Abstract: The emission profile of microwave plasma torch (MPT) discharge was studied with computed tomography. It was shown that the source was in good symmetry and there was a central channel which is beneficial to the introduction of samples. The optimum analytical zone is in the region from 5 to 10 mm above the top of the torch. The laser Thomson scattering and Rayleigh scattering were used to study the electron temperatures, electron number densities and gas temperatures of ArMPT and HeMPT discharges. The electron temperature of the MPT was shown to be very high and the gas temperature was relative low and, therefore, it was a non-thermal emission source. There existed an over-population of high-energy electrons and the excitation power of the source was very high.

Key words: Microwave plasma torch, Computed tomography, Laser Thomson scattering