Electrons in bubble chamber photographs?

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Discussion Overview

The discussion revolves around the nature of tracks formed by charged particles in bubble chamber photographs, specifically addressing the formation of these tracks, the presence of electrons, and the curvature of the tracks under magnetic fields. The scope includes theoretical considerations and experimental observations related to particle physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question why there aren't spirals of electrons along the entire track if charged particles leave a trail of ions by knocking electrons out of atoms.
  • Others suggest that low-energetic particles have a very small curve radius that may not be resolved in the photographs.
  • There is a proposal that straight lines in bubble chamber photographs could actually represent curves of very large radius due to the momentum of the particles.
  • One participant notes that muons from cosmic radiation, which typically have high energy, can result in large radius curves when influenced by a magnetic field.
  • A later reply mentions that "knock-on" electrons, or delta rays, require a significant amount of energy to be visible as separate tracks, indicating that they do appear under certain conditions.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of the tracks and the behavior of electrons, with no consensus reached on the specifics of the curvature or the visibility of electrons along the tracks.

Contextual Notes

Some assumptions regarding the energy levels of particles and the effects of magnetic fields on track curvature remain unresolved, as do the conditions under which delta rays become visible.

bubblechamber
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If bubble chamber tracks are formed by charged particles leaving a trail of ions as they pass through, by knocking electrons out of atoms, then why aren't there spirals of electrons along the whole track?

Also, are the straight lines in bubble chamber photographs actually curves of a very very large radius?
 
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Low-energetic particles have a very small curve radius - too small to get resolved.
Also, are the straight lines in bubble chamber photographs actually curves of a very very large radius?
If there is a magnetic field, they should be curves.
 
mfb said:
If there is a magnetic field, they should be curves.

So the straight lines are curves of very great momentum?
 
I don't see a way to get a (theoretical) straight line. Just curves with really large radius.
Simple example: Muons from cosmic radiation usually have an energy larger than ~10GeV. With a magnetic field of 1T, this results in a radius of ~30m or more.
 
Thank you very much!
 
bubblechamber said:
If bubble chamber tracks are formed by charged particles leaving a trail of ions as they pass through, by knocking electrons out of atoms, then why aren't there spirals of electrons along the whole track?

These "knock-on" electrons need to gain a fairly large amount of energy in order to be visible as separate tracks. It does happen sometimes.

http://teachers.web.cern.ch/teachers/archiv/HST2005/bubble_chambers/BCwebsite/gallery/gal2_12.htm

They're also called "delta rays." I saw plenty of these while working on a bubble chamber experiment as a graduate student long ago.
 

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