JEOL Probe Users Listserver Moderator: Ellery Frahm, [log in to unmask], Electron Microprobe Lab, University of Minnesota Post a message: send your message to [log in to unmask] Unsubscribe: send "SIGNOFF PROBEUSERS" to [log in to unmask] On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html * Hi Eric, > One "simple" way for a user to get low totals on EMP is to have the > sample out of focus during the analysis. We find some students > focusing with BSE or in transmitted light instead of reflected > light, or simply failing to check focus. With the SX-100 we use an > autofocus system but some students turn off that option. Once the > low total is obtained, one should immediately check in reflected > light to see if the sample is still in focus after the analysis > before moving the sample. This researcher is experienced enough to check for all those problems, and we're talking about bad results on a few specific samples (and not others run at the same time) over several sessions. But I'll still advice him to pay extra attention to these points next time. > Another problem is that students (and sometimes their advisors) > handle the sample, imparting oils to the carbon coat and causing > charging that is difficult to see if the sample doesn't fluoresce > (or we find that the user pays no attention to the flickering or > moving luminescence!). One can find salt crystals in swirls in some > cases. The only check for that is to repolish, reclean (a step that > lots of folks forget), recoat, and then immediately reanalyze. A possibility. I'll suggest that he repolish and reclean the samples in case of their surfaces weren't totally clean. Thanks, Ellery