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 nₑ=0.7×{}10²⁰ m^-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_⊥{}30 keV. The line-average energetic electron density in this energy range is approximately 10¹⁷ m^-3 during the rf.