Hacker News Reader

Comment by megous | Hacker News Reader

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?

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?

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

Thanks. :)

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.

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.

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.

Reply on news.ycombinator.com