David Kirtley

And in that magnetic field, plasma is trapped on that magnetic field.

But it's not very well trapped.

It can escape.

It can leave either down the ends, it can freely travel, or it can also travel

across the magnetic field.

And so we have a term called plasma beta, which gives us an understanding of how well trapped that plasma is.

So as you apply a magnetic pressure, a magnetic field to this plasma, it pushes back.

And does it push back a little or does it push back a lot?

And for a field reverse configuration in one of our plasmas, beta is very close to one.

Usually, by definition, one at any point in the system, which means that every time I apply a magnetic force on this donut to compress it, the plasma particles on the inside push back.

And what's really interesting is you have an equation for magnetic pressure, which is b squared over 2 mu naught.

The magnetic field squared is the external magnetic pressure.

Any magnetic field anywhere generates this pressure.

But the

plasma particles themselves also have a pressure.

This is the ideal gas law.

And we use the definition NKT, density, Boltzmann constant, and temperature for pressure.

And in high beta, they're the same.

B squared over 2 mu naught is NKT.

So for a known magnetic field, I know what the density and the temperature of the plasma is.