What does "beta" mean?

Discuss how polywell fusion works; share theoretical questions and answers.

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KitemanSA
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Post by KitemanSA »

With β=10%, the plasma pressure is LOWER than the magnetic pressure, so why would it expand?

MSimon
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Post by MSimon »

TheRadicalModerate wrote:I figured that I'd resurrect an ancient thread, rather than create a new one for this:

I've recently realized that I'm confused about beta, as well. Tokamaks have betas around 5-10%, but here's where I've fallen and can't get up: If the magnetic pressure is less than the plasma pressure, doesn't that mean that the plasma isn't in equilibrium, and the greater plasma pressure will cause it just to expand until it hits the vessel walls?

Since tokamaks seem to have a real live separatrix, I'm assuming that that's not what happens. So what other terms are there other than plasma pressure and magnetic pressure that keep the plasma bottled up?
Plasma pressure/magnetic pressure = .1

The plasma is bottled.
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TheRadicalModerate
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Post by TheRadicalModerate »

KitemanSA wrote:With β=10%, the plasma pressure is LOWER than the magnetic pressure, so why would it expand?
I kept staring at the definition and every time read it as magnetic/plasma, not plasma/magnetic. Tag this one as a brain fart. Thanks.

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