Robustness of RWM Feedback Performance in AT Plasmas*

High-speed actuators with frequency response of dc-40~kHz have been installed to upgrade the resistive wall mode (RWM) feedback capability in \hbox{DIII-D}. These actuators are configured to drive the \hbox{DIII-D} internal coil set (I-coils). The experimental observations qualitatively support that the voltage-controlled feedback does assist achieving long duration high beta plasmas. However, non-reproducibility of the RWM onset makes it harder to provide a quantitative measure of direct feedback and to separate the effects rotational stabilization. Possible causes of non-reproducibility are: (1)~coupling to ELMs, (2)~residual error field persisting even after the dynamic error field correction, (3)~possible coupling of RWM, ELMs and residual error field. The experimental observations will be discussed in light of these possibilities along with MARS-F analysis.