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Successful second round of fusion experiments with Wendelstein 7-X

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Re: Successful second round of fusion experiments with Wendelstein 7-X

#161
post #12

With fusion devices having trouble to confine the plasma for long times, I wonder if a massively-parallel fusion plant woud be feasible. Let's assume that plasma destabilisation does not damage the device, and is a mundane event. Build 10 or even 20 fusion devices (economy of scale!) feeding the common heat buffer, e.g. a large reservoir of a molten salt or metal. Feed conventional turbines off the heat of the heat t…

Why is this upvoted? It shows a severe lack of physics knowledge.

The whole goal of fusion is to get the energy amplification, Q, to be > 1, which requires the triple product n T t to be above some threshold. n is density, T is temperature, t is confinement duration. This is Lawson's criteria, you should look it up to educate yourself.

Your proposal doesn't help n, T, or t, hence doesn't help Q.

Also, there are economic and physical gains from concentrating your efforts into making your fusion reactor larger, rather than trying to make it 1/10 the size and have 10x of them.

The economies of scale will happen once fusion ignition (Q>1) is achieved and we start mass producing dozens of fusion plants around the world. But at this point we're likely 10+ years away from achieving ignition.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#162
post #21

Earlier quoted context omitted.

Just for the record, you don't re-create stellar-core conditions with earth-bound fusion devices: We don't have the means, and the yield would suck. Now, it is true that there's still fundamental research to be done until energy production via nuclear fusion becomes a reality, but we're reasonably confident that we could make the conventional approaches work. However, that research is Big Science, and there's no poli…

>>> However, that research is Big Science, Not all of it. The big science approach is a function of "pure" fusion research done from the assumption that containment/ignition only comes from magnetic fields and particle collisions. Some are approaching it from different directions, even using physical forces to trigger ignition (ie slamming the hydrogen with a big hammer). This isn't crazy stuff, just a more practical…

General Fusion changed their plan last year. The acoustic compression scheme, and the use of a spheromak plasma, are out. They discovered they have to limit the magnetic field to about 100T or else the induced currents start vaporizing the surface of the imploding liquid metal. This would be a disaster, as the metal vapor would have poor electrical conductivity and would penetrate into the plasma.

Confinement in the spheromak was also unacceptable; fast electrons were lost too easily from the edge, causing too much cooling.

Instead, the new scheme compresses more slowly, and compresses a spherical tokamak plasma. This scheme will have a solid post running down the center of the plasma, and the metal will implode from the sides at lower speed. The burn will take about 1 millisecond.

I am skeptical of this approach, since the center post will be exposed to extreme conditions (average neutron fluence two order of magnitude higher than in conventional fusion reactor designs) without a thick layer of liquid metal to shield it. The non-acoustic compression scheme also means the reactor vessel will have to withstand extreme pressure.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#163
post #3

Experiments like Wendelstein remind me that the only thing holding back fusion power is money for research like this. Every year, we spend billions on fossil fuel exploration because the return on investment is quick - just think about all the wells going in to extract shale oil. What if we collectively had the will to invest this much into fusion?

> What if we collectively had the will to invest this much into fusion?

The big problem is that fusion has reached its end-game in military applications: we have the h-bomb. Sure, there's the hypothetical fusion submarines and carriers, but what do those really provide beyond their fission equivalent?

If we could find some novel thing that fusion power solves for the military, then fusion would be solved.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#164
post #45

Earlier quoted context omitted.

If the Stellerator, or any of its descendants, turn out to be the answer to practical fusion, it would have been contingent on vast quantities of computational power being available cheaply. It does not matter how much money you poured into your Stellerator project in 1970, you could never have built the 7-X, because there would have been no way to produce that design in the first place. Personally, I think one of th…

Pouring in money advances computation. Microprocessors were a direct result of the space race and space weapons systems. No other industry would have justified the trillions of dollars in investment that was required to fit advanced computers into a small space when mainframe systems did the job just fine. Missiles and spaceships required systems that could calculate trajectories and be small enough to launch into sp…

The Farnsworth fusor was very well within the realm of affordability. Unfortunately, it was not a design that could break even, which destroyed the future of its creator.

https://en.m.wikipedia.org/wiki/Fusor

Re: Successful second round of fusion experiments with Wendelstein 7-X

#165
post #138
post #121

Earlier quoted context omitted.

>> when mainframe systems did the job just fine. Didn't people see the value that cheaper/more compute power will give them back than ?

This can be seen as a consequence of https://en.wikipedia.org/wiki/Jevons_paradox . It is called a paradox because seeing it in action usually catches people by surprise. And this is true whether you're talking about the consumption of coal to power factories, or the consumption of electricity to power computing (and in each case the myriad of new uses that efficiency promoted). In Science Fiction over and over again…

> In Science Fiction over and over again the trope was of a giant computer that acted like an oracle.

