ZEUS – A new two-petawatt laser facility at the University of Michigan | Hacker News Reader

ZEUS – A new two-petawatt laser facility at the University of Michigan

news.engin.umich.edu

126 pointsvoxadam107 comments

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.

So.. We just need to figure out wormholes and make an infinite loop the laser goes through and harness its true power!!

I understand that you're being silly, but even in this silly theory land how is that supposed to work? While the laser is in a loop it's not hitting anything, and if you let it out it's the same as when you put it in.

You're right, I am being silly because I am too uneducated to really make sense of any of it.

I love smart people who work on this stuff, a lot of what I take for granted is due to their efforts :)

I figure it's a matter of stacking/charging the laser in that loop with a lot of pulses, then letting that all out at once? Like, what if we shot pulses into the orbit of a mini black hole, but then managed to unwind it back out into a single direction?

In that case the problem is you're only charging the loop with about 1 watt of laser on average. It's going to take two weeks just to reach a megajoule. So you can do one really cool shot, and then you have to wait months.

The article said 2 Petawatts for 25 quintillionths of a second. That's about 50mJ.

That's about the amount of power used in your phone's flash when taking a picture, not a few seconds, but the LED being on for about 50-100 milliseconds.

Not sure if the article is accurate (the accuracy of numbers in written text took a nosedive concurrent with the rise of LLMs), but the capabilities page of the laser’s website claims 23 femtoseconds pulse duration, 2 PW power, 50 J energy, and 1 shot per minute. 50 J is roughly a 3W light for 15 seconds.

https://zeus.engin.umich.edu/about/capabilities/

> Not sure if the article is accurate (the accuracy of numbers in written text took a nosedive concurrent with the rise of LLMs)

Written text accuracy took a nosedive in the early '00s as newspapers couldn't afford to hire journalists with a scientific background, followed by universities not hiring scientists to write press releases any more. GIGO - garbage in, garbage out.

> completely destroy the University of Michigan in spectacular fashion

Sure, Ann Arbor may be destroyed, but that's a sacrifice I'm willing to make. For Science. /insert Lord Farquaad meme here

Go green

>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.

Also NIF is actually 192 laser beams with about 3 football fields of lab grade warehouse to house all those laser beams optics for beam pumping, shaping, etc.

Not sure you can move NIF like you would move excalibur

Finally, a use for aircraft carriers.

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".

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.

Laser facilities like this one are designed for incredibly short pulses that are femtoseconds long

"Look at the facts. Very high power, portable, limited firing time, unlimited range. All you'd need is a big spinning mirror and you could vaporize a human target from space."

Fun fact: these laser pulses are so short they are no longer a single wavelength. They have a spectrum due to the uncertainty principle. And at this short of a time scale, it’s pretty broad.

I might regret asking, but could you explain this? (At a physics 101 level)

Time and energy are “conjugated” quantities: the more one is sharp, the more the other one is broad (it’s the same concept as Fourier transforming a Gaussian: the more it’s peaked the more the transform is broad). In order for the time duration of the pulse to be so short, it must have a broad uncertainty in energy, which for light is the same as a wide spectrum of colors.

That’s why it’s very tricky to find materials for mirrors and lenses when working with these short pulses: they must work well over a large range of frequencies. If they happen to absorb some more than others not only they would burn, but they would also change the temporal profile of the pulse.

Thanks very much ziofill. Is this the same thing as the Heisenberg Uncertainty Principle? Or is there something else similar for time and energy?

Yes, it's the same thing in the sense that even if you work with a single photon the same applies (if you want its wavefunction to be narrow in time, its energy uncertainty must be broad)

For the most energetic, half a kilowatt hour makes me think of a high setting microwave for 30 minutes. Must be enough to roast a chicken?

Choose how ablated you want your chicken

For anyone interested, the most powerful one is in Romania at the Extreme Light Infrastructure (ELI) in Măgurele. It's about 10 petawatts.

In that case, the titles claim is false, right?

No. Maybe slightly ambiguous, but I immediately read the title as "most powerful laser in the US".

The title can be interpreted as "there's a new laser that is now America's most powerful"

> Optical devices called diffraction gratings stretch it out in time so that when the pump lasers dump power into the pulse, it doesn’t get so intense that it starts tearing the air apart.

Oh,my.

> "The crystal that we’re going to get in the summer will get us to 3 petawatts, and it took four and a half years to manufacture"

This entire thing is beyond cool. I hope the rest of the process goes smoothly for the teams involved!

I was hoping I could hear it make noise but it operates for millionths of nanoseconds. Human ears have trouble with anything less than 30 ms so when it runs a trillion times longer we’ll be able to hear it make a sound.

