Cryopompen

Cryopompen is a type of vacuum pump that uses cryogenic cooling to create ultrahigh vacuum conditions. The term is used in some languages for what is generally called a cryopump. It operates by exposing gas molecules to very cold surfaces, where they condense or adsorb and are removed from the gas phase.

The operating principle relies on condensation and adsorption. Gas molecules reaching the cold surfaces are captured either by freezing onto the surface or by adsorbing onto porous traps such as activated charcoal. Cooling is maintained by a cryocooler or by liquid helium or nitrogen, typically bringing temperatures from a few kelvin up to tens of kelvin. This makes cryopompen particularly effective for removing hydrogen, water vapor, and other condensable gases, while certain light gases may require special capture surfaces.

Construction usually includes a cryogenic cold head with capture surfaces, a cryocooler or cryogenic reservoir, and interfaces to fore-pumps such as turbomolecular or dry pumps. Trap materials and shielding are chosen to maximize adsorption and minimize re-evaporation. The system is designed to limit outgassing and to separate the cold stages from warmer regions to maintain efficiency.

Operation and regeneration involve continuous cooling to sustain the pumped vacuum. Gas molecules condense or adsorb on the cold surfaces and are retained until regeneration. Regeneration warms the surfaces to release trapped gases, which are then pumped away by the fore-pump. Periodic regeneration is required to maintain performance and prevent saturation.

Cryopompen are used in semiconductor fabrication, electron microscopy, mass spectrometry, and fusion research to achieve very low pressures with oil-free operation. They are highly effective for certain gases but less so for helium and may require long regeneration cycles and substantial cooling power.