Figure 1 - Upper condenser lens from a JEOL 6320 Scanning Electron Microscope.
Figured some of you would like to see this. Every Electron Microscope made today and the past several decades use electromagnetic coils that are Orthocyclic. This technique maximizes accuracy and fill (Compaction of wire) in winding which yields a more homogenous and powerful magnetic field, respectively. If you look closely
you can see where the wire steps up from one layer to the next.
Figure 2 - The wires that cuve differently than rest are stepping up from one layer of winding to start the next.
I am not sure if they use a copper alloy for these or if its pure, and not even sure the different EM companies use the same type of copper. I do know they are drawn thru a die for consistent diameter. The hole you see within the donut is where the beam passes right thru the axis. Not shown is a aluminum "liner" tube which is part of the high vacuum system. Not sure of the alloy its fabbed from, but 6061 is pretty easy to machine and common so thats my first guess.
If you would like to read more about Orthocyclic winding, wikipedia has a good description on this page.
New to my blog? Check out my previous posts on the theory, mechanics and electronics of Electron Microscopes.
Reviving a vintage Transmission Electron Microscope - The Philips EM 420 (part 1).
Turning up the Electron Beam on a Electron Microscope
Inside the stage of a 0.22 nanometer resolution Transmission Electron Microscope
JEOL 4000 EX 400kV Transmission Electron Microscope Specimen Holder Loading Mechanism.
Stay tune for many many more EM projects including sample prep and more theory!
