Air shower measurements with LOFAR

Air showers from cosmic rays emit short, intense radio pulses. The Low Frequency Array (LOFAR) is a new radio telescope, that is being built in the Netherlands and Europe. Designed primarily as a radio interferometer, the core of LOFAR will have a high density of radio antennas, which will be extremely well calibrated. This makes LOFAR a unique tool for the study of the radio properties of single air showers. Triggering on the radio emission from air showers means detecting a short radio pulse and discriminating real events from radio interference. At LOFAR we plan to search for pulses in the digital data stream-either from single antennas or from already beam-formed data-and calculate several parameters characterizing the pulse shape to pick out real events in a second stage. In addition, we will have a small scintillator array to test and confirm the performance of the radio only trigger. (C) 2009 Elsevier B.V. All rights reserved