Evolution of the electric potential and turbulence in oh and ecrh low-density plasmas at the t-10 tokamak

Plasma regime with a positive core electric potential (positive electric field) was obtained for the first time in a tokamak. This low-collisionality regime was reached by strong electron-cyclotron resonance heating (PEC = 2.2 MW) of the low-density (nе ~1.010 19 m) plasmas in the T-10 circular tokamak (B0=2.2 T, R=1.5 m, a=0.3 m, Ipl = 230 kA). The obtained positive electric field is not consistent with NC approach and suggests turbulence origins. The coupling of plasma potential and collisionality was extended towards the ‘banana’ collisional regime predicted for ITER, so the positive plasma potential is expected for ITER plasmas.