Search for Correlation Between Plasma Rotation and Electron Temperature Gradient Scale Length in LOC/SOC Transition at Alcator C-Mod*

Understanding the mechanism governing the linear ohmic confinement (LOC) and the transition to saturated ohmic confinement (SOC) has long been a focus of tokamak research. It is commonly accepted that at low density, the confinement is dominated by electron-scale turbulence while at high density, the turbulence is dominated by ion temperature gradient. At Alcator C-Mod, the core rotation reversal was shown to be consistent with this \textit{ansatz} [Rice \textit{et al}, Nucl. Fusion \textbf{53}, 033004 (2013)]. However a recent study at AUG suggests that the intrinsic rotation behavior is rather determined by local plasma parameters regardless of the heating method or the confinement regime [McDermott \textit{et al}., Nucl. Fusion \textbf{54}, 043009 (2014)]. Here, we follow this idea and search for dependence of intrinsic rotation on electron temperature gradient scale length, a quantity with a pivotal role in plasma transport. The high-resolution (1 $\mu $s, 7mm) electron cyclotron emission diagnostic at C-Mod (FRCECE) coupled with the B$_{T}$ jog technique allows direct $L_{Te}$ measurements. In the B$_{T}$ jog technique, a 1.5{\%} change in the toroidal magnetic field shifts the viewing volume of the ECE by $\sim$ 1 cm, and the ratio of the average of the signal to the change in the signal during its ramp-up yields $L_{Te}$.