\textbf{Measurements of CAE }\textit{\~{n}}\textbf{ in DIII-D and identification of intermediate frequency AEs}
POSTER
Abstract
New analysis is reported of recent measurements of fast-ion driven compressional Alfv\'{e}n eigenmodes (CAE, $\omega $\textless $\sim \omega_{ci})$ and intermediate frequency AEs ($v_{A}/R \ll \omega \ll \omega_{ci})$. These modes are of interest because they can potentially cause electron energy transport; additionally, these measurements advance the development of AE spectroscopy as a tool for non-invasive diagnosis of fast-ions in DIII-D and burning plasmas. Measurements of CAE radial structure obtained with an array of eight fixed frequency reflectometers are analyzed to determine absolute \textit{\~{n}}. Intermediate frequency modes preliminarily identified as Alfv\'{e}n eigenmodes (AE) were observed in beam-heated ELMing H-mode plasmas. However, the observed frequencies---$f \sim $1 -- 2 MHz $\sim $ 2 -- 5 $v_{A}$/2$\pi R$ (where $v_{A}$/$R$~$\sim $~0.03 $\omega_{ci})$---are too low for CAEs and too high for toroidicity-induced or reverse shear AEs. The observed frequencies and two-point toroidal mode number measurements (\textbar $n$\textbar $=$ 3 -- 6) will be compared with the spectrum of AEs predicted by the ideal MHD eigenmode code NOVA in order to potentially identify the type of mode observed.
*Work supported by US DOE grants DE-FG02-99ER54527, DE-FC02-04ER54698, DE-SC0019352, and DE-SC0011810