A DAQ for the Radio Detector System

1
A DAQ for the Radio Detector System

• By Denis Oliveira Damazio
• damazio_at_bnl.gov
• March 11, 2004
• Brookhaven National Laboratory

2
Introduction

• Modeling the signal
• Data Acquisition System
• Practical Considerations (RTLinux, GPS)
• Offline Analysis

3
Modeling the signal

• A rough model of the signal generation can be
  seen in the figure.
• A Turn on/off event should be produced in the VHF
  scale.
• At the same time, particles would be found
  between the signal generation and reception.

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Data Acquisition System (hardware)
Yagi Antenna
Two Log-Periodic Dipole Array
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Data Acquisition System (hardware)

• The Computer Controlled Radio Receivers are tuned
  to TV VHF channels 2 and 4 (DTV).
• A Sound Card (7 chs _at_ 96 KHz) acquire the
  signals.
• The sound is recorded in wave like format to a
  fast HD.
• A GPS clock sets (once a minute) the Acquisition
  PC clock.

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Data Acquisition System (software)

• Special libraries used to reduce software
  development time.
• The software was developed for the Linux
  environment.
• Posix Threads are used to synchronize sound
  capture and recording.
• QT Libraries for GUI design and data display.
• Online Spectrograms available (FFTW library).
• CVS repository.

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Data Acquisition System (GPS issues)

• In order to assure correct time-stamping. A GPS
  clock is used.
• It is, however, impossible to assign good clock
  to a PC (error of the order of seconds).
• Inclusion of GPS as an extra DAQ channel treated
  separately.
• GPS signal not completely recorded.

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Data Acquisition System (RT issues)

• Looking more precisely into 2003 data, gaps could
  be easily spotted in data (thanks to the GPS
  signal).
• Different operating systems were tried (RTLinux
  GPL, different Linux kernel versions and
  low-latency patches).
• A combination of OS resources, buffering and
  software redesign (priorities avoid SysCall)
  solved the problem.

9
Usage of the Sound Card in the bottle experiment

• Instead of using a complex electronics to detect
  coincidences in the bottle experiment, one can
  feed their signal directly to the sound card.
• Together with the GPS, a nice and very cheap
  measurement system can be built.

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Usage of the Sound Card in the bottle experiment

• The coincidence of the signals can be easily
  spotted.
• A simple shaping circuit can improve the signal
  resolution and peak detection.
• A small LapTop could be used to record GPS sum
  of bottles signals.

11
Offline Analysis

• The offline analysis chain is adaptive to couple
  with the varying background.
• The detection is performed by a simple two level
  peak algorithm.

12
Some Results

• These are the results for some recording days.
• More results to come with the RTGPS improvement.

13
Conclusions

• A data acquisition system for the Cosmic Rays
  Radio Detector System is presented.
• So far the emphasis has been in data quality
  issues (signal model, time-stamping, continuity
  of data acquisition).
• In terms of hardware, the system is based on
  Antennas, simple Radio Receivers and a special
  sound card. A GPS is used for time refference.

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Conclusions

• The techniques developed are based in a custom
  software design (use of Posix threads) together
  with an adequate OS choice to ensure IRQ handling
  in a deterministic time interval.
• The software design is general enough to be used
  in other fields (for example, bottle or
  scintillation counters DAQ).

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Conclusions

• An offline detection procedure based in adaptive
  algorithms was implemented
• The offline analysis taken so far showed the
  sensibility of the technique to meteor ionization
  clouds.
• Other techniques are being envisaged (matched
  filter, wavelets, NN). Any other suggestions?!
• A web page for this part of the work can be found
  in http//www2.bnl.gov/damazio/log