Catching tokamak fastballs: Controlling runaway electrons

Nov 11, 2011
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 energy—can, 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 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 . 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 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 experiments such as ITER."

Explore further: Scientists in search of explanation of high-temperature superconductivity

Provided by American Physical Society

4.6 /5 (9 votes)

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Callippo
1.5 / 5 (8) Nov 11, 2011
The hot fusion research is an impressive drain of money - a dozens of technical problems, each of it is worth of its own research base stuffed with theorists, computers and technicians... Many physicists, who are getting disappointed with vague results of collider research are surreptitiously looking at the another job perspective, like the ITER. It's not so surprising, the cold fusion which doesn't doesn't provide such impressive overemployment is ignored in quiet.
antialias_physorg
5 / 5 (8) Nov 11, 2011
Yet: one produces results (has achieved fusion and is getting ever better at it) and the other doesn't.

So what is better?

Something expensive that works
or
Something cheap that doesn't

vacuum-mechanics
1 / 5 (4) Nov 11, 2011
Yet: one produces results (has achieved fusion and is getting ever better at it) and the other doesn't.

So what is better?
Some thing which is not so expensive, but could work!
Something expensive that works
or
Something cheap that doesn't


Some thing which is not so expensive, but could work!
TheGhostofOtto1923
4.3 / 5 (12) Nov 11, 2011
Yet: one produces results (has achieved fusion and is getting ever better at it) and the other doesn't.

So what is better?

Something expensive that works
or
Something cheap that doesn't

Tokamaks will be useful for storing plasma in bulk which will be important as more materials in plasma form are created and used. For instance antimatter. How else will you be able to store large quantities of that? Stellerators?
Callippo
5 / 5 (2) Nov 11, 2011
Tokamak for storage of antimatter? Physics is not your primary hobby, does it?
Cynical1
1 / 5 (1) Nov 12, 2011
Those researchers should read Physorg. There was an article on here about coating the inside of the Tokomac with lithium reducing impurities(?). Anyway. what about runaway electrons? It's gonna be something forehead-smackingly simple like that.
axemaster
4.8 / 5 (6) Nov 12, 2011
It's not so surprising, the cold fusion which doesn't doesn't provide such impressive overemployment is ignored in quiet.

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.
Callippo
1 / 5 (5) Nov 12, 2011
It's not conspiracy. Conspiracy considers close group of people manipulating the others, not the omnipresent pressure of many ordinary people, who are just seeking safe and stable jobs. You just didn't understood the dense aether model. In this model the Germans didn't murdered the Jews because the Hitler wanted so, but because most of Germans agreed with murdering of Jews on background, so they allowed the Hitler to grow. In the same way most of physicists kill the cold fusion research just because everyone of them don't wants the cold fusion to be researched.

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.
Callippo
1 / 5 (5) Nov 12, 2011
...Sorry for grammar, I haven't time to correct it because of 3 minute limit.

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.
Callippo
1 / 5 (5) Nov 12, 2011
As an evidence, this simple strategy doesn't work can serve the many years standing ignorance of cold fusion and many other important findings. These findings are ignored with physicists just because their implementation would restrict their own jobs in another areas. So they're ignoring them for decades and the rest of human society is even paying for this ignorance. The human society has no feedback in this matter - they're all hostages of limited group of people.
TheGhostofOtto1923
4.3 / 5 (12) Nov 12, 2011
Tokamak for storage of antimatter? Physics is not your primary hobby, does it?
Like I said zyppher, how else are you going to store antimatter in bulk for very long periods of time? It is easier to confine plasma if you keep it moving, than in a magnetic bottle for instance. Because plasma won't stop moving.

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.
TheGhostofOtto1923
4.4 / 5 (13) Nov 12, 2011
AND I think research on the other forms has been suppressed for this Purpose. Bussard for instance sat on polywell for decades, producing one rinkydink cage after another with little serious engineering or effort.

