A point has been made that the plasma in a polywell is out of thermodynamic equilibrium. However:
- the thermodynamic disequilibrium is as observed locally over a small volume.
- I recall mention that the mean free path in a polywell is comparable to the size of the magrid.
- It seems to me that discussing thermodynamic equilibrium over a volume smaller than the mean free path is of limited significance.
So, does it make meaningful sense to talk of thermodynamic equilibrium in a polywell over a volume smaller then the whole confined plasma? My gut says that over that global volume the plasma is in thermodynamic equilibrium. That would tend to shoot holes in some arguments against the polywell.
Thermodynamic equilibrium in a Polywell
The idea of "mean free path" in a plasma is sort of difficult. All the charges are interacting with each other all the time. If you take the mean deviation from a straight line to be some small amount and call anything less than that "no collision", then the system is collisionless within the volume of the Polywell. That's really good news for modeling!
Thermodynamics is about average energy. If the average energy only changes due to collisions, and the particles don't collide (too much anyway), then the system can be out of thermodynamic equilibrium for a long time.
If the particle distribution is non-Maxwellian, then the system can be called "not in thermodynamic equilibrium". There can still be an average energy of the particles and they can stay non-Maxwellian especially if there are no collisions.
Its not so much volume as phase space. If you look at the velocity distribution in any volume, you may get different distributions - all of them non-Maxwellian, but different depending on the volume in question.
Does that make any sense? The concept of "equilibrium" is tied to "Maxwellian", but the Polywell needs to be far away from Maxwellian as long as possible for maximum power.
Thermodynamics is about average energy. If the average energy only changes due to collisions, and the particles don't collide (too much anyway), then the system can be out of thermodynamic equilibrium for a long time.
If the particle distribution is non-Maxwellian, then the system can be called "not in thermodynamic equilibrium". There can still be an average energy of the particles and they can stay non-Maxwellian especially if there are no collisions.
Its not so much volume as phase space. If you look at the velocity distribution in any volume, you may get different distributions - all of them non-Maxwellian, but different depending on the volume in question.
Does that make any sense? The concept of "equilibrium" is tied to "Maxwellian", but the Polywell needs to be far away from Maxwellian as long as possible for maximum power.