Solid angle acceptance of a muon telescope

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Discussion Overview

The discussion revolves around calculating the solid angle acceptance of a muon telescope composed of two aligned square detector panels. Participants explore different methods to derive the solid angle from first principles, considering both theoretical and practical aspects of the setup.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using the solid angle of a pyramid with a base of size x squared and a height of 0.5L to calculate the solid angle acceptance.
  • Another participant suggests that the solid angle can be defined by the formula [(x squared)/(L squared)], assuming the detectors are much further apart than their size.
  • A question is raised about the derivation of the solid angle formula, prompting a response that references the definition of solid angle and the small angle approximation (sin(a) = a).
  • Concerns are expressed regarding tracks that hit the second detector outside of a specific point, questioning how these are accounted for in the solid angle calculation.
  • It is noted that for any given point on the second detector, the same area of the first detector corresponds to the same solid angle, although the corners of the detectors may see slightly different solid angles.
  • A comparison is made to optical detectors, where the maximum angle versus the unvignetted angle is discussed in relation to the solid angle calculations.

Areas of Agreement / Disagreement

Participants express differing views on the correct method to calculate the solid angle acceptance, with no consensus reached on a single approach. The discussion remains unresolved regarding the best way to account for all possible muon tracks.

Contextual Notes

Participants highlight limitations in their assumptions, such as the distance between detectors relative to their size and the implications of ignoring corner effects in the solid angle calculations.

stakhanov
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I am trying to work out the solid angle acceptance of a muon telescope. The telescope is comprised of two aligned square detector panels (of size x squared metres) set at a distance apart of L metres. The way I was initially working it out (by using the solid angle of a pyramid of base x squared and height 0.5L, containing [as I thought] all the possible muon tracks through the telescope) is completely different to that which my friend insists is the right way (a solid angle defined by [(x squared)/(L squared)]).

Any help on how to find the solid angle from first principles and a resultant equation?
 
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Remember it's all possible tracks through the distant square to a single point on the near detector.
Assuming the detectors are much further apart than their size then x^2/L^2 sounds right.
 
And how would you derive that?
 
From the definition of solid angle. And by assuming that sin(a) = a for small angles.
 
Ok, so you have all possible tracks going through the first detector to a single point on the second detector (effectively a pyramid) but what about the tracks that hit the second detector outside of the point?
 
For any given point on the 2nd detector there is the same area of initial of detector 1 at the same distance and so the same solid angle.
The corners of the detectors do see slightly different solid angles and so the corner-corner angle is larger - this is normally ignored if L is much greater than the size of the detector.
In optical detectors it would correspond to the maximum angle vs the unvignetted angle.
 

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