How mathematical modelling may be the key to successful fusion power
The air molecules in a room move constantly, colliding with each other, the walls and anything else that happens to be in there. The velocity of these molecules is what gives the air its temperature, the faster the motion the hotter the air. However not all the molecules are moving at the same speed. They follow what’s known as a Maxwell- Boltzmann distribution, a bell curve of velocities that mathematically describes most fluids in equilibrium. The physics of fluids with such Maxwellian temperature distributions is well established and models many ordinary every-day fluids extremely well. However when it comes to more complicated situations such as the flow of super high temperature plasma in a fusion reactor, it begins to fall down. Dr Mathew Hole and Dr Michael Fitzgerald are two scientists aiming to put this right.
"Most of our existing theoretical models of plasma fusion reactors rely to a greater or lesser extent on simple Maxwellian distributions," Dr Hole explains, "But in a fusion reactor we know that there are times when the distributions are far from Maxwellian." This is because of the extreme conditions within a reactor and the fact that unlike many fluids, plasma is electrically charged.
Fusion can only take place when the plasma reaches a temperature of many millions of degrees and the only way to hold something that hot is within a magnetic bottle. The problem is that you can’t get it that hot without using powerful microwave fields and injected beams of super energetic particles. Both make the plasma non-Maxwellian, and the introduced hot particles generate their own magnetic fields as they twist and weave along an externally applied magnetic containment field. The beam particles also inject momentum, spinning up the plasma. Now add to that the additional magnetic and electric fields generated by charged energetic alpha particles produced by fusion reaction, and you have mathematician’s nightmare.