nuclear physics - Gaseous fission: Has it even been demonstrated experimentally?

I've been reading quite a bit about gas-core reactors, a theoretical reactor design where the fissioning of Uranium(along with Plutonium & possibly Thorium)occurs in gas phase. The result is that the heat of the reaction converts the gaseous nuclear fuel into plasma which can be contained in a magnetic bottle. The most feasible design for such a reactor is cylindrical metal reactor vessel with a magnetic solenoid where the electromagnets push inward radially; confining the plasma. I would imagine that such a reactor would need an inner lining of neutron reflecting material to deflect neutrons and bounce them back and forth across the chamber. But do to the chemical properties of Uranium Hexafluoride gas it might be more prudent to use a single, supercritical solid fuel rod assembled vertically inside of a vacuum solenoid. The fuel rod would then be bombarded by intense microwaves from directly above to convert it into plasma after the electromagnets are turned on. But the question remains if it is even possible to compress the plasma to a high enough density to initiate fission. Has this experiment ever been tried? If so, what were the results?