Observations of macroscopic oscillations of the detachment front for injection of H2, He, and Ne into the simulated baffled divertor

Oscillations of the position of the detachment front have been observed in a linear machine with a simulated baffled divertor with a He plasma for various species of injection gas, i.e., helium, neon, and hydrogen. The oscillation, with a back-and-forth motion, of the detachment front along field lines, accompanies a significant oscillation of the neutral gas pressure in the divertor region. This is due to the fact that plasma plugging depends on the position of the detachment front. The amplitude and period of the oscillation of the gas pressure are largest for neon and smallest for hydrogen, which can be closely related to the plasma pressure at the entrance of the divertor region for the particular gas species.