First post! I hope to add more posts as I got along.
Currently working on aluminum/glass version of vacuum enclosure for the stepped attenuator.
The acrylic version had too high a leak rate to allow the vacuum to last for months/years. Aluminum and glass are much better vacuum materials. Glass is 3 mm thick and aluminum end caps are 6 mm thick. Laser cut Viton seals are used.
Prototype aluminum/glass version of stepped attenuator enclosure
Prototype acrylic version for comparison