How does magnetic fusion work?

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Discussion Overview

The discussion revolves around the mechanisms of magnetic fusion, specifically how magnetic fields interact with plasma during the fusion process. Participants explore the nature of plasma, the role of charged particles, and the effects of magnetic fields on these particles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions how magnetic fields can affect neutral plasma, suggesting a need for clarification on the nature of plasma in this context.
  • Another participant proposes that while plasma is neutral overall, the positive and negative charges within it will spiral along magnetic field lines in opposite directions (clockwise and counterclockwise).
  • A later reply agrees with the notion that while the plasma is uncharged, the individual particles within it are charged, which allows them to be influenced by magnetic fields.
  • Further elaboration indicates that the magnetic field is applied externally and decreases in strength with distance into the plasma, while collisions within the plasma help maintain containment.
  • Participants discuss the use of magnets not only for confinement but also for heating the plasma, comparing the process to how a transformer induces current in a conductor.
  • There is mention of the challenges in maintaining stability within the plasma confinement system.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the interaction between magnetic fields and plasma, with some agreeing on the basic principles while others remain uncertain about specific mechanisms. The discussion does not reach a consensus on all points raised.

Contextual Notes

Some assumptions regarding the behavior of charged particles in magnetic fields and the specifics of plasma containment are not fully explored, leaving certain aspects unresolved.

Ben.meyer
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Magnetic fusion is controlling plasma while its undergoing fusion. Right? Well if plasma is neutral, how can the magnetic fields affect it?
 
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currents running through wires are neutral but the magnetic field still affects them.
im not sure how it works, but i suspect that the positive and negative charges will spiral along the magnetic field lines with opposite senses (CW CCW)
 
alemsalem said:
im not sure how it works, but i suspect that the positive and negative charges will spiral along the magnetic field lines with opposite senses (CW CCW)
Right.
While the total plasma is uncharged, (nearly) all objects in the plasma are charged.
 
alemsalem said:
currents running through wires are neutral but the magnetic field still affects them.
im not sure how it works, but i suspect that the positive and negative charges will spiral along the magnetic field lines with opposite senses (CW CCW)
Correct, nuclei and electrons spiral along the magnetic field lines, and by that, the magnetic field lines are used to exert pressure on the plasma. The magnetic field is applied from the outside, and the strength falls off with distance into the plasma. Inside the plasma, it's the collisions that maintain containment. Neutral atoms (from recombination) may leak out of the plasma.

Magnets are also used to heat the plasma. A large central magnetic can be used to induced a current in the conductive plasma, just like a transformer core induces a current in a metal conductor. This current also induces a magnetic field that confines and compresses the plasma. Other fields help support the confinement and as well as provide some stability (which is very challenging).
 

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