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.
Callippo
1 / 5 (4) Nov 12, 2011
Like I said zyppher, how else are you going to store antimatter in bulk for very long periods of time?
A hint: the antimatter is already stored for weeks in CERN and another research facilities, and I never heard of usage of tokamaks there. Try to read a bit about Penning's trap and related stuffs first, before you'll start to invent and promote meaningless stuff here next time.
So he was tasked with sitting on electrostatic fusion in order to suppress it.
Yep, the promoters of tokamak fusion are fight against proponents of inertial fusion and/or against proponents of sonoluminiscent fusion. Well and from the very same reason all these people will fight together against proponents of cold fusion, because this technology is threatening them all.

Nothing really strange is about it, you just explained us, how the scientific research is really working on background.
Callippo
1 / 5 (3) Nov 12, 2011
Meanwhile dozens are building little fusion cage machines in their garages.
We should realize, the more easier some technology is realizable, the more it threatens not just nuclear of fossil fuel lobby, but the promoters of more expensive, still alternative technologies too.

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.
TheGhostofOtto1923
4.2 / 5 (12) Nov 12, 2011
A hint: the antimatter is already stored for weeks in CERN and another research facilities, and I never heard of usage of tokamaks there.
In what quantities? Try to read a bit about Penning's trap -which is for storing minute numbers of particles for study. To do this they remove energy from particles by using buffer gas cooling, resistive cooling, and laser cooling. You may not want to REMOVE energy from bulk plasma stored for use in other ways.
and related stuffs first, before you'll start to invent and promote meaningless stuff here next time.
Well thats not fair, you get to do it all the time.

No seriously, how do you think a bottle could ever be devised to store plasma in bulk indefinitely? Have YOU ever looked into this?
antialias_physorg
5 / 5 (2) Nov 12, 2011
Before we worry our pretty little heads about storing antimatter in bulk we should worry about being able to create some in bulk (we're currently only creating individual atoms at best - and at atrocious energy costs)

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.
TheGhostofOtto1923
4.2 / 5 (13) Nov 12, 2011
"As the plasma is made up of charged particles, the magnetic fields may act on them. If this same plasma is bathed in a rectilinear magnetic field, the particles wind around the field lines and will no longer touch the side walls.

"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
TheGhostofOtto1923
4.6 / 5 (11) Nov 12, 2011
Before we worry our pretty little heads about storing antimatter in bulk we should worry about being able to create some in bulk (we're currently only creating individual atoms at best - and at atrocious energy costs)
Details.

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.
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.
antialias_physorg
5 / 5 (2) Nov 12, 2011
Think solar antimatter factories in close solar orbits, or vast solar farms beaming microwaves farther out to conversion facilities.

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.

antialias_physorg
5 / 5 (2) Nov 12, 2011
For the record: A half gram of antimatter contains, if brought into contact with half a gram of matter (at 100% efficient use) about half as much as the Hieroshima bomb (ca. the equivalent of 10kT TNT)

Sounds like a lot, but stretched over a few decades/centuries that's not so much.
TheGhostofOtto1923
4.3 / 5 (12) Nov 12, 2011
Whut? What have microwaves to do with antimatter?
Making antimatter takes a lot of energy. I assume.
Remember that the storage isn't free. It requires a lot of energy to keep the confinement up.
Civilization is a record of the steady increase of energy production and use per capita. I my truck I command the power of 300 horses.
but the storage of the fuel is passive and indefinitely achievable...and a LOT less dangerous in the case of a microleak.
Thats what they said about the steam engine.
http://www.steampunklab.com/
For the record: A half gram of antimatter contains, if brought into contact with half a gram of matter (at 100% efficient use) about half as much as the Hieroshima bomb (ca. the equivalent of 10kT TNT)
Beauty.
antialias_physorg
3.7 / 5 (3) Nov 12, 2011
Civilization is a record of the steady increase of energy production and use per capita.

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?
TheGhostofOtto1923
4.6 / 5 (11) Nov 12, 2011
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)
You're not taking into consideration all the forms of energy we use, and for what. And your timeframe is too small.

Once humans begin living in space and on other planets, per capita use will leap again, as it did during the industrial revolution.
but that's a bit of a stretch for the short, middle or even long term, don't you think?
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.
TheGhostofOtto1923
4.4 / 5 (7) Nov 12, 2011
One way to look at it is, the more energy we have available to use, the more uses we will find for it. People dreamed about flight for centuries but only internal combustion made it possible. And then energy use per capita to transport people skyrocketed as they found all sorts of reasons to travel.

