The Power of Vacuum Technology: Applications and Advancements

Vacuum technology encompasses all procedures and measurements conducted in environments with lower-than-normal atmospheric pressure. These processes are typically performed in a vacuum for several reasons:

1. To eliminate atmospheric components that might cause chemical or physical reactions during the process, such as vacuum melting of reactive metals like titanium.
2. To disrupt equilibrium conditions present at normal room settings, including the extraction of trapped or dissolved gas or volatile liquid from materials (e.g., oil degassing, freeze-drying) or the desorption of gas from surfaces (e.g., cleaning microwave tubes and linear accelerators during manufacturing).
3. To increase the distance particles must travel before colliding, allowing them to move without collision between source and target. This is useful in applications such as vacuum coating, particle accelerators, and television picture tubes.
4. To decrease the frequency of molecular impacts, thus reducing the likelihood of contamination on surfaces prepared in a vacuum, which is beneficial for clean-surface studies.

Each vacuum process has a maximum allowable pressure, determined by factors such as the number of molecules per unit volume, the mean free path, or the time required to form a monolayer.

At standard temperature and pressure, one cubic foot of air contains about 7 × 10^23 molecules moving randomly at speeds around 1,000 miles per hour. The resulting force on walls equals 14.7 pounds per square inch. Atmospheric pressure was traditionally expressed in millimeters of mercury (mm Hg), with one standard atmosphere equaling 760 mm Hg. The term “torr” was introduced to reconcile these units, where 1 torr = 1 mm Hg. In 1971, the SI unit pascal (N/m^2) replaced the torr, with one pascal equaling 7.5 × 10^-3 torr.

Vacuum technology found its first significant industrial application around 1900 in electric light bulb production. Subsequently, other vacuum-dependent devices emerged, such as electron tubes. It was discovered that certain processes yielded superior results or achieved otherwise impossible outcomes when performed in a vacuum. Examples include improving lens light transmission, preparing blood plasma, and producing reactive metals like titanium. The 1950s nuclear energy boom accelerated vacuum equipment development on a large scale. New applications for vacuum processes continued to emerge, including space simulation and microelectronics.

Various devices have been created to generate, maintain, and measure vacuums, with several significant types described in subsequent sections.