Laser measurements of electron density and temperature spatial distribution in the FT-1 tokamak

The radial distribution and time dependence of the electron density and plasma temperature were measured on the FT-1 Tokamak by the Thomson scattering method. The experiments were carried out in a regime where the average electron density in the discharge was 5x1012 cm-3. The hydrogen pressure in the chamber was (0.8-3)x10-4 Tor, the toroidal magnetic field being 5-10 kOe. The discharge current was the same in all the experiments and equalled 27 kA. A ruby laser with pulse energy of 5 kJ was used. The radial distribution of the plasma parameters was used to estimate the discharge characteristics: the energy lifetime (1-1.2 ms) and the effective ion charge Zsub(eff)=sigmasub(theor)/sigmasub(exp)=2, where sigmasub(theor) and sigmasub(exp) are the theoretical and actual average value of the conductivity of the plasma filament respectively. It was established that at introducing a HF pulse into plasma a change in the profile of the electron temperature was detected. The measurements showed that the complex of diagnostic equipment used for the Thomson scattering method enables one to carry out plasma investigation at a low electron density