Previously in the comments, Olivier suggested the vacuum pressure is too high. Indeed, at 1.66 millitorr the pressure was higher than I wanted.
My first goal today is to check the empty vacuum chamber with blank flanges. A best case scenario.
With the initial pump down I only got down to ~3 millitorr… about the same as last time. I used the stethoscope to listen for a leak but did not hear one.
I tried tightening the flanges one last time, and suddenly the pressure started dropping again. I forget how much torque these conflat flanges need to fully seal.
Now I am seeing pressure in the range of 0.098 millitorr and dropping. Much better!
So now let’s install the electron gun, and see what we get.
With the electron gun components in the chamber I am able to get down to 0.27 millitorr… not bad!
But when I turn on the electron gun… still no beam.