Success!

After many trials, the attenuator pictured below successfully holds a vacuum for 24 hours and likely much longer. The attenuator has a glass cylinder and aluminum end plates. The end plates include the flex cables openings to allow electrical connections between the vacuum chamber and the control and connector printed circuit boards.

Next step - build a new set of relay switched ladder attenuator sections.

Successful vacuum test on this attenuator including glass and aluminum vacuum chamber.