EX/6-1 · Compatibility of advanced tokamak plasma with high density and high radiation loss operation in JT-60U
H Takenaga1), N. Asakura1), H. Kubo1), S. Higashijima1), S. Konoshima1), T. Nakano1), N. Oyama1), G.D. Porter2), T.D. Rognlien2), M.E. Rensink2), S. Ide1), T. Fujita1), T. Takizuka1), Y. Kamada1), Y. Miura1), JT-60 Team1)
1) Japan Atomic Energy Research Institute, Naka, Japan
2) Lawrence Livermore National Laboratory, Livermore, USA
Abstract: Compatibility of advanced tokamak plasma with high density and high radiation loss has been investigated in both high bp H-mode plasma with a weak positive shear and reversed shear (RS) plasma. In the high bp H-mode plasma, high confinement (HHy2=0.96) is maintained at high density ([`n]e/nGW=0.92, where nGW is Greenwald density) with high radiation loss fraction (frad ~ 0.9) by utilizing high-field-side (HFS) pellets and Ar injections. In the RS plasma, high confinement of HHy2=1.3 is achieved at the high density above nGW ([`n]e/nGW=1.1) even with NB fuelling only. In these plasmas, the high [`n]e/nGW is obtained due to a peaked density profile inside the internal transport barrier (ITB). The pedestal bp, defined as bp-ped=p- ped/(Bp2/2m0), where p-ped is the plasma pressure at the pedestal top, is almost proportional to the total bp (bp-tot) in the high bp H-mode plasma with the HFS pellets and Ar injections, as well as without Ar injection. On the other hand, dependence of bp-ped on bp-tot is weak in the RS plasma. The radiation loss profile in the main plasma is peaked due to impurity accumulation in both plasmas. The impurity transport analyses indicate that core radiation loss from Ar impurity more accumulated by a factor of 2 than the electron, as observed in the high bp H-mode plasma, can be compensated with slightly enhanced confinement in a fusion reactor.
Keywords: advanced tokamak scenarios, confinement studies, Greenwald density, impurity puffing/injection, radiative cooling,