Nonthermal electron velocity distribution measured by electron cyclotron emission in Alcator C tokamak

The nonthermal electron velocity distribution of lower-hybrid-rf–heated plasmas in the Alcator C tokamak is deduced from measurements of electron cyclotron emission with a specialized vertical viewing optics arrangement. At a density of n${¯}_e$=0.7×${10}^{20}$ ${\mathrm{m}}^{\mathrm{-}3}$, the reconstructed distribution function in the range 50 keV≤E≤230 keV shows enhancement in the parallel direction with a perpendicular spread equivalent to $T_{\perp }$≊30 keV. The line-average energetic electron density in this energy range is approximately ${10}^{17}$ ${\mathrm{m}}^{\mathrm{-}3}$ during the rf.