Measurement and scaling of the radial correlation lengths of turbulence at the plasma edge of ASDEX Upgrade

With the single-frequency swept reflectometry diagnostic on ASDEX Upgrade radial correlation lengths of the plasma turbulence can be determined by a new quasi-simultaneous correlation technique. The scaling of the observed microturbulence is investigated in detail through the correlation lengths measured 2 cm inside the separatrix. During the low-temperature L-mode and near the L-H transition these scale according to the resistive ballooning turbulence model. For L- and H-mode plasmas with higher temperatures the correlation lengths scale with the effective Larmor radius as expected for dominantly ηi driven turbulence. (author)