Ultrahigh Vacuum Hardware

My remarks are offered as personalized comments concerning the “nitty gritty” of uhv hardware. These opinions are drawn from 18 years of work-a-day experience with large and small uhv systems (no unannotated literature survey here). Emphasis is placed on valves, permanent and demountable joints, gaskets, flanges, and vessels rather than pumps, traps, baffles, bell jars, complete systems, and other uhv hardware. My remarks are offered under the assumption that it is more fruitful in the practical world (as well as in theory) to define uhv as a multiparameter environment, a crucial step being to identify and control those parameters of importance in each specific application. (Note: pressure in a gas and/or the sum of the partial gas pressures are seldom of much importance.) What can be tolerated can be as important as how much. Proceeding thus, the probability of molecules entering and leaving a system as a function of time, temperature, chemical and physical kind, history, techniques, materials, work processes, pumps and equipment used, geometry, etc. is a focusing point of view. Consequently, stress is placed on handling, cleaning, machining, welding, surface treatment, and fabricating (in addition to design) in order to provide guidelines about what to do and avoid.