Do Particle Accelerators Experience Torque?

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Discussion Overview

The discussion centers around whether particle accelerators, particularly non-linear ones, experience torque due to the forces exerted by particle streams or individual particles on the accelerator structure through magnetic fields.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions if the particle stream imparts a vector force on the accelerator structure via the magnetic field.
  • Another participant suggests that while a force must exist, it may not apply a torque.
  • A third participant explains that in the LHC, acceleration is achieved through electric fields rather than magnets, and discusses the forces on the magnets arising from countercirculating beams and internal stresses.
  • One participant speculates that the field strength might be greater than the angular momentum of the particle stream, implying no torque is generated.
  • Another participant references Newton's 3rd law, stating that any acceleration of mass by a field will have an equal and opposing effect on the apparatus, suggesting a relationship between forces and torques.
  • A later reply confirms the inquiry about Newton's 3rd law and its relevance to the discussion.

Areas of Agreement / Disagreement

Participants express differing views on whether torque is experienced by the accelerator, with some arguing against it while others provide reasoning that suggests a more complex interaction may exist.

Contextual Notes

Discussion includes assumptions about the relationship between field strength and angular momentum, as well as the application of Newton's laws in this context, which remain unresolved.

bacon555
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In particular, ones that aren't linear, of course.

Does the particle stream or individual particle, whatever they're firing, impart some sort of vector force on the structure of the accelerator itself via the magnetic field, and into the magnets?
 
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It must. I don't think the force would apply a torque though.
 
In the LHC the acceleration is accomplished not by magnets but by electric fields, namely eight superconducting RF cavities with a field gradient of 5 MV/m.

Forces on the magnets arise from the two countercirculating beams but also from internal stresses due to the maximum magnetic field of 8 Tesla. The beam energy is 350 MJ, but the energy stored in the magnets is much greater, 11 GJ.
 
So basically, no, because the field strength is higher than the angular momentum of the particle stream?
 
I'm going to assume you're wondering if Newton's 3rd law applies (in this case torques only exist in equal and opposing pairs), and it does. Any acceleration of mass by a field will ultimately have an equal and opposing effect on the apparatus (and whatever the apparatus is attached to, such as the earth) that generated the field.
 
That's exactly what I was wondering, thank you.
 

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