Methods of Producing Ultrahigh Vacuums and Measuring Ultralow Pressures

Abstract

Ultrahigh vacuum (UHV) or ultralow pressure is here defined as a pressure range below 10⁻⁹ Torr (1 Torr = 1 mm Hg = 133 Pa = 133 N m⁻²). The decade of the sixties saw ultrahigh vacuum technology develop from a field of active research whose outlines were only dimly visible to one whose major components became commercially available with an accompanying decline in fundamental research activity. Today, all the components necessary for producing and measuring UHV may be purchased. Systems in which UHV has been produced range from space simulation chambers the size of a small house,⁽¹⁾ through 2 km of 6-in. tubing in the CERN intersecting storage ring accelerator,⁽²⁾ to small laboratory systems with a volume of a few liters.^(3,4) The volume of the universe at UHV far exceeds the volume at higher pressures. Indeed, it has been suggested that the universe itself originated as a spontaneous event in vacuum⁽⁵⁾! The development of UHV has stimulated a rapid growth, both experimental and theoretical, in the fundamental study of solid surfaces.⁽⁶⁾ The great bulk of the vacuum market still rests above the UHV range, but it may be expected that UHV will play an expanding role in the fabrication of surface-sensitive devices, where extreme purity is important.