Observation of m=1, n=1 oscillations following the injection of a fuel pellet into the Alcator C tokamak

Immediately after the injection of a fuel pellet into the Alcator C plasma, strong m=l, n=l oscillations of the soft X-ray signals are observed. Measurements of the electron temperature during this period indicate that the X-ray fluctuations cannot be accounted for by temperature variations. This implies that the densities must vary. Experimental data and computer calculations show that a low level coherent fluctuation of the electron/proton density and a light impurity can account for the observations.