MARIACHI Project Data Acquisition in Physics Experiments

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MARIACHI Project (Data Acquisition in Physics
Experiments)

• By D. Denis O. Damazio

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Introduction

• All physics experiments produce some kind of
  electrical analogic signal.
• To easily manipulate and profit from powerful
  computing systems, the signal are converted to
  digital samples.
• The processing of this samples is called Signal
  Processing.
• We will also see some data acquisition details
  about our experiments.

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Analog Devices

• Continuous signals, continuous time.
• Energy converters. Persistency.

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HEP Experiments

• Rutherfords experiment to probe the Atom nucleus
  was very simple, but used the same general
  concepts still used in modern experiments A
  source of events and a detection system.
• Rutherford could not benefit from the powerful
  computer resources one can nowadays.

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Detection Process

• Modern experiments use the same ideas.
• But they record the produced signal with a Data
  Acquisition System.

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Analog to Digital Conversion
Sound Card

• The Analog signals produced by the detectors must
  be acquired to produce a meaningful readout.

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Analog to Digital Conversion

• Sampling rate -gt Keeping a good signal
  description data amount. Important
  restrictions.
• ADC counts -gt calibration.

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Analog to Digital Conversion

• Simple systems can perform simple Analog to
  Digital conversion.
• The circuit must be more complex to handle faster
  acquisition rates.

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Analog to Digital Conversion

• The samples (digital integers) can be processed
  by a computer.

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Digital Signal Processing

• The samples acquired with the ADC can be
  processed to extract important features from the
  signal.
• Some processing techniques are based in looking
  at the frequency components of the signal.
• Mobile phones, CDs, DVDs all use such technology.
• DSPs (Digital Signal Processors) are processors
  like Pentium, AMDs, but specialized in Digital
  Signal processing.

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Digital Signal Processing

• In our experiment we use the frequency/time maps.
• In such maps the power in a given frequency/time
  coordinate is given by a color code.

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Our Experiments

• Scintillators Radio
• Our experiment consists in trying to find signals
  that can trigger both the scintillator detection
  array and the radio system.
• We want to keep costs down to be able to provide
  many detectors to cover a large area (schools).

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Scintillators

• The analog signal is converted to digital in the
  sound card and sent (via PCI bus) to the PCs
  memory.
• The bytes are finally written to a large storage
  removable disc.

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Radio Detector System (principle)

• The Radio Detector System has been proving to
  work fine for meteor detection.
• Could it detect also cosmic rays?!

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Radio Detector System (demodulation)

• The signals to be reflected by meteors, or cosmic
  rays must be in a frequency around (50-90MHz).
• To be able to sample this signal, one can filter
  and demodulate the signal before performing the
  ADC conversion.
• Any Radio receiver performes demodulation and
  detection (AM, FM,SSB, CW).

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Radio Detector System (description)

• Our system is operating with radio and
  scintillator signals.
• The GPS provides precise timing.

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Radio Detector System (meteor signals)

• Meteor signals have a larger duration.
• Summing the power for a given frequency range
  makes the event more evident.

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Radio Detector System (cosmic ray signal?!)

• We have some events which look like cosmic ray
  events.
• Only using more than one detection station we can
  get rid of anomalous signals (noise).

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More information

• You can visit the main Mariachi Web Site
  http//www.cosmicray.bnl.gov
• Or the Mariachi LogBook http//www2.bnl.gov/dam
  azio/log
• Also, emails are welcome damazio_at_bnl.gov