Damazio

1
A Radio Detector System for Ultra High Energy
Cosmic Showers Study

• Denis Oliveira Damazio Helio Takai
• damazio,takai_at_bnl.gov
• Brookhaven National Laboratory

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Topics

• Introduction
• Data Acquisition System
• Offline Methodology
• Results
• Conclusions and future steps.

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Introduction

• The nature and origin of Ultra High Energy cosmic
  rays are not still fully understood.
• Events can be found above the GZK limit of 1019
  eV.
• The event rate is, however, too small (less than
  1 event per square kilometer per year).

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Introduction

• Our approach is to use a passive bistatic CW
  radar system, tuned to the lower VHF frequency
  (TV channels 2 4).
• Particles showers and meteors interacting with
  the atmosphere produce ionization clouds.
• These clouds reflect radio emissions from TV
  stations.

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Data Acquisition System

• The Data Acquisition System is composed of a two
  different antennas An Yagi and a Log-Periodic
  Dipole Array.
• Three computer controlled radio receivers are
  used to demodulate the signal producing a base
  band (2.8 KHz ).
• A high acquisition rate sound card is used to
  provide a detailed sampling of the signal.
• A GPS clock is used to produce a time stamping of
  the signal.

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Data Acquisition System

• Two LPDA antennas at BNL and the GPS antenna.

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Offline Methodology

• The analysis of the spectrogram (time-freq maps)
  helps to detect events.
• However, a huge amount of interference can make
  the detection task more complicated.

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Offline Methodology

• A complex signal processing was designed to make
  more evident the events.
• Local mean and variance estimative help to
  control the signal to noise rate.

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Results

• When comparing the original signal with
  calculated power, the advantage of the offline
  methodology appears.
• A two level peak detection algorithm is then
  applied for triggering the events.
• Feature extraction is then performed for the
  selected events.

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Results

• For example, the time duration of the events can
  be computed.
• 83.9 of the events lasted less than 0.5 second.
• Some events lasted more than 8 seconds.
• Clustering algorithms applied on variables such
  as event peaks, reflect power and width could
  lead to subset definitions.

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Results

• During three days the system acquired a lot of
  data and more than 17880 events were found.
• The system stopped because of the NY blackout
  (Aug 14).
• A 24 hours periodicity can be seen in the number
  of events

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Conclusions and Future Steps

• A Radio Detection System for UHE cosmic showers
  was discussed.
• The detector can detect TV emission signals
  reflected by ionization clouds produced by UHE
  cosmic rays and meteors.
• Two different antennas are used in the tests
  performed for technology evaluation.
• A GPS clock is used being used for time stamping.

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Conclusions and Future Steps

• A complex signal processing algorithm is being
  used for event detection.
• Features extracted from the events can be used to
  identify different event origin (meteors or
  cosmic rays).
• Multiple stations are being built to find event
  position.
• To confirm particle shower detection,
  scintillating detector arrays are also being
  built and will be spread in high-school in Long
  Island.
• To confirm meteor detection, a video camera
  connected to a DVD recorder is also being used.