Study of MARFE Phenomena on TH-7 Tokamak

摘要

MARFE phenomena on HT-7 tokamak is sudied in this paper. A best correlation has been found between the total input ohmic pwor and the product of the edge line average densiy and Z_eff. MARFEs which is storngly correlated with impurity density, always occurs at Z_eff=3～8 ohmic discharges. In HT-7 tokamak high Z_eff discharges, it is found that the MARFEs usually occura t values of Z~1/2_eff ρ in lthe range of 0.5～0.7, where ρ=π~α~2n_e/P(10~20 MA~-1). In the case of good wall condition (Z_eff=1～2), the onset of MARFEs have nto been observed before reaching the Greenwald density limit. on HT-7. An improved confinement mode plasma which is induced by the MAREE is observed, the global particle confinement time increases. 1.9 times. The relaxation time between the MARFE event trigger and the L-H transition is about 1.4 ms, the followed L-H transition time is 1.9 ms, the improved confinement mode pahse is maintained for about 40 ms. MARFE cools the plasma edge, and the electron desnity profileis observed to become more narrow and peaking.