U.S. Laboratory Breaks Laser Record | Hacker News Reader

U.S. Laboratory Breaks Laser Record

npr.org

37 points3lit3H4ck3r25 comments

Sorry, but The goal of the facility is to validate simulations of Hydrogen Bombs and test high energy laser not to generate net energy as they don't have anyway to capture energy produced in this test.

Still cool though.

But validating simulations of hydrogen bombs is fusion research, isn't it?

Except not all fusion research is particularly useful for building a fusion power plant. I mean if we where really desperate we could dig a large hole fill it with water, set a H-Bomb off under it and then extract energy from that water. However, while that works the ROI is rather limited compared to say just extracting geothermal energy in the first place.

PS: That could actually work, at 5% thermal efficiency a Castle Bravo device ~= 63,000TJ = 17500000000.014kwh *.05 = ~1GW for 1 month.

It couldn't work on that scale, because it's not practical to contain that big of an explosion. This is your Castle Bravo crater; it's more than a mile wide.

http://goo.gl/maps/KEfZ

Moreover, about 2/3rd of the energy in that device were from fission (not fusion), so for any possible claimed advantage of fusion over fission, it's not here. The lowest fission-fraction test to date was Tsar Bomba, at 3% yield from fission. That was also the largest explosion to date (50 megatons!), which makes it even less feasible.

I think this is a fundamental tradeoff: you can't make a mostly-fusion weapon unless it is extremely large, as there's some minimum size for a fission explosion that achieves fusion conditions.

http://nuclearweaponarchive.org/Usa/Tests/Castle.html

http://en.wikipedia.org/wiki/Tsar_Bomba#Design

There was research project at Los Alamos about this general idea (Project Pacer), but it didn't go anywhere. According to Richard Garwin, they thought it was hopelessly uneconomical.

http://en.wikipedia.org/wiki/PACER_(fusion)

http://www.aip.org/history/ohilist/4622_3.htmlz

Not exactly. Or to put it more precisely, the goal is to better understand fusion, which by the way, helps us better understand bombs that use it and perhaps more importantly the old bombs we have laying around that we knew would work in 1974 but now we aren't so sure.

That said, one application of the NIF is as the ultimate incinerator. Using it to literally rip apart hazardous waste (either the nuclear or more mundane variety) into lower atomic number atoms which are not a problem.

And of course if they can get out more than they put in, then an energy neutral (and fast) disposal system.

That said, the physics of the place are astounding, I got to tour the place about 10 years ago when it was still being built and man, it is right up there with the LHC in terms of extremely large and at the same time precise physics machines.

How?

In the tour video they show a stream of plasma directed at the 'waste' of interest. This has two effects, one it disassembles any molecular bond reducing complex (and perhaps toxic) substances into their base atomic components, and two it accelerates the decay of unstable nucleotides into stable ones. I suspect that video is up on the NIF web site somewhere.

That's real but that's not NIF or anything resembling it. The temperatures to tear apart molecular bonds are less than 10,000 degrees. NIF operates at nuclear fusion temperature s -- 100,000,000 degrees.

http://en.wikipedia.org/wiki/Plasma_gasification

http://www.netl.doe.gov/technologies/coalpower/gasification/...

https://lasers.llnl.gov/programs/science_at_the_extremes/

That may be the goal they sold to Washington, D.C., but the real goal was to develop high power laser technology. "Nuclear stockpile stewardship" was just a way to keep the tokamak politicians from killing the project out of spite.

Where do you get this impression? I'm a grad student at Los Alamos National Lab, a partner of Lawrence Livermore and a major contributor to NIF. I don't do nuclear physics, but I've attended a couple talks on NIF and spoken to several of the contributing physicist. The impression I get is that the number one purpose of the NIF is stockpile stewardship. Fusion energy research is a side project which is highlighted mostly for public relations.

In particular, I never hear anyone talk about the laser technology in anything but instrumental terms. (Instrumental to understanding the nuclear physics.)

