[ohiovr]

"There are three boxes we need to tick, in order to overcome this repulsion I mentioned before and get the nuclei very close. And this is not an easy feat. We need high temperature (think a hundred million degrees), high density (have a lot of these nuclei in a very small space), and keep the nuclei in that small space long enough for them to “react”. "

High temperatures are usually used because the nuclei must have a lot of force to counter that of the liked charged partner. The most obvious way to do this is with heating the plasma because individual particles, when they collide head on, can have the combined momentum to plow their way together.

But Philo T Farnsworth found a clever way to get them close with electrostatic forces. If it weren't for those darned wires.

With millions of degrees that plasma viciously expands. An even more incredible contraction force must be used to keep this together long enough for "interesting results". This is done with inertial confinement like the Hbomb or emulations of it. Magnetic confinement merely slows the expansion, but it must at some point touch the walls.

Actually, heat is not wanted. You only need to get the nuclei close enough that they quantum tunnel to each other to relieve their own stress in their environment. 2 Dueterons spread farther than helium3 does. Think of it like phase changes in condensed matter. Except we don't care at all about electrons, simply move them somewhere that the fuel ions wish to congregate at. Fortunately this can be a single point, as charges are concentrated on pointy things, as Faraday found in his experiments. The other side is full of the fuel ions. They don't have to be hot but warming them a little in an environment that is under 770 giga-pascals of pressure might be enough to moderate a nuclear combination process. It isn't hard to create two chambers in a crystal and make them undergo reductions or oxidations to free ions or electrons (tragically this happens with lithium ion batteries all the time). If they are surrounded in an environment that is very hard, very good dielectric strength, ions or electrons can be freed with no where to go. This is known as a meta-stable state and many crystal patterns exhibit this. The best dielectric known is diamond and it's also the hardest and has a ton of other helpful properties. If diamond couldn't do this, then nothing can. A mad genius with money and time would not have to go further than it to rule it out completely.

Say my fancy idea doesn't work, if colliding macro projectiles is something useful to the author have they tried something like levitating pyrolytic carbon and propelling it with laser ablation? It could be done in a loop if part of the magnet can de-energize fast enough to allow the tiny block of carbon to escape.

The plan they have seems very Wile E. Coyote to me but fun and cool. I hope they succeed.

[thehappypm]

Hard to imagine a crystal can hold together atoms that need millions of degrees of temperature to fuse

[ohiovr]

If you had fingers small enough, you could bring together two nuclei at room temperature and they would fuse.

[drdeca]

By “fingers” do you mean “things which can apply precisely controlled forces to individual atoms”, or..?

If you have two atoms in a vacuum with one moving directly towards the other at a not very high speed, I’m pretty sure they don’t fuse.

There’s a repulsive force, right? Like, the (expectation of) potential energy goes up (up to a certain point) as the centers of their nuclei get closer together (after perhaps getting lower for a bit because maybe they form a bond or something)?

So, presumably the “fingers” would have to do enough work to get past this potential energy barrier? (Or at least, make it high enough up this barrier that the probability of tunneling through becomes non-negligible?)

[ohiovr]

That's basically it. The strength of your fingers are more than enough to overcome the charge of 2 individual nuclei. Perhaps we need a shrink ray..

[drdeca]

I can believe that, yeah, that sounds likely enough. However, even if my fingers overall can easily exert the necessary force, it isn't clear to me that this should imply that any individual molecular bond between atoms in my fingers should be able to withstand the necessary force.

To me, it feels like it shouldn't be able to? (I say "feels" because I have not like, looked up any of the numbers about this or anything like that, and I could easily be wrong)

And, perhaps this could be the/a reason one might doubt that containing it in a diamond would work as an alternative to things like parts being brought together suddenly through precise collisions or using confinement from magnetic fields and such?

Though, of course, I'm not saying that doubting for that reason would probably lead to a correct conclusion. I wouldn't know much of anything about how one would achieve nuclear fusion, or how strong chemical bonds are, etc. .

[ohiovr]

I think the problem with trying to fuse two nuclei with your fingers is that the recoil from the reaction is really going to hurt. In a diamond this will destroy it. So it would seem like the only way it could work is if it were done as a burst. With a reasonable fraction of a coulomb of charge on each side rushing together and blocked by a thin layer of diamond, for a brief moment a lot of nuclei will be hopping on top of each other. If the ions and electrons are liberated instantly, immediately after there will be a high energy explosion. So shhh.. don't tell anyone like General Groves.

[dotancohen]

I believe that you are correct.

In nature, those "fingers" are more often than not hydrogen atoms, and the force acting on them is gravity. 10^30 kilograms of hydrogen, in a stack 600,000 kilometers tall, makes for high enough forces for the hydrogen to fuse.

[pencilguin]

They are already succeeding: they have got the investors' money, and no force on Earth is powerful enough to make them give any of it back.

There was a movie with Gene Wilder and Zero Mostel, a few years back, about this business model.

[ohiovr]

You aren't wrong. I've thought this way about most commercial attempts. I'd have to check out the movie. Gene Wilder, this should be good!

[pencilguin]

"The Producers."

And, yes, classic.