Catching tokamak fastballs: Controlling runaway electrons
A computer-generated 3-D view shows runaway electrons in DIII-D based on high speed 2-D images of synchrotron emission from electrons traveling near the speed of light inside the tokamak. Credit: N.W. Eidietis and M.R. Wade, General Atomics
a leading design concept for producing nuclear fusion energycan, under certain rare fault conditions, produce beams of very energetic "runaway" electrons that have the potential to damage interior surfaces of the device. In the event of such a fault, a tokamak-based nuclear fusion power plant will have to employ protection systems to prevent any damage. Now, scientists at the DIII-D National Fusion Facility have demonstrated a new method for controlling these high-energy electrons.
This work, reported at the 53rd APS Division of Plasma Physics conference, could help overcome a significant challenge to designing tokamak-based fusion power plants.
In a tokamak, enormous electrical current (up to many millions of amperes) is driven through a donut-shaped ring of plasma to contain this ionized gas at the extreme temperatures (100 million °C) required for nuclear fusion. Significant system faults may cause a tokamak discharge to rapidly terminate, or "disrupt," losing its entire plasma current in a few hundredths of a second. The rapid drop in current during a disruption can accelerate electrons in the plasma to near the speed of light, forming a beam of high-energy runaway electrons.
By purposely causing a rapid drop in plasma current in the DIII-D tokamak, scientists at General Atomics in San Diego are producing 300,000 Ampere beams of runaway electrons and learning how to control them. Plasma physicist Nick Eidietis and his coworkers apply rapid pre-programmed changes in magnetic control coils to move the runaway electron beam away from interior surfaces so that automatic feedback control can keep them from slamming into interior surfaces. Magnetic field measurements and images from high-speed cameras allow scientists to determine their location and spatial structure.
Having established control, the team is exploring two methods for dissipating the runaway electron beam before it can do any harm. If ample time is available, the electron beam current is slowly reduced using the magnetic control coils. If time is of the essence, the second method injects large quantities of noble gases such as argon, neon, or xenon, into the beam to more rapidly dissipate the energy of the electrons. Both methods lead to a much more benign interaction with interior surfaces.
Runaway electron beams are of particular importance for the design of the ITER tokamak presently under construction in France. Designed to produce up to 500 MW of fusion power, ITER will be many times larger than existing tokamaks and thus capable of producing much higher runaway electron currents during a disruption than seen in the DIII-D experiment.
"One of our next steps will be to adjust our control system to simulate the characteristics of the ITER system to evaluate the feasibility of this approach to catching and controlling runaway electrons," said Dr. Eidietis.
According to Dr. Dave Hill, Deputy Director of the DIII-D National Fusion Program, "This is an exciting research result which we look forward to successfully testing in future larger fusion experiments such as ITER."
Provided by American Physical Society
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Nov 11, 2011
Rank: 1.5 / 5 (8)
Nov 11, 2011
Rank: 5 / 5 (8)
So what is better?
Something expensive that works
or
Something cheap that doesn't
Nov 11, 2011
Rank: 1 / 5 (4)
Some thing which is not so expensive, but could work!
Nov 11, 2011
Rank: 1 / 5 (1)
Nov 11, 2011
Rank: 5 / 5 (2)
Nov 12, 2011
Rank: 1 / 5 (1)
Nov 12, 2011
Rank: 4.8 / 5 (6)
Ah yes, it's all a conspiracy... After all, no scientist could possibly want the unimaginable fame and fortune that would result from discovering a viable method for cold fusion. We're all just a bunch of ascetic monks.
Nov 12, 2011
Rank: 1 / 5 (5)
Whole the tokamak research should wait one hundreds of years, until we wouldn't have some usage for it. We can spend all money in research of far side of Pluto - but what such research will be good for? The useful research must come first.
Nov 12, 2011
Rank: 1 / 5 (5)
The whole problem is, the scientists itself aren't motivated and competent enough to define their priorities. They're just adhering on single philosophy, which is serving just for their community: every research is equally important, because it CAN be useful later.
This is simply not true. In addition, many results of basic research will become obsolete sooner, before they can be used for additional research. So they're developed again and again. No group of people should define the rules of their of importance into account the others.
