[mrpdaemon]

The main challenge in working with these high temperature plasmas is confinement. In order to achieve nuclear fusion matter needs to be heated to immense temperature, so that the kinetic energy of nuclei colliding can overcome the electrostatic force of the protons pushing each other away and "fuse" into larger nuclei (held together by the "strong force"), converting a fraction of the reaction mass into a relatively large amount of energy in the process.

In order to keep the plasma at the temperatures where fusion can occur, rather extreme measures have to be taken. In the Tokamak approach, the plasma is placed in a toroidal vacuum chamber, and "suspended" in the center of the torus by using electromagnets that line the Tokamak chamber's walls. At such high temperatures the plasma is so energetic that it is very hard to contain such fast moving particles. If the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly cools down to temperatures below where fusion can happen.

The immense engineering challenge here is to heat plasma to ridiculous temperatures, and keep it confined in a very small volume at great temperature and pressure to mimic conditions that give rise to nuclear fusion in the center of stars.

[anotheryou]

With confinement being the challenge, wouldn't duration of the containment at those temperatures be important too?

I see Wendelstein 7-x is attempting 30 minute burns soon https://www.ipp.mpg.de/4413312/04_18?c=4313165

[throwawayaway12]

>The immense engineering challenge here is to heat plasma to ridiculous temperatures, and keep it confined in a very small volume at great temperature and pressure to mimic conditions that give rise to nuclear fusion in the center of stars.

This is not exactly true. Inertial confinement fusion has conditions that are similar to stars. The engineering challenge for magnetically confined fusion to keep the low density plasma confined for long time durations for fusion.

For anyone interested in further reading, look up the Lawson Criterion.

[qwerty456127]

> If the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly cools down to temperatures below where fusion can happen.

Sounds relieving. I used to think that «if the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly…» disintegrates everything around or, when the power is huge enough, causes an apocalypse…

[jniedrauer]

One of the beautiful things about nuclear fusion reactors is that they are inherently unstable at STP. In the event of a catastrophic failure, they will simply stop working (potentially after some large bangs).

Nuclear fission reactions can continue on their own for quite a while. This is one of the reasons they can be so dangerous.

[sergiosgc]

At those temperatures, it will disintegrate whatever it touches. It's just that, unlike fission, fusion is unstable[1] so it quickly fizzles out, and damage will be local.

[1] Unstable in the sense that it is hard to maintain fusion conditions, not in the Hollywood sense that it blows up if you look at it sideways.

[robin_reala]

It’s not particularly hard to maintain fusion conditions, you just need a stellar mass levels.

[Dylan16807]

That description of destruction is entirely correct, it's just that the amount involved is tiny. Just like a big enough firecracker could destroy anything, but the ones we make just go pop.

[opwieurposiu]

TFA claims the stored energy is 300kj, which is roughly equivalent to the energy you get out of eating one apple.

[ambicapter]

This is not a very useful comparison. You can say that there is less energy in a stick of dynamite than a chocolate chip cookie, and yet, that stick of dynamite should still be handled carefully.

[snarfy]

Yep even if it's hot enough it still needs the correct densities. It's akin to trying to compress a balloon with your hands. If enough 'hands' all push simultaneously it can work, but you can imagine the instabilities.

[shusson]

this is what Doctor Octavius was trying to do in Spiderman 2.

[b_tterc_p]

This is helpful. Thank you.