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 Steve, Yes, I've seen that before on our 8900. It is dirt in the lower column charging, which deflects the beam as it becomes increasingly charged. Then it discharges, and the beam "snaps back" to its starting position again. You'll probably see it happen faster with a larger beam current. The dirt is most likely in the lower column, probably just inside the objective lens pole piece or very near it -- something from the chamber deposited there. Cleaning the objective lens pole piece should fix that problem. Best, Ellery ----------------- Ellery Frahm Senior Research Fellow, Department of Geology & Geophysics Manager & Principal Analyst, Electron Microprobe Lab University of Minnesota - Twin Cities campus Lab website: http://probelab.geo.umn.edu/ Personal: http://web.mac.com/elleryfrahm/