A quick and easy way to shut down instabilities in fusion devices

August 18, 2017
Eric Fredrickson, lead author of the paper, in the NSTX-U control room. Credit: Elle Starkman/PPPL Office of Communications

Scientists have discovered a remarkably simple way to suppress a common instability that can halt fusion reactions and damage the walls of reactors built to create a "star in a jar." The findings, published in June in the journal Physical Review Letters, stem from experiments performed on the National Spherical Torus Experiment-Upgrade (NSTX-U), at the Department of Energy's Princeton Plasma Physics Laboratory (PPPL).

The suppressed instability is called a global Alfvén eigenmode (GAE)—a common wave-like disturbance that can cause reactions to fizzle out. Suppression was achieved with a second neutral injector recently installed as part of the NSTX-U upgrade. Just a small amount of highly from this second injector was able to shut down the GAEs.

Akin to a snake or dragon

Such instabilities are akin to a snake or dragon that swallows its own tail. Stirring up GAEs are the same neutral beam particles that heat the plasma, which are ionized into electrons and ions, or atomic nuclei, inside the gas. Once triggered by these fast ions, the GAEs can rise up and drive them out, cooling the plasma and halting .

Suppressing this arousal were beams from the second injector, which flow through the plasma at a higher pitch-angle, in a direction roughly parallel to the magnetic field that confines the hot gas. Physicists call such beams "outboard" to distinguish them from the "inboard" beams that the original NSTX-U injector produces, which flow through the plasma and the magnetic field in a more perpendicular fashion.

Injection of the outboard beam suppressed GAEs in milliseconds. Fast ions from the beam combined with those from the inboard beam to increase the density of the ions and alter their distribution in the plasma. The sudden alteration reduced the gradient, or slope, of the ion density, without which GAEs were unable to form and ripple through the plasma.

Good news for fusion development

These remarkable results were good news for fusion development. "Normally, when you inject energetic particles, you drive up instabilities," said Jonathan Menard, head of research on NSTX-U. "The fact that the second neutral beam was able to turn them off by varying the fast-ion distribution with a small amount of particles provides our research with flexibility and is a welcome discovery."

The result validated predictions of a computer code called "HYM," developed by PPPL physicist Elena Belova, and could prove useful to ITER, the international fusion facility under construction in France to demonstrate the ability to confine a burning and produce 10 times more energy than it consumes.

"This research demonstrates suppression of GAEs with just a small population of energetic ," said physicist Eric Fredrickson, lead author of the journal article. "It gives confidence that by using this code, reasonable predictions of GAE stability can be made for ITER."

Explore further: Updated computer code improves prediction of particle motion in plasma experiments

More information: E. D. Fredrickson et al, Suppression of Alfvén Modes on the National Spherical Torus Experiment Upgrade with Outboard Beam Injection, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.265001

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sevensixtwo
2 / 5 (4) Aug 18, 2017
It's nice to see a scientist with an appropriate look on his face for a change.
Da Schneib
4.6 / 5 (9) Aug 18, 2017
Oh, gee, look there, they ran a simulation-- something #sciencecranks deny works-- made a prediction based on it, then built equipment to test it, and it worked. What a surprise <-sarcasm.
gculpex
Aug 19, 2017
This comment has been removed by a moderator.
cantdrive85
1 / 5 (5) Aug 19, 2017
Akin to a snake or dragon
Such instabilities are akin to a snake or dragon that swallows its own tail.

The Ouroboros is an archetype from antiquity found all over the world. Seems as if our ancestors were

https://en.m.wiki...uroboros
cantdrive85
1 / 5 (5) Aug 19, 2017
Akin to a snake or dragon
Such instabilities are akin to a snake or dragon that swallows its own tail.

The Ouroboros is an archetype from antiquity found all over the world. Seems as if our ancestors were aware of plasma formations as shown by Anthony Peratt and his analysis of petroglyphs found globally. There is prodigious evidence these formations were witnessed in the pre-historic sky.

https://en.m.wiki...uroboros
http://plasmauniv...rth.html
Chris_Reeve
1.5 / 5 (8) Aug 19, 2017
The irony of this whole class of articles is that the Sun is of course doing its job without these forcing tricks which are applied by laboratory fusion scientists.

The difference, it seems, boils down to the existence of double layers. If these fusion theorists were to simply charge-load a sphere in a vacuum, they would immediately understand that the NATURAL way to solve these problems is to permit and facilitate the formation of double layers -- which do not really need to be forced. They just happen. Those double layers serve much the same purpose as all of these tricks in stabilizing the plasma are meant to force.

