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New theory could help clear fusion power hurdle


April 24, 2012

Fusion power would allow electricty to be generated using the same processes taking place in the Sun (Photo: NASA)

Fusion power would allow electricty to be generated using the same processes taking place in the Sun (Photo: NASA)

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While solar power harnesses energy produced by the Sun, fusion power seeks to harness the very process used by the Sun to generate a practically limitless supply of clean electricity. Despite decades of research and numerous breakthroughs, “net-gain” nuclear fusion is yet to appear. One of the hurdles is the so-called density, or Greenwald, limit that sees the plasmas within experimental fusion reactors (called tokamaks) spiraling apart and disrupting the fusion process. Now scientists have come up with a new theory as to why this occurs that, if proven, could provide a way to clear the density limit hurdle.

In fusion power, energy is generated through the combining of atomic nuclei in plasmas of sufficient heat and density. However, in experiments, minute, bubble-like islands appear in the plasma and collect impurities kicked up from the tokamak wall that cool the plasma. Since tokamak plasma densities are much lower than the Sun’s, tokamak plasma temperatures need to be even hotter than those in the Sun, so any cooling of the plasma can disrupt the process. But surprisingly, simply pumping up the heat doesn’t solve the problem.

“The big mystery is why adding more heating power to the plasma doesn’t get you to higher density,” said David A. Gates, a principal research physicist at the U.S. Department of Energy’s (DoE) Princeton Plasma Physics Laboratory (PPPL) and co-author of a proposed solution with Luis Delgado-Aparicio, a post-doctoral fellow at PPPL and a visiting scientist at MIT’s Plasma Science Fusion Center. “This is critical because density is the key parameter in reaching fusion and people have been puzzling about this for 30 or 40 years.”

The scientists believe that the islands’ detrimental effect on the fusion process is actually twofold. While the impurities cool the plasma, they believe that they also act as shields that block out added power. When the islands grow large enough, more power escapes from the islands than can be pumped into the plasma using ohmic - or joule - heating, causing the electric current that helps to heat and confine the plasma to collapse. This allows the plasma to fly apart in a flash of light.

Using a tokamak called Alcator C-Mod located at MIT, and the DIII-D tokamak at General Atomics in San Diego, Gates and Delgado-Aparicio hope to put their theory to the test in a number of experiments. One of these will involve injecting power directly into the islands to see if that leads to higher density. If it does, it could allow future tokamaks to attain the extreme density and temperatures that fusion requires.

Source: PPPL

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

This illustrates the damage that Eco-Greenies have done to the environment as well as science. Ignoring (or just ignorant of) the science of the sun - nuclear energy - they've lined their pockets with billions wasted on wind and other greenwashed boondoggles. Money diverted from real science (nuclear power) and into the feelgood pseudoscience that brought us 'global warming'.

When fusion kicks in a few years from now, billions more will have to be spent to remove windmills and their ilk from the land and seabeds. The pedal-powered cars will be tucked into the closet.

With power as unlimited and plentiful as the sun, Green Luddites will have to endure prosperity across the world instead of their self-hating prison of trickle-up poverty.

Todd Dunning

No, this illustrates your complete lack of knowledge. IF this theory pans out, and IF in the next twenty years they manage to build one and IF they find a way to contain it and IF they have a solution for the waste, and IF the sites can be secured from terrorist threat, and IF they can be built cheaply enough, then we can relax and enjoy the benefits. Until then the Eco-Greenie scientists can continue to offer clean renewable power that is scalable and is beginning to compete financially with the fossil fuels and to employ tens of thousands of people. :>)

Paul Smith

Your both right (Todd & Paul), hopefully nuclear fusion is the future, but it is at least a decade away...more likely 2 decades. We need to have power until that time, so we need to continue investing in other forms of energy capturing/creating methods.

Derek Howe

Fusion is a will-o'-the-wisp that helps keep us from using technology that works.


Can we quit repeating the nonsense that "fusion power seeks to harness the very process used by the Sun"? The proton-proton fusion event is very low probability, so that even at the density of the solar core, it produces about as much heat per second per cubic inch as the metabolism of a resting human. The sun is very very big, so that's a lot of heat: but run that process in a power station, and you would not "generate a practically limitless supply" of electricity, clean or otherwise. Earthbound fusion power efforts don't start with protons (hydrogen nuclei). They use deuterium (proton with an added neutron) or tritium (with two), using much higher tempertaures and muchlower densities. They may succeed something good, or they may not, but the sun is not a proof of possibility.


I wonder why people think this will be any safer or less polluting than Fission? Yes, the energy gains would be great but what about waste etc. Our Sun gives off some pretty nasty energies - using the same process even at a reduced scale would give off the same energies wouldn't it? Just spit balling here.


