5 ms·

This tweet claims that 500MJ of energy was required: https://twitter.com/latzenpratz/status/1602686252486217728 https://twitter.com/latzenpratz/status/160268625

This tweet claims that 500MJ of energy was required: https://twitter.com/latzenpratz/status/1602686252486217728 https://twitter.com/latzenpratz/status/1602686252486217728 > "had to put 500 megajoules of energy into the lasers to then send 1.8 megajoules to the target - so even though they got 2.5 megajoules out, that's still far less than the energy they originally needed for the lasers," says Tony Roulstone of the University of Cambridge. But it's good to finally see progress. Very few technologies can transform the world the way a practical fusion reactor could.

Robotbeat 4y ago
That’s only because they’re using old school flash pumped lasers, not the new solid state lasers you’d use today if you wanted to make a power plant demo.
- BeetleB 4y ago
  Can solid state lasers produce the high energy needed here?
  - Robotbeat 4y ago
    Yes. https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy#Mercury https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy#M...
    - px43 4y ago
      I'm not really seeing any convincing numbers there. Mercury lasers seem to only be 10% efficient. I get that this is better than the lasers that were just used at NIF, but that still seems pretty far from useful.
      - Robotbeat 4y ago
        It’s useful enough to produce significant net energy if they continue with the gain scaling that ignition allows.
- sillysaurusx 4y ago
  It just seems a little strange to take credit for a milestone when the milestone everyone cares about is yet to be reached. (More energy out than in.) Good to hear that there's a laser design that might achieve that.
  - nilsbunger 4y ago
    It's a significant milestone because demonstrating you can get net energy from the reaction removes a lot of uncertainty of whether it's possible in the real world. It starts to turn inertial fusion into an engineering problem of how you increase the efficiency of each stage.
  - simplicio 4y ago
    I think the confusion here is at least partially due to most articles obscuring the primary purpose of the NIF. Its not supposed to support commercial energy development, its supposed to support nuclear weapons development under the Nuclear Test Ban Treaty, where testing bombs via setting them off is banned. So the NIF is supposed to give a testbed to study implosion created fusion reactions that produce enough energy to "ignite", that is, propegate the reaction to the rest of a hypothetical bomb. In that case, the amount of energy needed for the infrastructure to produce the initial implosion doesn't matter, what matters is that the energy coming out is more then the actual energy that triggered the reaction, so that the hypothetical bomb would blow up and not fizzle.
    - geysersam 4y ago
      Exactly! It's so strange this is somehow made to be about fusion as an energy source. I'm happy to announce that Q>>1 has already been achieved on multiple occasions. In the cores of the thermonuclear devices tested by the US and USSR in the 50s. (Unfortunately that technology proved unviable as a path to civilian fusion power.)
  - ganbatekudasai 4y ago
    Don't take it too personally, but you, and many others here, need to rethink their approach. You see a short tweet without context about a topic you clearly know nothing about (which is totally, fully okay, it's a complex topic), and think you are now able to criticize milestones in this impossibly complex topic. Not even ask questions, not something like "hey, I saw this tweet, I know it's just a tweet, but can someone help me understand context?", no, you actually go ahead and criticize work that you know nothing about, and when confronted, you double down. On some level, you must know yourself that it might be better to ask as many unloaded questions as you want, but otherwise sit this one out in terms of assessment.
- worik 4y ago
  Why are they using these "flash pumped" lasers if more efficient ones are available?
  - jcarreiro 4y ago
    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.
    - Aeolun 4y ago
      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.
      - nrki 4y ago
        300MJ ~= 83kWh which is like, $2000 in CA
        IanCal 4y ago
        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?
        nrki 4y ago
        You're right of course, messing up my units again.
      - kragen 4y ago
        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
Rebelgecko 4y ago
It was discussed a lot in the threads about this yesterday, but apparently the lab had relatively inefficient lasers. Newer ones are an order of magnitude more efficient
- petilon 4y ago
  This is what I captured from the press conference: 300 megajoules was used to generate the laser (this is also captured in [1]). They also mentioned that newer lasers have 20% wall plug efficiency. If so, they need to improve the energy output by 5x in order to break even relative to wall plug energy consumption. [1] https://techcrunch.com/2022/12/13/world-record-fusion-experiment-produced-even-more-energy-than-expected/ https://techcrunch.com/2022/12/13/world-record-fusion-experi...
  - jameshart 4y ago
    “Wall plug energy consumption” I don’t know why but this caused me to picture Alec from Tech Connections in a few years time, showing off his fusion laser plugged in to a kill-a—watt, while he explains carefully, through the magic of buying two of them, why you can get more power out than you put in, and why these old inertial confinement fusors were pretty neat actually.
  - LarryMullins 4y ago
    That's just the lasers, the rest of the plant needs power too. Big water pumps are big power hogs, as is the rest of the supporting equipment that any power plant requires to operate. Far over "wall plug" break even is required for commercial viability.
    - ncfausti 4y ago
      Just bootstrap a second fusion power plant with the first, then continue on, similar to how compilers for a language can be written in the language itself.
      - 4y ago

Robotbeat 4y ago

That’s only because they’re using old school flash pumped lasers, not the new solid state lasers you’d use today if you wanted to make a power plant demo.

