title: Note: reliable and reusable ultrahigh vacuum optical viewports.
abstract: We report a simple technique for the realization of ultrahigh vacuum optical viewports. The technique relies on using specially designed thin copper knife-edges and using a thin layer of Vacseal(®) on tip of the knife-edges between the optical flat and the ConFlat(®) (CF) flange. The design of the windows is such that it gives uniform pressure on the flat without breaking it. The assembled window is a complete unit, which can be mounted directly onto a CF flange of the vacuum chamber. It can be removed and reused without breaking the window seal. The design is reliable as more than a dozen such windows have survived several bake out and cooling cycles and have been leak tested up to 10(-11) Torr l/s level with a commercial Helium leak detector. The advantages of this technique are ease of assembly and leak proof sealing that survives multiple temperature cycling making the windows reliable and reusable.
authors.affiliation: Time and Frequency Division, National Physical Laboratory (CSIR-NPL), Dr. K. S. Krishnan Road, New Delhi 110012, India.
authors.forename: P
authors.initials: P
authors.lastname: Arora
authors.forename: A
authors.initials: A
authors.lastname: Sen Gupta