Optical design and measurements of a dynamic target monitoring spectrometer for potassium spectra detection in a flame

Abstract

We present the optical design, laboratory calibration and first field measurements of a dynamic target monitoring spectrometer (DTS) for detection of potassium emission lines at 766.491 and 769.897 nm in a flame under the two-dimensional orthogonal observation mode. DTS can provide high-spectral-resolution, high-spatial-resolution and high-throughput measurements by using imaging spatial heterodyne spectroscopy. Combined with a 0.035 nm spectral resolution and a 1.2 mrad spatial resolution in one dimension for each channel, 7.2° × 7°(vertical × horizontal) field of view is achieved in DTS. The high spectral resolution is important for identifying a very dim signal by a few spectra lines, and the high spatial resolution is a significant parameter for inferring accurate location of a flame per exposure and monitoring the trace of a dynamic flame varying from exposure to exposure. Finally, we demonstrate the ability to measure potassium spectra in a rapidly changing flame by DTS through a series of laboratory calibrations and field measurements.