My Custom Scanning Electron Microscope

Hi guys and girls!

I have been busy the last few months relocating to the Netherlands, so the project was halted for a while, after making many parts I am considering ways to scale down the manufacturing effort, simplifying the design, now that I more or less managed to dominate magnetic lenses simulation and got consistent results with the reality I feel more confident to deviate from the original Zeiss design I was following.

The biggest issue I see is the current design cannot be manufactured in a mini lathe and one of my goals, for this project, is to be accessible to hobbits that want to explore this field.

Another aspect is the number of parts and seals themselves, I think there are too many. Also, some parts are really hard to machine, like the condenser assembly, the anode and the cathode.

Anyways I just want to leave my thoughts here and give a quick update.

I still need to find a hackerspace or a friend with a machine shop to continue the work, meanwhile, I will work on the 3D model and simulations in my spare time. 

Cheers,

Vini

I released a new repository with the COMSOL simulations for the magnetic lenses and electron gun.

It is available at: https://github.com/VinisLab/VinisLabSEM-Simulations

Here are some simulation images for 30KeV, Max magnification and shortest focus length (this is the setting where the currents on the lenses are the highest).

In addition to the Mechanical repository now the Electronics one is available too:

https://github.com/VinisLab/VinisLabSEM-Electronics

I created a public repo with my component libraries for Altium to facilitate:

https://github.com/VinisLab/VinisLabAltiumLibraries

You must install the lib to get the correct references.

When the project is ready I would like to find a collaborator to port everything to KICAD.

This is the cathode or filament assembly. Since my lack of experience and this being the first thread I had to match it was a bit challenging, the small size of the parts also presents a challenge when machining specially the bore operations.

Many signals must be routed to the core of the objective assembly.

There lives the main scanning coils, the aperture imaging coils, and the stigmator octopole

The scanning coils run at high speed when scanning in video mode, so to avoid crosstalking with the stigmator coils the traces routing had to be considered carefully.

A ground plate was introduced to shield the stigmators and the routing was made so that the traces crossing are made perpendicular between each other when the ground plane is not available.

Today’s part seals the objective liner tube to the aperture chamber. I during the machining I already made some modifications to this part, mainly in the detail B the journal for the O-Ring is not practical to machine. So I machined from the back the larger diameter and will machine an extra plug to retain the oring. Also a few changes will be added to reduce machining time.

Cathode Filament/Wehnelt holder. Electron Gun assembly release screw. My dirt hand :)

This was my first kinda successful attempt to nickel plate a part. I still need to perfect my setup and the voltage applied so the part does not have blackened spots and looks dull. The coating is functional just does not look as pretty. I will probably give a light polish on this part for cosmetics.

This parts connects a KF50 bellow to the anode body. I am really proud of my work here. No small machining mistakes and the finishing is just great. I had stainless steel on the size needed so this one will not need nickel plating.

High voltage electron gun connector/feedthrough. The threads was a bit of a challenge on the mini lathe since I could not disengage the cross slide. So I had to turn them manually.