BEXCO - Room F(201/202/203/204)
[CRI103] On timing accuracy in observing radio impulses associated with Extensive Air Showers
- Alain LECACHEUX
- Alain LECACHEUX (CNRS-Observatoire de Paris, France)
A large subset of EAS radio observations by CODALEMA experiment in Nançay was used to measure the departure from a plane of the signal arrival times to the antennas. The study was done at two different scales in terms of range to the EAS axis. Below about 300m, by using a 10 antennas array triggered by neighbouring surface detectors, the average departure was found to be negligible (i.e. lower than the measurement incertitude of about 2-3 ns), leading to an equivalent "wavefront curvature" radius larger than 30 km. Above the 300m range, and within the first kilometre, an extended array of several tens of self-triggered antennas was used. The measurements suggest the existence of significant time departures (up to 60 ns. at 900m range), which corresponds to an apparent curvature radius of at least 18 km. The main limitation of the method, in addition to the inferior time precision due to self-triggering, was the lack of accurate knowledge of corresponding EAS core locations, especially when those cores are located well outside the surface detector extent.