Today's forecast: How to predict crucial plasma pressure in future fusion facilities

Today's forecast: How to predict crucial plasma pressure in future fusion facilities
Physicist Michael Churchill. Credit: Elle Starkman/PPPL Office of Communications

A key requirement for future facilities that aim to capture and control on Earth the fusion energy that drives the sun and stars is accurate predictions of the pressure of the plasma—the hot, charged gas that fuels fusion reactions inside doughnut-shaped tokamaks that house the reactions. Central to these predictions is forecasting the pressure that the scrape-off layer, the thin strip of gas at the edge of the plasma, exerts on the divertor—the device that exhausts waste heat from fusion reactions.

Researchers at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have developed new insights into the physics governing the balance of pressure in the scrape-off . This balance must ensure that the pressure of the plasma throughout the tokamak is high enough to produce a largely self-heating fusion reaction. The balance must also limit the potentially damaging impact of heat and that strike the divertor and other plasma-facing components of the tokamak.

"Previous simple assumptions about the balance of pressure in the scrape-off layer are incomplete," said PPPL physicist Michael Churchill, lead author of a Nuclear Fusion paper that describes the new findings. "The codes that simulate the scrape-off layer have often thrown away important aspects of the physics, and the field is starting to recognize this."

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 are seeking to replicate on Earth for a virtually inexhaustible supply of power to generate electricity.

Key factors

Churchill and PPPL colleagues determined the key factors behind the pressure balance by running the state-of-the-art XGCa computer code on the Cori and Edison supercomputers at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility. The code treats at a detailed kinetic—or particle motion— level rather than as a fluid.

Among key features found was the impact of the bulk drift of ions, an impact that previous codes have largely ignored. Such drifts "can play an integral role" the authors wrote, and "are very important to take into account."

Also seen to be important in the momentum or pressure were the kinetic particle effects due to ions having different temperatures depending on their direction. Since the temperature of ions is hard to measure in the scrape-off layer, the paper says, "increased diagnostic efforts should be made to accurately measure the ion temperature and flows and thus enable a better understanding of the role of ions in the SOL."

The new findings could improve understanding of the scrape-off layer pressure at the divertor, Churchill said, and could lead to accurate forecasts for the international ITER experiment under construction in France and other next-generation tokamaks.


Explore further

Seeing clearly: Revised computer code accurately models an instability in fusion plasmas

More information: R.M. Churchill et al, Pressure balance in a lower collisionality, attached tokamak scrape-off layer, Nuclear Fusion (2019). DOI: 10.1088/1741-4326/ab2af9
Citation: Today's forecast: How to predict crucial plasma pressure in future fusion facilities (2019, September 20) retrieved 17 October 2019 from https://phys.org/news/2019-09-today-crucial-plasma-pressure-future.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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Sep 21, 2019
Not much physical happening yet.
But new accuracy on where the energy is determines the next physical steps so this is good news overall.
The field needs good news, this technology expected to be widespread ten years ago. So many steps have been discovering what does not work, this is a positive step.

Sep 21, 2019
"Potentially damaging effects." Big questions remain concerning the containment of "particles."

Sep 21, 2019
The Balance of Pressure in the Scrape-off Layer

This balance
Must ensure
That the pressure
Of the plasma
Throughout the Tokamak
Is high enough
To produce a largely self-heating fusion reaction
The balance must also limit
The potentially damaging impact
Of heat and plasma particles
That strikes the diverter
And other plasma-facing components of the Tokamak

Fusion in the Sun relies on flares
Relies on heat and plasma particles
So, what is this we hear?

"The potentially damaging impact of heat and plasma particles"

Now, if we take steps
To mitigate this heat, flares and particles in these fusion reactors
These fusion fires will subside

It matters not
That these fusion flares, heat and particles
Are destroying these fusion reactors

These flares are millions of degrees centigrade
This is fusion, get over it, stop damping down these flares, or we'll never achieve fusion!
If you can't stand the heat, get out of the kitchen!

Sep 21, 2019
These flares are millions of degrees centigrade

There is no metal in this Universe
That can stand
Fusions millions of degrees

The trick is to contain these flares
In magnetic fields
Just as our Sun contains these flares

So that these flares
Are kept at a distance
Where the heat does not melt the reactor walls

As to the particles
they have to be diverted
Back, into the plasma, so the particles heat is not lost

Because, what we are aiming for
Is a glowing ball of plasma, at millions of degrees centigrade
Held magnetically, inside a steel ball

Sufficiently far from these millions of degrees
That we can takes this heat away faster than this steel ball is melting
And use it to boil water for electrical steam generators

Sep 22, 2019
Precisely. However -- The products of the Fusion process are enough to destroy any Tokamak, thereby rendering any Tokamak made of metal about as strong as candlewax. The Sun is not held in a containment vessel and it is free to send out its flares and solar radiation all over. Which is why Fusion on the Earth cannot work inside a Tokamak all because of the inhibiting factor of those walls.
Will these researchers ever understand this simple and easy fact? Fusion is like a wild animal that cannot survive if it is caged. It must be set free. True Fusion cannot be controlled on a planet unless the whole planet becomes the Tokamak without walls.

