Stellarators with Permanent Magnets

Discuss how polywell fusion works; share theoretical questions and answers.

Moderators: tonybarry, MSimon

Post Reply
Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Stellarators with Permanent Magnets

Post by Nanos »

https://scitechdaily.com/fusion-energy- ... -stronger/

Which mentions:

Reference: “Stellarators with Permanent Magnets” by P. Helander, M. Drevlak, M. Zarnstorff and S. C. Cowley, 5 March 2020, Physical Review Letters (PRL).

https://journals.aps.org/prl/abstract/1 ... 124.095001
> DOI: 10.1103/PhysRevLett.124.095001

PDF download available here:

https://journals.aps.org/prl/pdf/10.110 ... 124.095001
-----------
Stellarators with Permanent Magnets

P. Helander ,1,2 M. Drevlak,1,2 M. Zarnstorff,3,2 and S. C. Cowley3,21Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany2Max Planck/Princeton Research Center for Plasma Physics3Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA

(Received 2 July 2019; accepted 6 January 2020; published 5 March 2020
-----------

Giorgio
Posts: 2908
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Stellarators with Permanent Magnets

Post by Giorgio »

While in "theory" this solution seems a simplification of a Stellarator design, in practice it will negatively effect the working operations of a Stellarator.
It has been already proved in the W7-X that to suppress plasma turbulence and micro instabilities (while creating a stable operational regime) it is necessary to operate in a maximum-J regime.
J (the second adiabatic invariant of a plasma) is the longitudinal invariant of a particle trapped in the plasma.

There are several stable configurations that can be obtained according to the plasma parameters, but obtaining a stable maximum-J regime requires a constant variation and balancing of the current that is supplied to each one of the coils of the Stellarator, to properly shape the magnetic bottle according the plasma variations during the fusion process.

Exchanging part of the coiled superconducting magnets with permanent magnets will greatly reduce the amount of control we have on the magnetic shaping while introducing extra instabilities from the permanent magnets that will react to plasma variations in an uncontrollable way thus inducing extra instabilities.

In theory is quite a nice idea, but experimentally it has already been surpassed.

Good finding nevertheless!
A society of dogmas is a dead society.

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

Makes me ponder, could you have a backbone of permanent magnets, supplemented by electromagnets to give you that fine control ?

I guess there are two approaches to that even, one with them side by side so to speak, and one where the latter overlays the former.

I suppose you could have a third approach and have mechanically adjustable permanent magnets, but I guess their response times would be too slow ?

Giorgio
Posts: 2908
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Stellarators with Permanent Magnets

Post by Giorgio »

Nanos wrote:
Tue Aug 17, 2021 6:39 pm
I suppose you could have a third approach and have mechanically adjustable permanent magnets, but I guess their response times would be too slow ?
Correct.
Firstly permanent magnets are not permanent as their flux energy will decrease over time and their strength will be influenced by different operational regime conditions of the Stellarator.
Secondly, permanent magnets have a reactive behavior so their response to reach a new equilibrium position is slower than a coiled superconductor that can be strengthened or softened by instantly varying the supplied current and it can be done in advance by looping a feedback from the other coils.
It also needs time to reach the new equilibrium position, but the overall reaction time is orders of magnitude faster than a permanent magnet.
A society of dogmas is a dead society.

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

Would this suggest that using permanent magnets in an electric motor design is not the way forward ?

If so, I wonder why Tesla is heading in that direction ?

Related links:

https://uk.motor1.com/news/462107/video ... explained/
> Tesla Model 3's IPM-SynRM electric motor explained

https://electrek.co/2018/02/27/tesla-mo ... net-motor/
> Tesla motor designer explains Model 3’s transition to permanent magnet motor

I'm also interested in electric motor design, as I'd like more torque for hill climbing with less complicated gearing requirements, and higher efficiency for use in my own EV, without needing to spend $15,000 for a +97% efficient motor. ( Since my budget doesn't stretch that far ! )

Someone else's example link:

https://www.youtube.com/watch?v=dUGi50F_bwc
> Electric motor 7kW test run

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

----------
permanent magnets have a reactive behavior so their response to reach a new equilibrium position is slower than a coiled superconductor
----------

Does that vary depending upon the material construction of the permanent magnet ?


Makes me think of:

https://en.wikipedia.org/wiki/Herbertsmithite
> Herbertsmithite

Related links:

https://physics.aps.org/articles/v3/s49
> Do frustrated magnets go critical?

https://physics.aps.org/articles/v6/s71
> Pool of Candidate Spin Liquids Grows

Which leads me also to:

https://physics.aps.org/articles/v14/51
> Boosting Inertial-Confinement-Fusion Yield with Magnetized Fuel

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

Talking of electric motors, reminds me this unusual design:

https://en.wikipedia.org/wiki/Lynch_motor
> Lynch motor

https://endless-sphere.com/forums/viewtopic.php?t=71193
> Lynch motor how it works

https://www.quora.com/How-does-a-Lynch-DC-motor-work
> How does a Lynch DC motor work?