Does Todd Dunning prefer trickle down prosperity for the few at the expense of the many? Or does he think that the general "greenie" efforts are just self-serving and not for the benefit of the earth's long-term habitability? Can we afford nuclear now or maybe just wait for the fusion fantasy to arrive? Looks like his focus is nuclear without regard to many other more realistic and immediate solutions. Is he just another closed minded republicon? Probably.

Phillip Noe

Practical fusion is probably decades away. Meanwhile, we should look into LENR heat producing reactions such as the one used by Rossi's E-Cat. He is supposed to have a 1 Mw plant completed in the US this year that will be open to public inspection. LENR type reactions in the E-Cat produce low temperature steam (higher temperatures cause instability) but Siemens has taken an interest and is designing a turbine that could be used. If practical LENR devices could be made safe for home use in 5-10 years, then I would like to purchase one.

Adrian Akau

Solar PV, Wind, and increasingly, the emerging wave or ocean generated power is already very cost effective at almost any scale. Once the hardware is built these systems have long lives and typically few environmental downsides. Earlier attempts sometimes have some issues but the industry has evolved very fast over the last ten years and will continue to improve. The sun gives us more energy in an hour than we consume in ALL forms in a year so it is entirely possible to derive ALL of our energy needs and also a lot of material needs from manipulating solar energy. Batteries are getting better, slowly, but it is happening, there are other energy storage methods, hydrogen, water impoundment, compressed air, bio-mass, etc, all of which will have a useful niche. Collectively these opportunities can reshape industry, our economies, and societies. Unlike Slowburn's clear desire to have everyone using the same coffee can for dinnerware, a personal shower and can-to-take-a-dump-in, mankind can live well and nondestructively at the same time.


I really would like to have a mr.Fusion of my own but they are right the nasty byproducts are quite nasty. We dont even need fusion we already got it (the sun) we havent even been able to properly crack the efficiency/power problem from our only example what makes you think we are capable of earth based fusion that wont kill us all? Read a scifi story when i was a kid about how the first successful attempt at fusion turned earth into a selfconsuming black hole because we didnt know how to handle or use all that power.


what a waste- only working versions are all suns and they want at least one on this planet. solar power- fusion reactor at a safe distance.

as far as the math- don't forget to add the three or four extra dimensions when you try to determine the degrees of freedom that keep it from being just another black hole.


@ Paul Smith and @ johnqp Your comments show just how much you know about Fusion....Just because the word "nuclear" is in front of a term, doesn't make it bad! First off...waste? What waste? The fuel is nothing more than heavy water....the waste? water. No, not nuclear irradiated water, just water, plain and simple water, nothing else! The only concern is that the actual Fusion process is quite dangerous...for that, they are developing magnetic containment systems...so no danger there... So Nuclear Fusion is the future...don't poo-poo it just because it has the word "nuclear" in it!


While nearing the end production of fossil fuel. We need to embrace ALL the good ways of power and another good one in the near future, will be 'Fusion' Awesome:)

Paul Perkins

re; johnqp

There is a lot more stuff than just hydrogen and helium in the sun. If you know what you put in and how they will react you know what will come out. ......................................................................................................................

re; Phillip Noe

Todd Dunning and I prefer technology that works, provides power on windless nights, far from the coast. We want enough power to provide prosperity for every one including the poor. this can be done with nuclear or coal. ..........................................................................................................................

re; MasterG

If there was a possibility of creating a black hole on earth with the compression of a fusion reactor the earth would have already collapsed into a black hole from the fusion bomb tests.

What you read was fantasy.


In the US, 53% of the population lives in the 17% of land considered coastal, and that number is steadily increasing (source: NOAA), and worldwide that number is closer to 80%, so being 'far from the coast' isn't a big consideration for the majority.

Fission is certainly good on emissions, but it's also a finite resource: if the entire world switched to nuclear we would run out of uranium within 20 years (source: USGS, UK gov), though it would help a lot if we could gather the political will to build LFTR reactors. Thorium holds much promise too, but the US doesn't seem very interested in it since it has no military upside. A nice quote: "4 guys, between morning coffee break and their lunch break can dig, with shovels, enough thorium to power a city of one million for one year".

Coal is dismal in so many respects - in practice it's far more dangerous than any other generation mechanism, adversely affecting the poor more than any other demographic, and its environmental impact is far worse than anything else. Unlike nuclear, coal power adversely affects large numbers of people when it's working properly, killing over 10,000 per year in its mining alone! Its only upside is its low up-front cost, but post-consumption costs such as increased health costs make it the most expensive fuel source overall (source: US DOE). In all ways that matter, coal power is the worst choice available. If you're going to burn stuff, gas is a better choice.

Slowburn appears to have a weirdly polarised viewpoint, making out that all renewables are bad. Making use of wind and solar doesn't need to be exclusive - there are many areas of the inland US that are ideal for solar, and when the sun isn't shining you can use other sources. The US national academy of sciences analysed winds on the US east coast over 5 years and determined that a well-distributed wind generation programme would provide a sufficiently reliable output (i.e. in practice, the wind doesn't drop to 0 everywhere at once). It's all a matter of producing as much as we need with the least cost and environmental impact in an appropriate manner for the location.