You can hear femtosecond lasers because they ionize the air, creating a spark. They buzz at the pulse repetition frequency.

Do you know how often this one pulses? I was getting the impression it fires once per hour given the power levels.

Big powerful lasers can actually be quite noisy. Once I was talking on the phone with a friend who was working on one of the big lasers (don't remember which one, but it was in the bay area) and he said,"What? What? I'm sorry I can't hear you over the sound of my laser!". When he could hear me, I told him that was one of the coolest things I'd ever heard anyone say.

It's usually the accessories and support equipment that makes lasers loud. Cooling equipment, electrical stuff, etc.

If those can be put in another room then the noise goes way down.

I got a tour of the lab during construction. As a software engineer, what I found most incredible about the project was how well they stuck to their delivery proposal and timeline over the course of five years of development.

It's a good reminder that behind every flashy breakthrough, there's a ton of careful planning and execution most people never see

china is on track to have a 100pettawatt laser operating this year called "The Station of Extream Light", SEL for short, which is going to be used to try and seperate energy and matter by breaking empty space. think that this links to the place building it http://english.siom.cas.cn/Newsroom/rp/202207/t20220701_3071... all in all good to have a competitive environment in reseach.......though the US government, cough, cough, might, nudge, think about, some funding there

> Extream

[sic]?

There's a Youtube channel looking for a low cost laser backstop material. They have 10-100?kW class single mode fiber lasers that can burn holes in almost anything Real Genius style. https://youtu.be/n3ssikDQva0

How's that compare to the peak power output of a bubble collapsing in a liquid, over similar timescales? A genuine question, as I know bubbles pack quite a punch (can cause fusion) but can't find any numbers.

Instead of petawatts I’d love to hear what it can destroy.

I imagine a scale like:

1: Mosquito

…

10000: Planet (Death Star)

To kill a mosquito, you need "a few tens of millijoules, delivered within a few milliseconds" [0], so let's say 10W. To destroy the Earth (so that it turns into scattered dust and never reforms) you need about 10^32 J [1]; if we assume this is applied over maybe 100s, the laser would be 10^30W.

So the log10 scale goes from 1–30, where mosquitos die at 1 and the Earth dies at 30. The 2 PW in the article is about a 15.3. The Vulcan 20-20 project (set to complete in 2029) will register at about 20PW, or a 16.3 on the mosquito-Death Star scale [2].

So on a log scale, we're over halfway to building the Death Star.

[0]: https://spectrum.ieee.org/backyard-star-wars

[1]: https://www.scientificamerican.com/article/how-much-energy-w...

[2]: https://news.sky.com/story/worlds-most-powerful-laser-to-be-...

Thank you for this, I will be using this for the rest of my life!

This is awesome! Thank you!!

I’m still not sure what 15.3 on the MDS scale can destroy but I am sure the Emperor will be pleased to hear that we are half-way to building the Death Star.

The on a log scale is doing a fair amount of lifting here I think

Next question: on what planet/moon should the mosquito be to be _just_ safe from the laser?

Well, mass scales as the cube of radius, and we have 15 orders of magnitude to work with, so I guess it should be an object on the order of hundreds of meters in radius. But as noted, the duration of firing matters as well. Given https://news.ycombinator.com/item?id=44054239, the actual laser can only vaporize much smaller things.

I don’t like log scales, they’re not intuitive.

> if we assume this is applied over maybe 100s

I think this is the crux of the assumption right here. It sounds like this is apply for well under a nanosecond.

I think we're closer to maybe killing a mosquito than "half way to building a Death Star on a log scale" (which, I guess is already much closer to a mosquito than a planet).

If we're comparing lasers that go for seconds and lasers that go for femtoseconds, I think measuring watts is way too misleading.

Measured in simple joules, mosquito is .04, earth is 10^32, and this laser is 50.

If we make a joules version of the 1-30 scale, the laser in the article would only score a 4.

So I could kill all the mosquitoes in my yard in one pulse with this laser.

If they get close enough together for that pulse to hit them all.

Just send me out there and aim the pulse at the one spot in the middle of my back I just can't quite reach.

For sure; using total energy delivered makes a lot more sense. But then I think it would be better to use whatever tool humanity has that delivers the max total energy; let’s say Tsar Bomba.

Let’s say the mosquito is 1 again, so Death Star is 34. Tsar Bomba would be about 17.3. Over halfway again!

It’s kind of surprising that our max power output and max energy output are about the same on these scales.

Every step is a doubling of the previous step, no?

So true "half way to a death star" is step 29/30?

They used log10, so each step is 10x the previous, so in a linear sense, it would double when going from about 29.7 to 30. But it seems that humans tend to improve tech at exponential rates, where we are constantly making improvements here and there that keep stacking up, when it comes to things that are actually in a developmental stage anyways.

