Versatile Sub-THz Spectrometer for Trace Gas Analysis

A THz sensor system based on a commercially available multiplier chain is applied to the analysis of trace gases. Frequency modulation of the source is used to achieve the high sensitivity required. Particular attention is paid to the line broadening effect caused by the modulation as this can hamper the quantification of the various chemical species being monitored. A numerical model using a Voigt absorption profile along with a single calibration step is used to provide quantitative information. The sensitivity obtained by this prototype instrument permits the analysis of various samples extracted during the industrial sintering of iron ore as part of the manufacturing of steel.