Statistical characteristics of the SOL turbulence in the first divertor plasma operation of W7-X using a reciprocating probe

The statistical characteristics of the scrape-off layer (SOL) turbulence have been investigated in the first divertor plasma operation of W7-X using a reciprocating probe. The turbulence spectra, auto-correlation time and the statistical parameters are analyzed in three magnetic configurations. In standard and high mirror configurations, the SOL turbulence can be classified into four patterns from the outer SOL to the inner SOL, and each pattern is characterized by the poloidal cross correlation spectrum and the turbulence propagation property. A strong dependence of the SOL turbulence on the magnetic topology is demonstrated experimentally. In high iota configuration, the SOL island is relatively narrow and consequently the fluctuation level of turbulence is weak in the far SOL but enhanced significantly in the near SOL. In the reversed field case, the SOL turbulence reveals similar propagation properties and statistical parameters with those in the normal field case, demonstrating the same turbulence structure in both toroidal field directions.