Evaporation of Pellets Injected into Tokamak Plasmas and the Classical Flux-Limit Parameter

The steady-state saturated-evaporation theory of a cold cloud in a hot tenuous atmosphere developed by Cowie and McKee is applied to the evaporation of pellets injected into tokamak plasmas. The agreement with limited experimental results is found to be quite good, and extrapolation of the theory to a reactor-size tokamak indicates a required pellet injection velocity of 5×{}10⁶ cm/sec. Finally, the experimental evaporation times can be viewed as a measurement of the classical flux-limit parameter, which is found to be $f=0.6$.