5 ms·
> The results from the experiment on 8 August indicate an energy output of over one mega-joule, which marks the threshold agreed for the onset of 'ignition' and
by web007 5y ago
> The results from the experiment on 8 August indicate an energy output of over one mega-joule, which marks the threshold agreed for the onset of 'ignition' and is six times the previous highest energy achieved.
They got 1Mj output from > 500TW input - this is a "major milestone" but only a small step on the path to fusion.
NIF is fascinating, and has been promising for the past decade. The idea of kick-starting fusion with lasers sounds awesome, and then more awesome when you realize just how much energy you need for fusion. They're shooting terawatts of laser at a target the size of a hollow grain of rice, and they're not there yet!
- cstross 5y agoNIF, remember, is funded by the DoD. It's not a civilian reactor research program: it's a device for testing fusion reactions in the lab now that the Comprehensive Test Ban Treaty means that they're not allowed to test H-bombs out in Nevada. This is not to say that it isn't fascinating and there won't be spin-off findings of use to the development of civil fusion reactors, but actual reactor research (e.g. JET, ITER, Wendelstein-7X) is all about magnetic containment for protracted periods (tens to thousands of seconds). And ITER, running on tritium and deuterium, is supposed to use 50 MW of heating power to create a plasma of 500 MW (thermal) for periods of 400 to 600 seconds. No need for a 500TW peak power input (actually much, much lower when you look at it in terms of megajoules delivered in a few nanoseconds).
- pxhb 5y ago>NIF, remember, is funded by the DoD. It's not a civilian reactor research program: it's a device for testing fusion reactions in the lab now that the Comprehensive Test Ban Treaty means that they're not allowed to test H-bombs out in Nevada. *DOE’. There is a quasi-separation of powers, where DOE ‘owns’ the weapons and the DOD ‘uses’ them. ‘See for example the NNSA.
- avs733 5y agoThe DOE is a fascinating organization btw…anyone who is so nonchalant about public oversight and security practices that the DOD gets angry at them has to be fun at parties.
- jameshart 5y agoWhy are you comparing energy and power numbers directly? Without a time component I can’t tell whether those numbers are ridiculous or impressive. If your 500TW laser only fires for 1 nanosecond then you’re only putting in 500kJ so you’re getting 200% yield. If you’re firing your 500TW laser for an hour, well that obviously isn’t as impressive.
- zaarn 5y agoThe 500TW are meaningless, the actual input is around 1.5MJ, meaning they got almost 80% of their input as energy back.
- leephillips 5y agoWhere did you get this number? It’s a couple of orders of magnitude too low.
- zaarn 5y agohttps://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.245003 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12... This article mentions they used 1.5MJ of energy for the fusion process, it seems to be related to this news, on wikipedia you can find a cited NYTimes article stating 80% of the energy input was released. And I don't get where you get "couple order of magnitude too low" from, 500TW means nothing, it's a workload, not the total work the laser performed. Over a few nanoseconds, that checks out.
- leephillips 5y ago(1) That’s from 2018. (2) It does not say what you say it says. It does not state how much energy was “used”. The laser is about 1% efficient. (3) That 80%, which is the number that goes with this recent news, has nothing to do with the “energy input”. It is 80% of the energy that their models say was absorbed by the hohlraum. These are part of where my couple of orders of magnitude remark comes from.