8 ms·

Burning plasma achieved in inertial fusion

117 points by 317070 5y ago

p1mrx 5y ago
This is from the National Ignition Facility, so it's a repeat of the news you've probably seen 10 times over the past 6 months.
- nuccy 5y ago
  Thanks to another today HN submission [1] we now know that authors of this paper payed 11,390 USD to make it "open access" :) 1. https://news.ycombinator.com/item?id=30081034 https://news.ycombinator.com/item?id=30081034
  - deleted 5y ago
    [deleted]
- civilized 5y ago
  "The NIF reached a milestone of unclear importance to anyone outside the NIF" has been a recurring news item for the past couple decades.
  - sneilan1 5y ago
    That sentence succinctly summarized this entire article. Props to you and your sense of humor :)
nuccy 5y ago
There is quite some misleading terminology being used in the field of nuclear fusion (see excellent overview here [1]). So I was genuinely curious what kind of Q is used in this paper, so here it is: > In this regime, self-heating from α-particle deposition exceeds the external heating input into the DT8; this ratio is denoted Qα, where the self-heating is taken relative to the heating power to the plasma—for inertial fusion this is the PdV compressional work on the fuel and not the total laser energy (P, pressure, dV, volume change). Qα > 1 is a burning plasma. So as far as I understand such Qα > 1 can be reached without sustaining neither pressure or volume, so one can think about it as an explosion rather that intuitive burning (somewhat continuous process). To summarize: Q_total = total_energy_out / total_energy_in is what matters, not any Q related to plasma energy. Since to build a power plant we just care what it consumes in comparison with what it produces. For this particular case even though Qα > 1 you likely can extract just a tiny fraction of that energy stored in plasma, while spending huge amounts of energy to heat it in the first place. 1. https://www.youtube.com/watch?v=LJ4W1g-6JiY https://www.youtube.com/watch?v=LJ4W1g-6JiY or as an article http://backreaction.blogspot.com/2021/10/how-close-is-nuclear-fusion-power.html http://backreaction.blogspot.com/2021/10/how-close-is-nuclea... Edit: I'm a big proponent of nuclear fission and fusion since both are the best (current and future) way of getting carbon neutral energy, which can cover the spikes in the grid and sun/wind-less days. It is just important to be careful with the terminology, which can be used to make research results more optimistic.
- ninkendo 5y ago
  So their denominator (energy in) is calculated in terms of the work that was usefully done in compressing the plasma, and not the total energy they used to make said work happen? Any idea what multiple of PdV the input power was? (ie. energy used to power the lasers?) I'm curious what their total Q value would be in this experiment...
  - leephillips 5y ago
    This type of laser is about 1% efficient (someone will correct me if I’m out of date on this, but it’s not likely to be better than 10%). Laser fusion really has nothing to do with energy production.
- jahnu 5y ago
  That's a great video. Her videos often offer a really refreshing sceptical balance to the dominant overly optimistic and downright incorrect pop-sci stuff out there.
- ncmncm 5y ago
  And, even if they got the actual Q up by two orders of magnitude, inertial D-D fusion can never be practical, because you can't fuse enough. And, even if you confined it magnetically, it costs so much to extract D-D energy that it can never compete even with fission. So it is really a dead end.
- dwwoelfel 5y ago
  At the end of the video you linked, she accuses the author of The Star Builders of "only briefly mention[ing] the total energy gain and never giv[ing] a number". I had just started the book when I watched her video, and I counted four separate times where he did mention total energy gain. In one chapter (pg. 142 in my kindle edition), he quotes from a source who lays out the distinction she claims people in fusion research want you to be confused about: Like First Light Fusion, Tokamak Energy is much more interested in power production than energy breakeven. "Achieving a of one is a scientific goal," Jonathan Carling continues, "but it's nowhere near enough to produce commercial energy, which requires a Q [in the region] of tens." As mentioned previously, Q is the ratio of fusion power out to heating power in. His strong view is that unless other star builders have a credible plan to get to factors of twenty or thirty more power out than they put in, then they're in the science game and not the fusion energy game. This video by the Improbable Matter channel has a good response to Dr. Hossenfelder's general remarks: https://www.youtube.com/watch?v=KtqC8W0_Ups https://www.youtube.com/watch?v=KtqC8W0_Ups
dnautics 5y ago
I still don't understand what the game plan is for laser-induced fusion. How do you collect the energy? By contrast: I have a vague idea of how one might do it for magnetic confinement, and I even remember one magnetically confined system where there was direct electrical potential generated and extracted from the system.
- DennisP 5y ago
  Simple, heat something up and run a turbine. With D-T (the easiest fuel), the energy output is 80% neutron radiation so a heat cycle is your only option regardless of reactor design. To avoid a turbine, you need a fuel whose output is mainly fast-moving charged particles.
- ncmncm 5y ago
  There is no such game plan. It is a giveaway to military contractors, corporate welfare. Magnetically confined D-He3 or H-B fusion could, in principle, be viable, because there is no detour through collecting hot neutrons, but is harder to achieve.
  - e4e78a06 5y ago
    It is research for nuclear stockpile maintenance, which depending on how you view nuclear weapons could be a bad thing but is absolutely not a giveaway to the MIC. You'll notice all the main authors of the paper work at national labs which are funded directly by the federal government.
    - ncmncm 5y ago
      You are aware, are you not, that the national labs in question are operated by military contractors, literally under contract? And that the people nominally working for these labs are actually, literally, employees of those contractors? You propose a distinction where there is no difference.
- samcheng 5y ago
  As far as I know, this kind of system is most useful for simulating nuclear explosions while remaining compliant with the Nuclear Test Ban Treaty of 1963.
gtsnexp 5y ago
I wonder about the scale of the device where the experiment was done. How far from a tabletop scale are talking about?
- thinkcontext 5y ago
  The National Ignition Facility is enormous and cost $Bs. But don't let its large size make you think its anywhere near practicality, it is not. https://en.wikipedia.org/wiki/National_Ignition_Facility https://en.wikipedia.org/wiki/National_Ignition_Facility
- oivey 5y ago
  It was at NIF. The facility is huge and costs many billions of dollars.
_dain_ 5y ago
8 years later, little has changed: https://scottlocklin.wordpress.com/2014/03/05/anatomy-of-a-fusion-press-release/ https://scottlocklin.wordpress.com/2014/03/05/anatomy-of-a-f...