This snippet from the wikipedia entry:

-------
Lynch motors are mentioned as being a unique product in the documentary "The White Diamond" about a lighter than air ship: "This is actually an interesting motor. It is designed by somebody called Lynch in England. He never went to University and doesn't know any mathematics and stuff like that, but he taught himself electrical engineering. And it turns out the motor he made is one of the world's leading motors in terms of power and mass. Lynch developed his own kind of algebra to do that but no other academic can understand what he's doing, but he seems to know more than many academics in electrical engineering departments because this motor is of very good performance ... the best that I could find.
-------

Makes me ponder that there are still unexplored avenues out there.

Giorgio
Posts: 2908
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Stellarators with Permanent Magnets

Post by Giorgio »

Nanos wrote:
Tue Aug 17, 2021 10:49 pm
Would this suggest that using permanent magnets in an electric motor design is not the way forward ?
You are comparing incomparable technological designs.
Electric motor use permanent magnets as a mean to transform an electrical current into a circular motion, a completely different field from their use a field generator for confining a fusion process.
A society of dogmas is a dead society.

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

> Electric motor use permanent magnets as a mean to transform an electrical current into a circular motion
>, a completely different field from their use a field generator for confining a fusion process.

You can get electric motors that don't use permanent magnets can't you ?

I see lots of overlap myself.

Some related links that might spark ideas/etc.


https://www.thefusionpodcast.com/blog/2 ... technology
> ROTAMAKS: YET ANOTHER IGNORED FUSION TECHNOLOGY

https://www.sciencedaily.com/releases/2 ... 142402.htm
> Twisting magnetic fields for extreme plasma compression

https://www.sciencedirect.com/topics/ph ... ic-mirrors
Article top right:
------
1977
John Sheffield, in Fun in Fusion Research, 2013

The Elmo Bumpy Torus
------

https://avs.scitation.org/doi/10.1116/1.570890
> ELMO Bumpy Torus: An alternate concept to tokamaks and mirrors

Nanos
Posts: 351
Joined: Thu Jul 05, 2007 8:57 pm
Location: Treasure Island

Re: Stellarators with Permanent Magnets

Post by Nanos »

I'm also reminded of:

https://en.wikipedia.org/wiki/Spin-stab ... levitation
> Spin-stabilized magnetic levitation

https://www.youtube.com/watch?v=pCON4zfMzjU
> Electromagnetic Levitation Quadcopter

https://citeseerx.ist.psu.edu/viewdoc/d ... 1&type=pdf
> About Strange Effects Related to Rotating Magnetic Systems

And:

https://www.ge.com/news/reports/not-you ... dge-magnet
> Not Your Average Fridge Magnet: These High-Tech Magnets
> Will Keep Your Butter (and Beer) Cold

Which links to:

https://en.wikipedia.org/wiki/Magnetic_refrigeration
> Magnetic refrigeration

Giorgio
Posts: 2908
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Stellarators with Permanent Magnets

Post by Giorgio »

Nanos wrote:
Wed Aug 18, 2021 11:51 am
You can get electric motors that don't use permanent magnets can't you ?
You can, but the extra complications and costs is simply not worth the hassle.
Economic is more important than engineering in this case.
A society of dogmas is a dead society.

Skipjack
Posts: 6338
Joined: Sun Sep 28, 2008 2:29 pm

Re: Stellarators with Permanent Magnets

Post by Skipjack »

I believe that the fine tuning of the electromagnets is necessary because the W7X is not a perfectly aligned design yet. In other words W7X is a test bed where they are trying to figure out the perfect Stellarator shape. Once they have figured that out, permanent magnets might work.
That said, I am not a huge fan of doughnut shaped designs. I think that they are a fools errand born out of the fact that Russians had semi- decent from their Tokamak. Ever since then the whole world seems to be dead set on doughnut shaped fusion generators. Somehow that made everyone believe that a viable fusion generator has to be that shape. There are so many options that have been ignored ever since :(

Giorgio
Posts: 2908
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Stellarators with Permanent Magnets

Post by Giorgio »

Skipjack wrote:
Sat Aug 21, 2021 9:36 am
I believe that the fine tuning of the electromagnets is necessary because the W7X is not a perfectly aligned design yet. In other words W7X is a test bed where they are trying to figure out the perfect Stellarator shape. Once they have figured that out, permanent magnets might work.
That said, I am not a huge fan of doughnut shaped designs. I think that they are a fools errand born out of the fact that Russians had semi- decent from their Tokamak. Ever since then the whole world seems to be dead set on doughnut shaped fusion generators. Somehow that made everyone believe that a viable fusion generator has to be that shape.
Fine tuning in Stellarators will "always" be necessary, like in all other magnetic confinement devices.
The main reason is the impossibility to tune in advance electrostatic micro instabilities as well as the instabilities generated from different working parameters and from the interaction between magnetic field generators and imperfections in the homogeneity of the structural shell/components of the fusion apparatus.
This has been probably the first thing that W7-X has taught us.

Skipjack wrote:
Sat Aug 21, 2021 9:36 am
There are so many options that have been ignored ever since :(
Indeed, and is sad that no one is caring to finance them. Even negative results will bring a plethora of new understandings that could be used to mainstream designs....
A society of dogmas is a dead society.

Post Reply