Joint operation of the LSS and CODALEMA to explore high energy cosmic ray physics

Arnaud Belletoile
LOFAR Transients Key Project Meeting, Meudon, December 2011

Transcript

1. 16/12/2011 Arnaud Bellétoile High energy cosmic rays with CODALEMA and LSS? Arnaud Bellétoile 1 Friday, December 16, 2011
2. 16/12/2011 Arnaud Bellétoile High energy cosmic ray physics • The cosmic ray spectrum ✓ Measured via the extensive air showers ‣ Flux too low for direct measurement ✓ Described by a power law ✓ Several remarkable features ‣ Knee, 2nd knee, ankle and the cut-off • Interpretations are subject to debate ✓ Particle physics reasons ‣ New kind of interaction at high energy ? ✓ Astrophysical reasons ‣ Limit of galactic accelerators ? ‣ Transition from galactic to extra galactic CR ? ‣ Interaction with the CMB ? • At extremely high energy ✓ What is the source of the most energetic CR ? 2 Grigorov JACEE MGU TienShan Tibet07 Akeno CASA/MIA Hegra Flys Eye Agasa HiRes1 HiRes2 Auger SD Auger hybrid Kascade E [eV] E2.7F(E) [GeV1.7 m−2 s−1 sr−1] Ankle Knee 2nd Knee 104 105 103 1014 1015 1013 1016 1017 1018 1019 1020 • CODALEMA objectives ✓ Explore the 1017-1018eV energy range ‣ Gal./extra gal. transition? Composition? ✓ Develop a tool for ultra high energy cosmic rays ‣ Radio emission Nakamura et al., 2010 Friday, December 16, 2011
3. 16/12/2011 Arnaud Bellétoile Radio signal from air showers • Two mechanisms in the shower ✓ Negative charge excess ✓ Geomagnetic deflection of charges • Electric field emitted ✓ Depends on the observer position ✓ Depends on the longitudinal profile ‣ Primary energy and nature • Several theoretical descriptions ✓ MGMR, SELFAS, REAS3, boosted Coulomb ... ✓ Different approaches ‣ Macroscopic / microscopic description... ‣ Refractive index ‣ Relative contributions ✓ Convergence of several models • Very promising tool for HECR ✓ High duty cycle ✓ Low cost of the detector ✓ Sensitivity to shower parameters 3 Scholten et al., 2007 Friday, December 16, 2011
4. 16/12/2011 Arnaud Bellétoile The original CODALEMA setup • Dipole Antennas array ✓ 24 Active Dipoles ✓ EW polarization • Particle detectors array ✓ 13 plastic scintillators ✓ Act as a reference : ‣ Trigger ‣ EAS parameters - (θ,φ), core position, primary energy • Signal acquisition ✓ On trigger from part. detector ✓ Digitized as a function of time ✓ ADC : 12 bits, 1 GHz, 2560 ns 4 • Some numbers ✓ Operating since 2006 ✓ Effective area of 0.25 km2 ✓ Particle detector energy thres. around 1016eV ✓ Energy resolution ~ 30% at 1017eV Friday, December 16, 2011
5. 16/12/2011 Arnaud Bellétoile Signal processing • Each array treated separately • Antenna array ✓ Data analysis on temporal waveform ✓ Search for transient signals ‣ Performed on each individual antenna ‣ Numerical filtering in the ad hoc band ‣ Voltage threshold - Adjusted on galactic noise ✓ On transient detection ‣ Peak amplitude ‣ Arrival time ✓ If more than 3 antenna touched ‣ Arrival direction reconstructed - planar wavefront • Particle detectors array ✓ Estimate particle densities ✓ Adjust NKG lateral distribution ✓ Energy estimated for internal events ‣ CIC method 5 0 500 1000 1500 2000 2500 ï150 ï100 ï50 0 50 100 150 voltage (mV) bin number 0 20 40 60 80 100 120 −130 −120 −110 −100 −90 PSD (dBm/Hz) Frequency (MHz) a3 − EW polarisation Friday, December 16, 2011
6. 16/12/2011 Arnaud Bellétoile EAS radio detection validation • Comparison of the 2 arrays ✓ Arrival direction ✓ Arrival time • Validation ✓ Time difference < 100 ns ✓ Angular difference < 20o • Radio relative efficiency ✓ Detection threshold ~ 5x1016 eV ✓ 100% > 5x1017 eV 6 16.5 17 17.5 18 18.5 10ï1 100 101 102 103 Log Energy (eV) Entries Scintillator array Antenna array Friday, December 16, 2011
