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DanielleFong's profile
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@DanielleFong

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@DanielleFong

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Empire of the Future
Joined February 2008

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    1. Sabine Hossenfelder‏Verified account @skdh 29 Jul 2021

      Does anyone know whether nuclear fusion energy gain numbers contain energy requirements for keeping the magnets cooled and the vacuum at high quality?

      25 replies 16 retweets 123 likes
    2.  🤷🏻‍♀️‏ @DanielleFong 29 Jul 2021
      Replying to @skdh

      usually not; the Q for ignition (5) is basically about the amount of energy absorbed by alpha particles directly, the physicists handwave away the magnet cooling and vacuum maintenance energy costs as something that asymptotes out; micro reactor people sometimes factor it in

      4 replies 2 retweets 33 likes
    3. Seb Tallents‏ @SebTallents 29 Jul 2021
      Replying to @DanielleFong @skdh

      When I left, there was some debate on desirability of ignition (Q>5 -> inf). Alpha's in the core might drive MHD/kinetic instabilities and disruptions; so accepting first orbit loses of alpha, forgoing ignition and focusing on high but not infinite Q might be more practical.

      2 replies 0 retweets 1 like
    4.  🤷🏻‍♀️‏ @DanielleFong 29 Jul 2021
      Replying to @SebTallents @skdh

      but it is going to be a vastly less expensive thing if it’s self heated rather than requiring a bunch of circulating power

      1 reply 0 retweets 1 like
    5. Seb Tallents‏ @SebTallents 29 Jul 2021
      Replying to @DanielleFong @skdh

      Not really, counter intuitively. If you need aux heating to get to ignition, then all you are doing is having that aux heating sitting around doing nothing, and capex and finance costs more than the electricity consumed. The whole thing is driven hugely by capex, not opex...

      2 replies 0 retweets 0 likes
       🤷🏻‍♀️‏ @DanielleFong 29 Jul 2021
      Replying to @SebTallents @skdh

      most aux heating operates in burst mode, to adapt it you need at minimum new cooling and probably a lot of other stuff, and you need a bunch of stuff to power it, all of which has inefficiencies. it adds up!

      11:44 AM - 29 Jul 2021
      • 1 Like
      • Seb Tallents
      1 reply 0 retweets 1 like
        1. New conversation
        2. Seb Tallents‏ @SebTallents 29 Jul 2021
          Replying to @DanielleFong @skdh

          Iirc the idea was keep the plasma going and pulse the heating so you get periods of fusion. Either way the point is the difference between ignition and non ignition is the cost of electricity to run heating, and depreciation of the capital invested in the aux heating kit.

          1 reply 0 retweets 1 like
        3.  🤷🏻‍♀️‏ @DanielleFong 29 Jul 2021
          Replying to @SebTallents @skdh

          yeah i guess that kind of subcritical rundown could make sense if the physics works out but you’re still trading one problem (physics of alpha heating) for another (physics of pulsed operation). still think near continuous operation is a better bet but it’s a theory really

          1 reply 0 retweets 1 like
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