Perturbative Thermal Transport Studies on Alcator C-Mod and ASDEX Upgrade

Perturbative thermal diffusivity has been measured on Alcator C-Mod and ASDEX Upgrade via the extended-time-to-peak method with heat pulses generated by partial sawtooth crashes. Heat pulses generated by sawtooth crashes have been used extensively in the past to study perturbative diffusivity [Lopes Cardozo, N.J., PPCF 37, 799 (1995)], but the details of the sawtooth event lead to non-diffusive ``ballistic'' transport, invalidating their use for measuring perturbative diffusivity [Fredrickson, E.D. et al., PoP 7, 5051 (2000)]. Partial sawteeth generate a heat pulse without the ballistic transport of full sawteeth [Fredrickson 2000]. Partial sawtooth analysis was applied to over 50 C-Mod shots containing both L- and I-Mode, as well as ASDEX Upgrade plasmas, though partial sawteeth were less common on AUG. Results indicate correlations between perturbative diffusivity and confinement regime (L- vs. I-mode), as well as correlations with local temperature, density, the associated gradients, and gradient scale lengths (a/LTe and a/Ln). Finally, diffusivities calculated from partial sawteeth were compared to perturbative diffusivities calculated with the GYRO gyrokinetic code, leading to quantitative agreement with multi-scale GYRO simulations.