Building upon recent findings showing the promise of coating the inner surface of the vessel containing a fusion plasma in liquid lithium, researchers have determined the maximum density of uncharged particles at the edge of a plasma before certain instabilities become unpredictable. The research includes observations, numerical simulations and analysis from their experiments inside a fusion plasma vessel called the Lithium Tokamak Experiment-Beta (LTX- ). This is the first time such a level has been established for LTX- , and knowing it is a big step in their mission to prove lithium is the ideal choice for an inner-wall coating in a tokamak because it guides them toward the best practices for fueling their plasmas.