Multi-Channel Analyser: Scintillation Counter Usage

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Discussion Overview

The discussion revolves around the functionality and calibration of Multi-Channel Analyzers (MCAs) in scintillation counters, focusing on how they categorize voltage pulses and the relationship between energy and channel settings. It includes technical explanations and personal experiences related to MCA usage in experimental setups.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires whether an MCA splits voltage pulses into several amplitude channels proportional to energy.
  • Another participant clarifies that an MCA categorizes each pulse according to amplitude without pulse splitting, using upper and lower level discriminators for each channel.
  • Questions arise about the role of energy relationships for each channel and the necessity of calibration using known radiation sources.
  • Calibration procedures are discussed, detailing the acquisition of energy spectra from known sources and the calculation of energy per channel.
  • Participants share personal experiences regarding the number of channels in MCAs, noting that some newer models can have upwards of 8192 channels, while older models had 1024 channels.
  • There is a mention of the dependency of MCA performance on the quality of the detector used, suggesting that a low-resolution detector may not benefit from a high-channel MCA.

Areas of Agreement / Disagreement

Participants express differing views on the operation of MCAs, particularly regarding pulse categorization and calibration methods. There is no consensus on the best practices or the implications of detector quality on MCA performance.

Contextual Notes

Some assumptions regarding the calibration process and the relationship between channel settings and energy increments remain unaddressed. The discussion does not resolve the technical details of MCA operation or the implications of using different detectors.

Who May Find This Useful

Individuals interested in the technical aspects of scintillation counters, radiation detection, and the calibration of Multi-Channel Analyzers, including students and professionals in experimental physics and engineering fields.

retupmoc
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What does it do in a scintillation counter, does it split the voltage pulse into several amplitude channels which are proportional to energy?
 
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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.
 
Where does the energy relationship for each channel come into play?
 
retupmoc said:
Where does the energy relationship for each channel come into play?
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
 
imabug said:
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
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
 
dlgoff said:
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
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.
 
Thanks Bug. Wish I was still working with accelerators.

Don
 

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