The suppression of edge density turbulence during H-mode phases of tokamak idscharges has long been associate with the formation of an edge transport barrier and a reduction in edge plasma transport. Recent results [1,2] suggest a similar correlation between core turbulence and reduced core transport during optimised or reversed central magnetic shear discharges with an internal Transport Barrier. It is believd that ITBs may be formed through a combination of E*B velocity shear magnetic shear stabilisatio nof plasma turbulence and instabilities [3]. In JET optimised shear discharges [4], results show that the turbulence reduction occurs in two stages. Low frequencies are suppressed throughout the plasma core by a toroidal velocity shear, then high frequencies are locally suppressed around the steep gradient region of the ITB, consistent with E*B poloidal shear.
展开▼
