Study of power width scaling in scrape-off layer with 2D electrostatic turbulence code based on EAST L-mode discharges

The study of the power width in the scrape-off layer (SOL) is very important for the design and operation of ITER. In this paper, a 2D electrostatic turbulence code is employed to study the power width scaling in L-mode plasmas. It is found that the electron and ion turbulent transports dominate the radial heat fluxes, and the electron heat conduction and the ion heat advection dominate the parallel heat flux in the near and far SOL in L-mode plasmas.

The simulated SOL power width agrees well with the Eich scaling [T. Eich et al., Nucl. Fusion 53, 093031 (2013)] and the predictions by the heuristic drift-based model [R. J. Goldston, Nucl. Fusion 52, 013009 (2012)] for selected EAST L-mode discharges. A numerical scaling has been performed based on one of these discharges.

The scaling dependence on the safety factor is consistent with the Eich scaling and the scaling exponent of the edge electron temperature is close to that in the ASDEX-Upgrade L-mode scaling [B. Sieglin et al., Plasma Phys. Controlled Fusion 58, 055015 (2016)]. The investigation of the obtained numerical scaling for L-mode plasmas reveals that the SOL power width is influenced by the safety factor, the edge electron density, and the edge electron temperature through the parallel heat transports, the radial turbulent heat transports, and both the parallel and radial heat transports, respectively.

The formulation of the turbulence model suggests that the scaling dependence on the poloidal magnetic field (or the plasma current) for the experimental scalings is essentially the scaling dependence on the ballooning length, q95R. Based on this idea, a further numerical scaling gives λ-q ∝ q951.30Bt−0.33R1.32 ∝ Bt−0.29(q95R)1.33, which has a strong scaling dependence on the major radius that is different from the Eich scaling.