Broadening the SOL Heat Load Width by Turbulence Spreading

SOL widths in H-mode scale unfavorably with poloidal field. Since pedestal turbulence persists in H-mode, we calculate the turbulence intensity flux from the pedestal necessary to broaden the SOL beyond pessimistic HD predictions. A SOL width as a function of spreading flux is derived. In turn, the requisite intensity flux is related to pedestal turbulence levels and the transport barrier shear, so the conditions for SOL broadening are determined, explicitly. Turbulent pedestal states, such as “grassy ELMs”, wide pedestal QH mode, etc., are identified as desirable regimes, as they produce higher pedestal turbulence, which in turn broadens the SOL. Interesting implications for SOL stability in the case of strong layer broadening are discussed.