[ Ivan Dimkovic @ 08.10.2013. 11:02 ] @


Researchers at a US lab have passed a crucial milestone on the way to their ultimate goal of achieving self-sustaining nuclear fusion.

Harnessing fusion - the process that powers the Sun - could provide an unlimited and cheap source of energy.

But to be viable, fusion power plants would have to produce more energy than they consume, which has proven elusive.

Now, a breakthrough by scientists at the National Ignition Facility (NIF) could boost hopes of scaling up fusion.

NIF, based at Livermore in California, uses 192 beams from the world's most powerful laser to heat and compress a small pellet of hydrogen fuel to the point where nuclear fusion reactions take place.

The BBC understands that during an experiment in late September, the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel - the first time this had been achieved at any fusion facility in the world.

This is a step short of the lab's stated goal of "ignition", where nuclear fusion generates as much energy as the lasers supply. This is because known "inefficiencies" in different parts of the system mean not all the energy supplied through the laser is delivered to the fuel.

But the latest achievement has been described as the single most meaningful step for fusion in recent years, and demonstrates NIF is well on its way towards the coveted target of ignition and self-sustaining fusion.

Vrlo zanimljivo!
[ ventura @ 08.10.2013. 19:39 ] @
I jedan vrlo interesantan komentar na temu:

I posted this in r/science but maybe there will be some high energy density physicists in here who would be interesting to talk to as well, so I'm going to cross post here too.
Yes, the title contains the phrase "fusion milestone passed", plz refrain from moistening your collective nuclear panties.
The BBC story gives almost zero useful detail here, as is to be expected from them on big science stories when the byline isn't my boy Pallab Ghosh <3. However, it appears an internal email of NIF relevant to this "milestone" was leaked to the local Livermore rag, The Independent, in which the following interesting information is conveyed and from which we can infer quite a lot:
"According to the email from program leader Ed Moses, in Saturday’s experiment, NIF fired 1.8 million joules of energy along its 192 arms, generating a record 15 quadrillion neutrons from a frozen heavy hydrogen (deuterium-tritium) target with an energy output nearly 75 percent higher than the previous record."
This, while interesting, is NOT something to flip out over, as I will explain in detail why below. Also notice that while the BBC doesn't the word "breakeven" (the specific fusion parameter of Q≥1) outright, that is indeed what they are claiming has occurred here when they say:
"The BBC understands that during an experiment in late September, the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel."
This is a highly dubious claim and I strongly suspect some very creative number fcking is going on behind the scenes if this is indeed the claim being made by NIF. Since we can easily deduce the total energy released by fusion reactions in a shot with a credible yield of 1.5x1016 (15 quadrillion) neutrons each possessing a kinetic energy of 14.1 MeV as must be the case in deuterium tritium fusion reactions of the kind this laser is attempting - the answer is ≈40 Kilojoules - there is obviously some accounting to be done between that number and the number of Kj the target likely absorbed.
Now, the laser itself consumes about a hundred metric FUCKTONS of energy to fire a single shot: the capacitor bank that fires the thousands of enormous xenon flashlamps to pump the neodymium doped laser glass of the system together consume nearly HALF A GIGAJOULE of electricity when charging up. Clearly that is NOT the comparison they're making to that 40Kj of fusion energy out that would meet breakeven. What about the energy of the laser itself, maybe that's the comparison? No. NIF produces 4 megajoules in 192 beams of near-infrared radiation which is then frequency converted to the ultraviolet for a total of ~2 Mj of 351 nanometer UV laser light. Clearly that is not the comparison either. What about the thermal x-rays inside the gold hohlraum in which the fuel is contained and on which the lasers impinge that's depicted in that inset picture in the article? Nope, there's about a megajoule of x-rays inside that little pencil eraser sized oven at the bangtime. Ok, well then what about the total energy of x-rays actually delivered to the BB sized hydrogen fuel capsule surface itself during the actual microballoon ablation and implosion drive of the fuel? NO. After all that, about 200 Kj of x-rays are being delivered to the capsule during the 10 nanoseconds of fuel assembly and adiabatic compression.
So HOW did this notion of breakeven start to get bandied about somewhere behind the scenes here? Well the only way I can see, is that they're using the energy actually deposited inside the compressed hundred micron diameter ultrahot core of the imploded fuel pellet at the time of maximum compression and density which, considering the inefficiencies of core compression and ablative blowoff of the rest of the outer layers of the core during assembly, MAY approach the low end of the ~50-100 kilojoule range. That's pretty damn deceptive if you ask me. 40Kj out with 400+ MJ in = hilariously abysmal wall plug efficiency.
Why am I being so critical? Because this device was sold to the public as AN IGNITION MACHINE. The scientists working on the project over the past 2 decades were so confident that it would achieve ignition and burn with very high gain factors of Q>100 in some simulations that they put the word ignition in the goddamn title of the project. It is now clear, in spite of "hopeful" stories like this one that they seem to be pumping out with strange regularity, that NIF will NEVER achieve ignition, and that is because the gap between the current fusion yields, even the latest one they're singing hosannas about here that's nearly 2X the last highest yield achieved last year, are still well over an order of magnitude away from achieving the goal of ignition. And nobody has the slightest fcking clue why. There are practically innumerable energy sapping mechanisms that suck energy away from an imploding capsule during a shot: stimulated Brillouin scattering, x-ray heating of the hohlraum, stimulated Raman scattering, two-plasmon decay, Rayleigh-Taylor hydrodynamic instabilities in the imploding fuel layers, inverse electron-cyclotron resonance heating of the electrons in the capsule blowoff plasma, etc., etc., etc., etc. and just like all the previous huge laser fusion experiments done since the 70s, nobody knows where the excess energy leakage is going on these new experiments. Everyone thought that this was going to be it, that 2 MJ of UV radiation was going to be enough to get this shhit done. Well it wasn't, and this is now the sad, ignominious, devastating 4 billion dollar end of the road for laser fusion.
[ Ivan Dimkovic @ 09.10.2013. 10:36 ] @
Zanimljiva analiza.

