Measurement of Plasma Displacement Due to Resonant Field Amplification in High Beta DIII-D Plasmas Using CER Spectroscopy*

In a plasma with beta above the no-wall limit, externally applied magnetic perturbations can couple to the rotationally stabilized RWM via resonant field amplification [1]. This phenomenon is routinely exploited in the technique of active MHD spectroscopy to test the stability of the RWM [2]. We utilize measurements of the ion temperature from charge exchange recombination spectroscopy at two toroidal locations during MHD spectroscopy experiments to obtain a direct measurement of the $n=1$ plasma fluid displacement due to the RFA. The displacement profiles are compared with those expected for the stabilized RWM. \par\vskip6pt\noindent [1] A.M. Garofalo, et al., Phys. Plasmas 10, 4776 (2003).\par\noindent [2] H. Reimerdes, et al., Phys. Rev. Lett. 93, 135002 (2004).