
Artistically shaped magnets may make stellarators easier to manage than ITER - okket
https://arstechnica.com/science/2017/06/wibbly-wobbly-magnetic-fusion-stuff-the-return-of-the-stellarator/
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dmix
I was just reading about stellarators in the book "A Piece of the Sun" [1]
about the history of fusion. I find it fascinating (and a bit worrying) they
are still basically attempting to optimize the same two approaches that were
developed in the 50s/60s, tokamak and stellarator.

I respect the scientists who continue to work on this. Many people have spent
their whole careers on it and have died without making significant progress.
It's inherently challenging because it's super expensive and working at super
high temperatures. But the potential of the end goal might be enough to keep
people working on it perpetually.

[1]
[https://www.amazon.com/gp/aw/d/1468304933/](https://www.amazon.com/gp/aw/d/1468304933/)

~~~
theothermkn
> I find it fascinating (and a bit worrying) they are still basically
> attempting to optimize the same two approaches that were developed in the
> 50s/60s, tokamak and stellarator.

This would be a bit like worrying that aerospace engineers are still
optimizing wings. Like wings, tokomaks/stellarators are the best tools for the
job, as dictated by the underlying physics of the systems in question.
Basically, donut-shaped magnetically-confined plasmas "leak" into themselves,
rather than out into the world.

> Many people have spent their whole careers on it and have died without
> making significant progress.

This is a popular view that is entirely wrong. The figure of merit, which is
the triple product of confinement time, density, and temperature, outpaced
Moore's law right up until a gain of about 0.95, when the magnetic technology
of the day caused the necessary size increase to put ITER in the realm of
international cooperation. ITER absolutely will produce more power than it
consumes. The plasma physics are just that well understood. The problem is
size.

MIT have recently worked out that a new breed of superconducting magnets can
more than double the available field strength, resulting in a 16-fold
reduction in reactor size (due to a 4th power gain in confinement strength as
a function of field strength). They hope to achieve a gain of about 2 with a
university-scale reactor _before ITER, designed with the magnets available at
the time, is complete_.

Most, if not all, of the above comes from
[https://www.youtube.com/watch?v=L0KuAx1COEk](https://www.youtube.com/watch?v=L0KuAx1COEk).
ARC and SPARC, the MIT reactor concepts, are the most exciting thing I've
heard about in...gosh, I guess my whole life. They could pull it off. If they
do, we could save the planet with fusion-powered CO2 scrubbing. We could avert
disaster.

~~~
lwlml
You know, I had a sad thought about fusion-powered CO_2 and that was once it
will be built, the energy is likely to be used not for CO_2 scrubbing but
instead to mine Bitcoin.

~~~
flashman
"Cheap energy means cheap air conditioning. We don't have to change a thing!"

~~~
tomaskafka
That's how it worked ever since, including coal and oil.
[https://en.m.wikipedia.org/wiki/Jevons_paradox](https://en.m.wikipedia.org/wiki/Jevons_paradox)

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crimsonalucard
>"Let me make it very clear: fusion is, if you simply look at the carbon
dioxide goals we have, fusion would be too late to bring those carbon dioxide
emissions down at the rate that we need. If renewables do the job, fusion
could become part of a network of dispatchable power generation units.
However, if renewables don’t do the job, fusion will be too late to prevent
serious damage. In that scenario, we would find ourselves in a bad situation
for a period of time that extends beyond when the first fusion reactors come
on line."

This quote is so telling on the limits of technology. So many people think of
fusion as a technological miracle that can save the world. Here we have a man
telling the world that we're fucked if we just sit on our asses waiting for
this miracle.

~~~
pirocks
Couldn't you just pump co2 out of the atmosphere if you had sufficient
energy/money ?

~~~
crimsonalucard
pump it where?

~~~
ItsDeathball
Several options: pump it back down the oil wells it came from, use fast-
growing juvenile trees to "pump" it into house frames and libraries, use algae
to "pump" it into useful plastics, or, if you have infinite money, bottle it
and shoot it at Mars to thicken the atmosphere.

~~~
wolfram74
You also forgot synthesizing diamonds, which, pulling it out of my butt, I
imagine is on similar energy budget with dumping it on Mars.

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tekkk
I watched this video called "MIT's Pathway to Fusion Energy (IAP 2017) - Zach
Hartwig" which I thought was interesting (and which I submitted here two days
ago but went unnoticed as it's the faith of many interesting HN submissions).

[https://www.youtube.com/watch?v=L0KuAx1COEk](https://www.youtube.com/watch?v=L0KuAx1COEk)

There Zach gives a quick overview (well hour long) of the current state of
fusion and what its future is going to be. He didn't talk too much about
stellarators but I feel I have now a better overall understanding of fusion
physics thanks to him.

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maxxxxx
If you speak German, this podcast is fantastic:
[https://alternativlos.org/36/](https://alternativlos.org/36/). The sheer
number of technological challenges in a fusion reactor is just crazy. Besides
plasma physics you have to invent welding techniques, materials and a lot of
other stuff. Everything is on or over the limit of what we can do now.

~~~
someSven
Yeah, I thought there was also one in English. I may confused it with one of
those:
[http://omegataupodcast.net/tag/fusion/](http://omegataupodcast.net/tag/fusion/)

~~~
maxxxxx
This one is good too but it's about ITER.

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Animats
There was a previous article on HN about the WX-7. It's an incredible piece of
mechanical engineering. It's more symmetrical than it looks at first.

The thing has the thermal management problem from hell. The magnet coils are
superconductors and have to be maintained down near liquid helium
temperatures. The plasma is at a few million degrees. These are inches apart.

3D printing might help when the next one is built. Rocket engines have some of
the same problems - they're plumbing parts filled with cooling hollows. Those
take way too many joints and welds to build. The Space-X Dragon spacecraft has
3D printed engines, which gets the part count down.

If we ever get room temperature superconductors, these things will be much
simpler. If we ever got high temperature superconductors, so that the whole
thing could run hot, like a boiler, that might make it economically feasible.

~~~
bradleyjg
If they have to keep the temperature down near liquid helium they must be
using (and need) type I superconductors. If we get room temperature
superconductors any time in the near future it will almost certainly be type
II.

~~~
vilhelm_s
What's the difference between them? When would you need one or the other?

~~~
bradleyjg
Turns out I was wrong. These applications use niobium-titanium or niobium-tin,
both of which are type II superconductors. They do have relatively low Tc --
10-20 kelvins versus >80 kelvin for the best HTSC, and are cooled even lower
to maximize the critical field and current (i.e. maximum they can withstand
before losing superconductivity).

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astrodust
It's like Frank Gehry designed a reactor.

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erikpukinskis
I wonder if you could make it in the form of a tree, where you took the leaves
and wrapped them around to join the roots, like an inside out donut.

So in the middle you'd have your conjoined mega stream, and then that would
flow upward, be separated out into filaments which then curl around in all
directions down to the roots where they are re-merged into the megastream.

Probably too much turbulence at the branches, but maybe they can use vibration
and learning to find beneficial harmonics. I would hire sound engineers.

I just have an intuition that a single stream will never have adequate
confinement and you'll need redundancy in the geometry to get good
concentration.

~~~
bdamm
You should build your design and tell us if it works. Or even better, patent
it and maybe make millions from licensing it to a conglomerate.

~~~
erikpukinskis
Why would I build it? You have to model this stuff computationally before you
even have a whiff of an idea whether it would work.

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0xbear
This is what real engineering looks like.

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sulam
I kept waiting for the artistic magnets. Sadly the opening image the best you
get.

~~~
karlshea
There's a bunch of pictures of them in the article's slideshows.

