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126 points voxadam | 2 comments | | HN request time: 0s | source
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owenversteeg ◴[] No.44055538[source]
I see a number of comments here misunderstanding the power of this laser. Laser facilities like this one are designed for incredibly short pulses that are femtoseconds long, and total energy per pulse is typically on the order of tens of joules, roughly equivalent to a few seconds of your phone flashlight. They can’t destroy much of anything on human scales. They are made to do physics research, and there is absolutely no pathway from a 2 petawatt laser that delivers a few joules a minute to a 2 petawatt laser that hits full output power for a few seconds: that would be 10^16 times more energy, and of course that brief pulse would use more electricity than all the US uses in a year and completely destroy the University of Michigan in spectacular fashion (very roughly equivalent to a five megaton nuclear explosion.)

If you’re interested in the most energy per pulse, you want the “most energetic” laser, which is the NIF at LLNL. That’s about 2 megajoules per pulse or half a kilowatt hour. Definitely enough to kill a mosquito, but it doesn’t even register on the scale of Death Star style lasers from fiction.

And if you want the most destructive power, those are all military lasers. Which can absolutely destroy things science fiction style, but on a fairly small scale and with some important limitations.

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rl3 ◴[] No.44056467[source]
>And if you want the most destructive power, those are all military lasers. Which can absolutely destroy things science fiction style, but on a fairly small scale and with some important limitations.

https://en.wikipedia.org/wiki/Project_Excalibur

Once upon a time we tried developing a nuclear-pumped X-ray laser for use in strategic defense, which if my napkin math is correct was probably in the neighborhood of NIF in terms of energy output (despite the conversion efficiency being terrible). Notable is that NIF continues existing after it fires.

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1. jpmattia ◴[] No.44058374[source]
Back in graduate school, I TA'd an electrostatics course. We were going through the details of the basic parallel-plate capacitor, and so Prof. Peter Hagelstein (of the project you listed above) used the example of how much energy was stored in a football-field sized set of parallel-plate capacitors with oil as a high-breakdown dielectric.

The students were dutifully copying the lecture while I was sitting there with my mouth agape realizing that he was working through a simplified example of what energy storage was required for the X-ray laser. IIRC Those guys had their own substation, and would charge the capacitors. The switch would get thrown and the sublasers would shoot at the molybdenum target, which would laze in the X-ray spectrum (and the molybdenum would vaporize, I think.)

Afterwards, I asked him how on earth the energy was transferred from the caps to the sublasers: He just smiled and said "very carefully".

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2. rl3 ◴[] No.44078740[source]
Thanks for this. Not only is it a great anecdote, but it's nice to be reminded that it's still a small world out there.