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Multi-Channel Analyser

  1. Mar 14, 2005 #1
    What does it do in a scintillation counter, does it split the voltage pulse into several amplitude channels which are proportional to energy?
     
  2. jcsd
  3. Mar 14, 2005 #2
    An MCA takes each pulse and categorizes it (increments a counter for each channel) according to amplitude based on it's settings for the upper and lower level discriminators for each channel. There's no pulse splitting taking place.
     
  4. Mar 14, 2005 #3
    Where does the energy relationship for each channel come into play?
     
  5. Mar 14, 2005 #4
    Any time an MCA is used, it needs to be calibrated using two or more radiation source with known energies (Co-57, Cs-137 are some typical calibration sources). Most MCAs can be programmed or set so that each channel represents a particular energy increment or unit (usually 1 eV/channel, or 1 keV/channel) depending on the energy range of interest.

    A typical MCA calibration sequence would go something like:
    [*]Acquire energy spectra of some known sources (each with different photopeak energies at opposite ends of your energy range of interest)
    [*]Identify the channels associated with each photopeak energy.
    [*]calculate the eV or keV/channel
     
  6. Mar 14, 2005 #5

    dlgoff

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    Back when I was is school, our MCA had 1024 channels for the 2MEV Van de Graff. Just curious how many channels MCAs have now days?

    Regards
    Don
     
  7. Mar 14, 2005 #6
    Some of the newer digital MCAs I've seen do upwards of 8192 channels. I think some of the newer PCI MCA boards you can get are only limited by your available memory. Of course, what you get out of your MCA is only as good as your detector. You're probably not going to get much benefit coupling a NaI detectory with low energy resolution with an 8k channel MCA.
     
  8. Mar 14, 2005 #7

    dlgoff

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    Thanks Bug. Wish I was still working with accelerators.

    Don
     
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