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.
holoman
3.5 / 5 (2) Nov 12, 2011
After 40 years $100 billion plus, 20 countries and over
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.
antialias_physorg
5 / 5 (2) Nov 13, 2011
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.

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.

One way to look at it is, the more energy we have available to use, the more uses we will find for it.

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.
TheGhostofOtto1923
4.2 / 5 (10) Nov 13, 2011
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.
So was I. Nothing I mentioned requires new science except the formula for antimatter. And a few advances in superconductors.
Unlimited growth isn't a reality. There are always saturation effects.
And I predict that in 100 years or so a significant factor in global warming will be waste heat.
Callippo
1 / 5 (4) Nov 13, 2011
The understanding, why tokamak, lasers or other brute force ways to the cold fusion are essentially silly approach follows from at least two reasons:
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?
Callippo
1 / 5 (3) Nov 13, 2011
The understanding and modeling of cold fusion requires just one thing to realize. The heavy atoms don't appear like tiny dense droplet of dense nuclei, which could separated with sparse atmosphere of electrons easily like the stone from apricot fruit. Instead of it, there's an energetic continuum. To strip the first electron from nickel atoms requires the energy of fraction of electronvolt, which can be made easily. But with increasing number of electrons the energy required for their removal increases exponentially. To create nickel atom nuclei free of all electrons requires the energy in the megaelectronvolt range, which would destroy the nickel nuclei itself. Such nickel nuclei behave rather like seed inside of mango fruit, which cannot be removed from flesh without broking the seed itself.
Callippo
1 / 5 (3) Nov 13, 2011
One consequence of this fact is, at the case of deuterium-deuterium fusion the electrons flying around atom nuclei pose no advantage for fusion, because they can be separated quite easily. At the case of heavy atoms (like the nickel) the situation is different. Its electrons at the bottom orbitals are forming compact, negatively charged mass, which is relatively dense and it represents an effective shielding environment for repulsive charge of protons inside of atom nuclei. In addition, the fusion is initiated with neutrons, which are of neutral charge and they can leave atom nuclei at distance. In this case the electrons can penetrate deeply inside of atom nuclei (which results into so called K-capture) - and vice-versa, the neutrons can penetrate into electron orbitals (so called the "halo" nuclei).
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
TheGhostofOtto1923
4.6 / 5 (10) Nov 13, 2011
So callippo you didnt acknowledge that toroidal confinement is currently the only known way of storing plasma in bulk, and that if we expect to be doing this at some time in the future, learning HOW to do it would take a certain amount of time and money.

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.
rawa1
1 / 5 (2) Nov 14, 2011
ITER still doesn't exist, it will cost 16billions euros at least (and we can expect even twice as more based on experience with similar projects) and it will not finished before 2040 (btw ITER project was originally launched in 1985 and still doesn't exist even the building).

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
Callippo
1 / 5 (1) Nov 14, 2011
The storage of antimatter is very poor argument for development of 16 billion project, like the ITER.
TheGhostofOtto1923
4.6 / 5 (10) Nov 14, 2011
The storage of antimatter is very poor argument for development of 16 billion project, like the ITER.
Creation, storage, manipulation, and application of materials in plasma form will be a central technology in the future. The fact that we are expending this level of effort at present to develop this capability can give us an idea of when it may be needed.

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.
TheGhostofOtto1923
4.6 / 5 (10) Nov 14, 2011
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
Directly south.

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.
Callippo
1 / 5 (2) Nov 14, 2011
Creation, storage, manipulation, and application of materials in plasma form will be a central technology in the future.
Come on. Tokamak is very special device. Thousands of researchers are facing lost of their jobs by now. The cold fusion will render them useless.
TheGhostofOtto1923
4.6 / 5 (10) Nov 14, 2011
Directly south.
And closer to potential equatorial launch facilities.
Come on. Tokamak is very special device. Thousands of researchers are facing lost of their jobs by now. The cold fusion will render them useless.
Not if toroidal confinement is being researched for Purposes other than to produce fusion power. There are many variations on the tokamak. The stellerator is something else again.

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.