7. 16/12/2011 Arnaud Bellétoile Geomagnetic contribution • Arrival directions of radio detected cosmic rays ✓ North/South asymmetry ✓ Lack of event in the geomagnetic vector direction • Coverage map reproduced ✓ Emission proportional to F=qVxB ✓ projection along the EW axis • Trigger effect • Clear signature of geomagnetic emission ✓ First order contribution 7 U (SouthïNorth axis) V (EastïWest axis) ï0.8 ï0.6 ï0.4 ï0.2 0 0.2 0.4 0.6 ï0.8 ï0.6 ï0.4 ï0.2 0 0.2 0.4 0.6 0.8 Friday, December 16, 2011
8. 16.5 17 17.5 18 18.5 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 log Energy (eV) log (E 0 /||vxB EW ||) (µV/m) East ï West axis (m) South ï North axis (m) ï100 ï50 0 50 100 ï100 ï50 0 50 100 • Correlation of E0 with primary energy ✓ Estimated with particle detector array • Shift of the radio core position ✓ With respect to the particle core position ✓ Interpreted as a charge excess signature 16/12/2011 Arnaud Bellétoile Electric field profile • Exponential dependence of the electric field with impact parameter ✓ E(b) = E0 x exp(-b/b0) • 4 parameters fitted ✓ Amplitude parameter E0 ✓ Field extension b0 ✓ Shower core position X0,Y0 8 Friday, December 16, 2011
9. 16/12/2011 Arnaud Bellétoile Toward higher energy • Increase the detection area ✓ Standalone detector needed • The CODALEMA station ✓ Butterfly antenna ‣ Dedicated lna ‣ 2 polarisations ‣ Increase sensitivity ✓ Triggering ‣ Trigger on the radio signal ‣ External input ✓ Timing system ‣ Embedded GPS ‣ 1 ns resolution ✓ ADC ‣ 12 bits / 1 GHz / 2560 ns ✓ Embedded computer ‣ On board processing ✓ Data transfer ‣ Optical link or wifi transmission ✓ Power supply ✓ Shielded electronic box 9 Friday, December 16, 2011
10. 16/12/2011 Arnaud Bellétoile The CODALEMA Standalone Antenna Array • Around the existing apparatus • Deployment status ✓ 33 standalone stations deployed last spring ✓ 27 more within a few months • Covered area ✓ Nearly 1.5 km2 10 Friday, December 16, 2011
11. 16/12/2011 Arnaud Bellétoile Transient radio background • Several sources ✓ Mainly of anthropic origin : ‣ power lines, voltage transformers ✓ Atmospheric : ‣ thunderstorms • Airplane trajectories ✓ Calibration tools! • Remain the main radio detection issue ✓ Reduce effective time of observation ✓ Imply large amount of data storage • Enhancing background immunity ✓ More elaborated embedded algorithms ‣ Restrictive conditions on pulse shape ‣ Periodicity mask ‣ Directional mask • Occasional solution ✓ Hybrid trigger with associated plastic scintillator ‣ Narrow time coincidence window ‣ Extremely low fortuitous rate • 11 Friday, December 16, 2011
12. 16/12/2011 Arnaud Bellétoile Toward pure radio identification criterion • One month of science data taking ✓ June 2011 ✓ Time Coincidences searched • 4 EAS candidates identified ✓ Time coincidences with particle detector array ‣ Within 10 µs • Orientation of the Electric field vector ✓ Expected orientation ψth ‣ vxB vector projected on the ground ✓ Measured orientation ψmeas • Validated candidates 12 WestïEast direction cosine SouthïNorth direction cosine Predicted s values (o) ï1 ï0.5 0 0.5 1 ï1 ï0.8 ï0.6 ï0.4 ï0.2 0 0.2 0.4 0.6 0.8 1 10 20 30 40 50 60 70 80 E field EW NS ψ Friday, December 16, 2011
13. 16/12/2011 Arnaud Bellétoile A revolutionary profile 13 Corstanje et al., ICRC 2011 Friday, December 16, 2011
14. 16/12/2011 Arnaud Bellétoile The neighborhood 14 LSS LOFAR from J. Girard Friday, December 16, 2011
15. 16/12/2011 Arnaud Bellétoile Conclusion • The radio detection technique reaches progressively maturity ✓ Understanding of the electric field emission progresses ✓ EAS identification based on radio signals only seems feasible ‣ Toward autonomy of radio with respect to particle detectors ✓ Access to the primary composition is the next objective • The CODALEMA Standalone Antenna Array will be soon complete ✓ Dedicated to the 1017-1018 eV energy range ‣ 1.5 km2 of effective area ‣ 60 autonomous detectors ✓ A cosmic ray radio detector of 2nd generation • The LSS is very interesting for CODALEMA physics ✓ Different length scales, different energy range, complementary designs • The Nançay LOFAR station could also bring interesting informations 15 Friday, December 16, 2011