Temperature measurements of a laser induced plume by emission spectroscopy

A high power CO2 laser at the maximum power of 5 kW of multi-mode beam was irradiated on to mild steel and carbon graphite targets, positioned typically 10 mm below the focus point, both in air and argon, and at pressure ranging from 2 to 101 kPa. Spectra from plume were measured by a spectrometer. Temperatures of atoms were calculated from their spectra, assuming a local thermal equilibrium conditions of the plume.For the mild steel plume, spectral lines due to excitation of atoms were obtained and the temperatures was calculated as at 3000 K. On the other hand, spectral lines due to C2 molecules were observed for carbon plume. The vibrational temperature of C2 was analyzed corresponded with the rotational temperature. The temperatures of the carbon plumes was evaluated in a range from 4000 to 6000K depending on experimental conditions such as laser power and ambient pressure.