Today I did another test of the CRT based electron gun in the vacuum chamber.
Spoiler alert: I didn’t see an electron beam.
This time I put a grounded piece of phosphor right in front of the beam path:
Here is a closeup of the grounding wire:
I printed the phosphor holder with 1% infill so it’s basically hollow, then I drilled it with holes to allow gas to escape:
The vacuum reached 1.66 millitorr which is not amazing, but good enough for this run.
I tested the wiring with the unbroken CRT, and it looked good:
Then I wired the power supply to the vacuum chamber feedthrough:
The I fired it up, you can see the hot cathode working:
But no beam.