Improving the magnetic bottle that controls fusion power on Earth

Improving the magnetic bottle that controls fusion power on Earth
Physicist Nate Ferraro. Credit: Elle Starkman/PPPL Office of Communications

Scientists who use magnetic fields to bottle up and control on Earth the fusion reactions that power the sun and stars must correct any errors in the shape of the fields that contain the reactions. Such errors produce deviations from the symmetrical form of the fields in doughnut-like tokamak fusion facilities that can have a damaging impact on the stability and confinement of the hot, charged plasma gas that fuels the reactions.

Researchers led by scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have found clear evidence of the presence of fields in the initial 10-week run of the National Spherical Torus Experiment—Upgrade (NSTX-U), the flagship fusion facility at the laboratory. The exhaustive detection method they used could provide lessons for in future fusion devices such as ITER, the large international fusion facility under construction in France to demonstrate the practicality of controlled fusion energy.

Fusion powers the sun and stars

Fusion, the power that drives the sun and stars, is the fusing of light elements in the form of plasma—the hot, charged state of matter composed of free electrons and atomic nuclei—that generates massive amounts of energy. Scientists around the world are seeking to replicate on Earth for a virtually inexhaustible supply of power to generate electricity.

At PPPL, researchers have put together a combination of experimental data, detailed measurement of the position of the magnets, and computer modeling of the response of the plasma to locate the source of the NSTX-U error fields. The analysis uncovered a spectrum of small error fields—an inevitable result of the fact that a tokamak cannot be perfectly symmetrical—but most had an easily correctible impact on the plasma. However, one major find stood out: a slight misalignment of the magnetic coils that run down the center of the tokamak and produce the fields that wrap horizontally—or "toroidally"—around the interior of the vessel.

The clue scientists sought

This misalignment was the clue the scientists had sought. "We looked for the source of the error with the biggest impact on the plasma," said physicist Nate Ferraro, first author of the research that reported the search and discovery in Nuclear Fusion. "What we found was a small misalignment of the center-stack coils with the casing that encloses them."

The slight misalignment generated errors that resonated in the behavior of the plasma. Among the issues was a braking and locking effect that kept the edge of the plasma from rotating, and increased localized heating on plasma-facing components inside the tokamak.

Discovery of the misalignment followed shut-down of the tokamak for ongoing repairs in the wake of a coil failure. The misalignment findings are now being used "to drive new engineering tolerance requirements for NSTX-U as it is rebuilt," the researchers said. Such requirements call for tighter tolerance between the center stack and the casing that encloses it. The tighter tolerance would narrow the deviation from optimal alignment of the two components to less than two one-hundredths of an inch along the vertical axis of the center stack.

The adjustment would alleviate concerns about increased localized heating and would reduce the magnetic braking and locking, according to the authors. Such developments would thereby improve the stability of the . "Every tokamak is concerned about error fields," Ferraro said. "What we are trying to do is optimize the NSTX-U."

Partnership with experiments

The findings demonstrate the relationship between the PPPL Theory Department and the NSTX-U experiment, said Amitava Bhattacharjee, who heads Theory. "This is an excellent example of the NSTX-U-Theory Partnership program that has been beneficial for both the NSTX-U and Theory Departments at PPPL, and which continues even when NSTX-U is in recovery," Bhattacharjee said.

Members of the research team included scientists from PPPL, Sandia National Laboratory, General Atomics and Oak Ridge National Laboratory. The DOE Office of Science funded the work.


Explore further

Discovered: A new way to measure the stability of next-generation magnetic fusion devices

More information: N.M. Ferraro et al, Error field impact on mode locking and divertor heat flux in NSTX-U, Nuclear Fusion (2019). DOI: 10.1088/1741-4326/ab22c4
Citation: Improving the magnetic bottle that controls fusion power on Earth (2019, August 6) retrieved 21 August 2019 from https://phys.org/news/2019-08-magnetic-bottle-fusion-power-earth.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Aug 06, 2019
"two one-hundredths of an inch"

Oh  for   p i t y ' s   sake

Aug 06, 2019
Fusion will not work and it is not what fuels the Sun!

Aug 06, 2019
Fusion will not work and it is not what fuels the Sun!


Yes it is. Read a textbook or two.

Aug 06, 2019
in future fusion devices such as ITER,
Will that thing ever be completed? Or is it doomed to always being a work in progress?

Aug 06, 2019
in future fusion devices such as ITER,
Will that thing ever be completed? Or is it doomed to always being a work in progress?
says c_u

I would say the latter. As I have said before in another phorum, and to which some agreed must be the case, the fusion that is ongoing in the Sun (a Star) is not cooped up and contained within a physical 'container such as a Tokamak' that limits the Plasma, as well as the continuous process of Fusion. This means that the SUN's Fusion process is in FREE MOTION that enables its Plasma to travel outwards from the Sun's outer layer.
The Plasma within a Tokamak doesn't have that freedom of movement/motion as what is occurring in the Sun. Instead, the Plasma and its heat is held fast inside an artificial container where it can't flow out. The Sun is not encumbered with such an imprisonment of its Energy. It is free within the Vacuum of Space.

