The production of hot dense plasmas in the lab, similar to those generated by the interaction of the solar wind with a planet's magnetic field is reported online this week in Nature Physics. While providing a means to study the dynamics of planetary magnetospheres, the device could also enable new approaches to achieving fusion-based power generation.
The unconventional device used to create the plasmas ― based on a levitated half-tonne superconducting magnet ― recreates an unusual effect often seen in space plasmas but never before in the laboratory. This effect, known as a 'turbulent pinch', enables the density at the core of a hot plasma to be significantly increased. Turbulence in a plasma usually smoothes out variations in its density or temperature, and so should cause the core density of a plasma to decrease. But when a plasma is trapped by certain magnetic-field configurations, such as those generated near a planet, turbulence can have the opposite effect, and drive the diffusion of particles against a density gradient.
Michael Mauel and colleagues believe that if such turbulence-induced density enhancement could be realized in larger devices, it could enable them to recreate the conditions necessary to sustain fusion reactions in a tritium-free plasma. Tritium is one of the two hydrogen isotopes (along with deuterium) that are essential to fusion reactions that will take place in ITER, the International Experimental Fusion Reactor currently being built in Cadarache, France. But because tritium is radioactive and does not occur naturally, generating and handling it represents one of the key engineering challenges faced in the development of fusion-based power stations.