Nov 12, 2011
Rank: 1 / 5 (5)
Nov 12, 2011
Rank: 1 / 5 (1)
I know 'tokamak' means the ways in which plasma is heated in addition to configuration. But tokamak experiments are giving us a great deal of info on how to confine and manipulate plasmas in a toroidal configuration, which is what I think they are primarily for.
There are easier and cheaper ways of producing fusion power - z pinch, inertial confinement, and polywell for instance. But most research money is going into toroids. I think this is because toroidal storage tech needs to be developed now so as to make it available when it will be needed. Producing power with it is probably not as practical as the other methods. Even cold fusion which is probably real.
Nov 12, 2011
Rank: 3 / 5 (2)
As a former assistant director of the NEC he was well aware of the Bigger Picture and of the political and strategic necessities of pacing the development of fusion power.
So he was tasked with sitting on electrostatic fusion in order to suppress it. After all if dr bussard says polywell is moving as fast as it can, who is to argue with him? Meanwhile dozens are building little fusion cage machines in their garages.
Nov 12, 2011
Rank: 1 / 5 (4)
Nothing really strange is about it, you just explained us, how the scientific research is really working on background.
Nov 12, 2011
Rank: 1 / 5 (3)
Just from this reason the research of most universal and cheapest technology is always considered and started at the very end - because it always gets the largest number of enemies naturally. We should understand the mechanisms of competitive nature of technological evolution before we attempt to optimize it. Such optimization really needs an open mind, free of any illusions about moral nature of human civilization and/or unmistakable power of scientific method.
Nov 12, 2011
Rank: 2 / 5 (2)
No seriously, how do you think a bottle could ever be devised to store plasma in bulk indefinitely? Have YOU ever looked into this?
Nov 12, 2011
Rank: 5 / 5 (2)
And even if we were able to: would you like to be close to something that stores antimatter in bulk? Like on the same planet?
Not a good idea.
Nov 12, 2011
Rank: 2 / 5 (2)
"So as to avoid losses from the edges, we close off the magnetic bottle by creating a torus.
The magnetic field thus created by a series of magnets surrounding the plasma is called a toroidal magnetic field. The magnets generating this field are the toroidal magnets."
-So you see mr zephelin, the reason science is pursuing toroidal magnetic confinement to begin with is because the most effective way of closing off the bottle is by making a doughnut out of it. Kapiert?
If you prefer pictures well here you go:
http://www-fusion...es02.htm
Nov 12, 2011
Rank: not rated yet
We will, and we shall. Eventually. It will be the most efficient way of storing energy for propulsion. Think solar antimatter factories in close solar orbits, or vast solar farms beaming microwaves farther out to conversion facilities.
Nov 12, 2011
Rank: 5 / 5 (2)
Whut? What have microwaves to do with antimatter?
Remember that the storage isn't free. It requires a lot of energy to keep the confinement up. So if we store antimatter then we'll have to keep the containment vessel running for the entire trip (decades/centuries if we want to go extrasolar). If we stick to sub light speeds this upkeep will far outweigh any gain we get from the few particles of antimatter we could put in there. We're not talking tons, here. The size of something like the ITER tokamak (big) contains 0.5 grams(!) of plasma in 876 cubic meters using 16MW power for the confinement.
A fusion reactor would probably be better. Less efficient per pound of fuel, but the storage of the fuel is passive and indefinitely achievable...and a LOT less dangerous in the case of a microleak.
Nov 12, 2011
Rank: 5 / 5 (2)
Sounds like a lot, but stretched over a few decades/centuries that's not so much.
Nov 12, 2011
Rank: 1 / 5 (1)
http://www.steampunklab.com/
Beauty.
Nov 12, 2011
Rank: 5 / 5 (2)
Use per capita in the US dropped 2008-2009. (due to the recession, but the point is that it doesn't have to go on that way...just like infinite economic growth infinite energy consumption growth is a myth)
10kT of TNT will get you (if we use a decade travel time as the assumption) a net continuous power of about 13kW (at 100% efficiencey)
at 16MW containment cost we'd be 15.987MW short of break-even with antimatter as fuel.
So we need to get 99.92% more efficient at storing antimatter via tokamak and create a perfect conversion powerplant before we could even hope to have a break even.
Now I know things are getting ever more efficient - but that's a bit of a stretch for the short, middle or even long term, don't you think?
