Study of Electron Temperature Profiles in GDT during Neutral Beam Heating by Thomson Scattering System

Thomson scattering system based on a ruby laser was applied in the GDT to measure the electron temperature during intense neutral beam injection. The system is capable of measuring the radial profile of electron temperature in the midplane over plasma radii varying from 0 to 12 cm. For this purpose the focusing lens is moved from shot to shot along the laser beam. The scattered light condenser with the polychromator is correspondingly rotated. Angle of scattering is in the range of 86–97 degrees. Thomson scattering system enables measurement of the electron temperature at minimal plasma density of ∼10¹³ cm⁻³. The time between shots (about 3 minutes) is long enough to collect, store the data and subsequently calculate the electron temperature. In the paper, the data on radial profiles and temporal behaviour of electron temperature during neutral beam heating at GDT are presented. In the experiments, electron temperatures of the target exceeding 100 eV was observed.