Abstract
The electron excitation temperature Texc, vibrational Tvib, and rotational Trot temperatures were measured in a high-pressure line-shaped microwave plasma source in argon over a wide range of gas pressure and microwave power, by using optical emission spectra. The selected ArI transition lines 5p-4s and 4p-4s were chosen to calculate electron excitation temperature using Boltzmann's plot method. Meanwhile, the emission spectra of hydroxyl OH molecular (A2Σ+−X2Πi,Δν=0) band and the nitrogen N2 second positive system (C3Πu−B3Πg,Δν=+1), both second diffraction order, were used to evaluate the vibrational Tvib and rotational Trot temperatures using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. The components of the overlapped spectrum are greatly influenced by the gas pressure; however, they are independent on microwave power. For temperatures, it was found that the Texc dramatically decreases from 2.5 to 0.75 eV, which qualitatively agrees with Te deduced from zero-global model. Both of Tvib and Trot significantly decrease with as gas pressure increase from 0.4 to 50 Torr. Yet, they behave differently with microwave power.
Published Version
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