ABSTRACT
One of the most important ingredients of ultrahigh-vacuum technique is the use of metal gaskets, which not only eliminates the concern about permeability but also reduces the outgassing rate compared to elastomer gaskets by 10 to 1000 times. Many important applications of ultrahigh vacuum are associated with the requirement of keeping surfaces clean. In addition, it is possible for some alloys to produce a large crystal grain structure on the surface to reduce the amount of gas contained in the grain boundaries. In addition to the need for precise dimensions, the ultrahigh-vacuum demountable joints must have precise control of material properties. Con-Flat flanges of good quality are made from selected stock to assure correct metallurgy and low level of inclusions in the microstructure. Most high-vacuum technologists do not associate ultrahigh-vacuum with ordinary mechanical vacuum pumps. The reason for this is the incorrect interpretation of the performance display graphs and an incomplete understanding of the term "ultimate pressure."
