Z-Pinch Renaissance

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Giorgio
Posts: 2779
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Z-Pinch Renaissance

Post by Giorgio »

williatw wrote:
Thu Oct 22, 2020 11:22 am
Not to interrupt you gentlemen's interesting technical discourse but what about a compromise? Say one of those small modular nuclear reactors of the type that Trump just approved funding for?
What me and Skipjack are digressing about is not on the type of power reactor that is needed but on the need itself of a secondary power source to be coupled to the ZAP engine. In other words we do not agree on the Technology Readiness Level (TRL) of the ZAP design.

We do both agree that if the need of a standby reactor for power production will arise than the whole ZAP engine will lose appeal.



That said, and out of context from the discussion above, a normal fission reactor like the one proposed by NuScale would still be too much massive. For space application I would follow the route of a Molten Salt Reactor, and more specifically of a Liquid Fluoride Thorium Reactor that gives you the lowest footprint and mass for MW. d
Here is a good report on the technology.
Again, this is quite offtopic so if you have any interests or wish to discuss ideas on the LFTR I suggest you ope a new thread.
A society of dogmas is a dead society.

Skipjack
Posts: 6110
Joined: Sun Sep 28, 2008 2:29 pm

Re: Z-Pinch Renaissance

Post by Skipjack »

Giorgio, the paper you quoted is from 2006. Since then Uri and his team have made a lot of progress and so far the scaling laws are holding, suggesting that thermalization is not a real issue. Back in 2006, they did not even have ZAP-HD yet which scaled the input current to 50 kA and since then their follow up to ZAP- HD, FuZE has scaled up to 400kA and from all that I have read, the scaling laws are holding very well. If thermalization was a big problem, it would likely have reared it's ugly head by now. Don't you think?

Giorgio
Posts: 2779
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Z-Pinch Renaissance

Post by Giorgio »

I am quoting that 2006 paper because is the only paper where they mention the issue. After this paper in no other public paper or presentation that I have read the thermalization issue was ever mentioned as "overcome" or "tested" or "solved".
The scaling laws in the ZAP-HD and FuZE machines are holding for increase in current density and magnetic field, but we are still into the highly stable regime because the pinch radius is still 3 mm with a Q<<1, while all the issues (including thermalization) will appear when the radius start to be reduced to reach Q>1 and you enter the boundary of unstable regimes.

They carefully hinted this in their 2017 paper when they wrote in the conclusions:
"Sheared flow stabilization appears to be robust over a range of plasma parameters as shown in Secs. III and IV.
However, scaling to even higher parameters may introduce phenomena that cannot be stabilized or mitigated by sheared flows."


It might have been just a cautionary statement, but I would really love for them to address this issue in one of the presentations they make because I am sure that I am not the only one seeing the thermalization of Alphas as a big roadblock in front of the ZAP to reach Q>1.
A society of dogmas is a dead society.

Skipjack
Posts: 6110
Joined: Sun Sep 28, 2008 2:29 pm

Re: Z-Pinch Renaissance

Post by Skipjack »

They might not be mentioning the issue anymore because it turned out to be a non issue. I mean, we will see what happens. From what we know, they are planning to achieve a notional Q~1 within the next 3 years (I read an earlier statement that said 2 years). Until then, we can only speculate. I prefer to be optimistic.

Giorgio
Posts: 2779
Joined: Wed Oct 07, 2009 6:15 pm
Location: China, Italy

Re: Z-Pinch Renaissance

Post by Giorgio »

Considering the importance of the issues (and the constant need of research funds they have) I would have expected them to rise to general attention the overcoming of this issue as a major point in favor of financing their tech.

Anyhow, I like your optimism and I deeply wish you to be totally right and me totally wrong. We are in dire need to leapfrog the limits in energy production where we have been stuck for the last 60 years.
A society of dogmas is a dead society.

Skipjack
Posts: 6110
Joined: Sun Sep 28, 2008 2:29 pm

Re: Z-Pinch Renaissance

Post by Skipjack »

This one will be interesting:
https://meetings.aps.org/Meeting/DPP20/Session/CP20.10
Deformation of Plasma-Facing Surfaces in the ZaP-HD Device:
Target surfaces are analyzed with a scanning electron microscope and energy-dispersive x-ray spectroscopy. Stagnated plasma is found to limit the heat flux to the solid surfaces by slowing the diffusion of the magnetic field into the targets. The orientation of the solid surface to the plasma flow affects the surface topography seen in micrographs. These preliminary results provide a foundation for designing an electrode configuration for a higher-power sheared-flow-stabilized Z pinch device.

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