Looking closely at figures 5-8 of appendix 3 of the Lugano report, I believe we can see evidence for the evolution of a mass 69 species during sputter-cleaning of the samples while undergoing ToF-SIMS analysis in a scanning electron microscope.
Figure 5 provides what amounts to a control run for these observations, with only a carbon sticker present. The mass 69 peak in the spectrum is barely visible, way down in the noise. My rough estimate from zoomed-in analysis of the printed graph gives a count of ~530, or 5.3E+2. Figure 6 shows the mass spectrum for raw fuel grains before sputter-cleaning, and the mass 69 peak is still way down in the noise, although in the graph the count is approximately 6.0E+3 - somewhat higher, but most notably, the 69 peak is a small fraction of the Ni-60 and Ni-58 peaks. Figure 7 shows the mass spectrum for the same raw fuel grains following 180 seconds of sputter-cleaning. Besides the absence of (presumed) siloxane peaks, there is now a robust mass 69 peak, ~3.0E+4, which is nearly equal in magnitude to the mass 60 peak. I believe that this peak indicates evolution of the mass 69 in-situ during sputter-cleaning, likely as an intermediate product in the nickel-lithium cyclic reaction which is driving the observed enrichment processes. Following an additional 16 hours of inactive storage in the SEM vacuum chamber, figure 8 shows the same sample material now has the siloxane signature apparent once again, but the mass 69 signal is appearing with the same relative abundance as the mass 60 peak. I do not have any direct experience with SEM analysis methods, and I am not entirely certain what the significance of the ion source enrichment in Ga-69 implies. However, I have a difficult time reconciling this series of graphs with the notion that this peak-69 is occurring as purely instrument artifact, owing to the great variability in abundance. In addition, I highly suspect that peak 23 represents a reactant, despite the warnings from the report text that this could be an artifact. Once again, I am hoping for further clarification from experts in ToF-SIMS analysis to help clarify these interpretations. -Bob Ellefson
