Fusion energy breakthrough by US scientists boosts clean power hopes (2023 Update)

Interesting link.

If you mean the NIF thing, it made more energy out than laser energy in, but is wildly unlikely to ever be a practical power source. Wall-plug efficiency is still minute, and neutrons are hard to convert to electricity.

We did the master timing system and two generations of beam modulators. We recently redesigned the modulators because ultra-precise low-noise optical waveforms are needed to stably compress a fuel pellet to fusion density using 192 laser beams, sort of like squeezing a balloon (or a plutonium sphere.) Tokamaks have a similar compression instability problem.

I think NIF got over unity once in a single freak shot last year that was unexplained. Maybe with better theory (and better gear!) they can do it repeatedly.

A step in the right direction.

Maybe I will see a sustained reaction sometime in my life.

That's somewhere around 20 years, maybe.

boB

On a sunny day (Tue, 13 Dec 2022 07:48:52 -0800) it happened John Larkin snipped-for-privacy@highlandSNIPMEtechnology.com wrote in snipped-for-privacy@4ax.com:

Sorry wrong link, this was the intended one:

Was also on CNN today, so must be real ;-(

If its real then its cool!

confinement fusion is noting new, look up 'Farnsworth fusor'

kids have done it. but break-even sure is!

Only another factor of about 1k to go. Don't hold your breath.

What's the efficiency of their lasers, really? And what about the efficiency of the whole facility?

Jeroen Belleman

It's air conditioned to +- millikelvins, in Livermore CA.

Possibly the world's biggest clean room.

Is that even possible, conditioning air to millikelvin stability? I don't believe it.

Jeroen Belleman

For a small enough volume of air it is certainly possible. For a space as big as the whole NIF it would be tricky - but they might stabilise important individual air volumes that well, with separate air-conditioners.

John Larkin has clearly misunderstood something, and he's no more likely to tell how he got it wrong than Flyguy would be.

They might need to stabilise the air in individual light paths to that degree if the light paths were routed through air, but it would be easier to evacuate them.

In tabletop-sized volumes, yes. You put a box in a box, and stir the space between with a fan. Over an entire building? Ambitious. ;)

Cheers

Phil Hobbs

Our gear, in the Master Oscillator Room, is spec'd to work over a

+-0.3c range, but MOR isn't as stable as the laser lines. We're in a rack with some horrificly hot Tektronix gear, and MOR gets a lot of tourists.

We have an oven inside our box to control the optical modulator to a few mK.

On a sunny day (Thu, 15 Dec 2022 06:24:51 -0800 (PST)) it happened Fred Bloggs snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:

My first thought it was perhaps a 'Reagan' tactic Reagan had laser weapons ready to defeat the USSR... Next US would claim it has a fusion powered space force ...

May still go! :-)

Yes! The news is that they got net 3MJ out of the reactor, without mentioning that the lasers used 300MJ from the grid. And "out of the reactor" isn't right - it's heat in the reactor. A factor of 1k is underestimated, looking at it from the grid.

The whole fusion thing is just going on inertia - too many people would have to admit it's off-base to stop it. Too many people invested.

Well, they're up front about it--it's called "inertial confinement fusion". ;)

Cheers

Phil Hobbs

Why not? Other than a gas thermometer, how would you even calibrate millikelvin sensors? Fine control of atmospheric pressure (and related adiabatic heating) is the hardest part.

Platinum RTDs are available with millikelvin calibration. Or for just equality and stability, calibrate a batch yourself.

Whenever you have some bit of equipment with dissipation, you get a convective plume. A normal semiconductor clean room has HEPA filters covering the ceiling, with corresponding vents in the floor, so that you get reasonably uniform, laminar downward flow of about 100 feet per minute.

But that's with ~10 foot ceilings. I don't know if you can maintain that in a space with a less flat aspect ratio.

Cheers

Phil Hobbs

The problem isn't in getting a measurement to that accuracy. The problem is that a room full of equipment that dissipates power will have warm and cool spots, even if the RTD never gets to see them.

Jeroen Belleman

This says +- 0.25 c. That's also our spec for rackmount gear in the master oscillator room. We insisted that our gear be in the bottom of the rack so we get the fresh air ducted in from below, before all the power hog Tek stuff heats it up.

That misses the point; gas thermometry is an absolute standard, tied by laws of physics to a limiting case of dilute gas at temperature... a platinum resistor is more complex, and would only serve as a secondary element in a temperature calibration chain.

NIF just needs stability, not absolute temperature.

You can buy standard RTDs spec'd to 0.15c, and they are typically much better. One could keep a bunch of them in a lab as your reference, and test every other one against them, for mK repeatability.

Even the 1206 surface-mount thinfilm platinum RTDs are crazy accurate. Their manufacturing must be interesting. Imagine keeping the temperature constant while they are laser trimmed.

Platinum RTDs are used by standards organizations to interpolate between cardinal points on the temp scale. Of course they can't be cardinal points themselves.