How many magnets are in the CMS experiment

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Discussion Overview

The discussion revolves around the configuration and characteristics of the magnets used in the CMS (Compact Muon Solenoid) experiment, specifically addressing the presence of a 4 T magnet and an additional 2 T magnet. Participants explore the placement and function of these magnets within the detector, as well as the implications for the magnetic field lines.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes the existence of a 4 T magnet and questions the placement of an additional 2 T magnet, suggesting it does not encircle the entire detector.
  • Another participant suggests looking for more images and mentions the "magnet return yoke" as a potential source of information.
  • A participant expresses confusion about how the return yoke confines the magnetic field and questions whether it alters the direction of the field lines.
  • One participant explains that magnetic field lines are closed circles, indicating that if the field in the center goes in one direction, it must return in the opposite direction elsewhere.
  • Another participant acknowledges the explanation but remains puzzled about the field direction in the endcap of the detector, questioning if there are additional mechanisms for deflection beyond the solenoid's normal behavior.
  • There is a request for specific images that illustrate the cylindrical nature of the detector and the associated field lines.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the magnetic field configuration and the role of the return yoke. There is no consensus on the specifics of how the magnetic fields interact within the CMS detector.

Contextual Notes

Participants reference diagrams and descriptions from the CMS page, indicating potential limitations in understanding due to the complexity of the magnetic field interactions and the need for visual aids.

BillKet
Messages
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30
Hello! When I google about the CMS magnet I see that there is a 4 T magnet. However in the diagrams with muons, like this one, it seems to be another 2 T magnet beyond that. Where is that placed exactly. I assume it doesn't go around the whole detector, as that would affect the central region (the one with 4 T), but I am not sure where it is placed exactly.
 
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BillKet said:
I assume it doesn't go around the whole detector

You should look for more pictures.

You should also Google "magnet return yoke".

This should answer all your questions.
 
Vanadium 50 said:
You should look for more pictures.

You should also Google "magnet return yoke".

This should answer all your questions.
I am not sure that helps me understand. On the CMS page it says: "The outer part of the detector, the iron magnet “return yoke”, confines the magnetic field and stops all remaining particles except for muons and neutrinos." I am not sure I understand how confining the magnet is equivalent with making the lines go in the opposite direction. Is this like a structure that actually rotates the field lines after a point?
 
Magnetic field lines are closed circles. If the field in the center of CMS goes in one direction then the field must go back in the other direction somewhere farther out. Here is a simple solenoid field.
 
BillKet said:
I am not sure that helps me understand.

You really want to get more pictures than that one. You really do.
 
mfb said:
Magnetic field lines are closed circles. If the field in the center of CMS goes in one direction then the field must go back in the other direction somewhere farther out. Here is a simple solenoid field.
Thanks for this! It makes more sense now. However I am still confused about how the field can point in the opposite direction (at least based on their diagram) in the endcap of the detector (it should point at an angle due to the curving of the field lines). Do they have some way to deflect it even more than just the normal deflection of the solenoid?
 
Vanadium 50 said:
You really want to get more pictures than that one. You really do.
Showing me one such picture would be helpful. It's kinda hard to look for better pictures if I don't know what I am looking for. All diagrams showing the trajectory of a muon in the detector (including the CMS logo) are like that picture, so I am not sure what pictures are you referring to.
 
Well, a picture that shows that the detector is cylindrical was what I was hoping you'd find.

The field lines look like this.

1604923915082.png
 

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