ondervacuum

Ondervacuum refers to the state in which an enclosed space or chamber is evacuated to a pressure well below atmospheric, creating a vacuum environment used across science, engineering, and industry. The term is common in Dutch-language technical literature and is often synonymous with being “under vacuum” in English. Vacuum levels are typically described by pressure ranges: rough or low vacuum (roughly from 1,000 to 1 Torr), high vacuum (about 10^-3 to 10^-9 Torr), and ultra-high vacuum (below 10^-9 Torr). In practice, ondervacuum describes operating conditions inside a vacuum chamber, with the exact grade chosen to suit the process.

Applications include vacuum deposition and coating (physical vapor deposition and sputtering), vacuum drying and freeze-drying, semiconductor processing, electron microscopy and lithography, vacuum packaging, and various surface analysis techniques. In research and manufacturing, operating ondervacuum reduces oxidation, minimizes contamination, and provides controlled environments for reactions, measurements, or material processing.

Typical equipment involves vacuum chambers, pumping systems (roughing pumps, turbomolecular or diffusion pumps, and backing pumps), and measurement devices such as Pirani, Penning, or ionization gauges. Achieving and maintaining ondervacuum requires leak-tight seals, materials with low outgassing, and procedures such as bake-out to remove adsorbed gases. Control systems monitor pressure and gas composition, while safety measures address implosion risks and vacuum-related hazards.

History and development: practical use of vacuum environments advanced with improved pump technologies and sealed systems in the 20th century, enabling reliable ondervacuum for manufacturing, analysis, and experiments.