They'll spend at least $5 billion on the project. That is enough money to completely remanufacture the entire arsenal several times using existing designs that are good enough.

They have been working on laser fusion since the 1970s, when they could test bomb designs by just setting them off. Indeed some of the early inertial confinement research was conducted using nukes as the radiation source.

Yes, it is true that the NIF data can be used to design and maintain bombs, but it is not required. We could provide a deterrent force without it. Therefore the real reasons are something else, my guess a combination of laser research, commercial and rocketry fusion research, and a large serving of national prestige.

> They'll spend at least $5 billion on the project.

That's stretched well over a decade. The US's stockpile stewardship program cost billions per year; only a fraction of it goes to the NIF.

> That is enough money to completely remanufacture the entire arsenal several times using existing designs that are good enough.

That's not an option. The US has been sticking to a policy of not building new nuclear warheads. All of our warheads are at least 20 years old.

If you're in the Bay Area, the LLNL tour [1] is well worth it. Ever seen an 800-pound crystal [2]?

[1] https://www.llnl.gov/about/tours.html [2] https://lasers.llnl.gov/multimedia/photo_gallery/overview/?i...

Sorry guys, I'm having an off day.

Can someone explain this a little bit? They were able to put 500 terawatts into this beam, I think I understand that part. But that's 1,000x more energy than the US is using right now.. so did they actually create that much energy to begin with? This is where I'm failing at understanding.

A watt is a unit of power, not energy. Power is energy per unit time, so NIF works by storing large amounts of energy in capacitor banks (transferring it from the grid slowly) in preparation for a shot and then releasing all of that energy over a very short timespan. Since the timespan is short, the power to target is extremely large.

An example to back you up: if the laser pulse was 1 nanosecond, the energy required to make the beam a 500 terawatt beam would be 500 kJ, or the energy released by the combustion of one gram of gasoline

http://www.wolframalpha.com/input/?i=%28500e12+Watts%29+*+%2...

*Edited because of wrong numbers

Once I got the "for dummies" (Thanks james!) I immediately made the connection that it was an extremely short pulse-

However that really puts it into perspective, thank you.

They spend 60 seconds charging 400 megajoules of capacitors, then they discharge them in a half-millisecond pulse. The peak electrical power is one terawatt. The laser compresses this pulse further, so that the light pulse is only 3 nanoseconds long, but with a peak optical power of 500 terawatts.

https://lasers.llnl.gov/about/nif/how_nif_works/power_condit...

https://www.llnl.gov/news/newsreleases/2012/Jul/NR-12-07-01....

I took a tour of the NIF on Monday. The guide mentioned that the actual electrical cost of powering the lasers for a shot is about $5. Air conditioning is a bigger cost, because they have to keep the building at 68F +/- 0.5 degrees, in the Livermore summer (110 degrees is common).

Someone can probably explain this, but it seems odd that they took 192 beams to produce "about 100 times what any other laser regularly produces today." The semantic error aside, excluding the other most powerful lasers, how do you put together 192 beams and only get 100 times the power of an individual beam? Discuss...

Mostly, "about 100 times what any other laser regularly produces today" doesn't make any sense unless you include a timespan reference (since energy accumulates over time). Unless I'm being thick and "today" is a timespan reference (i.e. "24 hours") rather than a preposition (i.e. "currently").

192 laser beams to make one monolithic laser. They're saying that the monolithic laser is 100 times more powerful than any other monolithic laser out there.

There are two concepts "laser" here. They have 192 lasers and manage to combine their beams so that the resulting beam still is coherent. Because of that, they call the combined device "a laser", too.

I guess that "any other laser" similarly may be made of a bunch of other lasers. So, tha factor 100 is more "a hundred times as much power as any other coherent beam ever produced"

Did they put the lasers on a shark yet?

The National Ignition Facility is fully operational -- NIF Director Edward Moses

Fire at will, Commander -- The Emperor

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