1. Andreas Horneffer for the LOFAR Cosmic Ray KSP Air Shower Measurements with LOFAR Radboud University Nijmegen

2. 2 LOFAR for Cosmic Rays designed as an astronomical telescope not an air shower detector: “small” stations with lots of antennas in a small area different baselines between stations consequences: low effective area for the number of antennas high sensitivity very good calibration this makes LOFAR an unique tool to study air showers: Develop the method (triggering, reconstruction) Understand the emission process Air shower physics (new particles?) Change galactic→extragalactic cosmic rays

3. Radboud University Nijmegen 3 Radio Signature of Air Showers random arrival times and directions can ignore (man made) pulses from the horizon broad-band, short time pulse (~10ns) limited illuminated area on the ground depending on primary energy curvature of radio front similar (but not identical) to point source in few km height coincident with other air shower signs e.g. particle front

4. Radboud University Nijmegen 4 LOFAR Effective Area 48/96 antennas per station inter-station baselines from 100m to 100km beam-forming at each station

5. Radboud University Nijmegen 5 LOFAR-CR Energy Ranges Triggering on single-channel data Triggering on beam-formed data

6. Radboud University Nijmegen 6 VHECR-Triggering Station View

7. Radboud University Nijmegen 7 VHECR-Triggering Central Processor View

8. Radboud University Nijmegen 8 HECR-Triggering Central Processor View

9. Radboud University Nijmegen 9 VHECR Trigger I runs on the FPGAs of the TBBs pulse detection for single channels 1. digital Filtering of some RFI (IIR-filters) 2. peak detection 3. calculation of pulse parameters (position, height, width, sum, avg. before, avg. after) peak detected if: |x i | > μ i + k 1 σ i can be simplified to: |x i | > k 2 μ i

10. Radboud University Nijmegen 10 Transient Buffer Boards one TBB for 16 channels one FPGA for 4 channels larger FPGA allows 3 IIR filters plus peak detection per channel

11. Radboud University Nijmegen 11 VHECR Trigger II TBBs send “trigger messages” to station LCU coincidence trigger at station level filtering of “bad” pulses coincidence detection (direction fit) data dump if pulse is found stations send messages to CEP dump more (all) stations for large events

12. Radboud University Nijmegen 12 LOFAR Test Measurements one 48 antenna station and three 16 antenna stations already in the field two stations equipped with two TBBs each 64 channels available read out with low-level tools dump to “raw dump” files read in of raw-files or conversion to new file format

13. Radboud University Nijmegen 13 LOFAR Dynamic Spectrum

14. Radboud University Nijmegen 14 IIR Filtering No Filtering

15. Radboud University Nijmegen 15 IIR Filtering Filter at 88 MHz (FM-transmitter)

16. Radboud University Nijmegen 16 IIR Filtering Filter at 15 MHz (sw-band)

17. Radboud University Nijmegen 17 IIR Filtering Filters at 15 MHz and 88 MHz

18. Radboud University Nijmegen 18 Filtering results filtering of FM-transmitter increases SNR short-wave band filtering increases stability of SNR

19. Radboud University Nijmegen 19 LASA LOFAR Air Shower Array small particle detector array for triggering and additional data main goal: proof that we indeed detect air showers Needed to convince the cosmic ray community! 5 stations with 4 scintillators each around/inside the LOFAR “super-station” main challenge: RFI shielding

20. Radboud University Nijmegen 20 LASA Layout

21. Radboud University Nijmegen 21 Summary LOFAR is an unique tool for air shower measurements: high sensitivity excellent calibration measure in two modes: HECR: trigger on beam-formed data VHECR: trigger on single channel data all digital triggering for VHECR: filtering, peak detection, and pulse parameter determination in FPGA coincidence trigger at station level 2 nd level coincidence to trigger additional stations small particle detector array