Production of vacuum

A pump is required to produce vacuum. In mechanical pumps gas is initially trapped and compressed. Later gas is removed from the low pressure to the high pressure side of the pump, where it is expelled to the open air either directly or through a second mechanical ‘backing pump’. In diffusion pump, gas molecules are forced to interact with heavy molecules of pump fluid. In chemical pumps, gas molecules are allowed to combine chemically with highly reactive substances like titanium. Sorption pumps use charcoal or zeolites. They absorb gas molecules. Cryo pumps are vessels with chemically nonreactive internal parts. Another method is ionization of the gas where accelerating the ions in a high voltage field, the gas molecules are forced to move into a wall or target electrode.