# Presentation: 802492

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

- Denis Oliveira Damazio & Helio Takai
- damazio,takai@bnl.gov
- Brookhaven National Laboratory

## Topics

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

## 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).

## 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.

## 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.

## Data Acquisition System

- Two LPDA antennas at BNL and the GPS antenna.

## 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.

## 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.

## 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.

## 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.

## 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

## 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.

## 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.