Gas temperature measurements in a pulsed, low-pressure inductively coupled plasma in oxygen

摘要

Optical emission spectroscopy (OES) of the magnetic dipole allowed O-2(b(1)Sigma(+)(g)) to O-2(X-3 Sigma(-)(g)) transition was investigated as a non-intrusive gas temperature diagnostic for E-mode and H-mode inductively coupled plasmas (ICP) in oxygen. It was compared to tunable diode laser absorption spectroscopy using Ar admixtures, and OES of the nitrogen Second Positive System with nitrogen admixtures. O-2 OES provided accurate results for the E-mode ICP, 400-600 K for powers of 100-300 W, but in H-mode the method was unsuitable probably because of excitation of O-2(b(1)Sigma(+)(g)) by metastable atomic oxygen. Rotational temperatures were measured, using N-2 OES with N-2 admixtures, for pulsed operation of the ICP with a 30 ms pulse duration and 15% duty cycle. It took 1-3 ms before the steady-state rotational temperatures were achieved. In addition, a small variation of matching network settings affects the plasma ignition delay time by several ms. (C) 2020 The Japan Society of Applied Physics