The great irony is that the astrophysicists have gone to great lengths to refuse acknowledgement of double layers as astrophysical phenomena, and yet it appears to be the very concept they need in order to move these experiments forward.
Captain Stumpy
5 / 5 (3) Aug 19, 2017
@hannes/reeve the blatantly lying eu POS TROLL pseudoscience sock puppets
The great irony is that the astrophysicists have gone to great lengths to refuse acknowledgement of double layers as astrophysical phenomena
oh wow... not only is this a blatantly false claim, but it's also easily validated as stupidly false:

starting with the APS Plasma Physics Conference November 10, 2014 and ending with Space Plasma, Power, and Propulsion Group, Research School of Physical Sciences and Engineering in The Australian National University

of course, your claims are also proven false by using Google Scholar and looking at the relevant plasma physics data

heck your claims are proven false by a Phys.org only search!

lastly: just because you believe it to be true doesn't mean it is true

more to the point: just because your idiot pseudoscience uses jargon that isn't compatible with modern physics doesn't mean it's accurate or factual

you're illiterate
cantdrive85
1 / 5 (3) Aug 19, 2017
Akin to a snake or dragon
Such instabilities are akin to a snake or dragon that swallows its own tail

Here is something else that is akin to a snake or dragon that swallows it's own tail. And the result being similar to that of the above observation that cause the current to "fizzle out"...
http://newatlas.c...m/26075/
The electrical properties of plasma go all the way up, and all the way down.
RealityCheck
1 / 5 (3) Aug 19, 2017
@cantdrive85.
Akin to a snake or dragon
Such instabilities are akin to a snake or dragon that swallows its own tail

Here is something else that is akin to a snake or dragon that swallows it's own tail. And the result being similar to that of the above observation that cause the current to "fizzle out"...
http://newatlas.c...m/26075/
The electrical properties of plasma go all the way up, and all the way down.
Mate, can you please explain what you mean by that; and what it is you are claiming; and how your link applies to whatever it is that you are claiming? I only ask because there seems no scientific point being made/supported by you in this instance. I will await your response before concluding anything or commenting further re this. :)
cantdrive85
1 / 5 (2) Aug 19, 2017
Electrodynamic plasma processes are scalable, all the way up and all the way down. The circuitry that explains the instability in the plasma chamber is analogous to the circuitry of the storm eating it's tail and then "fizzling out". Keep in mind, it is an analogy but it is likely the circuitry is similar bit on a larger scale.
Whydening Gyre
5 / 5 (4) Aug 19, 2017
The irony of this whole class of articles is that the Sun is of course doing its job without these forcing tricks which are applied by laboratory fusion scientists.

The Sun, of course, having sufficient gravity to pull IN instabilities.
The difference, it seems, boils down to the existence of double layers.

Perhaps, concentric layers is a better description.
much the same purpose as all of these tricks in stabilizing the plasma are meant to force.

Tricks are necessary inasmuch as we attempting to CONTAIN without massive gravity.

The great irony is that the astrophysicists have gone to great lengths to refuse acknowledgement of double layers ...

The irony is only your own as you refuse to consider what CAUSES the "concentric" layering.
Whydening Gyre
5 / 5 (4) Aug 19, 2017
Akin to a snake or dragon
Such instabilities are akin to a snake or dragon that swallows its own tail

Here is something else that is akin to a snake or dragon that swallows it's own tail. And the result being similar to that of the above observation that cause the current to "fizzle out"...
http://newatlas.c...m/26075/
The electrical properties of plasma go all the way up, and all the way down.

Oroborus analogy is incorrect. It only represents a closed loop, when reality is an open loop.
Captain Stumpy
5 / 5 (4) Aug 19, 2017
@nazi sympathizing pseudoscience eu cult idiot
Electrodynamic plasma processes are scalable, all the way up and all the way down
and because of this knowledge that scientists, engineers and astrophysicists have collected that we have, we can then show where your eu bullsh*t pseudoscience isn't in any way descriptive of the universe, gravity, solar physics nor planet/oid formations

this isn't analogous to any Ouroboros in any way

more importantly:
the Ouroboros symbolize introspection, the eternal return or cyclicality and as such is far more likely circular "eating it's tail" due to the (gasp) circular nature of life and (double gasp) a f*cking *circle*

making the statement that "our ancestors were aware of plasma formations" is analogous to stating our ancestors were aware of the AS32P-19 Oshkosh Rapid Intervention Crash Firefighting truck in Roman/Egyptian times because they knew about the colours red or yellow
carbon_unit
5 / 5 (3) Aug 20, 2017
The irony of this whole class of articles is that the Sun is of course doing its job without these forcing tricks which are applied by laboratory fusion scientists.

The difference, it seems, boils down to the existence of double layers. If these fusion theorists were to simply charge-load a sphere in a vacuum, they would immediately understand that the NATURAL way to solve these problems is to permit and facilitate the formation of double layers -- which do not really need to be forced. They just happen.

You left out the part about adding the mass of a star to achieve "natural" containment ...
Whydening Gyre
5 / 5 (1) Aug 20, 2017
Ouroborus analogy is incorrect. It only represents a closed loop, when reality is an open loop.

Actually, the Buddhist have a thing more closely resembling reality.
Enso (ring). It's an ALMOST closed ring.
It represents "absolute enlightenment"..
(Many of my jewelry pieces now include it)
Da Schneib
5 / 5 (2) Aug 21, 2017
The entire difference between fusion reactors and stellar fusion is very simple, and @carbon_unit is right: stars have gravity, and fusion reactors do not. Fusion reactors have to use tricks with magnetics to form plasmas that support fusion; stars can use the relentless and simple compounded pressure of gravity. Our magnetic tricks must be subtle and powerful to duplicate this. It's really that simple.
FM79
5 / 5 (1) Aug 21, 2017
Oh, gee, look there, they ran a simulation-- something #sciencecranks deny works-- made a prediction based on it, then built equipment to test it, and it worked. What a surprise <-sarcasm.


Not all simulations and predictions turn out to be correct.
That's the point of the experiment.

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