1. Trigger Strategy for LOPESSTAR
Thomas Asch
for the LOPES Collaboration

2. 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 – 80 MHz
dual-polarisation (North/South & East/West )
triangular trigger structure

3. 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

4. Signal Chain 4
self-trigger
KASCADE-Grande trigger

5. 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

6. 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

7. 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

8. CR Detection data sample applying the self-trigger per software3
data sample
12. Dec 2006 – 07. Jan 2007 (27d)
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)

9. 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

10. 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 ≈ % (270)
detect radio emission of CRs
use expected pulse length & position
direction reconstruction (plane fit)

11. 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

12. 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

13. 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

14. 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)