Scintillators, DAQ boards, and
PMTs
Getting Familiarized With the
Equipment
By Melissa Sussmann and Alex Bonnifield
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
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
Photomultiplier Tubes (PMTs)
For a more visual approach, click here
Data Acquisition Board (DAQ board)
The data acquisition board basically counts the
time it takes for a scintillation to occur.
O It then discriminates between muons and other
particles or forms of error.
O The board then transmits that data to a PC
O
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.
Data Acquisition Board (DAQ board)
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.
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.
Data Acquisition Board (DAQ board)
Bibliography
http://microscopy.fsu.edu/primer/flash/photomultiplier/
http://en.wikipedia.org/wiki/Photomultiplier
http://ea.grolier.com/cgi-bin/article?assetid=0348390-00
QuarkNet/Walta/CROP Cosmic Ray Detectors User’s Manual