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>The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly. It's not that simple. The big probl

>The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly. It's not that simple. The big problem with magnetic confinement fusion is that you need to control turbulence in the plasma so that you can contain the reactions for a reasonable amount of time to extract useful energy. However, turbulence increases with stronger magnetic field gradients, which is exactly what you get when making a smaller reactor chamber with stronger magnets. This wouldn't be the first project claiming to be able to build a small reactor, only to discover that it's virtually impossible without a major theoretical breakthrough. This is usually left out in the venture capital advertisements for these fusion startups. There's a reason why so much money and effort is spent on ITER - it is the only more or less guaranteed path to fusion with the tech and knowledge we have today.

lambdatronics 5y ago
>However, turbulence increases with stronger magnetic field gradients Mmm, this isn't right. The stronger magnetic field reduces turbulence, it's the gradient of the pressure that generates turbulence. As best as anyone can tell, SPARC should be able to get Q~10 without any miracles involved -- the engineering rules of thumb and the advanced simulations all say the same. https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/status-of-the-sparc-physics-basis/B21625B93C0654B955B776566C96DF6B https://www.cambridge.org/core/journals/journal-of-plasma-ph...
- sigmoid10 5y ago
  >The stronger magnetic field reduces turbulence That's why I specifically said field gradients - i.e. the thing that gets larger when you have a stronger field in a smaller volume. >it's the gradient of the pressure that generates turbulence How exactly do you think that pressure is created? Also, that link you provided is an editorial from one of the directors behind SPARC. If you want an objective analysis that is not geered towards possible investors, you need to look elsewhere. FYI, anyone selling you Q~10 designs without a considerable theoretical breakthrough is almost certainly conning you. If you don't believe me just look at how Lockheed's compact fusion reactor panned out. Stronger magnets are not some kind of miracle solution that will enable fusion tomorrow.

lambdatronics 5y ago

>However, turbulence increases with stronger magnetic field gradients Mmm, this isn't right. The stronger magnetic field reduces turbulence, it's the gradient of the pressure that generates turbulence. As best as anyone can tell, SPARC should be able to get Q~10 without any miracles involved -- the engineering rules of thumb and the advanced simulations all say the same. https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/status-of-the-sparc-physics-basis/B21625B93C0654B955B776566C96DF6B https://www.cambridge.org/core/journals/journal-of-plasma-ph...

sigmoid10 5y ago
>The stronger magnetic field reduces turbulence That's why I specifically said field gradients - i.e. the thing that gets larger when you have a stronger field in a smaller volume. >it's the gradient of the pressure that generates turbulence How exactly do you think that pressure is created? Also, that link you provided is an editorial from one of the directors behind SPARC. If you want an objective analysis that is not geered towards possible investors, you need to look elsewhere. FYI, anyone selling you Q~10 designs without a considerable theoretical breakthrough is almost certainly conning you. If you don't believe me just look at how Lockheed's compact fusion reactor panned out. Stronger magnets are not some kind of miracle solution that will enable fusion tomorrow.