4 ms·

Can you explain what you mean by tokamaks "going against the physics"?

kuschku 11y ago
Tokamaks need, to contain the plasma, a continuously changing magnetic field. To create a continuously changing magnetic field, you need to continuously increase or decrease the current. The issue is that you can not turn up the current more than a maximum level, and you have to keep the direction the same (so you can’t switch between turning off and on). Stellerators instead solve this with complex geometry and the plasma creating its own continously changing magnetic field.
- drjesusphd 11y ago
  > Tokamaks need, to contain the plasma, a continuously changing magnetic field Do you have a citation for this claim?
  - kuschku 11y ago
    I could source one from German Wikipedia, but english wikipedia does not seem to have that information. You might be able to find some sources when you search for the reasons of Tokamaks pulsed usage.
  - fanf2 11y ago
    A tokamak is basically an AC transformer, with the plasma acting as one of the windings.
zamalek 11y ago
So far as I understand it (arm chair physicist), Stellerators "shape" the plasma in a "natural" way, Tokamaks force it into a more "unnatural" shape - like trying to put a beach ball [plasma] into a box [torus]. If I misunderstand it disregard my comment entirely, although I'd like to know why.
- drjesusphd 11y ago
  Here's how I understand it: - The simplest closed magnetic configuration is a torus. You can't smoothly "comb a hairy ball", but you can comb a hairy torus. - For a toroidal plasma to be stable, it needs magnetic field components both the "long way" around (toroidal), and the "short way" around (poloidal). - The tokamak generates the poloidal field from a current within the plasma, whereas the stellerator imposes that component with external magnets. So you could make a "natural" argument either way, and I was asking the grandparent in what sense the stellerator is more "natural".

Tokamaks need, to contain the plasma, a continuously changing magnetic field. To create a continuously changing magnetic field, you need to continuously increase or decrease the current. The issue is that you can not turn up the current more than a maximum level, and you have to keep the direction the same (so you can’t switch between turning off and on). Stellerators instead solve this with complex geometry and the plasma creating its own continously changing magnetic field.

drjesusphd 11y ago
> Tokamaks need, to contain the plasma, a continuously changing magnetic field Do you have a citation for this claim?
- kuschku 11y ago
  I could source one from German Wikipedia, but english wikipedia does not seem to have that information. You might be able to find some sources when you search for the reasons of Tokamaks pulsed usage.
- fanf2 11y ago
  A tokamak is basically an AC transformer, with the plasma acting as one of the windings.

zamalek 11y ago

So far as I understand it (arm chair physicist), Stellerators "shape" the plasma in a "natural" way, Tokamaks force it into a more "unnatural" shape - like trying to put a beach ball [plasma] into a box [torus]. If I misunderstand it disregard my comment entirely, although I'd like to know why.

drjesusphd 11y ago
Here's how I understand it: - The simplest closed magnetic configuration is a torus. You can't smoothly "comb a hairy ball", but you can comb a hairy torus. - For a toroidal plasma to be stable, it needs magnetic field components both the "long way" around (toroidal), and the "short way" around (poloidal). - The tokamak generates the poloidal field from a current within the plasma, whereas the stellerator imposes that component with external magnets. So you could make a "natural" argument either way, and I was asking the grandparent in what sense the stellerator is more "natural".