Nov 12, 2011
Rank: not rated yet
Once humans begin living in space and on other planets, per capita use will leap again, as it did during the industrial revolution.Well pretty obviously AP, no I don't. Room temp and above superconductors will change things drastically. Only one example.
Collider ring production facilities built around relocated asteroids and moons will change them again, and fully-automated robotic construction will make them feasible. Robots making robots - the next industrial revolution.
Once you take humans out of the mix anythings possible.
Nov 12, 2011
Rank: not rated yet
One might even suspect that society was reconfigured to force the development of transportation. I mean, what are vacations really for? And why do we need to fly cross-country to do business?
Flying cars are sitting just waiting for an adequate energy source to make them practical. Then they are going to be all over the place.
Nov 12, 2011
Rank: 3.5 / 5 (2)
200 PhD physicist. This research is still science fiction.
What is the success ? 5 nanoseconds and had to shut down
because of 300 million degree magnetic disconnects in 2009.
I am sorry to say that the assumptions made have given
unending perplexing problems or moving targets.
Hot electrons, magnetic fields, resonate microwaves and other areas I won't mention haven't even been addressed as yet.
I am hoping for fusion energy success but would anyone support a professional sports team that has failed for these many seasons.
I am hoping that fusion comes to pass but it doesn't seem
likely for many decades to come defined by present success.
Sorry for the brutal honesty.
Nov 13, 2011
Rank: 5 / 5 (2)
Yes,a nd teleportation, light sabers, force fields, black hole generators and FTL drives will all change the game. But I was discussing science - not science fiction.
Counterexample: The lighting imn your home is getting more efficient; the heating, too. The computer you use likely uses less power than the one before (so does your TV). Processor power on your machine has topped yout because there is no need for more speed beyond watching video.
Unlimited growth isn't a reality. There are always saturation effects.
Nov 13, 2011
Rank: 1 / 5 (1)
Nov 13, 2011
Rank: 1 / 5 (4)
1) The first one follows from Lawson criterion. The fusion is not just a matter of collision energy, but a time, during which the atom nuclei are in mutual contact. With increasing temperature the energy of Coulomb barrier becomes overcomed, but the speed and therefore the time of contact decreases too.
2) The second reason is, at low temperature the repulsive charge of atom nuclei are already shielded with layer of electrons, which are compensating it. If you heat these atoms, the shielding layer of electrons gets stripped and you'll just make troubles for yourself. Why not to work with fusion at the stage, when atom nuclei are as neutral, as possible? At the case of hydrides the net charge of hydride anion is even negative, so its attracted to the nuclei instead of repulsed.
If it's so, why to broke such state in tokamak or lasers?
Nov 13, 2011
Rank: 1 / 5 (3)
Nov 13, 2011
Rank: 1 / 5 (3)
If we wouldn't consider these details, then the cold fusion will remain mystery for us for ever, because our understanding of the atom nuclei/orbital interface will remain very schematic
Nov 13, 2011
Rank: 5 / 5 (1)
Which could explain the relative emphasis on tokamak R&D, and also the need to convince the public to spend money on it NOW by selling it as an energy source, whether it ever will be or not.
Nov 14, 2011
Rank: 1 / 5 (2)
Many of you will not live enough to experience the launch of this project. Hole in the Earth is the current status of ITER.
http://www.iter.o...5420.jpg
Nov 14, 2011
Rank: 1 / 5 (1)
Nov 14, 2011
Rank: 5 / 5 (1)
Is it possible there is some reason that a potential plasma storage facility is being built so close to the largest collider in the world? Could this collider be reconfigured to produce a material best stored in the huge toroid bottle being built in france? Only some 300 miles away - a short trip for relativistic particles.
Nov 14, 2011
Rank: 5 / 5 (1)
Youre saying tokamaks are being built for absolutely no reason whatsoever. I am saying there could indeed be very important Reasons which we are simply not aware of, and am giving you some evidence to support this.
Nov 14, 2011
Rank: 1 / 5 (2)
Nov 14, 2011
Rank: 5 / 5 (1)
Even if cold fusion is real it wont be applicable in all cases. We will still need to know how to work with large quantities of plasma. You will still need inertial confinement for propulsion. Cold fusion would not replace other forms of energy production. Even fossil fuels will still have their place.
Plasma research is giving us a wide range of capability which one would expect from People concerned with the future course of civilization.