A. Nelles et al., "Calibrating the absolute ampltiude scale for air showers measured at LOFAR," Journal of Instrumentation, V10, no. 11, pp. P11005, November 2015.
abstract:
Air showers induced by cosmic rays create nanosecond pulses detectable
at radio frequencies. These pulses have been measured successfully in
the past few years at the LOw-Frequency ARray (LOFAR) and are used to
study the properties of cosmic rays. For a complete understanding of
this phenomenon and the underlying physical processes, an absolute
calibration of the detecting antenna system is needed. We present
three approaches that were used to check and improve the antenna model
of LOFAR and to provide an absolute calibration of the whole system
for air shower measurements. Two methods are based on calibrated
reference sources and one on a calibration approach using the diffuse
radio emission of the Galaxy, optimized for short data-sets. An
accuracy of 19% in amplitude is reached. The absolute calibration is
also compared to predictions from air shower simulations. These
results are used to set an absolute energy scale for air shower
measurements and can be used as a basis for an absolute scale for the
measurement of astronomical transients with LOFAR.
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