Fig. 49.

Number of photons generated at the target within the spectrometer field of view (FOV) as a function of distance, for the ${\nu }_1$ mode of gypsum powder using the EQM SuperCam instrument. The result is based on data taken at these distances and knowledge of the spectrometer FOV convolved with an independent determination of the Raman efficiency of the sample. For a given sample, the number of Raman photons produced within the FOV depends on the alignment of the laser beam and the spectrometer FOV, which can degrade beyond a certain distance. The number of photons collected and detected by the instrument is a convolution of this curve with the $1/r^2$ losses with distance, as presented in Table 12