A new low-stress elastopolymer viewport seal compatible with ultra-high vacuum:
As reported in Review of Scientific Instruments (2014), a TRINAT co-op student developed a technique for a vacuum viewport seal that minimizes stress-related birefringence while maintaining ultra-high vacuum. One of many systematic effects that alters atomic polarization is imperfect circularly polarized light, and a common well-known difficulty is stress-induced birefringence (the same effect that produces the appearance of colors in stressed, otherwise clear and colourless, Scotch tape. The new technique keeps the circular polarization almost perfect.