Thomson scattering system for the diagnosis of the ETE spherical tokamak plasma

A 10 J ruby laser Thomson scattering system was implemented on the ETE spherical tokamak to measure the density n e and temperature T e profiles. The laser probes the plasma at the horizontal midplane of the torus and the collection optics allows the observation of up to 22 points inside the plasma in the same plane. Radial profiles of plasma density and electron temperature were obtained for different times during the discharge by shot-to-shot procedure. Temperatures of up to 160 eV and densities of 2.2×10 19 m −3 were measured. Since the level of stray light was too high, the calibration of the Thomson scattering system for density measurements was made using the nitrogen Raman technique instead of the usually applied Rayleigh method.