Gas-phase measurement of oil-like vapor in SF6 using FTIR

Fourier transform infrared spectroscopy (FTIR) can be a useful tool for the precise determination of the concentration of oil-like contaminants in SF₆. The presence of oil vapor in SF₆ has detrimental effects on its dielectric strength. Thus the study of the critical concentration responsible for dielectric breakdown becomes important. For that matter, we have carried out experiments using ethyl benzene (C₈H₁₀) as a contaminating agent in SF₆. The absorbance was recorded as a function of the measured vapor pressure in the frequency range where the stretching mode could be observed. Calibration curves of the oil concentration estimated from reference IR intensities were obtained within the pressure range 0.5<P (Torr)<6.0 at room temperature