Ako se ispostavi kao tacna, i ako je obmana rezultat rada ljudi zaposlenih na projektu onda ti ljudi koji su bili zaduzeni za publikaciju moraju biti otpusteni.

Inace, tajming je isto zanimljiv:



Scientists have come one step closer to harnessing the power of the sun. Researchers at the National Ignition Facility (NIF) have passed a milestone in achieving self-sustaining nuclear fusion -- but you won't hear about it from the researchers. The NIF team has been furloughed as a result of the U.S. government shutdown, which began on Oct. 1, and is not releasing updates to the press.

[ Nedeljko @ 21.10.2013. 10:57 ] @
Političari svih zemalja, siđite sa vlasti zato što ste lagali i obmanjivali narod!

Mislim da nauka ne funkcioniše tako. Rezultati se objavljuju u naučnim časopisima, koji imaju recenziju. Ako kriterijumi nisu zadovoljeni, on ne sme da prođe recenziju. Ono što časopis ne može da proveri, to je da li je eksperiment zaista izvršen ili su rezultati našarani onako kako autorima odgovara ili čak proizvoljno. Zato eksperiment mora da bude ponovljiv i proverljiv. Ako neko falsifikuje ishod eksperimenta ili posmatranja u naučnom časopisu, to je za diskvalifikaciju. Isto i ako se dokaže da je svesno prisvojio nečiji rezultat (tj. znao je da takav rezultat postoji). To šta će da blebeće po televiziji za nauku uopšte nije bitno. Uzmi primer Stivena Hokinga, koji prodaje naširim narodnim masama priče koje ne može da proda svojim kolegama. Lupa u javnosti šta mu padne na pamet, pa niko ne reaguje. Međutim, njegov rad iz 1972 u kome je dokazao da singulariteti nisu svojstvo samo poznatih modela OTR, već same teorije, tj. da se moraju pojaviti u svakom modelu OTR, je vrlo cenjen.
[ Ivan Dimkovic @ 21.10.2013. 13:57 ] @
To šta će da blebeće po televiziji za nauku uopšte nije bitno.

