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Spherical Tokamaks

Posted: Wed Aug 12, 2015 7:36 am
by crowberry
The Spherical Tokamak (ST) is a hot topic because it seems to have favourable stability properties compared to a traditional tokamak and in addition to that the additional benefits of smaller size, faster development cycles and lower cost. Dennis Whyte of MIT has been promoting the ST design called Affordable Replacable Compact (ARC). MIT has a new press release on ARC:
http://newsoffice.mit.edu/2015/small-modular-efficient-fusion-plant-0810#.Vcn7xPR5qw8.twitter

Here is the latest paper (paywalled) about the ARC design: http://www.sciencedirect.com/science/article/pii/S0920379615302337

I expect to hear a lot more about Spherical Tokamaks in the next few years. I would not be too surprised to see a company being formed around ARC in a similar way as the UK based Tokamak Energy is working on their own High Temperature Superconductor designs.

Re: Spherical Tokamaks

Posted: Wed Aug 12, 2015 4:18 pm
by Skipjack
crowberry wrote:The Spherical Tokamak (ST) is a hot topic because it seems to have favourable stability properties compared to a traditional tokamak and in addition to that the additional benefits of smaller size, faster development cycles and lower cost. Dennis Whyte of MIT has been promoting the ST design called Affordable Replacable Compact (ARC). MIT has a new press release on ARC:
http://newsoffice.mit.edu/2015/small-modular-efficient-fusion-plant-0810#.Vcn7xPR5qw8.twitter

Here is the latest paper (paywalled) about the ARC design: http://www.sciencedirect.com/science/article/pii/S0920379615302337

I expect to hear a lot more about Spherical Tokamaks in the next few years. I would not be too surprised to see a company being formed around ARC in a similar way as the UK based Tokamak Energy is working on their own High Temperature Superconductor designs.

Hehehe, ARC, someone has been reading too many comics ;)

Re: Spherical Tokamaks

Posted: Wed Aug 12, 2015 5:59 pm
by Giorgio
crowberry wrote:Here is the latest paper (paywalled) about the ARC design: http://www.sciencedirect.com/science/article/pii/S0920379615302337


Here is the un-paywalled paper for the curious ones:
http://arxiv.org/abs/1409.3540

Re: Spherical Tokamaks

Posted: Thu Aug 13, 2015 3:43 am
by Tom Ligon
Dr. Bussard liked spheromaks. We had a visit from Paul Koloc one day, where they discussed their ideas for fusion. Paul was using spheromaks as a model for ball lightning at that point. Essentially, a spheromak's shape is so natural for the magnetic fields that it can exist without the physical machine.

Re: Spherical Tokamaks

Posted: Thu Aug 13, 2015 1:56 pm
by Skipjack
I definitely like it better than other tokamaks. I wonder how favorably it compares to the Dynomak from the UW.
Still, it only doing T+D which means you have all the problems coming with that. I believe (but I am not sure), that the Dynomak can theoretically do D+D/He3 (though they will have T+D side reactions due to being steady state).

Re: Spherical Tokamaks

Posted: Fri Aug 21, 2015 5:02 pm
by TheRadicalModerate
Tom Ligon wrote:Dr. Bussard liked spheromaks. We had a visit from Paul Koloc one day, where they discussed their ideas for fusion. Paul was using spheromaks as a model for ball lightning at that point. Essentially, a spheromak's shape is so natural for the magnetic fields that it can exist without the physical machine.


Note that "spheromak" and "spherical tokamak" have nothing to do with one another.

Re: Spherical Tokamaks

Posted: Fri Aug 21, 2015 6:14 pm
by Solo
You have to read between the lines a bit to understand this proposal. MIT is going to be forced to shut down C-Mod, their high-field tokamak. They would like to continue by building a new, higher-field tokamak. I'd give both this and the dynomak a snowball's chance in hell of being built in the current funding climate though. The ARC design is pretty much a Hail Mary pass. That doesn't mean it's not a good idea though, just that most ideas, even good ones, are not going to get funding right now. Not from the Fedigov at any rate.

