Alvarez's x-raying of the Gizeh pyramid

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Discussion Overview

The discussion revolves around the use of cosmic muons for "x-raying" the Great Pyramid of Gizeh, particularly focusing on the techniques and probabilities involved in detecting muons as they pass through dense structures like pyramids or volcanoes. The conversation touches on theoretical aspects of muon energy, scattering, and ionization events.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant highlights the refinement of muon detection techniques for applications such as pyramid imaging and volcano tomography.
  • Another participant questions the probability of detecting two ionization events in a spark chamber for high-energy muons, suggesting that while muons can travel unscattered, they do experience small scattering angles.
  • A later reply provides specific energy values for muons and discusses their energy loss in different materials, proposing that ionization events occur frequently enough in air to support detection.
  • Further clarification is made regarding the frequency of ionization events, with a participant suggesting that high-energy muons are necessary for effective imaging of large structures.

Areas of Agreement / Disagreement

Participants express differing views on the scattering behavior of muons and the implications for detection probabilities, indicating that the discussion remains unresolved regarding the specifics of muon interactions and their detection in dense materials.

Contextual Notes

The discussion includes assumptions about muon energy levels and their interactions with various materials, which may not be universally accepted or fully explored.

DrDu
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I had a fascinating read about Alvarez "x-raying" the great pyramid in Gizeh in the 1960ies using cosmic muons:
www2.lns.mit.edu/fisherp/AlvarezPyramids.pdf
The technique has been refined and used even to make tomographies of a volcano in Japan.

What I wonder: To obtain the direction of the muons, one needs two ionization events. Isn't the probability for two ionizations in the spark chamber very low for muons which are so energetic that they can run unscattered trough the whole pyramid or a volcano?
 
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Isn't the probability for two ionizations in the spark chamber very low for muons which are so energetic that they can run unscattered trough the whole pyramid or a volcano?
They are not unscattered, but their scattering angle is very small over the whole length.
 
Ok, I just read that the muons have on the mean 4 GeV of energy when they reach the surface and that they loose about 2MeV per g cm-2. So they can travel about 20 m in e. g. water. On the other hand, this makes still about 1 keV loss per cm of air. Given that ionization requires some 10 eV, there should be about one ionization event every 0.1 cm.
 
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On the other hand, this makes still about 1 keV loss per cm of air. Given that ionization requires some 10 eV, there should be about one ionization event every 0.1 cm.
Every 10µm?
For pyramids or mountains, you need the high-energetic muons.