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Most turbomolecular pumps employ multiple stages, each consisting of a quickly rotating rotor blade and stationary stator blade pair. The system is an axial compressor that puts energy into the gas, rather than a turbine, which takes energy out of a moving fluid to create rotary power, thus "turbomolecular pump" is a misnomer.
Generally, axial pumps tend to give much lower pressures than centrifugal pumps, and a few bars is not uncommon. Their advantage is a much higher volumetric flowrate. For this reason they are common for pumping liquid hydrogen in rocket engines, because of its much lower density than other propellants which usually use centrifugal pump designs.
In general, molecular drag pumps are more efficient for heavy gasses, so the lighter gasses (hydrogen, deuterium, helium) will make up the majority of the residual gasses left after running a molecular drag pump. [4] The turbomolecular pump invented in the 1950s, is a more advanced version based on similar operation, and a Holweck pump is often ...
In December 1998, a modification to the vacuum pumping system that began in 1994 was completed. In particular, twelve turbomolecular pumps with oil bearings and four oil sealed rotary vacuum pumps were replaced with magnetically suspended turbomolecular pumps and dry vacuum pumps.
In the first stage, a roughing pump clears most of the gas from the chamber. This is followed by one or more vacuum pumps that operate at low pressures. Pumps commonly used in this second stage to achieve UHV include: Turbomolecular pumps (especially compound pumps which incorporate a molecular drag section and/or magnetic bearing types) Ion pumps
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Practically, the "vapor" cannot move around bends or into other spaces behind obstacles, as they simply hit the tube wall. This implies conventional pumps cannot be used, as they rely on viscous flow and fluid pressure. Instead, special sorption pumps, ion pumps and momentum transfer pumps i.e. turbomolecular pumps are used.
Ion pumps are commonly used in ultra-high vacuum (UHV) systems, as they can attain ultimate pressures less than 10 −11 mbar. [1] In contrast to other common UHV pumps, such as turbomolecular pumps and diffusion pumps, ion pumps have no moving parts and use no oil. They are therefore clean, need little maintenance, and produce no vibrations.
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