Characterisation of plasmas produced by the "Torche a Injection Axiale"

Summary form only given. The Torche a Injection Axiale (TIA), i.e. torch with axial gas injection, was developed by the group of Moisan in 1993. We report on the investigations on two different kind of plasmas created by the TIA: one with helium and the other with argon as main gas. Using absolute line intensity measurements the densities of the excited states are determined. Applying the ideal gas law yields the ground state density. It is found that the excitation temperature ranges from 3000 to 11000 K. Apparently the atomic state distribution function (ASDF) does not obey the Saha-Boltzmann law. This indicates that these plasmas are far from local thermal equilibrium (LTE). From the shape of the ASDF it can be concluded that the plasma is ionising. The electron temperature and the electron density are determined using Thomson scattering. In the plasma with helium as main gas, temperatures around 25000 K and densities between 0.64 and 5.1/spl times/10/sup 20/ m/sup -3/ are found. In an argon plasma the electron temperature is lower and the electron density is higher: 17000 K and around 10/sup 21/ m/sup -3/ respectively. Using the electron temperatures and densities as found by Thomson scattering, it can be established that the ionisation rates of both plasmas am much larger than the recombination rates, which means that the plasmas are far from Saha equilibrium.