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 Probe folks; It's the holiday season, that means it's time for everyone's machines to break down, right? At least, that's what always happens to me. I've got a strange beam drift that started up a week ago without provocation. It might be hard to describe so I have a little movie of it to watch if you're so inclined. This is a (brown) JEOL 733, tungsten filament. We developed this issue where if you put the beam on a spot, there's drift. In fact there's a lot of drift. The drift is co-incident with the gun shift-x (but isn't in the gun shift-x, since the beam stays bright from end-to-end, whereas the gun shift of course it gets dark as the gun misaligns). It's 45 degrees to the "fine shift x y" on the mag box controls (like both were being adjusted at once). It's not stage drift, it's beam drift. Very conveniently we put the beam onto a fluorescing mineral so you can watch the beam drift on the optical microscope, that's what the movie is of. Here's the part that I find weird: The beam steadily drifts in one direction until it reaches it's end, then it instantly 'snaps back' to the start of the path it was following and repeats. I've likened it to using a manual typewriter and hitting the return for the carriage at the end of the line. Weirder still: If I put the PCD in, it appears to 'not' drift while the cup is inserted. That is, you put the cup in at a point, wait a little while, and when you withdraw the cup again the beam is at the same spot, and then continues on it's merry drift path. Probe does this regardless if imaging mode: spot, picture, reduced picture. The area scanned is just fine, it just progressively drifts up and to the right. This, however, makes it pretty much useless for work if it drifts off your spot during analysis. I've gone as far as to manipulate the mag box while this drift is going on. I can pull the mag box completely out of the frame (thus becoming unpowered) while the drift is going on and it has no effect. This 733 has one of those "JEOL Scan Clear Boxes" in it, I'm going to try and remove that from the system and see if that affects things. We've had weirdness before associated with the scan-clear-box's ground line. To me this looks like a progressive drift in the fine-shift alignment coils down in the objective lens. In the freaky department, I took the side panel off the 733 (the right side where you can get at the electronics rack) and it went away. Eventually it did come back though. Could this be a Deflector Amp issue? If you'd like to watch a little video showing what I'm talking about, you can check http://gallery.me.com/cogswell/100000 , it shows the image from the optical microscope as the beam (the bright fluorescing spot) moves along. At one point I put the PCD in and out, and you can see the beam disappear but come back to the same spot. I figured I'd go out to the experts here on the list and ask "Have you seen this before, any hints?", I'm not ambitious to tear down the deflector amp system looking for a needle in the haystack. and hey, Happy Holidays to everyone. Best regards, Steven Cogswell UNB Microscopy and Microanalysis