Fig. 6
(a) Box plot showing the index of the two main features at 1870 nm and 2257 nm. The extent of the box covers the 25–75th percentiles, with the red line indicating the median value. The horizontal line at Z = 0.5 marks the separation between the lanthanide-containing pellet spectra and all other pellet spectra. (b) Pairwise spectral information divergence (SID) scores for each of the pellet groups. SID is calculated based on bands 1 to 205 (949–2167 nm) in order to avoid the glass lid artefact around 2209 nm. Lower scores indicate greater spectral similarity. As with the Z-score, this measure shows that doped SIMFuel (Group B-2) and lanthanide-doped Split-SIMFuel (Group C-2) pellets are most similar to each other, and different from other pellet groups.