117 points by 317070 5y ago

This is from the National Ignition Facility, so it's a repeat of the news you've probably seen 10 times over the past 6 months.

nuccy 5y ago
Thanks to another today HN submission [1] we now know that authors of this paper payed 11,390 USD to make it "open access" :) 1. https://news.ycombinator.com/item?id=30081034 https://news.ycombinator.com/item?id=30081034
- deleted 5y ago
  [deleted]
civilized 5y ago
"The NIF reached a milestone of unclear importance to anyone outside the NIF" has been a recurring news item for the past couple decades.
- sneilan1 5y ago
  That sentence succinctly summarized this entire article. Props to you and your sense of humor :)

nuccy 5y ago

There is quite some misleading terminology being used in the field of nuclear fusion (see excellent overview here [1]). So I was genuinely curious what kind of Q is used in this paper, so here it is: > In this regime, self-heating from α-particle deposition exceeds the external heating input into the DT8; this ratio is denoted Qα, where the self-heating is taken relative to the heating power to the plasma—for inertial fusion this is the PdV compressional work on the fuel and not the total laser energy (P, pressure, dV, volume change). Qα > 1 is a burning plasma. So as far as I understand such Qα > 1 can be reached without sustaining neither pressure or volume, so one can think about it as an explosion rather that intuitive burning (somewhat continuous process). To summarize: Q_total = total_energy_out / total_energy_in is what matters, not any Q related to plasma energy. Since to build a power plant we just care what it consumes in comparison with what it produces. For this particular case even though Qα > 1 you likely can extract just a tiny fraction of that energy stored in plasma, while spending huge amounts of energy to heat it in the first place. 1. https://www.youtube.com/watch?v=LJ4W1g-6JiY https://www.youtube.com/watch?v=LJ4W1g-6JiY or as an article http://backreaction.blogspot.com/2021/10/how-close-is-nuclear-fusion-power.html http://backreaction.blogspot.com/2021/10/how-close-is-nuclea... Edit: I'm a big proponent of nuclear fission and fusion since both are the best (current and future) way of getting carbon neutral energy, which can cover the spikes in the grid and sun/wind-less days. It is just important to be careful with the terminology, which can be used to make research results more optimistic.

