Tying plasma into knots with powerful lasers (Vincent Kooij, Chris Smiet, Dirk Bouwmeester)

plasmaknot A self-generated knotted magnetic structure as observed in numerical simulations of decaying helical plasma.

 

Plasma is the most abundant form of ordinary matter in the universe but one also encounters this state of matter more closely to home in for example neon signs, the sun, lightning and nuclear fusion reactors. Due to the unbound electrical charges plasma can sustain extremely large currents and is susceptible to magnetic fields. But in itself, through its motion, plasma generates these magnetic fields as well. This interconnectedness opens up a myriad of interesting complex dynamics.

 

The challenge of current nuclear fusion research is the construction of a fusion reactor that reliably confines the plasma so fusion reactions can take place. The usual approach is to create the necessary complicated magnetic fields within the nuclear reactor using external electromagnets.

 

We take the opposite approach and search for a structure of plasma which itself creates the magnetic fields necessary for its own stability. The theoretical basis is rooted in the mathematical structure known as the Hopf fibration. This curious result from topology allows us to construct a magnetic field in which each and every magnetic field line is a perfect circle and is linked with every other magnetic field line. It has been theoretically shown that this configuration can be utilized to create a stable structure in plasma; the so-called magnetohydrodynamic soliton.

 

We want to make these and related structures in our lab. Using high power lasers one can create localized and high density plasmas that can be analyzed using for example Faraday rotation imaging. Also the investigation of the interaction of multiple plasmas might provide clues for the presence of special magnetic field structures. The ultimate goal is creating a self-organizing knotted magnetic structure in plasma.