A Statistical Analysis of Momentum Transport Scaling in Alcator C-Mod Plasmas with No Momentum Input

It has been observed that in L- to EDA H-mode transitions with no momentum input and in L-mode plasmas with auxiliary ICRF hearing in Alcator C-Mod tokamak plasmas there exists an anomalous momentum transport. A one dimensional, source free, momentum transport equation at the central chord of the plasma, ignoring convection and treating boundary conditions as a step function, was used to model the core velocity obtained by a high resolution x-ray spectrometer. It was found that the momentum diffusivity varied between D$_{\phi ,H}\sim $ 0.1 m$^{2}$/s and D$_{\phi ,L} \quad \sim $ 0.3 m$^{2}$/s which corresponded to a characteristic momentum confinement time ($\tau _{\phi ,L} \quad \sim $ 0.02 s, $\tau _{\phi ,H} \quad \sim $ 0.08 s). In order to find a plasma scaling law $\tau _{\phi }$ was compared to plasma parameters initially focusing on H-factor, energy confinement time, density, and current. Initial results suggest a positive correlation between H-factor and momentum confinement time.