The Effects of Neutral Damping on Resistive Wall Mode Physics

The physics of the dissipation mechanism responsible for rotational stabilization of the resistive wall mode (RWM) is an object of intense current research. On the HBT-EP tokamak there is experimental evidence that edge neutral damping is a significant dissipation mechanism that affects tearing mode behavior [1]. We describe initial progress made towards investigating neutral particle damping effects on RWM dynamics in HBT-EP plasmas. We will report on initial calculations using \href{http://psfcwww2.psfc.mit.edu/people/labombard/}{LaBombard's} (MIT) 1D space, 2D velocity kinetic transport model for atomic and molecular deuterium penetration to quantify profiles of these neutrals within the plasma [2]. In addition, the design, construction, and implementation of a 16-channel linear photo-detector array will be described, and its use to measure D$_{\alpha }$ emission, plasma fluctuations, and neutral penetration profiles. Initial estimates of the RWM dissipation parameter based on these modeling and measurement efforts will be discussed. \newline 1 E. D. Taylor, \textit{et al.,} Phys. Plasmas \textbf{9}, 3938 (2002) \newline 2 B. LaBombard,MIT PSFC RR-00-9, (2000).