Investigation of energy transport of high β_N plasma on EAST tokamak

In the past few years, the high normalized beta (β_N >1.8) discharges have been realized on the EAST tokamak with neutral beam injection(NBI) and lower hybrid waves(LHW). It is found that LHW most deposits in the outer region and drives small current fraction and does small effect on the increase of β_N. Sustained high β_N (~ 1.9) plasmas have been achieved on EAST tokamak with an internal transport barrier (ITB) in all channels. The central flat q profile with q(ρ) ~ 1 at ρ < 0.3 region and edge safety factor q₉₅ = 4.7. Linear analysis shows that the high-k modes instability (electron temperature gradient driven modes) is suppressed in the core region when the ITB is formed. Turbulence transport code TGLF[VX model, Jian et al., Nucl. Fusion 58, 016011(2018)] gives good agreements on temperature profiles prediction before the ITB formation. However, it could not reproduce the experimental temperature profiles when exist internal transport barriers. The reason is that the fishbone instability appears in the discharge, which could redistribute the fast ion and affect the energy transport while it is not considered in TGLF. The relationship between fishbone activity and the energy transport needs to be investigated for these high β_N discharges in order to validate this conjecture.