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Waxahatchee Stellarator

Don't let a partially-built tunnel go to waste!
  [vote for,

A couple decades ago there was a plan to build something called the SuperConducting SuperCollider near a town named Waxahatchee, in the state of Texas, USA. See link. It was funded for a few years of initial construction, and then abandoned. If it had been finished, there would have been an underground mostly- circular tunnel about 87 kilometers in circumference (lots bigger than the existing Large Hadron Collider).

A bit more than 1/4 of the tunnel was built before the project was canceled. I'd like to see it finished, not because we might put a big particle accelerator in there, but because we could put a big nuclear fusion reactor in there. There's a particular fact about magnetic-confinement fusion reactor designs that just begs to be put into a circular tunnel with a nicely lengthy circumference.

A fair number of experimental fusion-research devices have been built in the shape of a torus or doughnut. See 2nd link. Any torus has two significant measurements. One is the overall diameter of the ring ("major diameter"), and the other is the diameter of the tube that forms the ring ("minor diameter"). In the linked images you can clearly see that the major diameter is only a few times larger than the minor diameter. This is mostly a result of limited funding.

Here at the HalfBakery we sneer at limited funding, and I've actually mentioned this Idea before, in annotations of a completely different Idea (see 3rd link). I decided this Idea needed to be presented independently, partly because of a couple recent developments.

The first thing involves a type of fusion reactor design called a "stellarator" --see 4th link. You will note that a torus is involved, and here the major diameter is significantly larger than the minor diameter. There are two reasons for that.

See the 5th link for a depiction of a simple toroidal magnetic field. It is easy to tell that the magnetic field is a lot more concentrated in the middle of the torus, than on the outside of the torus. In a magnetic-confinement fusion reactor, that area of weakness invites the plasma to escape confinement, and shut down the reactor. Not good!

Well, the larger the major diameter of the torus, the more that the outside magnetic field will be similar in strength to the inside field.

Next, in a stellarator the confined plasma moves through the tube, flowing in the big major-diameter circle. Specially designed magnetic fields force the plasma to "twist", so that it spends part of its time near the inner region of the torus, and part of its time near the outer region of the torus. The net effect is that it stays confined more easily, experiencing an averaged- strength magnetic field. Building those twisty magnets is easier when the major diameter of the torus is numerous times larger than the minor diameter.

Well, the Waxahatchee tunnel can hold a decent-sized minor- diameter tube, but the major diameter is so much vaster that we might not even need twisty magnetic fields to keep the plasma confined. If so, its design would be significantly simplified.

The other recent technical advance involves the manufacturing of significant quantities of high-temperature superconductors (only need liquid nitrogen to keep it cool enough to superconduct). See the 6th link.

I really think we are getting really close to building practical nuclear fusion power plants. If THIS one was built, it likely could power a pretty sizable chunk of the entire USA.

Vernon, Feb 21 2016

Superconducting Supercollider https://en.wikipedi...ting_Super_Collider
As mentioned in the main text. [Vernon, Feb 21 2016]

Fusion Torus https://www.google....P0mMKHQMCAjEQsAQIOA
As mentioned in the main text. [Vernon, Feb 21 2016]

Earlier mention of this Idea in Annotations Efficient_20Electrolysis_3f
As mentioned in the main text. [Vernon, Feb 21 2016]

Stellarator https://www.google....P72MKHVQ6D5wQsAQILQ
As mentioned in the main text. [Vernon, Feb 21 2016]

Magnetic Torus http://www.tat.phys...images/Tayler_5.jpg
As mentioned in the main text. [Vernon, Feb 21 2016]

Superconductor Availability https://www.theengi...act-fusion-reactor/
As mentioned in the main text. [Vernon, Feb 21 2016]

Tevatron tunnel! https://en.wikipedia.org/wiki/Tevatron
Here is an existing reasonably-large circular tunnel that might be used for a fusion reactor. The Tevatron was still in use when I originally thought of this Idea (annotations in 3rd link above), but now that the machine has been retired.... [Vernon, Feb 21 2016]

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MaxwellBuchanan, Feb 21 2016

       My favorite part / I decided this Idea needed to be presented /   

       Because now I feel that my schemes for syfy channel specials have similarly been presented by virtue of having posted them on the HB. Syfy channel execs are you reading this? My rates are cheap!
bungston, Feb 21 2016

       For a rather-less expensive notion, but still possibly as workable because of the low curvature of the torus-tube around the circumference of the major diameter, see the "Tevatron tunnel!" link.
Vernon, Feb 21 2016

       //we sneer at limited funding//   

       [marked-for-tagline] ?
Vernon, Feb 22 2016

       A little reading has liberated me form uncertainty. I am now sure that I don't get plasma physics. I don't care too much, because I'm convinced plasma physicists aren't too much better off. Anyhow, the volumes and surface areas of this beast are pretty colossal, vacuum maintenance isn't going to be easy. Also, what effect does the huge magnetic field have when it interacts with the Earth's over such distances?
bs0u0155, Apr 27 2017

       [bs0u0155], a toroidal magnetic field is a closed/confined ring. And the Earth's magnetic field is a huge worldwide thing (tending to get distorted by various mineral deposits). Did I mention that the Waxahatchee tunnel is underground? If a stellarator was built there, I expect its magnetic field to not be very notice-able at the surface. There might be some distortion of the Earth's field, and that could be minimized by building a Faraday Cage into the walls of the tunnel.
Vernon, Apr 28 2017


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