Prometheus Fusion Perfection

All photos.

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.

:(

All photos.

Previously I tested out the electron gun and I didn’t see a beam on the phosphor. I wanted to rule out the possibility that there WAS a beam, but it wasn’t hitting the phosphor screen. By moving the screen closer I can see the beam no matter where it is pointed.

So I designed and printed this sweet phosphor holder:

I have a small piece of broken phosphor glass from the CRT. I used the excellent OpenSCAD polygon editor to make a form fitting mount:

In real life:

That was easy!