Problems with Nuclear Fusion

Kidphysics

I'm sorry why is this such a bad thing?

Joseph Chikva

Imagine the following design:
· ions source,
· then the coaxial chamber filled with gas (neutralizer),
· then the separation chamber magnetically declining particles (ions) still remaining charged while neutralized particles keep stright direction
· then the long pipe called in Russian "atomoprovod" ("atom conductor")
· then reaction chamber (vacuum chamber)
Atom conductor is equipped with deposited surface gas adsorbers keeping vacuum at acceptable level for certain (not long) time. As you can see that the chamber filled with gas is connected directly with vacuum chamber. Adsorbers are cooled to cryogenic temperatures.
And after each shot experimentators are forced to desorb those adsorbers by heating.
Such a design is acceptable at experimental level but impractical for real fusion reactors.
And as far as I know there is not any different NBI design.

Kidphysics

For sure JET has them and so does ITER...

Joseph Chikva

As far as I know all neutral beam injection (NBI) have described above design. And I am claiming that such design is impractical and less useful for commercial reactors.

From another side NBI is the most effective heating way at temperatures exceeding 1 keV.
The second application of NBI is to drive current (the so called "beam driving current") that converts TOKAMAK into "advanced" or "H-mode" or "high confinement mode", without which it is impossible to achieve minutes order confinement times already achieved in TOKAMAKs.

So, as you can see TOKAMAKs today also are not ready for commercialization.

I have one idea how to avoid nessecity of NBI in TOKAMAKs.
I think that at first we using TOKAMAK field configuration (the combination of poloidal and toroidal fields) can easily create in-situ in the reaction chamber the halo-layer of high energetic (several MeV) particles.

For this we have to performed consistently the following procedures (corresponding hardware should be included in toroidal fusion reactor):
• orthogonally to equatorial plane of toroidal vacuum chamber to create generally the time-dependent magnetic field (bending field) penetrating only its curvilinear segments,
• to apply axial (toroidal) magnetic field only in the regions located remotely from injection points,
• along the axis of toroidal vacuum chamber to inject 3 different kinds of pulse high current particle beams (two ions’ – reacting components and one – electron’s) with such a parity of particles’ kinetic energies allowing them the capability of moving in a given bending magnetic field on a common equilibrium orbit (gyro-radiuses (rg=p/qB) of all 3 spices are equal) in such a manner that faster ion beam passes through the moving at the same direction slower ion beam with sufficient for nuclear fusion collision energy and the relativistic electron beam moving oppositely to ions thus allowing to combined beam the self-focusing capability,
• to apply axial (toroidal) accelerating electric field compensating the occurring together with fusion two effects: tendency of alignment of velocities of reacting particles and also electrons’ energy losses via Bremsstrahlung.
(G.I. Budker says that number density up to 10^24 m^-3 and even higher is achievable in combined beam and as result of fusion the high energetic fusion products are produced, from which neutrons escape reactor while charged particles form halo-layer.)

Then once as result of fusion we create the halo-layer only then to create the plasma.

For this we have to do the following:
• from the walls with the help of corresponding valves to puff into the vacuum chamber the gas consisting the fuel components. And already being there halo-layer ionizes that gas and then generates the current similarly to that how current is driven by beam/beams of neutrals in modern TOKAMAKs.
• in regions being free from axial magnetic field to apply such a field at once after the end of injection.

And I am sure that this idea would make TOKAMAKs viable for commercial application right now.
As despite all other approaches the theory of TOKAMAKs is really well developed.