Autonomous radio detection of air showers with the TREND50 antenna array

Abstract

TREND50 is a radio detection setup of 50 self-triggered antennas working in the 50-100 MHz frequency range and deployed in a radio-quiet valley of the Tianshan mountains (China). TREND50 achieved its goal: the autonomous radiodetection and identification of air showers. Thanks to a dedicated offline selection algorithm, 564 air shower candidates were indeed selected out of 7 · 10 8 transient radio signals recorded during the 314 live days of data taken during the first two years of operation of this setup (2011 and 2012). This event rate, as well as the distribution of the candidate directions of arrival, is consistent with what is expected from cosmic-ray-induced air showers according to simulations, assuming an additional ∼20% contamination of the final sample by background events. This result is obtained at the cost of a reduced air shower detection efficiency, estimated to be ∼3%.ficiency is mostly due to the large amount of dead time of the setup. This result paves the way for the GRANDProto35 experiment, the first stage of the GRAND project.

The Giant Radio Array for Neutrino Detection

“…This is a challenge, as measurements have shown that, outside polar areas, the rate of transient radio signals due to background sources (high voltage power lines or transformers, planes, thunderstorms, etc.) dominates that of EAS in the tens-of-MHz frequency range by several orders of magnitude [22], a statement that will hold even truer for neutrino-induced showers. Two questions naturally arise from this observation: how to collect and identify EAS events, and how to single out neutrino-induced events among them.…”

“…• It has been shown already that EAS radio signatures clearly differ from background events: their time traces are usually much shorter [23], while their amplitude [24] and polarization patterns at ground [25] are very specific. Taking advantage of these unique features has already made it possible to perform a very efficent rejection of the background signals using radio data only [22]. EAS identification is thus not a physics issue, but a technical one.…”

GRAND: A Giant Radio Array for Neutrino Detection

“…GRANDProto35 is a combined array of 35 antennas and 21 scintillator detectors that is installed in the Tianshan mountains in China at the site of the 21CMA radio detector. The main purpose of this stage of GRAND is to verify the standalone trigger efficiency of radio detection of air showers as inferred from the TREND experiment [30] that was located at the same site. The TREND collaboration has performed a detailed study of the trigger efficiency and concluded that with a proper data acquisition system, trigger efficiencies of more than 80 % can be obtained using the radio technique.…”

Final results of the LOPES radio interferometer for cosmic-ray air showers

“…In parallel, progress was made on a variety of simulation and calculation tools [8][9][10][11], whose latest generations are generally able to reproduce measured radio signals. Together with the second generation of digital antenna arrays such as AERA [12], LOFAR [13], TREND [14], and Tunka-Rex [15], the measurements of LOPES and CODALEMA were critical to improve the understanding of the emission processes, in particular by comparing the measured radio signals with the predictions of Monte Carlo simulations of extensive air showers and to the data of the colocated particle detector arrays.…”