BeetleB 4y ago
Can solid state lasers produce the high energy needed here?
- Robotbeat 4y ago
  Yes. https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy#Mercury https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy#M...
  - px43 4y ago
    I'm not really seeing any convincing numbers there. Mercury lasers seem to only be 10% efficient. I get that this is better than the lasers that were just used at NIF, but that still seems pretty far from useful.
    - Robotbeat 4y ago
      It’s useful enough to produce significant net energy if they continue with the gain scaling that ignition allows.
sillysaurusx 4y ago
It just seems a little strange to take credit for a milestone when the milestone everyone cares about is yet to be reached. (More energy out than in.) Good to hear that there's a laser design that might achieve that.
- nilsbunger 4y ago
  It's a significant milestone because demonstrating you can get net energy from the reaction removes a lot of uncertainty of whether it's possible in the real world. It starts to turn inertial fusion into an engineering problem of how you increase the efficiency of each stage.
- simplicio 4y ago
  I think the confusion here is at least partially due to most articles obscuring the primary purpose of the NIF. Its not supposed to support commercial energy development, its supposed to support nuclear weapons development under the Nuclear Test Ban Treaty, where testing bombs via setting them off is banned. So the NIF is supposed to give a testbed to study implosion created fusion reactions that produce enough energy to "ignite", that is, propegate the reaction to the rest of a hypothetical bomb. In that case, the amount of energy needed for the infrastructure to produce the initial implosion doesn't matter, what matters is that the energy coming out is more then the actual energy that triggered the reaction, so that the hypothetical bomb would blow up and not fizzle.
  - geysersam 4y ago
    Exactly! It's so strange this is somehow made to be about fusion as an energy source. I'm happy to announce that Q>>1 has already been achieved on multiple occasions. In the cores of the thermonuclear devices tested by the US and USSR in the 50s. (Unfortunately that technology proved unviable as a path to civilian fusion power.)
- ganbatekudasai 4y ago
  Don't take it too personally, but you, and many others here, need to rethink their approach. You see a short tweet without context about a topic you clearly know nothing about (which is totally, fully okay, it's a complex topic), and think you are now able to criticize milestones in this impossibly complex topic. Not even ask questions, not something like "hey, I saw this tweet, I know it's just a tweet, but can someone help me understand context?", no, you actually go ahead and criticize work that you know nothing about, and when confronted, you double down. On some level, you must know yourself that it might be better to ask as many unloaded questions as you want, but otherwise sit this one out in terms of assessment.
worik 4y ago
Why are they using these "flash pumped" lasers if more efficient ones are available?
- jcarreiro 4y ago
  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.
  - Aeolun 4y ago
    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.
    - nrki 4y ago
      300MJ ~= 83kWh which is like, $2000 in CA
      - IanCal 4y ago
        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?
        nrki 4y ago
        You're right of course, messing up my units again.
    - kragen 4y ago
      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

Rebelgecko 4y ago

It was discussed a lot in the threads about this yesterday, but apparently the lab had relatively inefficient lasers. Newer ones are an order of magnitude more efficient

petilon 4y ago
This is what I captured from the press conference: 300 megajoules was used to generate the laser (this is also captured in [1]). They also mentioned that newer lasers have 20% wall plug efficiency. If so, they need to improve the energy output by 5x in order to break even relative to wall plug energy consumption. [1] https://techcrunch.com/2022/12/13/world-record-fusion-experiment-produced-even-more-energy-than-expected/ https://techcrunch.com/2022/12/13/world-record-fusion-experi...
- jameshart 4y ago
  “Wall plug energy consumption” I don’t know why but this caused me to picture Alec from Tech Connections in a few years time, showing off his fusion laser plugged in to a kill-a—watt, while he explains carefully, through the magic of buying two of them, why you can get more power out than you put in, and why these old inertial confinement fusors were pretty neat actually.
- LarryMullins 4y ago
  That's just the lasers, the rest of the plant needs power too. Big water pumps are big power hogs, as is the rest of the supporting equipment that any power plant requires to operate. Far over "wall plug" break even is required for commercial viability.
  - ncfausti 4y ago
    Just bootstrap a second fusion power plant with the first, then continue on, similar to how compilers for a language can be written in the language itself.
    - 4y ago