ninkendo 5y ago
So their denominator (energy in) is calculated in terms of the work that was usefully done in compressing the plasma, and not the total energy they used to make said work happen? Any idea what multiple of PdV the input power was? (ie. energy used to power the lasers?) I'm curious what their total Q value would be in this experiment...
- leephillips 5y ago
  This type of laser is about 1% efficient (someone will correct me if I’m out of date on this, but it’s not likely to be better than 10%). Laser fusion really has nothing to do with energy production.
jahnu 5y ago
That's a great video. Her videos often offer a really refreshing sceptical balance to the dominant overly optimistic and downright incorrect pop-sci stuff out there.
ncmncm 5y ago
And, even if they got the actual Q up by two orders of magnitude, inertial D-D fusion can never be practical, because you can't fuse enough. And, even if you confined it magnetically, it costs so much to extract D-D energy that it can never compete even with fission. So it is really a dead end.
dwwoelfel 5y ago
At the end of the video you linked, she accuses the author of The Star Builders of "only briefly mention[ing] the total energy gain and never giv[ing] a number". I had just started the book when I watched her video, and I counted four separate times where he did mention total energy gain. In one chapter (pg. 142 in my kindle edition), he quotes from a source who lays out the distinction she claims people in fusion research want you to be confused about: Like First Light Fusion, Tokamak Energy is much more interested in power production than energy breakeven. "Achieving a of one is a scientific goal," Jonathan Carling continues, "but it's nowhere near enough to produce commercial energy, which requires a Q [in the region] of tens." As mentioned previously, Q is the ratio of fusion power out to heating power in. His strong view is that unless other star builders have a credible plan to get to factors of twenty or thirty more power out than they put in, then they're in the science game and not the fusion energy game. This video by the Improbable Matter channel has a good response to Dr. Hossenfelder's general remarks: https://www.youtube.com/watch?v=KtqC8W0_Ups https://www.youtube.com/watch?v=KtqC8W0_Ups

dnautics 5y ago

I still don't understand what the game plan is for laser-induced fusion. How do you collect the energy? By contrast: I have a vague idea of how one might do it for magnetic confinement, and I even remember one magnetically confined system where there was direct electrical potential generated and extracted from the system.

DennisP 5y ago
Simple, heat something up and run a turbine. With D-T (the easiest fuel), the energy output is 80% neutron radiation so a heat cycle is your only option regardless of reactor design. To avoid a turbine, you need a fuel whose output is mainly fast-moving charged particles.
ncmncm 5y ago
There is no such game plan. It is a giveaway to military contractors, corporate welfare. Magnetically confined D-He3 or H-B fusion could, in principle, be viable, because there is no detour through collecting hot neutrons, but is harder to achieve.
- e4e78a06 5y ago
  It is research for nuclear stockpile maintenance, which depending on how you view nuclear weapons could be a bad thing but is absolutely not a giveaway to the MIC. You'll notice all the main authors of the paper work at national labs which are funded directly by the federal government.
  - ncmncm 5y ago
    You are aware, are you not, that the national labs in question are operated by military contractors, literally under contract? And that the people nominally working for these labs are actually, literally, employees of those contractors? You propose a distinction where there is no difference.
samcheng 5y ago
As far as I know, this kind of system is most useful for simulating nuclear explosions while remaining compliant with the Nuclear Test Ban Treaty of 1963.

gtsnexp 5y ago

I wonder about the scale of the device where the experiment was done. How far from a tabletop scale are talking about?

thinkcontext 5y ago
The National Ignition Facility is enormous and cost $Bs. But don't let its large size make you think its anywhere near practicality, it is not. https://en.wikipedia.org/wiki/National_Ignition_Facility https://en.wikipedia.org/wiki/National_Ignition_Facility
oivey 5y ago
It was at NIF. The facility is huge and costs many billions of dollars.

_dain_ 5y ago

8 years later, little has changed: https://scottlocklin.wordpress.com/2014/03/05/anatomy-of-a-fusion-press-release/ https://scottlocklin.wordpress.com/2014/03/05/anatomy-of-a-f...