X-ray elemental mapping on non-conductive samples

[Changkun]

Recently we are using our 8530F to get x-ray elemental maps of C, P, Ti, and Fe etc, as well as SE and BSE maps from unpolished fossil samples.

Accelerating voltage of 20kV, probe current of 200nA, and defocused beam of >10 um were utilized for a long time (1-2 days) mapping on large (>5 cm) samples. Only x-ray intensity maps are obtained with a defocused beam because fossil samples cannot be ground and polished.

Some samples have no problem to conduct x-ray mapping with above conditions after gold-coating.
(https://www.nature.com/articles/s41467-018-03464-w)

But mudstones preserving fossils were impossible to make them conductive even with a thicker gold coating, probably due to small grain sizes and pores. I am worried about any potential damage on detectors when the non-conductive samples are analyzed with the high current beam for the long time.

1) SE and BSE detector can be damaged by charging during long-time mapping?
2) Crystals can be contaminated during mapping on unpolished (not cleaned?) sample?
3) Any potential issues on these analyses?

Thanks,
Changkun