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Re: PPPL Colloquium: The Lockheed Martin CFR, Aug 6, 2015

Posted: Tue Aug 11, 2015 12:50 am
by Skipjack
pdxpyro wrote:As promised, the session was posted to the Princeton Media Central site.

https://mediacentral.princeton.edu/medi ... 1_5j8kix93

Thanks mate!

Re: PPPL Colloquium: The Lockheed Martin CFR, Aug 6, 2015

Posted: Tue Aug 11, 2015 8:54 am
by zapkitty
Nice Lockmart backstab on aneutronic: "pB11 = 30 years away"

Redefinition of a "fighter" possible as most current fighter deployments are for ground attack missions... but if a chem-powered fighter or SAM can down the new fusion-powered behemoth then what advantage? Fighter escorts for the new "fighter?"

Radiation shell game... touts ability of radiation to improve superconductors over time but fails to mention a couple of things: that those beneficial results are only from heavy ion radiation and that the heavy neutron flux from a power reactor destroys superconductivity at close range... close range as in the interior coils of the Lockmart design.

So... business as usual :)

Re: PPPL Colloquium: The Lockheed Martin CFR, Aug 6, 2015

Posted: Wed Aug 12, 2015 3:14 am
by mvanwink5
It was well worth a second watch, and likely I will watch it one more time. I would be interested in what others might posit would be potentially the more compact machine, Polywell or LM's CFR (assuming DT for both). It would seem to me that the deciding design advantage metric would be MW/meter**2 exposure and limits of the cusp magnets. In that regard, it would seem LM's CFR with its central cusp magnet would reach a materials limit before Polywell as the CFR's central cusp magnet would seem to have closer proximity to the highest flux of reaction neutrons by being at the center of the machine's plasma. But maybe I am wrong.

The other parameter that may be just as important is shielding weight of one machine vs the other, and for that I am unsure which has the advantage (again I think Polywell, but it may be a six of one, half dozen of the other wash). Dunno.

And more difference is that the CFR is posited to not require external running plasma heating, whereas Polywell would likely need some steady state e-guns (not as great as the jump start guns for fast start plasma inflation, but there may be a workaround for jumping to cusp plugging beta = 1 condition other than gigantic e-guns).

Of course, compactness and gross weight are unimportant for utility power plants and even for ships (within reason). However for exotic applications such as air transports and space travel such details would seem to likely be deciding criteria.

Re: PPPL Colloquium: The Lockheed Martin CFR, Aug 6, 2015

Posted: Wed Aug 12, 2015 7:48 am
by crowberry
The size of the reactors is an interesting question, but I'm not sure we really know enough yet to answer that question. The question of shielding size is a trade off between the wanted lifetime of the magnets and the affordable replacement time. All D-T reactors will need replacement of radiation damaged parts CFR, Polywell and Spherical Tokamaks. So if you have a geometry that allows for fast service with little downtime then you might design for less shielding to be replaced more often to save weight.

Re: PPPL Colloquium: The Lockheed Martin CFR, Aug 6, 2015

Posted: Wed Aug 12, 2015 2:36 pm
by D Tibbets
The size is of course based on unproven assumptions, but a one meter distance from the center to the proximal surface of the two internal ring magnets. That would give a rough diameter of ~ 2 meters wide by perhaps 4-6 meters length. Add external magnets, lithium salt cooling blankets, etc, and a diameter of ~ 4 meters and a length of perhaps ~ 6-10 meters long. I suspect that this speculative dimension may be similar to a Polywell or FRC except the Polywell may not be as long and the FRC may be longer.

The need to generate tritium from a 'near' first wall of lithium- in this instance I think liquid lithium salt serving as both coolent and neutron capture implies few neutrons would reach the superconductors. There is still the surface of the coolent pipes and magnet cans that would get a high exposure. With D-T fusion with a lot of energy in the neutro,n the thickness of a liquid lithium blanket/ coolent would have to be considerably more than that needed in a D-D reaction for several reasons. This makes for greater distance from the electromagnet superconducting core and the B field at the surface of the cans. This suggests to me that the B fields may have to be significantly greater for the same amount of magnetic confinement.

I am of the opinion that D-T fusion machines are very problematic, handling the 17 MeV neutron, and needing to generate replacement tritium fuel are both confounding additional requirements over the basic fusion physics issues. Thus I believe that any scheme that is limited to D-T fuel and does not have at least the promise of operating with D-D fuel (perhaps the 1/2 D-D catalyzed reaction) is at a distinct disadvantage. This should lead to a preference for designs that may do this. Funding should be distributed accordingly. A D-D reactor and especially a D-He3 or P-B11 has so many advantages. This excludes the ease of physics proofing, but if D-T works, it is unlikely that it can be deployed economically. The cost/ benefit ratio is too high.

Dan Tibbets