Two different kinds of plasmas created by the microwave driven Torche a' Injection Axiale (TIA) are investigated: one with helium and the other with argon as the main gas. By using abs. line intensity measurements, the densities of the excited states are detd. Applying the ideal gas law gives the ground state d. It is found that both plasmas are ionizing and that the excitation temps. range from 3000 to 11,000 K. The electron temp. and the electron d. are detd. using Thomson scattering. In the plasma with helium as the main gas, av. densities between 0.64 and 5.1 x 1020 m-3 and temps. around 25,000 K are found. In an argon plasma, the electron temp. is lower and the electron d. is higher: 17,000 K and around 1021 m-3 resp. Radial profiles of the electron d., obtained by focusing the laser beam, appear to have a donut-like shape. [on SciFinder (R)]