Aug 06, 2019
Oh dear! Where does one even start with the above? Fusion depends on two parameters - density and temperature. Without containing the plasma, there is no density. In the Sun this is achieved by the huge mass of the overlying gas that is not being fused. In a tokamak it is confined artificially. There cannot be p-p fusion at densities such as those found at the surface of the Sun.

Aug 06, 2019
This Damp Squid of a Fusion Reactor

Taking all things in consideration
A minute change in field coil enlightenment is not going to make a jot of difference
What is needed with these reactors is more power
More gamma-rays
More hot neutrons
In other words, make this fusion reactor behave like a common or garden star
As tinkering with this feeble puny magnetic field is going to make no never mind

Aug 06, 2019
Oh dear! Where does one even start with the above? Fusion depends on two parameters - density and temperature. Without containing the plasma, there is no density. In the Sun this is achieved by the huge mass of the overlying gas that is not being fused. In a tokamak it is confined artificially. There cannot be p-p fusion at densities such as those found at the surface of the Sun.
says Castrovagina

Wellll then, inside the tokamak, it ain't Fusion, my boy. In the Sun, that 'overlying gas' can be bypassed or punctured through by Plasma in its outward flow.

A tokamak will never be able to enable the temps and density that is required for true Fusion. You would need to build a hollow globe-shaped tokamak the size of the EARTH and place all the hardware, etc. into the exact middle of it, where any Plasma that is produced will have plenty of room to move about without touching any walls.
It cannot be done in a lab or similar facility. You need the equivalent of the Sun.

Aug 06, 2019
This Damp Squid of a Fusion Reactor

Taking all things in consideration
A minute change in field coil enlightenment is not going to make a jot of difference
What is needed with these reactors is more power
More gamma-rays
More hot neutrons
In other words, make this fusion reactor behave like a common or garden star
As tinkering with this feeble puny magnetic field is going to make no never mind
says granville

Precisely and well stated. The Mop man seems to think that a tokamak's walls will not have the usual difficulties as before. True Fusion will not occur no matter how many improvisations and tricks with chewing gum. As they say in the US, it is small potatoes.
The use of tokamaks to produce Fusion is unnatural. The whole process is bound to fail every time.

Aug 06, 2019
In a tokamak it is confined artificially.
And at much lower pressures and temperatures. Thus, we cannot expect at the current limits of our ability to make strong magnetic fields to do p-p fusion any time soon.

D-D and D-T fusion, however, we can do. The key is to keep the plasma contained, and finding out how these instabilities arise, and discovering we just need to make the alignment more precise, is a major step forward.

Aug 06, 2019
This Damp Squid of a Fusion Reactor

Taking all things in consideration
A minute change in field coil enlightenment is not going to make a jot of difference
What is needed with these reactors is more power
More gamma-rays
More hot neutrons
In other words, make this fusion reactor behave like a common or garden star
As tinkering with this feeble puny magnetic field is going to make no never mind
This is correct. What you need is more gravity...
And SEU,
Plasma does NOT puncture, it gets punctured...

Aug 07, 2019
@Whyde
Perhaps Plasma is heavy enough to pass through Castrovagina's overlying gases in the Sun. Puncture is incorrect. Thanks

Why would you need more gravity? The Plasma doesn't need to creep on the floor of the containment bottle. It needs a bit of 'anti-gravity', but not too much. It would need to be as fluidic as possible as a gas at millions of degrees without the heat melting the bottle walls.

However, as was said, the confinement of such temps and density in a tokamak is an unnatural process. The Sun is the "go-to" for the best instructions, and the Sun just happens to be UNCONFINED, regardless of a layer of gas....which is the reason why humans get dark or sunburnt easily.

Aug 07, 2019
In a tokamak it is confined artificially.
And at much lower pressures and temperatures. Thus, we cannot expect at the current limits of our ability to make strong magnetic fields to do p-p fusion any time soon.

D-D and D-T fusion, however, we can do. The key is to keep the plasma contained, and finding out how these instabilities arise, and discovering we just need to make the alignment more precise, is a major step forward.
says Schneib

Let's says that everything goes as planned; the tokamak is made to withstand all pressures, densities, temps, etc and everything has been taken care of so that not even one glitch is possible. And let's say that all is going well, and Plasma has been created, burning at more than a million degrees while circulating around the tokamak. The walls can withstand the temps, but eventually even the walls of the tokamak become brittle and worn. By then, Fusion has begun and more gases are slowly pumped in. Then {{{{BLOOOEY}}}}

Aug 07, 2019
A miniature Star is born IN THE LAB. The Plasma reaches a point where it is able to suck all the Oxygen in the room as it burns. What then? All we would read in the news is that a building that housed a lab blew up. Would the miniature Star survive being out of the tokamak? Possibly. Would it get bigger? Possibly. It then would have plenty of room and no longer be confined.
It might fizzle out, and it might not.

