This procedure/approach was developed because of problems that arose over time with the MFX slits movement. The identified issue was difficult movement by the M3 slit (+X movement slit) that resulted in extreme vibrations of the entire unit, and the MDrive17 knob when turned by hand felt like it was clunking into place/there was a lot of resistance in comparison to the other turning knobs.
Consult with JJ X-Ray identified one potential issue that would not yield opening up the beamline: inside the unit each slit is mounted on a lead screw. The lead screw is connected to the motor externally to rotate by a magnetic double plate system (one vacuum side and one not). These plates could be assembled in such a way that the gasket between them is pinched or flexed. This would lead to rubbing between the magnetic plate and cause disrupt in the movement of the slit. This would be the first way to approach the problem because it only requires venting the beamline. IF THIS IS NOT THE SOLUTION: you will have to open the entire beamline and remove the slit apparatus.
We began by venting the beamline according to the MFX protocol (found in MFX diamond window swap tab) with an additional PRV package at the downstream right-angle valve (preferred one has mud dauber screen and filter). Once the beamline is split open there needs to be an active purge of clean, dry nitrogen on both ends (open valve once split, before isn't necessary) and this would be the only way. Plenty of built packages are around.
For external assessment:
- Vent the beamline according to protocol (keeping in mind PRVs at the source and point of use, this will require a lot of nitrogen so plan ahead)
- Open the slit apparatus at the motor flange
- The motor is screwed to the flange from screws internally, so you will open up the top cover exposing the brain then find long internal screws to remove the motor itself from the flange. After that you will remove the flange from the six screws holding it into place. (THIS IS IF YOU WANT TO OBSERVE EXTERNALLY) The attached photo is what the flange looks like from the vacuum side with the special designed gasket removed to check for any of the interference that might have been occurring. No damage was assessed on our end, but there could be so check this area before proceeding to more drastic measures.
3. Next step after seeing no damage was to actually remove the slit from the beamline, at this point the downstream purge can be turned on (doesn't need to go on until there is a disconnection because when venting the upstream one reaches the end of the MFX beamline)
Internal assessment:
- Open up 6" portion of 0 degree adapter on beamline. We opened up the upstream side first and tied up the beam pipe (to 80/20 sheetrock support) to pull the slit forward. It is attached on the other side to a bellows welded to a chamber so we expanded the bellows and were able to work with more space to remove that 6" flange.
- No physical interference was noted through the 6" flange hole, so we opened up the 8" flange portion of the 0 degree adapter to have a full view of the slits. Initial notes: identified a long gray rod and one screw in bottom of chamber, magnetic limit switch tracker was magnetized to a different portion of the chamber. The screw found in the bottom of the chamber was the correct screw to mount the magnet and the rod was identified as the rod that sits on top of the slit itself (should be connected via VACUUM COMPATIBLE epoxy–they use krytox brand) and was from the -y slit in the opposite chamber side.
- The entire unit was pulled off the beamline and troubleshooting was done beneath a HEPA filter
- Our first line of thought was that there was friction between the components that would require greasing, so we greased in two spots. First was the lead screw where the actual slit translates in the chamber. Second was the ball bearings on either end of the lead screw where it is mounted within the chamber. The screw sits horizontal across a square box (like a chamber within the chamber). It is held on one side by a nut and the other side connects directly to the vacuum side of the motor flange. Each side of the internal chamber has a sunken hole where ball bearings rotate with the lead screw. RESULT: no change in motor's operation
- Our second thought was friction along the linear slides. Each of the slit lead screw apparatus are connected to a linear slide system at the back of the internal chamber. We greased along the slide portions. RESULT: no change in motor's operation