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

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

LOFAR Core Layout 48/96 antennas per station inter-station baselines from 100m to 100km beam-forming at each station

LOFAR-CR Energy Ranges Triggering on beam-formed data Triggering on single-channel data

VHECR-Triggering Station View

VHECR-Triggering Central Processor View

HECR-Triggering Central Processor View

VHECR Trigger pulse detection for single channels digital Filtering of some RFI (IIR-filters) peak detection calculation of pulse parameters (position, height, width, sum, avg. before, avg. after) coincidence trigger at station level filtering of “bad” pulses coincidence detection (direction fit) data dump if pulse is found dump more (all) stations for large events

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

LOFAR Test Measurements one 48 antenna station and three 16 antenna stations already in the field two stations equipped with two TBBs each largest problem currently: control software and stability

LOFAR Dynamic Spectrum

IIR Filtering No Filtering

Filter at 88 MHz (FM-transmitter) IIR Filtering Filter at 88 MHz (FM-transmitter)

Filter at 15 MHz (sw-band) IIR Filtering Filter at 15 MHz (sw-band)

IIR Filtering Filters at 15 MHz and 88 MHz

Filtering results filtering of FM-transmitter increases SNR short-wave band filtering increases stability of SNR

LASA LOFAR Air Shower Array small particle detector array for triggering and additional data main goal: proof that we indeed detect air showers 4 or 5 stations with 4 scintillators each around/inside the LOFAR “super-station” main challenge: RFI shielding

LASA Layout

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 2nd level coincidence to trigger additional stations small particle detector array