Na televiziji nije bitno (donekle) - medjutim ako je neko zaposlen u odredjenoj instituciji, i u svom zvanicnom polozaju iznosi netacne informacije za koje zna da su falsifikovane, to je dovoljan razlog za disciplinsku akciju ili otpustanje.

Problem je u tome sto su naucne institucije osim svojih naucnih aktivnosti, takodje, u poslu dobijanja resursa od strane drzave (obicno iz budzeta). Problem sa laznim PR-om, recimo, je sto moze da utice na alokaciju resursa i time nanese stetu celom stanovnistvu zbog ulaganja novca u projekat koji je, recimo, poznat kao neizvodljiv ali se to svesno prikriva. Zbog toga mora postojati odgovornost i u tom smislu.

Jasno je da za ciste naucne rezultate postoji uhodan sistem provere kroz peer-review kao i ponovljivost eksperimenata (mada i tu postoje komplikacije kada su enormni eksperimenti u pitanju koje nije moguce proveriti bez ulaganja milijardi - mada i tu postoje nacini da se mogucnost greske minimizuje kroz peer review samih eksperimenata, uslova i opreme a ne samo rezultata). Medjutim u ovakvim slucajevima nisu samo naucni rezultati na tapetu, vec i alokacija novca.

Kada bi ti li ja, recimo, podneli zahtev drzavi za, recimo, neku pomoc - i svesno lagali na formularu, mi bi smo bili krivicno odgovorni.

Tako isto i neka institucija, mora biti odgovorna za postupke koji su vezani, takodje, za alokaciju resursa od strane drzave.

To nije naucno pitanje, vec zakonsko.

Ne kazem da u ovom konkretnom slucaju postoji neka neregularnost - ali ako se ispostavi da je ono sto su neki ljudi pisali tacno, tj. da je doslo do vrlo upitnog "masiranja" rezultata, onda definitivno mora doci do istrage i, eventualnog, kaznjavanja pocinjenih zato sto se ovde ne radi samo o nekakvoj cistini naucnog istrazivanja i ponovljivosti rezultata, vec verovatno i o aktivnosti koja je usko vezana za konkretna ulaganja poreskih obveznika.
[ Nedeljko @ 21.10.2013. 22:07 ] @
Ivane, ti živiš u nekom nadrealnom svetu. U ovom mom se pare kradu i to masovno. Šta misliš, od onih milijardi za LHC, koliko je otišlo u privatne džepove? Ja ne znam, ali ubeđen sam da je procenat dvocifren. Postoji jedan izraz - alfa fizičar. Šta misliš šta on označava? Razne ustanove koje se finansiraju iz budžeta (što je OK) imaju potrebu da naduvavaju svoj značaj. Nauka tu nije nikakav izuzetak.
[ Ivan Dimkovic @ 21.10.2013. 22:34 ] @

Ne zivim ja u nadrealnom svetu - vec samo konstatujem sta bi trebalo da se desi ako je zaista doslo do manipulacije rezultata.

Da li ce se tako nesto desiti ili ne (ako se ispostavi da je u pitanju laganje, naravno) to je sasvim drugo pitanje. Vrlo verovatno se nece nista desiti ako je politicka uvezanost institucije dobra - ali, ko zna, mozda i hoce - i najbolje uvezana osoba ili institucija nije 100% bez rizika, zbog faktora na koje nema uticaja. Politicki termin je "pustanje niz vodu" - i postoji sa razlogom ;-)

Ali, elem, sve to je upitno posto je u ovom konkretnom slucaju sasvim moguce da je izvor konfuzije zapravo BBC novinar, posto je samo BBC izasao sa ovim, svi ostali se linkuju na njih.
[ Nedeljko @ 21.10.2013. 22:59 ] @
Eh, šta bi sve trebalo da se desi u smislu neke kosmičke pravde. Ja ti kažem da su ovakve stvari svakodnevne i da na njih niko ne obraća pažnju. Nisi nikada čitao obrazloženja predloga projekata, pa ti ovo izgleda neobično. U obrazloženjima predloga projekata po pravilu piše da će svinje da polete, samo ako se gurne kinta.