[ambicapter]

> under the LIFE project, including developing much more efficient solid state lasers, etc) but was correctly chastised for it being a waste of money

How is this a waste of money? Surely there are other applications which can use more efficient lasers?

[noobermin]

You have to understand. I got a PhD in this field. For years, scientists in droves stopped applying for grants saying they were actually doing fusion because funding sources just lost faith in the effort. ICF requires a lot more investment in capital to run than MCF generally, it seems. These scientists moved on to study things like novel radiation and ion beam sources (which similar laser-plasma interactions provide) but they stopped going for fusion specifically because the government just lost faith in the effort. Now, the pendulum will swing.

The answer is yes, we can use more efficient lasers. If you ever are lucky enough to get a tour of NIF, they have a cute little exhibit where they show you if they redesigned NIF with modern technology, they could fit the three football field machine into something the size of a table. That display itself is likely 10 years old by now, and laser science has advanced even beyond it. Now that NIF has proven it's possible, I imagine there will finally be money in fusion again (ICF specifically, if I were in MCF I'd be worried sick now) and someone somewhere will make the newer NIF that won't be just taking 300MJ in and 2MJ out.

[DennisP]

Other people are already developing the lasers. We have NIF-class lasers now with over 20% efficiency, compared to the <1% efficiency of NIF's lasers. We also have petawatt lasers that can fire once per second.

https://physicstoday.scitation.org/do/10.1063/pt.6.2.2021102...

[ambicapter]

Why isn't NIF using these lasers? Wouldn't bringing down the power requirements of their lasers have helped them get to "break-even" faster?

[Robotbeat]

Because they have limited money.

[DennisP]

And it's easy enough to figure out the overall ratio if they'd used newer lasers.

[Robotbeat]

Not these exact ones. And one of the important things required is scale: can you think of anything that requires tens of megawatts of average pulsed laser energy which ISN’T military? (And the military has very different requirements for wavelength, etc.) And those other efforts can also seek their own funding (there’s not a lot of money in fusion research).

If you’re in a budget constrained environment and you’re not already 100% certain this approach is the right one for future power plants, you focus on achieving the energy gain needed for such a power plant first, and the first step of that is ignition (ie where the heat of the reaction sustains some more of the reaction, not just external heat) and scientific breakeven. Once you’ve shown scientific breakeven and ignition, that’s when it makes sense to start investing a bit in the other balance of plant items.

But the bulk of the effort should still be in increasing the energy gain by leveraging ignition, IMHO.