Thursday, December 20, 2007

Mr. Fusion?

In a few months, we could be hearing exciting news about breakthroughs in nuclear fusion!

If the results of this test project, the culmination of years of Navy-funded research, are successful, a commercially-working fusion reactor could be operating withing 5 years at a cost of a mere $200 million.

By comparison, mainstream fusion-research Tokamaks, on which decades of time and billions of dollars have been spent, are still decades away from viability at best, and likely will never work.

This is not any kind of "new physics" or crackpot research; the basic concept of the fusor was successfully producing fusion since the 1960s and has its roots in simple vacuum-tube technology, and was conceived by Philo Farnsworth who pioneered television. The problem was the original design was inefficient and required more energy to operate than was created -- but it was fusing nuclei essentially on a tabletop!

Fusors are so simple, a high school student can build one for about $500.

In fact, many hobbyists have done so.

The standard fusion approach assumes a magnetic field squeezes ions together and circulates them until they collide and fuse -- but ions are heavy and the magnetic energy required is immense.

Fusors instead work on the idea of using electric rather than magnetic forces to accelerate the ions linearly: imagine a negatively charged cathode that attracts ions towards it in a spherical configuration; as they rush to the center they reach high speeds and head-on collisions can cause fusion. Any ions that miss will gradually slow down after heading through the focus, and then be pulled back in, to recirculate until they fuse.

Simple!

The problem, however, is sometimes particles hit the metal cathode grid, and eventually (rather quickly) melt it...

Oops!

Enter Prof. Robert Bussard -- with a PhD from Princeton and a former assistant director of the Atomic Energy Commission. His redesign of the fusor concept into the "Polywell" device may have solved such problems.

Though he passed away last October, his last prototype seemed to work well enough that a scaled-up version was given $2 million in followup funding by the Navy last summer to be built and to try to replicate their previous results.

Yes, that's a shoestring budget. Here is the official site for Bussard's Polywell, where you can donate to speed it along if you like.

If successful it could send shockwaves through the fusion community! Of course, there can always be unforseen snags in attempting to scale up the device -- but as far as I can tell, there is no obvious reason it shouldn't work. No radical new technology is apparently required; the engineering issues are complex but appear tractable.

Bussard recently gave a talk at Google; you can see the long 90 minute lecture here, or a short highlight version here.

And here is a site with good links to info on the Polywell fusion topic.

The idea is to use magnetic fields to hold a cloud of electrons at the center of the sphere, eliminating the need for a physical metal grid that would melt. Electrons, being lighter, are much easier to contain than heavy ions. The electrons then pull in the ions by the electric force.

It takes energy, of course, to make the magnetic fields, and some electrons get lost. But with the right geometric arrangement of coils, Bussard believed the efficient containment was possible.

The really exciting thing is the reaction is not confined to lighter ions like Deuterium, which tokamaks had to use; such reactions produce excess neutrons which break down the machine eventually and make its parts radioactive.

The Polywell can easily produce energies (it's just a simple particle accelerator after all!) to fuse p-B11, that is, a proton with a Boron atom. Boron is a very plentiful element, and the fusion products are simply a trio of alpha particles, i.e. Helium! Non-radioactive Helium!

We've even got a shortage of Helium...

There are no extra neutrons and no high-energy gamma rays produced -- just a little x-ray energy, easily shieldable.

And yet another bonus is the Helium nuclei, being high-speed charged particles, can be directly converted into electricity with about 95% efficiency instead of having to be used to very innefficiently heat a substance to make steam to turn a turbine to make electricity.

And the reaction can also be used as a clean fusion rocket for space travel, which will suddenly make colonizing the solar system cost peanuts by comparison to chemical rockets!

The device may be too large to be a "Mr. Fusion" to power your car...but it might power your house!

Of course, you can get a mini fission reactor from Toshiba if that suits you better...Not a hoax!
The Toshiba mini reactor is for real. They’ve been having some discussions with remote towns in Alaska. It’s an updated version of the old Army mobile reactors from the 1950’s that were used in Greenland and Antarctica. The idea is to have a very stable, safe plant with a very long life without refueling. The real market is future industrial applications.
In any event, those banking on energy being expensive and rationed in the future are going to be disappointed...

Watch for news of the WB-7 Polywell!

And in a case of life imitating art imitating life, Bussard is already "memorialized" in the future, according to Star Trek:
In 1960, Bussard conceived of the Bussard ramjet, an interstellar space drive powered by hydrogen fusion using hydrogen collected using a magnetic field from the interstellar gas.
...
A highly fictionalized variation of this concept appears in the Star Trek series as part of the "warp drive" that allowed Starfleet ships to travel faster than the speed of light. In the series, Bussard Collectors or Bussard Ramscoops were in place on the front of the warp nacelles, where they could scoop in interstellar gases for use by the ships' propulsion and power systems.
Right around the corner!

3 Comments:

Blogger M. Simon said...

If you want to get deeper into the technology visit:

IEC Fusion Technology blog

Start with the sidebar which has links to tutorials and other stuff.

BTW mini nukes in every neighborhood is not a good idea. I'll be posting on that in a while.

3:05 AM, December 21, 2007  
Blogger RDS said...

Great links, thanks!

PS I don't think mini-nukes are a great idea either, but it was so amusingly strange I couldn't resist mentioning it!

12:31 PM, December 21, 2007  
Blogger Robert said...

It takes all kinds, the beauty part of fusion is there are no by-products that can be used to make a bomb. The by-products have no sustainable life time and rapidly decay

10:33 AM, December 25, 2010  

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