Temperature estimation using Boltzmann plot method of many calcium emission lines in laser plasma produced on river clamshell sample

Abstract

Temperature as one very important characteristics of a laser-induced plasma was estimated using many calcium emission spectral lines. This was possible due to the availability of a wide coverage and high resolution optical multichannel analyser (OMA) system allowing a simultaneous detection of many emission spectral lines from one element. The plasma emission was produced after focusing an Nd-YAG (neodymium-doped yttrium aluminium garnet) laser onto a river clamshell samples under air as surrounding gas at low and high pressures. The emission spectrum was acquired using the OMA system equipped with an echelle spectrograph system. The clamshell sample was collected from Panga River, Panga, Aceh Jaya, Aceh, Indonesia. The plasma temperature estimation was carried out by Boltzmann plot method. All calcium spectral lines either atomic and ionic emission were identified including resonant emission spectral lines in the recorded spectrum. Boltzmann distribution function firstly was plotted for all identified calcium spectral lines either atomic and ionic emission including their respective resonant emission spectral lines. In the further stage, the resonant emission lines then were excluded from the Boltzmann plot. As the results, the estimated temperature changes significantly with the number emission lines included and also with inclusion of the resonant spectral lines. The plasma temperature heavily influenced by inclusion the resonant emission lines. Thus, this work demonstrated clearly the influence of number emission lines used in Boltzmann plot to the plasma temperature estimation. The results also demonstrated explicitly the apparent effect of self-absorption of the resonant spectral line in estimation the plasma temperature.