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essentially  electrical  in  nature,  meaning  that  the   it to process an event. This is related to the duration
          information  from  the  detector  is  transformed  into   of  the  pulse  signal,  and  during  this  time,  the
          electrical impulses that can later be digitalized.      detector can be insensitive to other events. It can
                                                                  also  generate  overlapping  pulses,  producing
           When  interacting  with  detectors,  charged           distortion of the first signal and loss of information.
          particles like muons, transfer their energy to matter   To avoid this, the counting rate of the detector must
          through  collisions  with  the  atomic  electrons,      be kept sufficiently low, so that the probability of a
          inducing excitation or ionization of the atoms. Even    second  event  occurring  during  the  dead  time  is
          if  ionization  is  produced,  a  certain  minimum      small.
          amount  is  necessary  in  order  for  the  signal  to  be
          usable. This lower limit  is determined  by  the noise   C. Scintillation Detection
          from  the  detector  and  the  electronics  of  the
          experiment.  This  noise  manifests  as  a  fluctuating   Once  radiation  of  charged  particles,  like  the
          voltage or current at the detector’s output and is      muons, reaches the detector, the form in which the
          always present wether there is radiation or not. As     converted  energy  appears  depends  on  the
          a  consequence,  the  ionization  signal  product  of   detector  and  its  design.  Scintillation  detectors
          the detection of radiation, must be larger than the     make use of the property of some materials to emit
          average  voltage  level  associated  with  the  noise.   a  small  flash  of  light  when  struck  by  radiation.  In
          Otherwise, the signal produced by radiation will be     scintillation detectors, the excitation and ionization
          indistinguishable from the noise of the detector and    produced by the radiation, contribute to inducing
          the electronics (Leo, 19994).                           molecular transitions which result in the emission of
                                                                  light.
           The output signal of electrical detectors is in the
          form of a charge or voltage pulse. The amount of         Scintillation detectors or scintillators, have a very
          ionization  in  the  detector  is  reflected  in  the   short  response  and  recovery  times,  compared  to
          electrical charge contained in this signal. Assuming    other  detectors.  Therefore,  the  time  difference
          the shape of the pulse doesn’t change from one          between  two  consecutive  events  can  be
          detection  to  the  other,  the  radiation  energy  is   measured with great precision. The materials used
          directly proportional to the pulse height.              in  scintillators  can  vary  from  organic  ones  like
                                                                  aromatic hydrocarbon compounds, or crystals like
           The  response  time  is  the  time  that  takes  for  the   anthracene  and  naphthalene;  to  solutions  of
          detector to form a signal after the radiation arrived.   organic  scintillators  but  in  a  plastic  solvent  like
          For a good timing, it is necessary for the signal to be   polyvinyltoluene  or  polystyrene.  Plastic  scintillators
          quickly formed into a sharp pulse with a rising flank   and, scintillators in general, are some of the most
          as  close to vertical as possible, so that the signal   used particle detection devices today.
          can represent more precisely an instant in time: the
          instant  in  which  the  radiation  arrived  to  the     When  coupled  to  a  signal  amplifying  device,
          detector.  Of  course,  the  determination  of  this    scintillations in the detector can be converted into
          instant  will  never  be  100%  accurate.  There  will   electrical  signals  that  can  be  analyzed  and
          always  be  a  small  interval  of  time  between  the   counted  electronically  to  get  information  about
          arrival of the radiation, the excitation or ionization   the  incident  radiation.  Photomultipliers  (PMT)  can
          of the atoms in the detector, and the emission of       do  just  that.  They  are  electron  tube  devices  that
          the signal. Ideally this time interval should be made   convert  light  pulses  into  a  measurable  electric
          as small as possible.                                   charge.


           The  duration  of  the  signal  produced  is  also      A  PMT  consists  of  a  cathode  made  of
          important  as  it  determines  the  ability  of  the    photosensitive  material  followed  by  an  electron
          detector  to  perceive  two  consecutive  events.  If   collection  system,  an  electron  multiplier  section,
          every  pulse  generated  has  a  very  long  duration,   called dynode, and an anode from which the final
          then  another  detection  that  occurs  during  that    signal  can  be  taken.  All  these  parts  are  usually
          time interval, will be overlapped to the first signal   housed  in  a  glass  tube,  at  vacuum.  When
          and information about both detections will be lost.     operating,  a  high  voltage  is  applied  to  the
          The dead time of a detector is the time required by     cathode,  dynodes  and  anode  so  that  there  is  a
                                                                  potential difference along the length of the tube.

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           Año 10 Núm. 30 septiembre-diciembre 2024                                    Tlahuizcalli ISSN: 2448-7260
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