[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.

[jamesfrank]

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.

[madvoid]

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

[MSM]

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.

[uvdiv]

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....

[jff]

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).