Central axial profiles of main gas density and temperature determined with Rayleigh scattering

Part of 15th International Conference on Laser Aided Plasma Diagnostics (15thLAPD). A method is presented to determine local values of the heavy particle density and temperature, na and Ta. The method, based on Rayleigh Scattering, is applied to a Surfatron induced plasma in argon operating at a fixed frequency of 2.45 GHz and a typical absorbed power of 45 W. Apart from the standard pressure of 20 mbar we also studied two lower pressures cases of 10 and 6 mbar. In order to measure the gas properties as function of axial position we used a co-axial alignment technique in which the position of the detection volume is kept constant with respect to the laboratory frame. New plasma locations are studied by shifting the plasma setup such that the central axis remains coincident with the laser beam. The challenge of this techniques lies in the treatment of false stray light, that is scattered light of the laser side-beams on the quarts surrounding the plasma. To handle this we used a method based on image inspection that is possible due to the application of a 2D iCCD array as detector. The uncertainty in the determination of na for the 20 mbar case is brought down to 12%