Demountable ultrahigh vacuum sections for ISABELLE

A sketch of the proposed design as applied to an experimental section is shown. The central idea is that the 4 arms coming out of an experimental intersection be terminated by ultrahigh vacuum gate valves, with matching valves terminating the main ring. With all 8 valves closed, a break would be made between the valves and the whole experimental intersection removed, probably on wheels. While the necessary valves are not currently ''on the shelf'' items, versions meeting everything but the closed conductance requirements do exist commercially, and valves which do meet these requirements are under development in several laboratories. The commercial nonavailability of the gate valves should not be grounds for rejection of this proposal if other advantages outweigh this element of risk. Sections which are not experimental sections may also be demountable. An estimate of $10,000 per valve might be reasonable at present