How is the Bethe-Bloch formula used in gamma-ray photon detection?

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Discussion Overview

The discussion revolves around the application of the Bethe-Bloch formula in determining the energy of gamma-ray photons in spark-chamber detectors. Participants explore the mechanisms of gamma-ray interactions, such as pair production, Compton scattering, and the photoelectric effect, in the context of energy measurement in these detectors.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants inquire about resources explaining the Bethe-Bloch formula's application in gamma-ray photon detection.
  • It is proposed that gamma-ray photons undergo pair production, with the energy from the resulting electrons and positrons collected in an EM-calorimeter.
  • One participant questions whether pair production occurs in spark chambers, suggesting that ionization in the gas is the primary mechanism, and that the Bethe-Bloch formula can be used to deduce the energy of the gamma photon from the energy loss of charge ions.
  • Another participant notes that pair production requires a minimum gamma-ray energy of 1.0221 MeV and suggests that Compton scattering is more likely than pair production in this context.
  • There is a clarification regarding the energy levels of gamma-rays involved, with a question about whether they exceed the threshold for pair production.

Areas of Agreement / Disagreement

Participants express differing views on the primary interactions of gamma-ray photons in spark chambers, with some advocating for pair production and others emphasizing Compton scattering and the photoelectric effect. The discussion remains unresolved regarding the predominant mechanism in this context.

Contextual Notes

Participants highlight the conditions under which pair production occurs and the energy thresholds involved, indicating that assumptions about the energy of gamma-rays and the nature of interactions in low-density gas environments may affect the discussion.

FNL
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can some one give me a link or an article or his argument which Explain how the Bethe-Bloch formula is used to determine the energy of a gamma-ray photon stopped in a spark-chamber detector.

thanks
 
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a gamma ray photon will undergo pair production, and it is the total amount of energy from those electrons and positrons that will be collected in an EM-calorimeter.
 
malawi_glenn said:
a gamma ray photon will undergo pair production, and it is the total amount of energy from those electrons and positrons that will be collected in an EM-calorimeter.

yes , it will be clear
thank you
 
malawi_glenn said:
a gamma ray photon will undergo pair production, and it is the total amount of energy from those electrons and positrons that will be collected in an EM-calorimeter.

Is this really what is occurring in such a spark chamber? From what I've understood, all it requires is that the gamma ray causes ionization in the active gas in the spark chamber. Then by looking at the energy loss of these charge ions, one can apply the Bethe-Bloch to deduce the total energy of all the created charge particle and deduce the energy of the gamma photon that cause this ionization in the first place.

In such a low-density gas, one seldom creates pair production.

Zz.
 
Here's a brief article on a spark chamber.
http://eppog.web.cern.ch/eppog/Resources/SparkChamber.html
Another discussion - http://www.ep.ph.bham.ac.uk/index.php?page=general/outreach/SparkChamber/index

Firstly, pair production requires gamma ray energy of at least 1.0221 MeV. PP would be possible in the boundaries and plates/electrodes.

Secondly, I believe Compton scattering is more likely than pair prodcution, and then there is the photo-electric effect.

Is it inferred that the gamma-rays are much greater than 1.0221 MeV?
 
Last edited by a moderator:
Yes ZapperZ, that is correct of you, forgot to read the last word 'spark chamber' properly :)
 
Thanks
 

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