When the beam gets out of focus

A project log for Metal 3D printer

Making an electron gun is a first stage of my future plans - to make DIY electron microscope/EBM metal 3D printer.

HynaHyna 04/20/2021 at 00:070 Comments

Melted solder on anode. About 200W by an accident.

As a next step, i need to redesign HV feedthrough. I used to use spark plugs, but for filament @2Amps, the spark plug resistance increased slowly from 5R to ~15 Ohm each. That is an issue, since the filament has 1 Ohm and  Im using 6s RC battery with stepdown. So there is no headroom for proper regulation.
I'm wondew what is inside of the spark plugs, or why the resistance increased.

Im facing hard decision to discard whole setup and start again. I want to increase accelerating voltage to 30kV. But with current setup with glass jar, it is big no no due to x-ray.

Also the electron gun deserves proper calculations/simulations.

Last thing is that e-gun is classified in my country as  "small" sources of ionizing radiation and undergo regulations. The State Office for Nuclear Safety has trainings for radiation safety, which is not that expensive. Maybe it is time to refresh some knowledge.

It will require some fundings to move to the next stage...