The first thing I would like to point out are the requirements I set to myself for this design:

• The instrument would be one person carriable.
• The column would be removable without loosing it's inner alignment.
• The column would not be water cooled.
• The instrument should have resolution better than 25nm.
• The parts would be optimized for easier manufacturability trying to use as much the mini lathe as possible and manual milling.
• The instrument lenses would be magnetic and not electrostatic.
• The High vacuum pump would be a Turbo Molecular Pump and not Diffusion Pump (Because oil sucks). 
• The electronics would be modular.
• The software would take as much as functions from the hardware as possible to reduce the electronics complexity (Everything that is reasonable goes via USB and is computed there = less MCUs = Less firmware to debug)
• The software should run in Win,Mac & Linux.
• Something else I am forgetting.

The column design is mostly finished, there are some details here and there which are missing, for example the HV connector for the cathode and the aperture selector which are minor things.

On the next post I will detail the column operation and it's parts.