Laser Fusion Passes Major Hurdle 354
chill writes "The National Ignition Facility at Lawrence Livermore National Laboratory has performed their first controlled fusion experiments using all 192 lasers. While still not ramped up to full power, the first experiments proved very fruitful. The lasers create a lot of plasma in the target container and researchers worried that the plasma would interfere with the ability of the target to absorb enough energy to ignite. These experiments show that not only does enough energy make it through, the plasma can be manipulated to increase the uniformity of compression. Ramping up of power is due to start in May." The project lead, Dr. Sigfried Glenzer, is "confident that with everything in place, ignition is on the horizon. He added, quite simply, 'It's going to happen this year.'"
Re:Terminology ? (Score:5, Informative)
Ignition means more fusion energy released than laser energy in. Yes, there are issues in scaling it up, but none that are known to be insurmountable. Already there have been experiments to look at target injection (a 2 GW power plant would be at the 5 - 10 Hz region), high rep-rate lasers (Mercury is an example of a high power, high rep-rate laser) and the lining up of the laser in this situation requires less precision than that of anti-missile systems that are around.
Also the Hohlraum approach is unlikely to be used in a power-plant, as it doesn't give the biggest energy gains, so this is basically a significant step towards projects such as HiPER [hiper-laser.org]. If NIF achieves success in ignition as is widely expected the money should be around for projects like HiPER.
Re:So... (Score:4, Informative)
Just don't take it any faster than 85 miles an hour.
Unless you want to visit the '80's, the '50's, or the old west.
It's actually 88 miles per hour.
Ignition = net positive energy (Score:4, Informative)
By definition, when they achieve ignition - there will be a self sustained, fusion reaction - the fusion reaction will sustain itself until its fuel is exhausted. More energy will be produced than was put in - a net positive in energy.
Of course there isn't any mechanism in NIF to collect the energy, but thats not really the point of the project...
Re:Yes, but is it REALLY working? (Score:5, Informative)
And, let's admit everything works: what quantity of nuclear waste will such a machine produce? And of what type?
Don't give me the "it's fusion, so it's clean, duh" line: this machine is going to generate an enormous amount of energy and a lot of that will in the form of a "carefully controlled thermonuclear explosion" (BBC dixit) -- which means radiation, which also means neutrons. And neutrons are not really good for your health.
Later in TFA it says they'll eventually be fusing a fuel containing a mix deuterium and tritium. Deuterium-deuterium fusion yields tritium and a neutron, and deuterium-tritium fusion yields helium-4 and a neutron. So the byproducts are Helium-4 (not radioactive in the slightest) and neutrons.
High energy neutrons are very bad for you, yes, but that just means you won't be standing near the unshielded reaction chamber. It's not like you have to dump a big pile of poisonous neutrons somewhere. The neutrons will affect the containment itself, but the biggest problem there is just that it becomes brittle, not necessarily radioactive.
It is basically true that fusion is clean. The waste is minimal.
Re:Ignition = net positive energy (Score:3, Informative)
More energy will be _released_ than was put in - a net positive in energy.
your don't produce energy. you release it. just saying.
Re:Ignition = net positive energy (Score:4, Informative)
uh... you must have a different definition of self-sustained than I do. Just because it isn't a star doesn't make it a failure. This isn't an infinite energy source they are producing. Its just one that will create a nuclear fusion reaction that doesn't require any more outside help to continue.
The reaction will be self-sustained until the fuel (a single tiny pellet) is exhausted.
Comment removed (Score:3, Informative)
Re:fusion has radioactive waste (Score:2, Informative)
This isn't strictly true. While the fusion reaction itself doesn't leave long-lived radionuclides that have to be disposed of, the fusion process generates neutrons with such high energy -- much higher than in a fission reaction -- that the shielding itself becomes activated. Additionally, since the interior of the reactor is exposed to such high flux, it degrades and has to be replaced. These both result in radioactive waste that have to be dealt with. Most of what I've read suggests that, indeed, the half-lives of most of the materials created this way are very much shorter than the waste that comes out of the non-reprocessed fission reactors in the U.S.A., but it's not negligible.
IAAHP (I Am A Health Physicist)
Re:Please calm down... (Score:4, Informative)
Nothing in the article or summary said the temperature was important. Temperature is a bit more of an abstract concept in this type of experiment, as the overall energy is small (kettle boiling energies). For fusion however it's temperature x density x volume that's the important thing, and laser fusion achieves very high densities.
The important points were that a) this is a record laser energy and b) the absorption in the holhraum from the laser was 95%, much higher than was expected. This means gain in a target (ignition) is looking very likely.
*I'm also in the field
Re:So... (Score:3, Informative)
Rare earth elements aren't actually that rare, and many are quite abundant. It's just one of those holdover terms, like using "atom" for describing something that isn't indivisible.
Re:Terminology ? (Score:5, Informative)
I agree with most of what you said but I don't know where you got "and the lining up of the laser in this situation requires less precision than that of anti-missile systems that are around". That's definitely not true. Laser irradiation on a direct drive target for ignition requires exquisite precision. We recently demonstrated a significant hit on fusion yield in implosions of cryogenic, layered deuterium tritium ice capsules when beam pointing was off by TEN MICRONS. If you're injecting targets into your reactor chamber at 10Hz, you are going to need some serious, super accurate laser pointing unless you want your fusion yield to be severely diminished. That means real time tracking of the target with hundreds of final focusing lenses that are all about 10 meters (at least) away from the target chamber center. Good luck!
You don't even want to get into the problem of the cryogenic microcapsules melting before they reach the target chamber center. I've seen DT ice filled microcapsules melt, boil and explode within ~3 seconds of exposure to the thermal radiation from the inner wall of the TC at ambient temperature. Wanna take a guess as to how much that time is going to be reduced when your TC is at 800 Kelvin reactor operating temperature? Yeah, that means you are going to need to inject the pellets at extremely high velocity to minimize the thermal exposure time, and your lasers will then have to track it that much faster. Furthermore, how the hell do you deal with the horrible vibration on your focus lenses created by detonating the equivalent of roughly 50 pounds of dynamite (200 MJ) in the TC at 10Hz. Yeah... I'm as excited about this as anyone, but we have a LOT of problems still left to solve.
Polywell (Score:3, Informative)
Re:Terminology ? (Score:3, Informative)
I agree with most of what you said but I don't know where you got "and the lining up of the laser in this situation requires less precision than that of anti-missile systems that are around". That's definitely not true. Laser irradiation on a direct drive target for ignition requires exquisite precision.
I think you seriously underestimate the precision required for missile defense.
10 micrometer at a distance of 5m corresponds to about 60cm at 300km.
True the beam is 1.5m across as it leaves the mirror but due to atmospheric turbulence you can never be quite certain which parts of the laser are gonna hit the target so I'd say despite all those factors mentioned above it still achieves higher precision.