LPP yields exceed NIF!
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markus7.
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July 13, 2011 at 9:50 pm #10306
jamesrParticipantAlthough interesting, the whole neutrons per Joule of input energy is pretty meaningless really for NIF unless they reach ignition at the centre of the pellet and have a burn wave that fuses enough of it before it blows itself apart.
July 13, 2011 at 9:53 pm #10307RezwanParticipantPlease elaborate. I’m not sure what you’re saying.
July 13, 2011 at 10:25 pm #10309jamesrParticipantThe NIF June update https://lasers.llnl.gov/newsroom/project_status/2011/june.php has more details on their progress.
From this you can work out figures. They quote, for example 4.5×10^14 neutrons from 1.33MJ of ultraviolet energy to the target, however the lasers are less than 1% efficient so they would have used around 330MJ of electricity.
So 4.5×10^14/330×10^6 = 1.4×10^6 neutrons/input_JouleIn all the recent DT shots they have not yet reached ignition, and only fuse a tiny fraction of the pellet. If they do, the yield will go up by several orders of magnitude.
There is a caveat though: Even if they reach ignition at the centre it is not yet clear whether the alphas produced heat the surrounding compressed plasma enough to create a fusion burn wave progagating out from the ignition point in the centre.
If the compressed plasma is either re-expands faster than the burn wave propagates, or the alphas fly out of the compressed region before depositing enough energy to heat the rest of the fuel to fusion temperatures then the whole thing will have been a bit of a waste.If the burn wave succeeds in fusing more of the plasma than just the central ignition region then the neutron yield will go up by a few more orders of magnitude.
July 13, 2011 at 10:37 pm #10310markus7Participantjamesr wrote: Although interesting, the whole neutrons per Joule of input energy is pretty meaningless really for NIF unless they reach ignition at the centre of the pellet and have a burn wave that fuses enough of it before it blows itself apart.
Jamesr, so an NIF supporter might argue that while neutrons per joule are low now, an initially ‘small’ incremental increase in neutrons that triggers ignition at the center of the pellet will increase neutrons/per input joule by many orders of magnitude? That is, the NIF can expect low yields until they achieve ignition, which will provide a step function to high yields.
In contrast, the DPF will not show such a strong discontinuity in approaching a practical level of output energy to input energy?
EDIT at 4:39
I did not see your #3 post above before posting this. In light of your second post, what do you think about the relative linearity we should expect in DPF devices since they do not depend on ‘ignition’ in the same way.
July 13, 2011 at 11:48 pm #10311RezwanParticipantThere are many variables between this present differential in n/J and ultimate project success. I had suggested adding the following to the press release to clarify the road ahead, but that didn’t happen.
While a lead in neutrons per joule is a great indicator, success is ultimately dependent on scalability from a small experiment to one that makes net power. This, in turn, is dependent on follow through and commitment to the experiment, in short, consistent funding and support. NIF researchers hope to achieve ignition (more energy out than in) within a year. They then hope to improve efficiency in a project called LIFE in the coming years, but LIFE’s funding is far from assured. LPP expects to widen its lead as early as this month as major upgrades to FoFu-1 are completed. FoFu-1 must then improve its performance by several orders of magnitude to demonstrate the feasibility of net energy.
Lack of public commitment to the fusion endeavor leads to a paucity of projects. To judge from the work of most scientists at the conference, an observer might think that there were only two approaches to fusion: NIF and ITER. These two approaches receive the bulk of government fusion funding, in an ever more fiscally austere funding environment. Many fascinating, fusion approaches are not pursued for lack of funds, and private investors have only recently begun to explore the possibilities of fusion. It is hoped that positive results in small scale projects encourages decision makers to expand both private and governmental fusion investment to include far more ideas, particularly LPP’s “lightning in a bottle.”
They said it sounded like begging, a bit of a downer. “Keep it simple”. But given the variables involved in the road to ignition, I thought this was a good way to go.
July 14, 2011 at 12:23 am #10312jamesrParticipantI did not see your #3 post above before posting this. In light of your second post, what do you think about the relative linearity we should expect in DPF devices since they do not depend on ‘ignition’ in the same way.
I don’t think either approach will be at all linear in their yield improvements.
Also since Focus Fusion never intends to use D-T using neutron count long term will be pointless (since we want as low a neutron count as possible with pB11). I think it would be better to quote yield as (Fusion energy released)/(Energy In), then later we can add figures for the recoverable portion of that energy, and finally the actually recovered portion.
In terms of fusion energy released I would expect less improvement between the first pB11 shots on FoFu-1 at full operating voltage, (so ignoring early low voltage test shots) and a final optimised pB11 shot in FoFu-1, than I would between NIF D-T shot currently and a D-T ignition at NIF.
NB. in ICF I take ignition as the point of starting a fusion burn wave, not necessarily more energy out than in. Whereas in MCF such as tokamaks, the ignition point implies a self sustaining reaction without the need for any more outside heating (although some may still be present to drive current for stability reasons)
July 14, 2011 at 2:50 am #10317zapkittyParticipantjamesr wrote:
Also since Focus Fusion never intends to use D-T using neutron count long term will be pointless (since we want as low a neutron count as possible with pB11)If pB11 works out as hoped then there will be some interesting looks on some faces when the Big Fusion backers are told that high neutron counts have suddenly become an indicator of waste, not efficiency.
July 14, 2011 at 5:59 am #10318LernerParticipantLPP too is seeking ignition. That would occur in a pB11 plasmoid if the fusion power produced exceed x-ray losses,os the plasmoid heats up from not only the beam heating but also the retained fusion energy in the trapped helium nuclei produced by fusion.
July 14, 2011 at 7:27 am #10319markus7Participantjamesr wrote:
I think it would be better to quote yield as (Fusion energy released)/(Energy In), then later we can add figures for the recoverable portion of that energy, and finally the actually recovered portion.
I certainly agree from a technical standpoint. However, part of the “charm” of quoting neutron production, in addition to showing a higher production efficiency than the best known competitors, is that neutrons are definite proof of fusion for people who might otherwise be suspicious of LPP results.
September 6, 2011 at 5:50 pm #1194RezwanParticipantCheck out LPP’s latest press release. Great stuff!
People have been saying that NIF has much greater fusion yields, and they do. But taking a look at the amount of energy put in to get those yields actually puts LPP’s experiment ahead! Very exciting.
Can they keep the lead? Which group will reach ignition first? Great times ahead for both projects!
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