Because they are researching inertial confinement fusion, not trying to build a working power plant. The efficiency of the lasers doesn't matter, since it doesn't affect their research.

Is energy on the order of 300MJ so cheap? You’d think that cutting it down to 150MJ would allow them to do more experiments.

300 megajoules is 83 kilowatt hours

a typical power price at trading hubs is US$40 per megawatt hour, though this varies considerably depending on many factors and is sometimes actually negative

a typical retail price is US$120 per megawatt hour

so this is about US$10 worth of electrical energy

300MJ ~= 83kWh which is like, $2000 in CA

I think you're out by some orders of magnitude. With the current energy issues in the UK it'd be under £100. Other things suggest in California it's more like 20 cents per kWh so were you thinking ~$20?

You're right of course, messing up my units again.

It's a very old lab, and replacing them isn't cheap/easy.

You don't need to use efficient lasers to get the scientific results they're after - other people have already very accurately measured the properties of modern lasers, so we can predict how they would perform without having to actually use them.

It’s a proof of concept. Upgrading lasers that already work is not necessarily the best use of limited funds.

They could get higher power out of more efficient lasers, enabling research at higher energies or bigger targets

That's not the purpose of the research, though. They are solely focusing on the energy transfer between the lasers themselves, and the output from the reaction. It's not clear that higher energies or bigger targets will teach us anything new.

Upgrading the lasers would slow the project down as new hardware is installed and issues are worked out. Not to mention I doubt the new hardware is cheap, and may be more expensive than burning excess energy using old laser tech in the meantime.

Other research groups work on laser efficiency, and the "final product" using this method (if it ever proves viable) would put together all the best pieces to get the best efficiencies.

Not to mention the money they would save on electricity bills.

The electricity bill is like $2000. It'd waste more money for a manager to think about how to replace equipment, at California pay rates. This whole thread is making me lose faith in HN.

Actually 83 KwH costs only about $20 in CA (avg $0.25 / KwH and probably LRL pays even less.