AMRAY Scanning Electron Microscope - Complete Optics and Stage Disassembly Part 2 of 3

Figure 1. Gun alignment coils, only two are visible here.

New to this? For part one go to:
Amray-scanning-electron-microscope-complete-optics-and-stage-disassembly-part-1

Next section to remove is the gun alignment “block” for lack of a better description. There are 4 coils mounted equidistant from each other on this aluminum column section. The block is secured to the Condenser lens section via 11mm bolts. These coils can have different electric currents applied to them to push the beam into the center of the condenser lens below them.

Figure 2. Looking down at the top of the alignment and condenser liner tube. The tube is under vacuum when the scope is functioning.

Figure 3. The liner tube, its I.D. I measured to be 6.97mm. The wide section to the left is what you are looking down at in previous picture. Many of the TEMs I have worked on have liner tubes just a little narrower, but have fixed apertures at the cross over points (100 -200 microns in diameter or so). I found no apertures in this scope.

Figure 4. Bottom view of the liner tube.

Figure 5. Condenser lens section, the liner tube runs right down thru the lens down to a valve assembly below. The iron core condenser lens sits inside this steel housing. The lackluster, thick, grey ring you see around the hole that the liner tube goes thru is the top of the pole piece assembly.

Figure 6. The condenser lens. The windings are TERRIBLE., you can see thru the yellow tape that they cross over each other at random. This had to create field aberrations and there for astigmatisms. Compare these to a JEOL Objective lens I wrote about previously. Seriously....look at those windings. Repugnant. The technology existed to make much better windings back then, so, either it was a patent rights issue or Amray was just being cheap. Or...learning curve?

Orthocyclic-coil-windings-in-a-electron-microscope

Figure 7. Top view of Condenser lens. Also, thankfully, there is this thing called spell check. The handwriting is however, way beyond repair.

Figure 8. Pole piece assembly. This thing was shimmed at the top with Teflon tape, which is something I have never seen before, and a rotten idea. The thermal expansion of teflon is about 10X that of iron, so when the lens gets warm, there would be spot drift. Now, if that teflon tape was perfectly balanced on all sides that drift would be minimal, however teflon is SLIPPERY so, it will shift over time. (1,2)

This puts us about 2/3 thru the entire optics and stage assembly, keep your eyes open for part 3 in the next few days or maybe a week, when I wrap this up.

Want to learn more about EMs? Stay tuned for ZEISS EM109 TEM complete column disassembly and a JEOL 6320F as well! Also, if you have been following the Philips EM420 revive series, I have not abandoned it, it is just on hiatus. Priorities change around here a lot.

(1)
https://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html

(2)
http://www.rjchase.com/ptfe_handbook.pdf