In many ways we're doing that exact thing. The computer at my desk is powerful but somewhat useless; the grand oracle in the form of Google et. al. does the real heavy lifting of giving me useful information. Whether it's a single computer or a bunch of separate ones acting as a whole is pretty immaterial in that sense.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#166

Earlier quoted context omitted.

I operate a fast camera at W7-X. It's a normal high-speed camera that records light in the humanly visible range, and the plasma emits in that range and reflects off the walls. IR cameras are most often used to gauge the temperatures of vessel wall components. Our camera looks through a pinhole in the vessel wall, but it sits a few meters away from the machine and gets that view through a bundle of optical fibers. Th…

> Our camera looks through a pinhole in the vessel wall, but it sits a few meters away from the machine and gets that view through a bundle of optical fibers. Wait, so does this mean that you have a camera obsucra with an array of optical fibres at its back, and then you have an ordinary CCD camera imaging the other end of the fibre array?!?!

I guess the word pinhole is misleading here, I think it's a few cm in diameter. Behind it there's an array of lenses that projects the view onto a fiber bundle, then a lens at the other end of the bundle projects that view out. That light goes through a beam splitter which shares it between our camera and another one in the shielding box.

Most imaging in fusion is done like this because of space constraints, magnetic fields, and neutron fluxes.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#167
post #3

Experiments like Wendelstein remind me that the only thing holding back fusion power is money for research like this. Every year, we spend billions on fossil fuel exploration because the return on investment is quick - just think about all the wells going in to extract shale oil. What if we collectively had the will to invest this much into fusion?

Err no, money is not "the only thing" keeping us from having fusion power. I can think of one other thing which is that it's damn hard to create stellar-core conditions inside of a small containment vessel on Earth. It's not obvious that throwing more money at the problem is going to change this. After all, fusion research has been funded in some form or another since the 1950s. I'll bet if you added up all the resea…

I'm a physicist by training working as a software engineer at one of the large tech companies. I have multiple physics friends doing the same.

We'd gladly be working on fusion (or other physics stuff) but our present jobs pay much better.

More money, and better pay for hard science careers, actually would make a difference.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#168
post #83

Earlier quoted context omitted.

Also Helion, TAE (formerly Tri Alpha), First Light Fusion, Tokamak Energy, General Fusion, and others. TAE is the biggest, with over $500M invested so far.

I have to shake my head at TAE, since their approach was brutally critiqued 20 years ago. It turns out being given $500M doesn't let you evade the laws of physics. https://www.researchgate.net/publication/235032059_Comments_...

I'm not a fusion scientist so I can't really judge, but in general I'm not sure it makes sense to say "it turns out" unless you know that experiments have proven it correct. From some quick googling it appears that TAE people responded to the critique and other people thought they made some valid points; see page 4 in this paper:

http://w3fusion.ph.utexas.edu/ifs/ifsreports/919_wong.pdf

Things seem to be going pretty well for TAE, at least as far as plasma confinement goes. Whether they can get net power from boron is another question, of course. I definitely see them as a dark horse compared to the tokamak companies.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#169

Earlier quoted context omitted.

A company like Apple has a quarter trillion in cash laying around, they could jump start fusion and control near-limitless energy in several decades. I wish there was more of a visionary drive among institutions for intellectual curiosity and pushing the boundaries of humankind. And yes, I know why they don't... shareholders business plans risk blah blah blah. Reality is just so BORING. Maybe one day we'll find a way…

Unfortunately, the irony is that the only way companies get a quarter trillion in cash laying around is by making investments that they understand. I suspect Apple has no way of making good investment decisions in relation to fusion energy.

This ignores the "disruptive technology" aspect. Consider that most of the largest corporations are very young. Even Apple is only half a century old. 2 decades ago, they were doing completely new things that no one had ever done before. No one "understood" mobile computing before it took off.

Companies get a quarter trillion in cash by doing something really well that others aren't doing. Nuclear fusion powered perpetual motion machines certainly fit the bill...

Re: Successful second round of fusion experiments with Wendelstein 7-X

#170
post #138

Earlier quoted context omitted.

This can be seen as a consequence of https://en.wikipedia.org/wiki/Jevons_paradox . It is called a paradox because seeing it in action usually catches people by surprise. And this is true whether you're talking about the consumption of coal to power factories, or the consumption of electricity to power computing (and in each case the myriad of new uses that efficiency promoted). In Science Fiction over and over again…

https://wikipedia.org/wiki/The_Feeling_of_Power asimov and manned-missiles

Good example.

Now compare with Franchise, Jokester, All the Troubles of the World, The Last Question and many more stories that feature as a plot device a very powerful centralized computer named Multivac. (See https://en.wikipedia.org/wiki/Multivac for a more complete list.)

How the same mind could have come up with the idea of androids with positron brains following the three laws of robotics, and yet missed pocket calculators baffles me.

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