Nuclear Fusion Idea: Using Magnetic Fields

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
Sign up Log in
33 replies · 5K views
Dt2000
Messages
17
Reaction score
0
I was wondering if you could use a very strong magnetic field to produce nuclear fusion. The basic idea is a spherical cavity containing Deuterium (and possibly tritium) nuclei whose walls will be electromagnets whose fields slowly increase in strength and will repel the nuclei and thus the ball of deuterium nuclei inside becomes smaller and smaller until finally the nuclei are close enough to fuse, could this work? If not why?
 
on Phys.org
Magnetic confinement fusion is currently the most popular type of fusion under investigation and a lot of literature has been written about it. How much have you read on this subject?
 
I'm not talking about using the field to confine plasma, I was thinking of actually using the field to cause fusion by producing a more powerful electromagnetic field of repulsion from the walls of the cavity then from the protons thus forcing them to crush together and hopefully fuse
 
Yes it will be ionized
 
Then you have magnetic confinement of a plasma, which would make this magnetic confinement fusion.

In any case, your basic idea is faulty. You can't compress the fuel until the nuclei are so close together that they fuse, as the repulsive force from the closely packed protons is much greater than the force applied by the electromagnets. Instead you would have to heat the fuel so that the kinetic energy of two colliding nuclei is great enough to overcome the repulsive force and allow them to fuse.
 
Okay, but can I see the calculations?
 
Then what do you base your claim off? Because to fuse correct me if I'm wrong but you need to give the nuclei 1MeV of force to overcome the coulomb barrier that force does not need to come from temperature, it could be done with a strong enough push, such as from an electromagnetic field
 
Do you need calculations to see a human cannot throw stuff into an Earth orbit from the ground?
In terms of missing orders of magnitude, this is much closer than the idea you suggest.

Calculate the repulsion of two nuclei of hydrogen at a distance of 5 femtometers, and compare this to a force gradient (over 5 femtometers) from external electromagnetic fields. They are vastly different.
 
I base it off of basic knowledge of physics. I can try to do some basic calculations later on, but I have to go apartment hunting right now. Perhaps someone else could explain things while I'm gone.
 
Dt2000 said:
Then what do you base your claim off? Because to fuse correct me if I'm wrong but you need to give the nuclei 1MeV of force to overcome the coulomb barrier that force does not need to come from temperature, it could be done with a strong enough push, such as from an electromagnetic field

How much reading about nuclear fusion have you actually done? What is your background?
 
So the formula for the coulomb force is
coulomb1.jpg

Therefore the force between 2 Protons at 5 femtometers is 9.24N, I guess you're right it is unlikely that there could be any net energy gain of this
 
Dt2000 said:
Then what do you base your claim off? Because to fuse correct me if I'm wrong but you need to give the nuclei 1MeV of force to overcome the coulomb barrier that force does not need to come from temperature, it could be done with a strong enough push, such as from an electromagnetic field
This is a faulty understanding. Firstly, 1 MeV is a measure of energy, not force. Secondly, one can determine the energy needed by integrating force over distance applied. Thirdly, force or pressure is quite high - take the force applied between two protons, which would be the same as between two deuterons or a deuteron-triton pair at the same distance, but now multiply by 1014, and see what pressures are involved.

Proton-proton fusion works in the sun, because the pressures are extraordinarily high, as in orders of magnitude greater than we can generate with many made systems on a large scale, the because the volume of the sun is so great.

For terrestrial fusion systems, we generally focus on d+t, which is the easiest reaction to achieve, or d+d which is slightly more difficult to accomplish. All the while, energy is radiating out of the plasma, and neutrals tend to leak out.

One needs to do some homework on fusion technology, magnetic confinement and inertial confinement.
 
Astronuc said:
Proton-proton fusion works in the sun, because the pressures are extraordinarily high, as in orders of magnitude greater than we can generate with many made systems on a large scale, the because the volume of the sun is so great.
Even if we could reproduce the conditions here on Earth, it would not help. The fusion power rate in the core is about ~200 W / m3. That's a lower power density than a human has!Concerning the force of magnetic fields: a gradient of 100 T/m gives about 10-24 N (calculation). We need a force gradient, so let's have 100T/m per centimeter, and consider the distance of 5 femtometers as above: 7*10-37 N difference in force between the protons. The force is 37 orders of magnitude too weak.
As comparison, the gravitational attraction between the protons is 7*10-36 N, 10 times stronger than the tiny magnetic effects. And we know gravity doesn't let hydrogen fuse.
All those numbers might be off by an order of magnitude or two, but certainly not by 37.
 
mfb said:
Even if we could reproduce the conditions here on Earth, it would not help. The fusion power rate in the core is about ~200 W / m3. That's a lower power density than a human has!
That is the other aspect. The power density (energy production rate) in the pp cycle is very low, besides the fact that the cross-section for the reaction is quite low.
 
Last edited:
Alright my mistake about the magnetic fields the protons interaction with it will be quite small but what about if the sphere was charged instead? I did some crude calculations using coulomb's law and found that the sphere would have to be very tiny to overcome the massive forces of repulsion while my calculations say the repulsion at 5fm is 9.2N I decided to do an upper limit at 230-231N at 1fm assuming a charge of 400C so the fusion would take have to take place in a chamber with a diameter of 0.1mm which is ridiculously small and would not produce very much energy output compared to the energy going into charge the plates but it is very tiny so a lot of these could be setup per cubic meter, so in theory could this work?
 
Wait sorry I'm not exactly that great at physics correct me if I'm wrong but isn't that law for electrostatics? What if there is current flowing?
 
Current flow adds magnetic fields.
Time-dependent charge distributions are a bit more complicated, but you still cannot generate a spherical symmetric attraction without a charge sitting at the center.
 
So, would there be a force acting on the protons? And of what magnitude?
 
That depends on the geometry.
You can estimate the order of magnitude with some charges somewhere. But not 400 Coulombs, that will lead to a huge explosion.
 
Dt2000 said:
I was wondering if you could use a very strong magnetic field to produce nuclear fusion. The basic idea is a spherical cavity containing Deuterium (and possibly tritium) nuclei whose walls will be electromagnets whose fields slowly increase in strength and will repel the nuclei and thus the ball of deuterium nuclei inside becomes smaller and smaller until finally the nuclei are close enough to fuse, could this work? If not why?

My guess:
If you were able to achieve good enough magnetic field, then presumably it would be easier just to construct something like:
https://en.wikipedia.org/wiki/Tokamak
 
So the idea could hypothetically work?
 
I don't mean a Tokamak I mean the idea stated in the first post on this thread except instead of a magnetic field current will be used to charge up the sphere to fuse the nuclei by creating a stronger force of repulsion than that from the protons
 
How about using fast neutrons? Say there's a highly pressurised container, containing the deuterium or hydrogen nuclei, with a source providing it with fast neutrons, if one of these were to be absorbed by the nuclei, assuming that the neutron is very high energy, would it increase the momentum to sufficiently high energy to fuse?
 

Similar threads

Nuclear Fusion Idea - Unlock the Future!
  • Aero Stud
  • · Replies 11 ·
  • Nuclear Engineering
Replies
11
Graduate Fusion Idea: Using Volcano Steam Rings in EM Fields
  • jumpjack
  • · Replies 14 ·
  • High Energy, Nuclear, Particle Physics
Replies
14
Graduate Using magnetic fields in place of heat shielding
  • FireStorm000
  • · Replies 6 ·
  • Astronomy, Astrophysics, Cosmology
Replies
6