$n>1$ Resistive Wall Mode (RWM) Identification,*

Resistive wall mode studies in DIII-D demonstrated the effectiveness of $n=1$ RWM feedback control beyond $n=1$ no-wall $\beta$ limit, where $\beta$ is the ratio between plasma pressure and magnetic pressure. However it is predicted that, as $ \beta$ increases, not only $n=1$ RWM but also $n>1$ RWM may become unstable. The presence of $n=3$ mode on top of $n=1$ mode has been observed in some recent DIII-D RWM shots. In order to accurately identify $n>1$ RWM, a set of matched filters associated with $n>1$ RWM is under development using the same method as developed for $n=1$ matched filter [1]. Specifically, based on the magnetic perturbations of each toroidal mode on plasma surface, the FARVAC code calculates the estimated signals for magnetic sensors to construct $n>1$ RWM matched filter. Along with the $n=1$ RWM matched filter, we plan to use these $n>1$ RWM matched filters to provide a more complete RWM identification to achieve higher $\beta$ operation. \par\vskip3pt\noindent [1] D.H. Edgell, et al., Rev. Sci. Instrum. \bf{73}, 1761 (2002).