1. Surrounding effects and sensitivity of the CODALEMA experiment
Thibault Garçon
SUBATECH
04/12/2018
ARENA Thibault Garçon

2. The CODALEMA experiments
The cabled arrays
Autonomous stations
04/12/2018
ARENA Thibault Garçon

3. Screening and surrounding effectsW S
The CODALEMA antennas or any future large autonomous array may have to face various vicinities. What is their impact on the radiodetection?
04/12/2018
ARENA Thibault Garçon

4. Screening and surrounding effects
North
Screening and surrounding effects
West
East
Selected events: cosmic ray events in coincidence between particle detectors and at least three antennas
West
East
North
acceptance effect
North
No noticeable screening effect. Even a specially unfavourable vicinity seems to have no impact on the detection of cosmic rays.
West
East
04/12/2018
ARENA Thibault Garçon

5. Distance to the shower axis (m)
A sensitive detector
Despite various environments, CODALEMA obtains high quality results
500
NS axis EW axis
500
Signals of 7 antenas (V)
NS axis (m)
E (µV)
E (µV)
EW axis (m)
Coordinate on the axis (m)
time (2.5µs)
500
E (µV)
500
Distance to the shower axis (m)
Accurate LDF (well fitted by an exponential function) and arrival direction reconstruction
04/12/2018
ARENA Thibault Garçon

6. Distance to the shower axis (m) Distance to the shower axis (m)
A sensitive detector
Unusual LDF can reveal a breakdown of one antenna
200
200
NS axis EW axis
NS axis (m)
E (µV)
E (µV)
EW axis (m)
EW axis (m)
Coordinate on the axis (m)
E (µV)
E (µV)
Distance to the shower axis (m)
Distance to the shower axis (m)
04/12/2018
ARENA Thibault Garçon

7. ARENA 2010 - Thibault Garçon
Autonomous detection
Autonomous station
Goal : 100% autonomous system (trigger, power supply and acquisition), robust, compact, cheap
Prototype station at Nancay : antenna, ADC, trigger , GPS, PC and control boards
04/12/2018
ARENA Thibault Garçon

8. ARENA 2010 - Thibault Garçon
Autonomous detection
ADC PC
Trigger
Power
GPS
Control
2 challenges: no self-induced triggering, no noise generation for other instruments of the Observatory (large and sensitive radio-telescopes)
04/12/2018
ARENA Thibault Garçon

9. Electromagnetic compatibility (EMC)
Tests of noise produced by the autonomous station : anechoic chamber, radioheliograph array and radiotelescope measurements
-50
• No noise radiated between 10 MHz and 4 GHz
• No self-induced triggering
 Green light for Nançay
Power (dBm/MHz)
Max Hold On / Off
Mean RMS On / Off
-90 50
Frequency (MHz)
500
04/12/2018
ARENA Thibault Garçon

10. Sensitivity of the autonomous detection
Radio Frequency Identification by the stations:
 evaluation of the quality of the autonomous detection
 mapping of noise sources
 determination of the optimal trigger threshold
NS axis (m)
EW axis (m)
Very close noise sources
North
East
West
Distant transmitters, planes
Thunderstorms
04/12/2018
ARENA Thibault Garçon

11. Sensitivity of the autonomous detection
Events observed in coincidence with the cabled array confirm the feasibility of autonomous radio-detection: ~10 coincidences in few weeks, one 2-fold coincidence few days after installation of the 3 antennas array.
Cabled array
Autonomous stations
3500
1500
NS axis EW axis
NS axis (m)
E (µV)
E (µV)
EW axis (m)
Coordinate on the axis (m)
EW,NS
3500
E (µV)
500
Distance to the shower axis (m)
04/12/2018
ARENA Thibault Garçon

12. Sensitivity of the autonomous detection
Galactic background is the ultimate boundary for radio-detection: autonomous stations detect galactic background variations due to the Galaxy drift
Galactic variation
Transmitters
Thermal noise?
EW,NS
Temperature of the galactic sky in galactic coordinates
Temperature of the galactic sky seen by the antenna in galactic coordinates
PSD (dBm/Hz)
Spectra obtained in Argentina with a CODALEMA station, during 24 hours.
Frequency (MHz)
Atmospheric effect on AM
04/12/2018
ARENA Thibault Garçon

13. Towards accurate physics?
Thanks to large sensitivity and precise knowledge of the antenna response, it becomes possible to reconstruct the cosmic ray frequency spectrum over a very wide band
Illustration with a powerful event (above 1018 eV) on CODALEMA
Huegue, Scholten
Toy model of cosmic ray spectra
Factor 100
D. Charrier, in this conference
inclined, 1018 eV or more, Nancay B-Field, 150 m a.s.l.
120 MHz
200 m or more
Antenna response (includes lobe antenna, impedance, LNA)
Simulated spectra as seen by the antenna
04/12/2018
ARENA Thibault Garçon

14. Conclusion and outlook
Screening effects (trees, other antennas) do not affect event detection statistics
Antenna response is very well understood: simulations allows to understand and correct specific interference effects
CODALEMA autonomous station is silent (no self-induced triggering, no outward noise)
Sensitivity of the galactic background (ultimate noise) is reached. Large background variation observed during galactic transit.
Well-known instrument: an accurate physics becomes possible, over a wide bandwidth (100 MHz)
Ready for installation of large autonomous station arrays
04/12/2018
ARENA Thibault Garçon

15. ARENA 2010 - Thibault Garçon
04/12/2018
ARENA Thibault Garçon