mvanwink5 wrote:One vast difference between Polywell and LM's fusion machine (CFR) is that Polywell uses high voltage to drive fusion, but for LM's CFR, they think that heat of fusion will drive the reaction after initial startup. They do this by retaining the fusion byproducts with recirculation aided by the outer mirror magnets.
So, it looks like the power transference will be thermal, possible with molten salt, but those details are to be developed down the road. McGuire's talk devoted a lot to the idea of how to achieve high project development speed.
It looks like the Lockheed machine is intended as a D-T ignition machine. Neutral beam heating drives the startup conditions, ignition may maintain operation thereafter.
There indeed is no electrostatic potential well. Both the electrons and ions are magnetically contained. He mentions that an ion executes a 1/2 gyroradius turn on the high Beta edge. Ion entrapment in the border sheeth and subsequent ExB losses enter the picture only if the ion undergoes a Coulomb collision on the edge. This presumably mitigates the ExB ion diffusion issues considerably. There are good magnetic curvatures everywhere except outside the two interior magnets so edge instabilities only occurs there. Apparently this will be only a small percentage of the magnetic bottle surface area and will only involve plasma that escapes through the cusps into this region, so the contribution may be small. Also, he mentioned the magnetic potential well. Somehow the instabilities in these cusp areas mentioned must preferentially inject the plasma back towards the center of the machine. I don't know how this would occur.
On the machine ends the spindle cusps are mentioned as a major loss areas. Apparently the produced alphas, after thermalization are expected to exit here and be removed via a diverter. Does the fuel plasma somehow recirculate here around the magnets?
The cooling with metal salts is mentioned. I suppose he means lithium salts, as tritium will need to be bred. The greatest thermal wall loading is expected to be at the inner edges of the two main internal magnets. The heating will be primarily from the D-T produced neutrons and may reach about 10 MW per square meter, a challenge in itself.
I didn't get any hint that this machine could use anything other than D-T fuel, and that optimistic Qs of 3-5 may be possible (if I heard right).
To error is human... and I'm very human.