Scintillators, DAQ boards, and PMTs

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Scintillators, DAQ boards, and PMTs

• Getting Familiarized With the Equipment

By Melissa Sussmann and Alex Bonnifield
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Scintillators

• Scintillators are substances that absorb energy
  from fast-moving particles to ultimately detect
  cosmic rays in our atmosphere.
• Our Scintillators are made out of a hard plastic
  containing an organic dye. They are meant to
  detect particles, particularly muons in our
  atmosphere. As the energy from the muons is
  absorbed, the scintillator produces a quick flash
  of light, which is detected by a photomultiplier
  tube

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Photomultiplier Tubes (PMTs)

• Photomultiplier tubes detect the light from the
  scintillator. They then use that energy to
  produce a small amount of electricity.
• How is it done???
• The light from the scintillator is detected by
  the photocathode and turned into electricity.
• Then, the electrons produced by the photocathode
  are bounced from dynode to dynode. Dynodes are a
  kind of electrode that multiplies the number of
  electrons for every dynode they touch.
• The more dynodes in a PMT, the more electrons are
  produced.
• Another electrode, called an anode flows electric
  current to the DAQ board

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Photomultiplier Tubes (PMTs)

• For a more visual approach, click here

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Data Acquisition Board (DAQ board)

• The data acquisition board basically counts the
  time it takes for a scintillation to occur.
• It then discriminates between muons and other
  particles or forms of error.
• The board then transmits that data to a PC

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Data Acquisition Board (DAQ board)

• First the electricity goes from the PM tubes
  through the input of the DAQ board.
• It is then pre-amplified to a factor set by
  resistors
• The small, amplified voltage then has to go under
  a set threshold voltage (from 0 to 750 mV) in
  order to be detected by the discriminators. If it
  is not detected, one can assume that the voltage
  that was produced was not caused by a muon.

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Data Acquisition Board (DAQ board)
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Data Acquisition Board (DAQ board)

• The TDC then receives the feed from the
  discriminator outputs.
• It measures the time a PMT pulse is below the
  voltage threshold.
• This information is then passed through the CPLD,
  better known as the fast logic board.
• It is called fast logic, because it has the
  capability of taking information from the TDC at
  very fast rates, in this case, nanoseconds.

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Data Acquisition Board (DAQ board)

• The information from the fast logic board is then
  transmitted to the microcontroller.
• The microcontroller is referred to as the MCU
  or the slow logic. It is called the slow
  logic board, because it measures time in
  microseconds not nanoseconds.
• The MCU makes the information given by the CPLD
  readable for the PC. This information is then
  displayed on your computer and therefore made
  accessible to the user.

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Data Acquisition Board (DAQ board)
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Bibliography

• http//microscopy.fsu.edu/primer/flash/photomultip
  lier/
• http//en.wikipedia.org/wiki/Photomultiplier
• http//ea.grolier.com/cgi-bin/article?assetid0348
  390-00
• QuarkNet/Walta/CROP Cosmic Ray Detectors Users
  Manual