Electron confinement measurements on the Ormak plasma using Thomson scattering

Measurements have been made of electron temperatures in the Oak Ridge Tokamak, ORMAK, using Thomsonscattered light from a Q-switched ruby laser. The measurements described were made during spring 1973. The measured electron temperature ranges from 0.20 keV to 1.2 keV for average electron densities of 1 × 1013 to 3 × 1013 cm−3. The radial electron temperature profiles observed in stable discharges are broad (flat over about 1/2 the limiter radius), while a tendency towards sharpened profiles appears when the discharges become unstable at low safety factor. In these measurements βp (plasma kinetic pressure/poloidal magnetic field pressure) is observed to vary as e/I, and the resistivity enhancement (experimental resistivity/Spitzer resistivity) as, at a constant current, 1/e. An empirical expression for the energy confinement time is discussed.