4 ms·

I think if I understand correctly, there'll be a fluid (FLiBe) between the plasma and the magnet coils that absorbs most of the neutrons. The FLiBe heats up an

by elihu 6y ago

I think if I understand correctly, there'll be a fluid (FLiBe) between the plasma and the magnet coils that absorbs most of the neutrons. The FLiBe heats up and is used to boil water to power a steam turbine. SPARC isn't particularly designed for durability, but for the ARC reactor which is meant to be the commercially-useful iteration they're looking at having solder joints on the superconducting magnet film so the whole top of the reactor can be removed so they can pull out the inner lining in one piece and replace it. (Apparently they figured out that regular non-conducting solder joints don't actually introduce very much resistance.) I don't think there's any plan to replace the ribbon.

jacquesm 6y ago
regular non-superconducting solder joints. They conduct, just not nearly as good as the material itself at that temperature. Still, interesting that that would not result in enough power to boil away the solder.
- elihu 6y ago
  Yeah, that's what I meant. Thanks. I guess if the solder joints are super-thin, there isn't much resistance. But still, it defies intuition. One of the other weird things the MIT group working on SPARC has been experimenting with that sounds like it totally wouldn't work but apparently it does is that they don't bother to insulate between the Rebco tape windings. The superconductor is just a thin layer on top of stainless steel, and the stainless steel is a sufficiently mediocre conductor that the vast bulk of the power takes the long way around following the superconductive layer rather than taking a shortcut through the stainless steel. Apparently the insulator is less durable than the tape itself, so not having to rely on it makes for a more durable device.
  - NortySpock 6y ago
    Huh. I would have assumed kapton tape wouldn't have been too hard to add, but if you can do just fine without that, it's even fewer manufacturing steps.
    - jamiek88 6y ago
      The best part is no part!

by elihu 6y ago

jacquesm 6y ago

regular non-superconducting solder joints. They conduct, just not nearly as good as the material itself at that temperature. Still, interesting that that would not result in enough power to boil away the solder.

elihu 6y ago
Yeah, that's what I meant. Thanks. I guess if the solder joints are super-thin, there isn't much resistance. But still, it defies intuition. One of the other weird things the MIT group working on SPARC has been experimenting with that sounds like it totally wouldn't work but apparently it does is that they don't bother to insulate between the Rebco tape windings. The superconductor is just a thin layer on top of stainless steel, and the stainless steel is a sufficiently mediocre conductor that the vast bulk of the power takes the long way around following the superconductive layer rather than taking a shortcut through the stainless steel. Apparently the insulator is less durable than the tape itself, so not having to rely on it makes for a more durable device.
- NortySpock 6y ago
  Huh. I would have assumed kapton tape wouldn't have been too hard to add, but if you can do just fine without that, it's even fewer manufacturing steps.
  - jamiek88 6y ago
    The best part is no part!