Study of confinement improvement in presence of a MARFE in the HT-7 superconducting tokamak

A new set of actively cooled toroidal double-ring graphite limiters have been developed on the HT-7 tokamk for long pulse operation. In this paper, a Multifaceted asymmetric radiation from the edge (MARFE) phenomena and improved particle confinement induced by a MARFE, characterized by Ho, line emissions drops and the line-averaged density increase have been studied in the HT-7 ohmic discharges (where the plasma current I-p = 145 kA, loop voltage V-loop =2-3 V, toroidal field B-T=1.7 T, and Z(eff)=2-8). It is found that the improved particle confinement phase exists for about 90 ms and the particle confinement time tau(P) increased about 1.6 times.