Sawtooth oscillations in the flux of runaway electrons to the PLT limiter

Increased fluxes of runaway electrons at the PLT limiter are observed in the few milliseconds following internal disruptions. These fluxes have an inverted (outside) sawtooth character. The time for the flux to reach a maximum after the disruptions has been studied as a function of the plasma parameters for thousands of PLT discharges. One interpretation is that this delay represents the time for a perturbation to the runaway electron population to travel from the q=1 region to the plasma boundary. These times are approximately 10-1 of the electron thermal confinement times and increase with the plasma electron density. (author)