Finite-βeUniversal-Mode Turbulence and Alcator Scaling

A self-consistent theory of finite-${\beta }_e$ universal-mode turbulence is developed. Saturation results from resonance broadening of the electron response due to magnetic shear. Electron diffusion, for ${\beta }_e>\frac{m_e}{m_i}$, is due to the magnetic part of the fluctuations. The diffusion coefficient, $D=0.1\mathrm{} {\left[\frac{T_e}{(T_i+T_e)}\right]}^4\left(\frac{m_e}{m_i{\beta }_e}\right){\left(\frac{L_s}{L_n}\right)}^2\frac{v_i{{\rho }_i}^2}{L_n}$, scales inversely with density, is independent of magnetic field, and is in excellent quantitative agreement with observations on the Alcator tokamak.