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SebTallents's profile
Seb Tallents
Seb Tallents
Seb Tallents
@SebTallents

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Seb Tallents

@SebTallents

Relapsed public servant, recovering management consultant and former physicist. Easily nerd-sniped. Likes, retweets or analysis are not endorsement.

London, England
Joined March 2010

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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. Seb Tallents‏ @SebTallents 29 Jul 2021
      Replying to @skdh

      Former fusion researcher: generally no - gain values quoted most in literature are thermal, particularly if the notation used is Q. The terminology for full system efficiency is often referred to as "wall plug efficiency" /1

      1 reply 1 retweet 32 likes
      Seb Tallents‏ @SebTallents 29 Jul 2021
      Replying to @SebTallents @skdh

      this latter figure takes into account the power input into aux heating (as opposed to deposited into the plasma), magnets etc. This is why Q=10 is considered the target for breakeven - Q=10 roughly corresponds to estimate for a genuine full system breakeven.

      10:14 AM - 29 Jul 2021
      • 29 Likes
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      3 replies 0 retweets 29 likes
        1. New conversation
        2. Sabine Hossenfelder‏Verified account @skdh 29 Jul 2021
          Replying to @SebTallents

          Cool, thanks so much. So the difference is roughly an order of magnitude or so? Do you have a reference?

          2 replies 0 retweets 5 likes
        3. Seb Tallents‏ @SebTallents 29 Jul 2021
          Replying to @skdh

          I've been out of the field for a decade - I worked on MAST in UK - and this sort of thing was more praxis/tacit knowledge. The literature focused on physics parameters rather than prospective commercial engineering - with reason: these were experimental devices, not prototypes.

          1 reply 0 retweets 6 likes
        4. Show replies
        1. New conversation
        2. Seb Tallents‏ @SebTallents 29 Jul 2021
          Replying to @SebTallents @skdh

          Obviously, with commercial reactors "always 20 years away" - it's hard to know what thermal efficiency should look for to achieve full system efficiency. It depends on efficiencies in magnets, how much field strength you need, efficiencies of different auxiliary heating etc...

          1 reply 0 retweets 1 like
        3. Sabine Hossenfelder‏Verified account @skdh 29 Jul 2021
          Replying to @SebTallents

          Exactly!

          0 replies 0 retweets 0 likes
        4. End of conversation
        1. Seb Tallents‏ @SebTallents 29 Jul 2021
          Replying to @SebTallents @skdh

          Seb Tallents Retweeted Seb Tallents

          made a bit of a mess of my threading - this below would probably go better herehttps://twitter.com/SebTallents/status/1420801171372052490 …

          Seb Tallents added,

          Seb Tallents @SebTallents
          Replying to @skdh
          IDK what state of the art is, but this paper from 2013 has NBI wall plug efficiency of around 30%. I can't remember what the losses are in neutral beam injected power is, but lets say 20%, and then 60% efficiency thermal out put to electricity... so on that basis Q_Eng ~ 10 Q_th
          0 replies 0 retweets 1 like
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