Lithium is considered a key ingredient in the future commercial fusion power plants known as tokamaks, and there are several ways to use this metal to enhance the process. But a key question remained: How much does it impact the amount of fuel trapped in the walls of tokamaks?

According to new research from a global collaboration spanning nine institutions, the dominant driver of fuel retention is co-deposition: a process where fuel is trapped alongside lithium. Co-deposition can happen with lithium that is directly added during plasma operations, or lithium that has been previously deposited on the walls, only to wear away and be redeposited.

The research also showed that adding lithium during operation is more effective than pre-coating the walls with lithium in terms of creating an even temperature from the core of the plasma to its edge, which can help create the stable plasma conditions needed for commercial fusion.