Fusion remains a distant goal, but the good news is that we have not lost pace and with the help of computer simulations we may even speed up a bit. Modelling magnetically confined plasmas on supercomputers is certainly not new, but Greg Foss and Anne Bowen at the Texas Advanced Computing Center at the University of Texas in the USA have used data from such supercomputer simulations to create stunning three-dimensional dynamic visualizations (pictured). The visualizations — featured this month at the SC14 conference — reveal the complexity of the structures present in the ionosphere and tokamak plasmas. These insights could complement traditional diagnostic methods and help improve current ITER tokamak design.

At Sandia National Laboratories in the USA researchers take an alternative approach to fusion (M. R. Gomez et al., Phys. Rev. Lett. 113, 155003; 2014). Their so-called Z machine uses the concept of magnetized liner inertial fusion. An extremely strong magnetic field generated by Helmholtz coils squashes deuterium fuel inside a thin, long tube — the liner. As the confinement is tightened, and just before implosion, a laser beam heats the fuel. In these conditions neutrons are created at a slower pace allowing more time for the fusion reaction to take place. The slower compression also prevents other materials from mixing with fuel and creating instabilities that could ultimately compromise fusion.

Credit: © TEXAS ADVANCED COMPUTING CENTER, THE UNIVERSITY OF TEXAS AT

The team measured the deuterium-deuterium neutron yield and surprisingly, they also observed a secondary signal from deuterium-tritium neutrons — one hundred times larger than expected. This hinted at the existence of extreme magnetic fields that slow down the tritium nuclei giving them time to react with the deuterium fuel. Computer simulations (P. F. Schmit et al., Phys. Rev. Lett. 113, 155004; 2014) confirmed this scenario, suggesting that the probability of fusion would increase thanks to the additional confinement created by these magnetic fields. The results seem promising, but as far as fusion is concerned, we're just not there yet.