Note: Mounting ultra-high vacuum windows with low stress-induced birefringence

We have developed a way to mount ultra-high vacuum windows onto standard ConFlat ® vacuum systems with very low stress-induced birefringence. Each window is sealed to a stainless steel flange with a compressed indium wire, and that flange is connected to a vacuum chamber with another indium seal. We find that deformation of a standard ConFlat flange during indium sealing dominates the stress on the window, so an extra-rigid flange is needed for minimal birefringence. With this mounting scheme, the typical residual birefringence is Δ n = 2.3 × 10 −7 and is unchanged by a 120°C bake.