I fit the copper to the plastic cavity today and the seams look excellent:
I am super happy having gone with computer-aided printing and cutting because the accuracy is unmatched not to mention the final product looks way cool! I am using the mismatched top and bottom plastic pieces first because I want to see how badly the plastic melts when brazing the copper lining. I should have time tomorrow afternoon to make an attempt, and living in a cold climate will be useful because I can do the brazing in the garage where it is about minus five degrees.
For the vacuum chamber, a friend who does glassblowing (Silica is his gaming handle which is fitting, eh?) for the University of Calgary suggested using a Helium leak detector, specifically a Varian 979.
Searching through the UofA’s inventory management system, it turns out they have one:
Property Tag Classification Description Manufacturer/Make/Model Custodian Name Status 443300 DETECTOR,VACUUM LEAK VARIAN 979 HELIUM CHEMISTRY ACTIVE
I guess we will be taking a trip to the chemistry department.
I finally won a digital vacuum gauge off eBay ($200CND shipped) and it comes with a Pirani sensor that can go from atmosphere down to one micron.