
Fusion in a magnetically-shielded-grid inertial electrostatic confinement device - carapace
https://arxiv.org/abs/1510.01788
======
Azrael3000
As this paper is from 2015 and I can't claim to understand it, is the follow
up paper by the first author [0] the reason why it actually doesn't work?

[0]: [https://arxiv.org/abs/1808.00622](https://arxiv.org/abs/1808.00622)

~~~
rolph
they are using electric charge to move plasma particles around, and a magnetic
field to enclose the charged electrodes and protect them from the plasma.

the electrode setup was a concentric ring setup so it was simpler than a
spherical setup like a fusor kind of device

[https://en.wikipedia.org/wiki/Fusor](https://en.wikipedia.org/wiki/Fusor)

[https://en.wikipedia.org/wiki/Polywell](https://en.wikipedia.org/wiki/Polywell)

the most common fusion concepts nowadays involve magnetic enclosure and or
compression, of plasma, and electric charge based acceleration of the plasma.

------
carapace
(2015)

Abstract:

> Theory for a gridded inertial electrostatic confinement (IEC) fusion system
> is presented that shows a net energy gain is possible if the grid is
> magnetically shielded from ion impact. A simplified grid geometry is
> studied, consisting of two negatively-biased coaxial current-carrying rings,
> oriented such that their opposing magnetic fields produce a spindle cusp.
> Our analysis indicates that better than break-even performance is possible
> even in a deuterium-deuterium system at bench-top scales. The proposed
> device has the unusual property that it can avoid both the cusp losses of
> traditional magnetic fusion systems and the grid losses of traditional IEC
> configurations.

~~~
skykooler
> Our analysis indicates that better than break-even performance is possible
> even in a deuterium-deuterium system at bench-top scales.

That means it should be relatively easy to verify in a laboratory, right?

~~~
Retric
Fusion over breakeven releases a boatload of ionizing radiation. So, it’s not
exactly a safe thing to put on a lab bench. As even a single watt of power
requires the kind of wall you put on a nuclear power plant.

As a rule of thumb, fusion is only really vastly better than fission once you
turn it off.

That said, I agree there is likely something wrong with the design.

~~~
gpderetta
you can build your own fusion reaction in the comfort of your home. Apparently
fusor devices [1] are hobbist level difficulty. They are nowhere near break
even, but they do generate a lot of radiation which can still be contained
safely on a benchtop apparently.

[1] [https://en.wikipedia.org/wiki/Fusor](https://en.wikipedia.org/wiki/Fusor)

~~~
Retric
At the hobbyist level they are making detectable amounts of radiation, but
only something like 1 trillionth of a watt worth of fast neutrons per second.

~~~
gpderetta
Right, I completely missed the point that you were concerned about the amount
of radiation at break even.

I wonder whether you could detect the increased efficiency well before
reaching break even (that wouldn't prove that you can reach break even of
course)?

~~~
Retric
Starting with HH vs DD fusion gives you validation with orders of magnitude
less radiation, lower pressures would be similarly useful. But, IMO partnering
with someone in the nuclear industry is probably the best bet.

Really, if your not asking for money just a location that's a fairly easy
sell. If it doesn't work at all that's no real cost to them. If it almost
works that's a cheap neutron source that's easy to turn on and off which is
valuable. And if it actually works that's one of those world changing things
people are willing to support.

------
DennisP
This design sure looks a lot like the illustrations I've seen for Lockheed's
fusion reactor design. Scroll down on this article, for example:

[https://www.forbes.com/sites/arielcohen/2018/08/01/will-
lock...](https://www.forbes.com/sites/arielcohen/2018/08/01/will-lockheed-
martin-change-the-world-with-its-new-fusion-reactor/#6bd10de34c49)

Compare that to the paper's figures, starting on page 2.

~~~
earthicus
Above the illustration in the text, the paper references work from 2001-2006
for motivating that geometry:

    
    
        [19]  J. Khachan and S. Collis, Phys. Plasmas8, 1299 (2001).
        [20]  J. Khachan, D. Moore, and S. Bosi, Phys. Plasmas10, 596 (2003).
        [21]  O.  Shrier,  J.  Khachan,  S.  Bosi,  M.  Fitzgerald,  and  N.Evans, Phys. Plasmas13, 012703 (2006)
    

In particular all three citations refer to Joseph Khachan's work:

[https://sydney.edu.au/science/about/our-people/academic-
staf...](https://sydney.edu.au/science/about/our-people/academic-staff/joe-
khachan.html)

And Bosi seems to have been at Sydney at the time as well:

[https://www.une.edu.au/staff-profiles/science-and-
technology...](https://www.une.edu.au/staff-profiles/science-and-
technology/sbosi)

------
dcminter
I was under the impression that bremsstrahlung losses were the main barrier to
breakeven in fusor-like devices. Is this not susceptible to that?

~~~
dcminter
Answering my own question: apparently not per section E.

~~~
jleahy
They're making the assumption that the ions and electrons can be held outside
of thermal equilibirium (and provide no evidence for this). In reality
thermalisation is likely to occur rapidly due to frequent collisions, once
thermalised a normal Maxwell distribution will apply and Bremsstrahlung losses
will return with a vengeance.

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houseboat
"... in a mysterious and highly fluid vacuum, the force is not very small; it
only moves at the speed and frequency of the plasma from two to three orders
of magnitude faster than the plasma of other electrons to three orders of
magnitudes..."

This makes me wonder what would happen to this device? Is it a device like the
SG?

------
ohiovr
Something has to hold the magnets and physical supports will cool the plasma.
Also there is a non trivial amount of magnetic force to contend with.

~~~
journalctl
So don’t bring your credit cards in to work!

~~~
sandworm101
Don't bring your dental fillings either.

~~~
ars
You are probably joking, but just in case not: dental fillings are not
magnetic. They are amalgams of mercury and silver.

~~~
ohiovr
Try dropping a neodymium magnet down a length of copper pipe sometime. I would
think that sensation would be quite disturbing from something hugging a tooth.

------
ben_w
I’ve been wanting to research magnetically shielded grids since 2007, but I’m
not formally trained in physics [0] and don’t know where to begin. Can anyone
make any recommendations for well-documented MHD simulator libraries?

[0] Informally I watch PBS Space Time and similar channels, but good though
that content is, it’s not the same as a real qualification.

~~~
ohiovr
someone did make a charged particle simulator for polywell. You might find it
by searching talk-polywell.org

[http://www.talk-polywell.org/bb/index.php](http://www.talk-
polywell.org/bb/index.php)

~~~
ben_w
Thanks :)

