Talk-Polywell.org

This "chipscale" laser device for fusion has been brievly discussed here before, IIRC. There is a small update on Next Big Future. No big news here, but the time is running out on the project. So maybe we will get to hear something (or nothing, since it is DARPA). Handheld fusion devices sure sound interesting (as do the other applications). I am just a layman, but the general idea does sound plausible. The big question for me is, will it ever have a Q>1?

Anyway, here is said update:

http://nextbigfuture.com/2009/12/compac ... s-and.html

Potentially a very rich field of research (and development) by he sound of it.

I read that EM noise is a big problem with experiments - there is just so much of it produced, right up into gamma, wipes out the detectors let alone the data.

For truly minaturised stuff though, i'd put my mony on approaches using quantum/Pauli principle.

Seems you cant get away from big fat lasers either way - whether for blatting, chirping or cooling.

added to my watchlist.

http://nextbigfuture.com/2009/12/quantu ... ts-at.html

Perhaps not so big and fat.

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Vae Victis

That is pretty cool if I read that right: 120 watts with a 400um wide device? That seems like a pretty decent size to output ratio. It also seems to work at room temp. Not bad.
I hope we will get to see some results from this, even though it is DARPA.
I love results!

You can buy 'hand-held' fusion reactors now, if you like.

http://www.nsd-fusion.com/

..but there is no prospect that such devices could return Q>1 with any technology currently known or even speculated on, especially the beam-solid target types as you are discussing as solid matter has too many energy-sapping electrons to take away any chance of success in this regard.

Such devices may have a place for specialist particle-generating capabilities (neutrons, in the case of nsd-fusion) but don't concern yourself with any prospect of energy generation just yet.

Well this DARPA project is aiming to achive a Q>20 even.
Pretty high goal then, I guess.

It's cobblers.

I guess, put enough project proposals in and eventually it gets signed off by someone who doesn't know the basics. Sorry, condescending to be sure, but beam into solid target is nonsense, for fusion power. Imagine if the applicants had put (genuinely) "Q>1e-9". Might not've got the funding then, I guess! Of course they're gonna put in "Q>20", else there's no point them asking for money in this crazy age of Alchemy. No "progressive" science any more - all-or-bust mentality only seems to get the attention these days.

I try not to be an arrogant elitist professional. I really do. But it's hard when outsiders spout nonsense that can be easily refuted by anyone who has had a single course in fusion physics. For those who might not know: Even if you can make a 0.5 MeV ion beam, and even if you can make it with 100% energy efficiency, when it slams into a solid target it will unavoidably lose more energy by heating the electrons in the solid than it will produce by fusion. This is true for D-T and it is 1000 times more true for p-B11.

Ok, cool then. I guess not handheld fusion reactors with a Q>1.
Oh well, would have been to good to be true
Still wondering how they got darpa funding though.

I don't think you need remotely apologise for being so, Art, if you choose to. There is too little of it these days, I think. That is not to say one should arrogantly put down, or ignore, things. What I would say is that there seems to be too much 'protectionism' over one's own research areas these days.

Rather than professional scientists simply actively making objective negative statements [like this; "...whaddabout the electrons..." - easy put-down in this case] they seem to clam up and no-one seems to actually progress a proper active dialogue on any topics these days. It all boils down to what gets publiushed as long drawn-out papers on obscure and arcane ideas that are so difficult to follow that the funding bodies seem to pay homage to the title of the comic it has appeared in, rather than actually taking a pragmatic and intelligent view on the actual physics content. I suspect this is exactly what has happened here - too many of the peer review panel have though "hmm... better let this through else someone might start looking at my ropey ideas".

Again, perhaps I am on the too-condescending side of things here but fusion science seems to be full of "Emperor's clothes" these days and someone needs to try to belt out the empty stuffing of some of these daft wastes of good [tax-payers'] funding money.

I for my part put a lot of weight on what Art says. If he says something has merrit, then it is worth a second look. If he says that something is off by a loooong shot, then it is not.

I don't see any condescension an all, Art.

What gets me is that perhaps the DARPA funders don't see Q>=~1 is impossible for solid target fusion, but the "researchers" making the funding requests do; Yet their absolutely bogus request for funding won't have negative consequence on their future funding requests.

There should be strong negative consequence for such proposals relative to future proposals, not because this line of research will fail, but because the request was based on false pretense in the first place. "Researchers" whom take funding through being fast and loose with the truth in the past should not get funds for future research.

Thanks for the explanation Art. Is there no theortical way around this limitation - eg. Fast ignition approaches, or use of electron/nuclear spin resonance?

The net output of any device will depend on the input energy of all types subtracted from all of the output energy of all types. Even if the input power only produces a tiny amount of fusions, you can still get usefull energy out if you can convert almost all of the waste energy/heat into useful energy. You might need conversion efficiency of the fusion energy AND waste heat/radiation energy at 99.999999935% . Lots of luck!

Dan Tibbets

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To error is human... and I'm very human.

a good reminder.
But still it can entail at least two methods i can think of, ie:
a) reduce the bandwidth of all side reactions/collisions, inefficiencies in the first place.
b) recycle them all (at some other efficiency) after they have occured.

(edit: maybe this is a sort of Quasineutrality view, 'in the large')

in either case, seems to me we might usefully consider the principles/methods of spectrography

i suggest that energies invoved with achieving approach a) are likely to be less than those for implementing b). therefore a) it is the logical direction to start. (though both, ultimately will be necessary)

re the 'Luck' thing, thanks. though i fear quite a lot of cash might be involved also.