Amplitude calibration of a digital radio antenna array for measuring cosmic ray air showers

TL;DR

This paper details the absolute amplitude calibration of a 30-antenna digital radio array to accurately measure electric field strengths of radio pulses from cosmic ray air showers, enabling better comparison with theoretical models.

Contribution

It presents a comprehensive calibration method for a radio antenna array, including electronic chain correction factors, to improve cosmic ray detection accuracy.

Findings

Achieved systematic uncertainties of about 20% in calibration.

Developed frequency-dependent correction factors for each antenna.

Enabled precise comparison of measured signals with simulations.

Abstract

Radio pulses are emitted during the development of air showers, where air showers are generated by ultra-high energy cosmic rays entering the Earth's atmosphere. These nanosecond short pulses are presently investigated by various experiments for the purpose of using them as a new detection technique for cosmic particles. For an array of 30 digital radio antennas (LOPES experiment) an absolute amplitude calibration of the radio antennas including the full electronic chain of the data acquisition system is performed, in order to estimate absolute values of the electric field strength for these short radio pulses. This is mandatory, because the measured radio signals in the MHz frequency range have to be compared with theoretical estimates and with predictions from Monte Carlo simulations to reconstruct features of the primary cosmic particle. A commercial reference radio emitter is used to estimate frequency dependent correction factors for each single antenna of the radio antenna array. The expected received power is related to the power recorded by the full electronic chain. Systematic uncertainties due to different environmental conditions and the described calibration procedure are of order 20%.