What happens to the Neutrons and Protons in a Tokamak reactor.

Click For Summary

Discussion Overview

The discussion revolves around the behavior of protons and neutrons in a tokamak reactor, particularly focusing on how magnetic fields interact with these particles in the context of plasma confinement and fusion processes. The scope includes theoretical aspects of plasma physics and practical considerations related to fusion reactor operation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how protons and neutrons are confined within the magnetic field of a tokamak reactor, given that electrons are confined due to their charge.
  • Another participant states that neutrons escape the plasma and must be absorbed by the reactor's first wall, while protons, being charged, follow magnetic field lines but have different cyclotron radii.
  • There is a suggestion to calculate the cyclotron radii of electrons and protons under specific conditions, highlighting the differences in their behavior in a magnetic field.
  • A participant mentions that the plasma tends to remain neutral, which influences the behavior of charged particles like electrons in the presence of a magnetic field.
  • Concerns are raised about the leakage of neutral particles formed from recombination, which poses challenges for magnetic confinement.
  • Another participant inquires about the possibility of adding additional fuel during the fusion process, prompting a response that ideally, fuel should be continuously supplied as it is consumed.
  • One participant expresses interest in working on the ITER project and acknowledges the need for further learning and research on practical problems related to fusion.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of neutrons and protons in a tokamak reactor, particularly regarding confinement and the implications for reactor design. The discussion remains unresolved on several technical aspects, such as the specifics of particle behavior and the challenges of maintaining plasma stability.

Contextual Notes

Participants mention various assumptions, such as the temperature of particles and the conditions under which calculations are made. There are unresolved questions about the implications of particle leakage and the operational challenges of maintaining a steady-state fusion reaction.

Who May Find This Useful

This discussion may be of interest to students and professionals in plasma physics, nuclear engineering, and those involved in fusion research, particularly in the context of tokamak reactor design and operation.

Pattonias
Messages
196
Reaction score
0
As I understand it, the magnetic field confines the electrons because of the repulsion of the electrons in the plasma and the electrons traveling in the magnetic current.
My question is what keeps the protons and neutrons released in the plasma from passing through the magnetic field in a tokamak reactor?
 
Engineering news on Phys.org
Neutrons pass right out of the plasma into the surrounding structure. The first wall must absorb the neutrons.

The protons are charged, so like electrons they travel around/along the magnetic field lines, but their cyclotron radius is different.
http://en.wikipedia.org/wiki/Gyroradius

As an exercise, take the electrons and protons to have the same temperature (kinetic energy, but different velocity due to mass difference) and assuming a 10T field, calculate the cyclotron radii of the electrons and protons. And actually, if one is using D+T, then its deuterons and tritons, as well as products like p, He-3, He-4 and n.

The plasma excludes the magnetic field, to the magnetic gradient sends the charged particles back into the plasma.

The plasma likes to stay neutral, i.e. balance of + an - charges, so an electron leaving not only experiences the local magnetic field, but also Coulomb attraction to the plasma, which would have a net + charge if the electron were to leave.

One problem for magnetic confinement is the leakage of neutrals, which are atoms formed from the 'recombination' of nuclei and electrons.
 
Can additional fuel be added once the fusion process is started? Or can only one reaction occur at a time?
 
That's the idea. Ideally they'd be pumping in fuel as fast as it's consumed.

But the have to get to steady-state beyond breakeven. That's hopefully what ITER will demonstrate.
 
I appreciate your input, it's making this a little clearer to me. I'm actually hoping to work on the ITER project once I finish my degree. I still have a lot to learn before I'll be able to contribute. The practical problem you suggested still has me doing some research. I appreciate your comments though.
 
Last edited:

Similar threads

Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 5 ·
Replies
5
Views
5K
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
9
Views
4K