Transport comparison of ASDEX Upgrade and Wendelstein 7-X ECRH hydrogen plasmas

Turbulence-induced heat transport is a challenging field of study in fusion energy science due to inherently complex and non-linear behavior. Here, the heat transport in electron cyclotron-heated hydrogen plasmas has been compared between the ASDEX Upgrade (AUG) tokamak and the Wendelstein 7-X (W7-X) stellarator using the ASTRA code to shed light on the effect of magnetic configuration on transport. While the electron heat diffusivity $\chi_e$ is comparable between AUG L-mode and W7-X plasmas when the input heating power is scaled to the plasma surface area, the ion heat diffusivity $\chi_i$ is lower in W7-X at mid-radius by a factor of 3 or greater. This is also seen when the analysis is performed using matched AUG and W7-X density and temperature profiles. This may be indicative of the $1/R$ dependence of interchange turbulence or reduced turbulent transport in the 3D magnetic field structure of W7-X.