Saying we shouldn't try is just dumb.


re; Synchro

I admit it coal is seriously nasty stuff but it can for the next hundred years do the job of generating the electricity that would eliminate the kind of poverty that sends children to bed hungry because their parents can't afford to buy food. On the plus side if you gasify the coal at the mine and then super heat the coke to drive off the other impurities for capture by burning high purity coke (activated carbon) and/or the less desirable and/or less containable components of coal gas it gets fairly clean especially if you use the waste heat to generate electricity or provide hot water for commercial or domestic uses. The resulting gas, liquid, and solid fuels have higher energy density by weight than coal as well. Much of the impurities driven off and captured have industrial uses as well and will reduce the amounts mined elsewhere.

Oil and gas are too valuable as motor fuel and other small scale uses too use for widespread electrical generation unless the current 'optimistic' estimates of reserves are low. .................

Even if we assume that there is only enough uranium to provide power for 20 years, given the right type of breeder reactors there is enough fuel for at least a century, and then there is thorium. .................

It is not that renewables are bad but we can take as a given that there won't be any new dams for hydro electricity in the USofA and only in limited numbers world wide, that solar is daylight only power capture, and that the wind does not blow all the time, and even ocean waves go flat occasionally.

It is not unfixable. Windmills should not directly generate electricity but instead generate storable potential energy (lift water or compress air) thereby providing even current on demand electricity.


The fusionists have been promising practical fusion power in just a few years for decades and have been living comfortable lives on the public dime for those decades of failure. Sometimes you have to say enough is enough. If you want fusion research set up a mutual fund to pay for it and if they succeed in producing cost effective power generation the investors get payed back in accordance with their percentage of the total private investment for the life of the patents.

From the history getting commercial power from fusion will require building very large very well insulated chamber and detonating fission/fusion devices in it and then tap the energy through piezo and thermal processes. ....................

One could argue that electricity should be generated as close to the point of consumption as possible to reduce line loss. This is true to the extent that line loss is greater than the energy consumption in bringing the fuel to the electrical generating plant.

If you were to find a place that freight trains routinely heavily brake and built an energy capture, store, and demand delivery device you would do the world some good and make money even after paying the railroad company for their inconvenience. but electricity needs to be generated at time of demand not whenever. Batteries are not particularly efficient and they have short lives.


Fusion as a power source would be great, but, there continue to be problems.

So far, Fusion has been a promise that is 'only 20 yeras away' since 1937.

The problem is that Plasmas conduct electricity, and are very responsive to magnetic fields. In fact, plasmas routinely generate magnetic fields which often negate the effects of the control magnets. Theta Pinch, Magnetic Reflector, Baseball, Tokomak, Synchrotron, self confined, inertial confinement, the list of past failures goes on and on. Really, we don't have anything on the books that might work.

Fission is a good filler. The previous poster is wrong about the amount of time that fission can last. It isn't just U235. U-238, Plutonium, Thorium can all be used. There are also some less useful other elements. The reactors we use today, were designed in the 1950's and early 1960's to produce Plutonium for military uses. But, that plutonium is also an unburned fuel. The Uranium quantities mentioned are also quite low. That is the deposits known in the early 1970's. But, there is much more still in the ground.

Solar isn't really economically ready to replace the base load of coal that all of the developed world currently uses for power generation. It's much closer than it once was, but it is still twice as expensive as coal. Cut off the government subsidies, and the entire solar industry will almost blow away in the wind. (That is exactly what has been happening this year, as the subsidies were reduced due to budget shortfalls.)

Wind power does work, but has a very high up front cost. Unlike Nuclear and Coal, the cost per KW doesn't come down very fast as the installed base gets bigger. That means that if the subsidies are withdrawn, wind power will fail.

There are also severe ecological impacts from both solar electric and wind electric generation. These impacts are usually ignored in popular articles on the subject. Real Ecologists, though know what these impacts are.

Solar covers ground that other species need, and thus competes with farmland and wilderness for acreage.

Wind Power kills flying wildlife indiscriminately. Wind power also removes energy from teh atmospheric transport systems that provide rainfall. It is not a coincidence that the areas with the highest amount of wind power are also areas where the downwind areas are experiencing decreased precipitation. Some scientists have calculated how much energy we can remove from the global wind systems before the results become catastrophic. The amount they came up with is around twice the installed capacity expected by 2020.

Just as Hydroelectric dams were the ultimate dream of 'renewable energy' in the early 1970's, then were found to be drowning entire ecosystems, so are the latest 'renewable' systems being found to have adverse impacts.

Everything, it seems affects everything else.

There is no such thing as a zero impact source of power.

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