Sep 22, 2019
Fusion: A Research Grant

Fusion is Like a Wild Animal
The products of the Fusion process
are enough to destroy
any Tokamak
thereby rendering
any Tokamak made of metal
about as strong as candle wax
The Sun is not held in a containment vessel
and it is free
to send out its flares
and solar radiation all over
Which is why
Fusion on the Earth
cannot work inside a Tokamak
all because
of the inhibiting factor of those walls.
Will these researchers
ever understand
this simple and easy fact?
Fusion is like a wild animal
that cannot survive
if it is caged
It must be set free
True Fusion cannot be controlled
on a planet unless the whole planet
becomes the Tokamak without walls
Fusion is Like a Wild Animal

A comparison of Solar Fusion within these Tokamak Lithium walls: by Surveillance_Egg_Unit

Sep 22, 2019
The "secret" of human survival on this planet might just be the recognition that using LESS energetic processes are a strategy. There were some voices in the past which suggested this, realizing that most of the biology ran on systems which had evolved to be parsimonious in the use of available energy.

Sep 22, 2019
Sufficiently far from these millions of degrees
That we can takes this heat away faster than this steel ball is melting
And use it to boil water for electrical steam generators

There are those who are developing fusion processes that create electricity directly from the fusion processes. Those who continue to rely on 19th century techniques to create electricity still don't grasp the advantages of fusion technology.

Sep 22, 2019
Sufficiently far from these millions of degrees
That we can takes this heat away faster than this steel ball is melting
And use it to boil water for electrical steam generators

There are those who are developing fusion processes that create electricity directly from the fusion processes. Those who continue to rely on 19th century techniques to create electricity still don't grasp the advantages of fusion technology.

Oops, meant to link to the scientists would actually understand how to create fusion energy on Earth.
https://lppfusion.com/

Sep 22, 2019
This article makes me feel that the tokamak is doomed to be a dead end.

Sep 23, 2019
This Diverter: That Exhausts Waste Heat from Fusion Reactions

Physicist Michael Churchill> Central to these predictions is forecasting the pressure that the scrape-off layer, the thin strip of gas at the edge of the plasma, exerts on the diverter, the device that exhausts waste heat from fusion reactions.

Brilliant
Its 2035, till we get, are next definitive firing, of our fusion reactor!

we never knew this fusion reactor
was manufacturing so much heat
that our reactor exhausts waste heat

we thought
we had been led to believe
our reactors have insufficient heat to achieve fusion

wonders will never cease
not only are we damping down these flares of fusion reactions
we are exhausting heat under the pretext of "Waste Heat"

this reactor design
is not producing sufficient heat to achieve sustainable fusion
this fusion reactor has no heat that can be defined, "Waste Heat"

Sep 23, 2019
Fore, we cannot, eternally, wait 35yrs

Aneutronic Fusion: by cantdrive85
Proton plasma fusion
Where a stream of protons
Then twists into tight coils liketh a coiled telephone flex

Aneutronic Fusion
Is any form of fusion power
In which the majority of the energy release
Is carried by charged particles
While the lowest-threshold nuclear fusion reactions
Release up to 80% of their energy in the form of (uncharged) neutrons
There also exist reactions in which the energy is released in the form of charged particles
Typically protons or alpha particles
Successful Aneutronic fusion
Would greatly reduce problems
Associated with neutron radiation
Such as ionizing damage
https://en.wikipe...c_fusion

In this Fusion, Tokamak world, different is good, different is novel
Different is freeing fusion from this same old mantra
Just one more 35 years

For cantdrive, are we any nearer to Aneutronic Fusion?
Nearer to any kind of Fusion
Fore, we cannot, eternally, wait 35yrs

Sep 23, 2019
For cantdrive, are we any nearer to Aneutronic Fusion?
Nearer to any kind of Fusion
Fore, we cannot, eternally, wait 35yrs

As Lerner states here;
https://youtu.be/YPwomqShioo
He is thinking they may be able to achieve results by 2021, if they do the machines could be on an assembly line in three or so years. That on a five million dollar budget while ITER has dumped billions in the hole.

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