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.
Okay, did some search:
- When two hydrogen nuclei combine, they produce an enormous amount of energy. That process is known as nuclear fusion.
- Light nuclei have to be heated to extremely high temperature, it is challenging to create a controlled, safe fusion reactor that offers more energy than it consumes. Once we have such we’d have a near-limitless source of clean energy.
- Nuclear fusion does produce radioactive waste. However, in contrast to fission produced wastes, they are short lived and decay to background levels in a very short time.
- Tokamaks try to do just that.
As there seems to be quite a lot of confusion in this thread about what this is, here's an excellent video giving an overview of the state of the art in fusion energy research that is understandable by a lay audience: https://www.youtube.com/watch?v=L0KuAx1COEk
(somebody posted that video on another recent HN fusion thread)
Is it just me, or have we converged on 1 reactor design (the tokamak) relatively early on in the process? I appreciate that funds need to be concentrated in order to have an impact, but we have built dozens of this design since the 1950s, yet here we are.
Since I don't see any comments mentioning this, I've heard a lot of talk about skepticism on other forums regarded Chinese scientific breakthroughs. I know on the state level, their numbers are not considered reliable (economic data for instance). Does anyone have thoughts on the reliability of this?
Let me ask a different question to the knowledgeable folk here. It has been noted that producing the temperature is not the hardest part but confining the plasma for long periods of time is.
On this note, do we have any reason to be particularly confident that magnetic confinement will ever break even and produce surplus energy? In nature fusion seems to occur through gravitational compression, so what makes us sure that we can simulate this by other means that will ever amount to more than just demonstrations?
As far as I know temperature is one of the important but not the only important parameter. Density and confinement time can be taken into account as well to get a number that better characterizes the performance of a reactor, iirc.
Edit: I think this is what I meant: https://en.wikipedia.org/wiki/Lawson_criterion
Can someone comment on what kind of economic effect that working fusion reactor technology would have?
I hear sometimes contradictory hear-say on the lines of "unlimited energy", "reactor would have to be fed constantly".
Please explain what does it mean and why is it good? :) Thank you.
I know very little about fusion.
Did the reactor produce more energy then was put into it? I just don't understand enough about the field to figure that out by reading the article.
100M seems insanely high, beyond what anything man made would be able to contain. Is it extremely short lived? Or over a very small area? Very interesting.
Anyone know what the 'standard' and state of the art approaches to inference are for fusion?
I.e. going from sensor readings to inference of the plasma state.
How are these results more (or less) significant than the stellerator (Germany) achieved earlier this year?
I thought the stellerator had already achieved 100M Kelvin?
If you added one gram of 100M degree material in a 5 sq meter room at 15 degrees C, how hot would the room get?
gravitational compression on the level of what occurs in the stars cannot be achieved on earth - - therefore, net positive fusion will never occur. Why not invest all that money in solar, wind and wave energy instead ? Anything radioactive at large scale seems to always be aligned with government / military industrial complexes.
Once we achieve sustainable fusion, will it be possible to "share" the energy with everyone else to create more independent fusions? Kinda like keeping the candle burning so as to light more candles because matches are too costly.
Now, I don't expect politics to allow sharing of fusion energy to help other countries.
Stories like this scare me. With all of the precautions, even things like Fukushima failed and will poison our ocean for millennia. What happens if we have a runaway fusion process through some pathway that was unexpected?
With all the talk about the LHC possibly producing mini blackholes or magnetic monopoles that could potentially cause protons to decay spontaneously, I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here.
Fusion was, and for the foreseeable future will be, a boondoggle. In the US it was a cold-war-era arms race program intended to scare the USSR and have them overextend, and now the Chinese are using it for propaganda and scientific Keyensianism.
The fact is, fusion generates neutron radiation that destroys the reaction vessel, making it an unviable technology. Nobody takes it seriously as a source of energy, aside from uninformed people. As cool as the idea of controlled fusion is, it is and will remain science fiction.
A tokamak is a kind of fusion reactor, and basically the most prevalent.
"100M degrees" (Kelvin) corresponds to 10 KeV (kilo electron volts), which is an important figure to exceed for D-T fusion. D-T fusion which is the kind of fusion the ITER Tokamak (a forthcoming fusion reactor and international megaproject) intends to demonstrate.
An older fusion experiment, JET (Joint European Torus) reached these levels, so this does not break new ground, but it is important if this Chinese Tokamak is going to provide data useful for ITER.
I will note that it's rather unusual to refer to plasma temperature in Kelvin rather than in KeV. I edited this comment with a few more details to try to make it easier for laypeople to understand.