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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.
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 ...
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.
Unlike turbomolecular pumps and cryopumps, diffusion pumps have no moving parts and as a result are quite durable and reliable. They can function over pressure ranges of 1 × 10 −10 to 1 × 10 −2 mbar (1 × 10 −8 to 1 Pa). They are driven only by convection and thus have a very low energy efficiency.
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.
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
Excessive fat around organs in midlife could contribute to Alzheimer’s risk due through neuroinflammation, the results of three small studies have suggested.
A cutaway view of a turbomolecular high vacuum pump. In a momentum transfer pump (or kinetic pump [16]), gas molecules are accelerated from the vacuum side to the exhaust side (which is usually maintained at a reduced pressure by a positive displacement pump). Momentum transfer pumping is only possible below pressures of about 0.1 kPa.