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 eternal motor package for rotation via 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 (two methods: one is remove motor first, other is leave motor on; both methods work MFX took off the motor, XCS did not)
- 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 (THIS IS IF YOU WANT TO OBSERVE EXTERNALLY for damage/warping). After that you will remove the flange from the six screws holding it into place. The attached photo is what the flange looks like when you open it up with the motor removed. You will see what they call the membrane (this is a thin flat copper gasket portion–the old design is the flat membrane with a fused o-ring on it. the fused portion has a smaller I.D. than a normal gasket)
- This is what the magnetic double plate system looks like from each end. The "clunking" that we felt as we rotated the knob of the MDrive17 motor was these circular divets bumping along into place as the plates rotate.
After seeing no damage, we decided to open up the 0 degree adapter on the side in question (NOTE: opening at the 6" portion leads to a very small window that is not large enough to observe much besides general location of the slits). This allows for internal assessment. We removed the slit from the beamline and opened up to the 8" flange.
Immediately after opening: noted a gray bar and screw sitting in the bottom of the circular chamber and the brown limit switch magnet was magnetized out of place. At the time of opening we saw no physical damage to the M3 slit we were investigating. Conclusion: the screw in the bottom of the chamber is for mounting the limit switch magnet to its place at the top of the M3 slit. The grey bar is a piece that lies on the edge of the slit itself on the internal edge (edge going towards the beam) but it was from the M1 slit on the opposite chamber side. From here we decided to remove the slit from the beamline and work under a HEPA filter.
4.
Internal assessment:
- 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