Trigger Strategy for LOPESSTAR Thomas Asch for the LOPES Collaboration

LOPESSTAR Plan of Site: KASCADE-Grande (Karlsruhe) Lofar PrototypE Station Self-Triggered Array of Radio detectors (H. Falcke: #1317) Plan of Site: KASCADE-Grande (Karlsruhe) Logarithmic Periodically Dipole-Antenna (LPDA) observe radio emission 40 – 80 MHz dual-polarisation (North/South & East/West ) triangular trigger structure

Design Study (for large scale arrays) detection of radio emission E > 5 · 1017eV geosynchrotron theory (T. Huege: #889 & #891) absolute calibrated system self-trigger observations in the framework of Pierre Auger Observatory (A. Berg: #176) LPDA

Signal Chain 4 self-trigger KASCADE-Grande trigger

Self-Trigger: basics H a = 65 m Antenna 1 Antenna 2 Antenna 3 suppression of horizontal radio frequency interference (RFI) minimise trigger rate per channel equilateral triangle for coincidence per event Δt < H/c = 180 ns => accept > H/c = 180 ns => reject

Self-Trigger: L0 Trigger observe data quality per channel => reduce rate RFI suppression (Karlsruhe: factor 2) signal-to-noise ratio (squared raw data) number of pulses length of pulse

Self-Trigger: L0 Trigger observe data quality per channel => reduce rate RFI suppression (Karlsruhe: factor 2) signal-to-noise ratio (squared raw data) number of pulses length of pulse envelope of the signal / check coincidence constraint define dynamic threshold per channel  envelope signal find coincidence of three channels => trigger further cuts on pulse parameters

CR Detection data sample applying the self-trigger per software 3 data sample 12. Dec 2006 – 07. Jan 2007 (27d) 102535 triggered events external KASCADE-Grande trigger (E > 1016eV) 2 4 1 (8 channels) applying the self-trigger per software do RFI suppression calculate signal-to-noise ratio and number of pulses of recorded time window (25 μs)

Quality Cut per channel = SNR > 75 AND # Pulses < 5 per 25µs accepted channels acceptance ≈ 20 % reject noisy channels plot content = 8 channels · number of events

Coincidence Decision check coincidence (per event) dynamic threshold  envelope check coincidence (180 ns) => at least one channel per antenna => allowed: different polarisations acceptance over all ≈ 0.026% (270) detect radio emission of CRs use expected pulse length & position direction reconstruction (plane fit)

Final Cuts expected time position from KASCADE-Grande expected envelope pulse length events with more than 2 channels containing one pulse => shower candidate 9 out of 102,000 events are left and including 5 shower events

CR Radio Emission @ FZK NS EW fixed scaling 1 LOPESSTAR Azimuth φ = 293° Zenith θ = 48° KASCADE-Grande Azimuth φ = 295° Zenith θ = 44° E ≈ 6 · 1017eV 2 3 4 3 2 1 4

CR Radio Emission @ FZK EW NS fixed scaling 1 LOPESSTAR Azimuth φ = 24° Zenith θ = 66° KASCADE-Grande Azimuth φ = 17° Zenith θ = 63° E ≈ 2 · 1017eV 2 3 4 3 2 1 4

Conclusion LOPESSTAR works in radio loud environments (Karlsruhe) self-trigger for radio emission developed monitor data quality per channel coincidence decision per event works in radio loud environments (Karlsruhe) 5 shower events (27d) CR energies E > 2 · 1017eV (KASCADE-Grande reconstruction)