seems on the right directjon but stjll lots of (careful) work to do !

No error bars on Eradio yet , no real atmosphere for Xmax

― A u g e r F D I C R C 1 7 M . U n g e r

Shower core ofuen outside

  • f the SC array: Epartjcle

underestjmated ! Betuer agreement using (Xc,Yc)radio for the Epartjcle estjmatjon

(Xc,Yc)radio

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SLIDE 12

L.M. ICRC July 2017 12

Conclusions and Outlook

  • CODALEMA is routjnely observing high-energy cosmic rays in the

1016 – 1018 eV range.

  • CODALEMA data compare well with SELFAS simulatjons: shower core

locatjons, Xmax and energies can be estjmated using the radio signals

  • Further improvements :

–

Careful estjmatjons of systematjcs, error bars and resolutjons

–

Analysis extended to the full CODALEMA set of data (especially at lower E)

–

Analysis method (comparison with simulatjons) extended to the two polarizatjons and the full spectrum

–

Sensitjvity and resolutjon estjmatjon for a sparser array

  • Analysis in progress in parallel with other R&D developments:

–

3-polarizatjon antenna, standalone and phased triggers, LF antennas...

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L.M. ICRC July 2017 13

Spares

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L.M. ICRC July 2017 14

Trigger and Acquisitjon systems

Analog T1 trigger : no permanent digitjzatjon

  • f the signals and a controlled energy

budget (~20W per statjon).

LNA

TRIGGER

selectjon

ADC

digitatjon

GPS

tjming

PC

selectjon

  • evt. build.

Central Acquisitjon System

selectjon

  • evt. request

monitoring storage T1 T2 T3

SA - multj-level triggering strategy:

  • T1 on trigger board: fjlter, threshold discriminatjon,

combinatjon of channels, coarse tjming...

  • T2 on local PC: tjming, pulse shape discriminatjon,

polarizatjon, spectral content...

  • T3 on central acq. syst.: relatjve tjming between

statjons, directjon of arrival, occurrence frequency…

SC – partjcle trigger selectjon:

  • Individual threshold (15 mV)
  • Multjplicity selectjon (5 or more over 13 SC)
  • Trigger GPS tjming
  • Trigger broadcast over the network

Autonomous statjons (SA) Scintjllators (SC)

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L.M. ICRC July 2017 15

Convolutjon of the antenna response

  • Electric fjeld patuern is not simple,

dependence to the (v,B) angle → compare to realistjc simulatjons !

  • Directjon ?

–

Deconvolutjon : data → Efjeld vs Model

–

Convolutjon : Model → ADC vs Data

  • Global transfer functjon :

–

H(f,θ,φ) = Hant.(f,θ,φ) Hana.(f) Hdigit.(f)

–

Calculated or/and measured transfer functjons

  • F
  • 1(H.F

(E(t,θ,φ))) = ADC(t)

NS signal EW signal Convolutjon + noise Hant.: antenna Hana.: analog chain Hdigit: digital chain *V.Marin et al., Astropartjcle Physics, Elsevier, 2012, 35, pp.733-741.

SELFAS* simulatjon

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L.M. ICRC July 2017 16

Extractjng cosmic ray features (II)

+ + + + + + + +