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U.S. Laboratory Breaks Laser Record

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Re: U.S. Laboratory Breaks Laser Record

#11

Post by uvdiv »

ChuckMcM wrote: post #6
Retric wrote: post #2

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.

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 mund…

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.

How?

Re: U.S. Laboratory Breaks Laser Record

#12

Post by MSM »

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.

Re: U.S. Laboratory Breaks Laser Record

#13

Post by jamesfrank »

MSM wrote: post #12

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.

Re: U.S. Laboratory Breaks Laser Record

#14

Post by madvoid »

jamesfrank wrote: post #13
MSM wrote: post #12

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

Re: U.S. Laboratory Breaks Laser Record

#15

Post by uvdiv »

Retric wrote: post #4
Cushman wrote: post #3

Earlier quoted context omitted.

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 Cas…

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

Re: U.S. Laboratory Breaks Laser Record

#16

Post by MSM »

madvoid wrote: post #14
jamesfrank wrote: post #13

Earlier quoted context omitted.

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.

Re: U.S. Laboratory Breaks Laser Record

#17

Post by CountHackulus »

wahsd wrote: post #8

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...

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.

Re: U.S. Laboratory Breaks Laser Record

#19

Post by uvdiv »

MSM wrote: post #12

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.

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....

Re: U.S. Laboratory Breaks Laser Record

#20

Post by ChuckMcM »

uvdiv wrote: post #11
ChuckMcM wrote: post #6

Earlier quoted context omitted.

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 mund…

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. 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.
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