Observation of inverse sawtooth activity on central soft X-ray emission during impurity injection in the J-TEXT tokamak

Short- and long-time lasting inverse sawtooth activities during neon (Ne) gas injection, not during helium (He) or argon (Ar) though, have been clearly observed on soft X-ray emissions from chords viewing the central plasma region of the Joint Texas Experimental Tokamak (J-TEXT). A self-consistent interpretation of the inverse sawtooth activity depending on the impurity radiation characteristics is proposed. It is evidenced that the radiation loss caused by the injection of noble gas not only depends on the amount of the noble gas itself, but also depends on the temperature region where the noble gas can reach.