Hot plasma is like a swarm of frantic fireflies darting around in a jar. Keeping it confined in an open magnetic trap is like trying to keep those fireflies from touching the glass. A new computer model shows how to do it more precisely.
Ions and electrons in plasma constantly collide, exchanging energy. In earlier calculations, such collisions were often simplified or ignored altogether. The authors added them to the model, and immediately saw the temperature even out between particles. It's as if in a swarm of fireflies, some glow brighter and others dimmer, but over time they all reach the same brightness.
The model accurately reproduces plasma behavior near the walls and throughout the trap. Comparison with another code, MIDAS, showed a difference of 15% in temperature and density. This matters: such calculations help build more efficient fusion devices.
The fireflies in the jar are now under control — almost.
In plasma, electrons move tens of times faster than ions, so an electric field arises near the walls that slows down the fast ones and speeds up the slow ones.
In Larry Niven's novel Ringworld, magnetic fields confine plasma in spacecraft engines — similar to open traps, but on a cosmic scale.