The NIF is convincing the News Media that they have achieved Net Gain.
Color me Skeptical. But, here is a link to an article that illustrates what you
get when you let a scientific illiterate cover the fusion beat.
Nuclear fusion has finally achieved a breakthrough that could soon allow the production of massive or even unlimited amounts of cheap clean energy. For the first time, a nuclear fusion reaction has been created that produced more energy than the was absorbed by the fuel in making it. Scientists are enthusiastic that this most recent milestone could solve the world’s energy crisis.
I think here’s the key point:
An experiment at the National Ignition Facility of Lawrence Livermore National Laboratory is the first time in history that a human-created nuclear fusion reaction has been proven to create more energy than [em]the amount absorbed into the reaction itself[/em].
In other words, this is not “more energy than was used”, merely “more energy than was [em]absorbed[/em]”. Lasers are not super-efficient, and much of the energy put into them comes out as heat, so this estimation does not include that, or any other inefficiencies. This is not “theoretical breakeven”, at least not as I’ve seen it defined.
The positive achievement was a nearly 10-fold jump in fusion yield from last year. With 400 MJ into the laser and 8kJ of fusion this is clearly not what most people think of as break-even.
only five orders of magnitude to go
Its not even “more energy than was absorbed” really, as they’re just counting the proportion absorbed in the compressed core of the pellet not the large fraction absorbed in the ablative outer layers (or by the hohlraum).
As far as I’m aware the big achievement is that the experimental yield is only a few percent away from the simulations – something that has dogged them for years. If the simulations now match that indicates they mostly understand the processes involved.
jamesr wrote: If the simulations now match that indicates they mostly understand the processes involved.
Or it might just mean they have a set of perfectly compensating errors. 😉
LLNL has made an official announcement:
LIVERMORE, Calif. – Ignition — the process of releasing fusion energy equal to or greater than the amount of energy used to confine the fuel — has long been considered the “holy grail” of inertial confinement fusion science. A key step along the path to ignition is to have “fuel gains” greater than unity, where the energy generated through fusion reactions exceeds the amount of energy deposited into the fusion fuel.
Though ignition remains the ultimate goal, the milestone of achieving fuel gains greater than 1 has been reached for the first time ever on any facility. In a paper published in the Feb. 12 online issue of the journal Nature, scientists at Lawrence Livermore National Laboratory (LLNL) detail a series of experiments on the National Ignition Facility (NIF), which show an order of magnitude improvement in yield performance over past experiments.
The paper (or the abstract, for those who haven’t paid for access to the full article), “Fuel gain exceeding unity in an inertially confined fusion implosion”, can be found here.
Well, I think its impressive. True, just because you produce more energy than you consume does not necessarily mean you can extract it (esp with a heat exchanger). Since the Carnot Eff is 50 percent (MAX) if I produce 3 thermo-watts more than I put into the system I still won’t have enough power to make a decent cup of coffee. Still, the Wright brothers only flew 100 ft and 50 years later we were flying at Mach.
From LPP’s February 2014 report, available here.
Russian lightning steals NIF’s thunder
[em]Plasma focus research moves forward as Russian device hits 30 J with deuterium-tritium[/em]
Many news outlets widely—and inaccurately—reported new results from the huge National Ignition Facility (NIF) as achieving the long sought-after goal of breakeven for fusion. What NIF in fact reported was a fusion yield of 17 kJ, more than the energy actually absorbed by the fuel pellet. The total input energy to the machine was far larger—some 500 MJ, so that 1 J of fusion was produced for each 30,000 J of input. This was indeed a big step upwards for NIF researchers but far from breakeven.
Meanwhile, science news reporters overlooked a major accomplishment in fusion a year ago by Russian researchers using a plasma focus device. These researchers performed their work at the Russian Federal Nuclear Center, All Russian Scientific Research Institute of Experimental Physics, in Sarov. They reported fusion yields of 30 J (1.3 x 10^13 neutrons) with the same deuterium-tritium fuel used by NIF. Since the total energy fed into the capacitors was 135 kJ, the Sarov team achieved a fusion yield of 1 J per 4,500 J of input, more than six times better than the NIF results. (The record for any DT fusion experiment is the JET tokamak in the UK, which in 1997 produced 1 J of energy per 450 J of input.)
While LPP’s FF-1 device is not intended for use with DT fuel, it is useful to compare our results with those of the Sarov machine when using pure deuterium, a far less reactive fuel. With pure deuterium (D), Sarov produced 1 J of output per 2.2 MJ of input. FF-1’s best results are 1 J of output per 400 kJ of input, about four times better. (The best results for any plasma focus using pure D are around 1 J for 100kJ of input, about the same as the best results ever obtained for tokamaks using the same fuel.)