Aug 07, 2019
There is no energy released from fusion! It typically occurs in free fall!

Aug 07, 2019
A miniature Star is born IN THE LAB. The Plasma reaches a point where it is able to suck all the Oxygen in the room as it burns. What then? All we would read in the news is that a building that housed a lab blew up. Would the miniature Star survive being out of the tokamak? Possibly. Would it get bigger? Possibly. It then would have plenty of room and no longer be confined.
It might fizzle out, and it might not.

You should know what happens if a pressurized vessel breaks. Explosion and release of what ever pressurized inside. Nothing would keep the fusion going as the pressure is gone and your sun would shut down.

Aug 07, 2019
Wellll then, inside the tokamak, it ain't Fusion, my boy. In the Sun, that 'overlying gas' can be bypassed or punctured through by Plasma in its outward flow.


Oh dear. More unscientific gibberish.

Aug 07, 2019
Was worried for a second....read it...not much to worry about...have a great day folks...

Aug 07, 2019
A miniature Star is born IN THE LAB. The Plasma reaches a point where it is able to suck all the Oxygen in the room as it burns. What then? All we would read in the news is that a building that housed a lab blew up. Would the miniature Star survive being out of the tokamak? Possibly. Would it get bigger? Possibly. It then would have plenty of room and no longer be confined.
It might fizzle out, and it might not.

You should know what happens if a pressurized vessel breaks. Explosion and release of what ever pressurized inside. Nothing would keep the fusion going as the pressure is gone and your sun would shut down.
says Cortezz

As it has never been tried quite in that fashion that I described, there is no way to know precisely what would happen until after the fact, Cortezz. The temperature will still remain at +1million degrees and will not cool down immediately.
Anyway, until such an event occurs, it is ALL still conjecture/hypothesis. But very interesting.

Aug 07, 2019
Wellll then, inside the tokamak, it ain't Fusion, my boy. In the Sun, that 'overlying gas' can be bypassed or punctured through by Plasma in its outward flow.


Oh dear. More unscientific gibberish.
says Castrovagina (rhetorically)

You are too late, Mopman. Whyde had already corrected me by saying, "And SEU,
Plasma does NOT puncture, it gets punctured..."

Aug 07, 2019
Hmmm, I don't think a tokamak exploding is very plausible. Experiencing a plasma excursion and damaging it inside, yes, that's been the problem the whole time. But by the time it does that it's not a plasma any more.

Aug 08, 2019
The Plasma remains a Plasma above a certain temperature. If the walls of the tokamak are compromised and weaken for whatever reason, it will leak and Plasma at a million degrees leaking will set the lab/facility on fire. Of course, sprinklers will turn on, hopefully.
It is the confinement of the Fusion process inside the tokamak that makes sustained Fusion almost impossible.

Aug 08, 2019
The Plasma remains a Plasma above a certain temperature. If the walls of the tokamak are compromised and weaken for whatever reason, it will leak and Plasma at a million degrees leaking will set the lab/facility on fire. Of course, sprinklers will turn on, hopefully.
It is the confinement of the Fusion process inside the tokamak that makes sustained Fusion almost impossible.


Wrong.

Aug 08, 2019
Wellll then, inside the tokamak, it ain't Fusion, my boy. In the Sun, that 'overlying gas' can be bypassed or punctured through by Plasma in its outward flow.


Oh dear. More unscientific gibberish.
says Castrovagina (rhetorically)

You are too late, Mopman. Whyde had already corrected me by saying, "And SEU,
Plasma does NOT puncture, it gets punctured..."


Then stop commenting on things you don't understand. How many times?

Aug 08, 2019
Somebody doesn't know how tokamaks work.

Gee, wonder who that is?

Alien mind-reading lizards, anyone?

Aug 09, 2019
The Sun is the "go-to" for the best instructions, and the Sun just happens to be UNCONFINED, regardless of a layer of gas....which is the reason why humans get dark or sunburnt easily.


What ???
We know the reason our skin darkens exposed to Sun, you've got the same effect emulated in every tanning salon on the planet - it's called UV radiation

Have a read, learn something ;)
https://en.wikipe..._tanning

Aug 13, 2019
The power of the sun in the palm of my hand!

I saw an episode of BBC's over the horizon where they investigated if commercially available fusion would be possible in our lifetime, to which the answer was: yes, if we want to.

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