What is plasma?

Stars, lightning and fusion energy – what do these things have in common? Plasma is often called the fourth state of matter. It happens when we superheat a gas.

Picture an atom, made of a nucleus and an electron. Extreme heat strips away the electron, creating a ‘soup’ of positive ions and electrons – that’s plasma. This heat along with pressure create the conditions where fusion can happen. The charged particles of our fusion fuels in the ‘soup’ are free to smash together and release their energy. This energy can then be harnessed to generate electricity in fusion power plants.

We’re researching how plasmas behave and how we can sustain plasmas in experiments in our MAST Upgrade fusion machine. To help us do this, we use diagnostics, modelling and simulations. We have decades of experience with plasma at UKAEA. And we’ve even broken records for plasma power with the iconic Joint European Torus (JET) in 1997, 2021 and 2023.

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