Credit: Image courtesy of UCSD/DOE-DE-FG02-07ER54917
Neutral argon line emission from the ablation plume of a frozen argon ice pellet as it traverses the plasma of the DIII-D tokamak (t is the time in milliseconds (ms)). From the brightness of this ablation plume, it is possible to deduce the rate at which argon gas is boiling off the surface of the pellet and ultimately estimate the fast electron content of the plasma.