Re: Spherical Tokamaks

Posted: Sat Aug 22, 2015 8:08 am
by Skipjack
Solo wrote:, just that most ideas, even good ones, are not going to get funding right now. Not from the Fedigov at any rate.

Helion got some government funding. But I agree, funding for fusion under the Obama administration has been shit. Not that it was much better under Bush, either. If I was a conspiracy nut, I would say that they are all in the pocket of coal and oil.

Re: Spherical Tokamaks

Posted: Sat Aug 22, 2015 4:41 pm
by hanelyp
The conservative political position asks why taxpayers should pay for something or government should pick winners and losers, energy research in this case.

The current putz occupying the White House has policies consistent with wanting energy poverty, and using energy policy to launder money to cronies.

Re: Spherical Tokamaks

Posted: Mon Aug 24, 2015 6:25 pm
by swamijake
Not sure how this discussion is relevant to the topic. From what I can glean, the spherical tokamak is a similar to a regular tokamak except the central portion of the toroid magnets is shared by all the segments. Some designs have this central pole basically exposed to plasma.

Apparently the skinnier you can make that central pole the better the stability. Not sure how you heat the plasma as effectively as this eliminates the inner poloidal coils, but I suppose you can just blast it with RF or neutral beam injection.

Its a bit confusing as Spheromak is an entirely different entity. If you peeled an orange and stuck a pencil down the center it would look pretty close to a Spherical Tokamak, so maybe we can call it the Orange-o-mak?

Re: Spherical Tokamaks

Posted: Tue Oct 25, 2016 7:44 pm
by crowberry
The NSTX-U has unfortunately a malfunctioning magnet, which can take up to a year to fix.
http://www.nature.com/news/us-left-with-just-one-working-fusion-reactor-for-now-1.20710

Re: Spherical Tokamaks

Posted: Mon Sep 17, 2018 3:48 pm
by crowberry
Reparing NSTX-U is a long term project. Here the status of the project is described:
Abstract: YO5.00002 : Status and Plans for the NSTX-U Recovery Project

The NSTX Upgrade device began operation in 2016 and performed 10 weeks of commissioning activities and initial scientific research. However, a number of technical issues, including the failure of a divertor magnetic field coil, resulted in the suspension of operations. In response, a facility-wide “Extent of Condition” review was initiated at the request of the Department of Energy. This review generated a comprehensive corrective action plan and organization of a dedicated “Recovery Project” to enable NSTX-U to be the most capable Spherical Tokamak in the world program while also improving facility reliability. There are eight major scope items in the NSTX-U Recovery Project including: (1) six redesigned inner PF coils, (2) redesigned upper and lower polar region structures, (3) redesigned select plasma facing components, (4) improved bake-out, (5) additional component stress/strain trending instrumentation, (6) enhanced test cell shielding, (7) implementation of the accelerator safety order, and (8) reassembly of NSTX-U components with improved alignment. Progress, status, and plans for the NSTX-U Recovery Project will be described.


http://meetings.aps.org/Meeting/DPP18/Session/YO5.2

Re: Spherical Tokamaks

Posted: Sun Aug 18, 2019 6:53 am
by crowberry
NSTX-U will be repaired with tighter tolerances to improve the performance:
https://www.pppl.gov/news/2019/08/improving-magnetic-bottle-controls-fusion-power-earth

Re: Spherical Tokamaks

Posted: Sun Aug 18, 2019 10:19 am
by Giorgio
It took 4 years to complete the upgrade, 3 years to pinpoint the issues after the upgrade, and who know how many more years will pass before (if) they will complete the renewal.
We can easily say that at least 10 years will elapse from when the machine was lastly used to when it will produce again some scientific data.

Not a good news for anyone...

Re: Spherical Tokamaks

Posted: Sun Aug 18, 2019 5:23 pm
by Skipjack
Meanwhile Tokamak Energy is ready to run their upgraded machine.