Say your "endstage" goal is GPU with 200 billion transistors. Using linear scale, the current biggest GPU is only halfway there, and it took all of human civilization to get this far, and it will take another civilization to get to 200b. In reality, we'll have that in a couple years with our current civilization.

>humans tend to improve tech at exponential rates

A hypothetical "death star" project like this would require improvements in energy generation/storage capacity/etc., which haven't improved in nearly the way transistor production has (and are also much more limited by physical realities, such as the specific heat, enthalpy of combustion etc. of materials).

Yes, extremely high sustained power lasers still have a hard time competing with hypersonic projectiles in energy delivered. The difference in being able to throw nuclei at the problem.

Zeus would like to file an injunction against the impostors associating his name with a something-equivalent¹ something. The Zeus brand stands only for supreme dominance. Zeus would not object to an actual zettawatt laser being named after him.

In this very interesting video, a Russian drone developer gives his thoughts about laser weapons. In theory they work, they test it always on ideal atmospheric conditions. In practice, they don't.

https://www.youtube.com/watch?v=RmfNUM2CbbM

I don't think anyone should be impressed by watts. Jouls are where all the real work is.

Asside for the PR article. What's the use case for pettawatt laser pulse lasting 25 quintillionths of a second?

A previous press release lists some research applications and potential practical developments. https://news.engin.umich.edu/2019/09/most-powerful-laser-in-...

Thanks. :)

Laser pulses can ablate materials and the shorter the pulse the crisper the edges. Back in the 90’s or early 00’s they demonstrated pulses laser cutting of tissue where the heat damage to surrounding tissue had a width of a single cell.

What, like a surgical laser?

"Okay, hold really still..."

Yeah and I think this and radiological tools are why chemo tattoos exist. The system has to react to the twitch you can’t control when a weird noise happens next to your head. Instead of stabbing bolts into your skull through your skin with a device Torquemada would have been proud of, they target versus the dots and if the dots move? Well this is where my knowledge runs out. Either they shut down the beam or they target in realtime. But either way the payload is delivered where it’s supposed to be or not at all.

I don’t know if they are using laser scalpels in surgery. My medical fascination mostly ends at diagonostics and experimental procedures. If I don’t know anyone with a disorder I tend not to hear about new procedures. My friend in college was helping a prof work on picosecond violet lasers and now we are on femtosecond.

Some radiation therapy machines use metal fiducial markers and can account for movement such has patient breathing

So it’s for targeting rather than aborting a treatment?

I'm not certain, probably both. If the pt jumped out of frame it would probably abort. But they allow the pt to breathe normally and still receive treatment.

At femtoseconds, assuming your tracking matches, you could probably sit a sugar-loaded kid in a chair without instructions and just make it work.

Probably like watching people play war sims with a sniper rifle. Just waiting for the crosshairs to bounce over the target’s head and then blam.

Bigger problem I suspect is children with white coat syndrome. When I was a kid doctors got away with being monstrous to children.

Why the Dougie Howser hate?

Well you probably don't want a petawatt laser lasting a second, cause it'll obliterate a lot more than what you wanted to.

Including of course the laser. It's about 240 kilotons of TNT, or over 10 times the power of the nagasaki or hiroshmia bombs.

Yeah, or even if it were some more reasonable amount of energy that doesn't self-destruct it, there are probably applications where you want to hit a small area quickly without burning things around it.

Watts are just joules per second.

It doesn't make any sense to measure joules alone. _Any_ laser can output 2 petajoules. The only question is how long it takes to do that: hence Watts.

Seems like you always start somewhere. First you have 25E-18, then bump it up to 1e-15, and maybe someday you are at 1e-9 and are doing inertial confinement fusion.

The fact that this is an NSF user facility is hugely encouraging. It means ZEUS isn't just a trophy project, but a tool the broader scientific community can build on

Mount it in a jet and you could pop an entire house full of popcorn in seconds.

In femtoseconds!

That’s popcorn. Get it away from me, I can’t stand popcorn. I hate popcorn.

More for us, then!

It's an on topic movie quote: https://www.imdb.com/title/tt0089886/quotes/?item=qt0435723&...

Point it downwards and make that hole through the center of Earth.

Two Real Genius references on one page. Life is good.

Ah yes, this Large Pulsed Plasma Laser (LPPL) has a lot of interesting research potential.

star wars??? space wars???

I am embarrassed to admit of thinking there’s a Family Guy joke somewhere in that headline.

Could you explain the joke?

Probably Peta => Peter who is one of the main characters in the show.

What if we tried more power?

I'm assuming this is an XKCD reference.

https://what-if.xkcd.com/13/

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