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A turbomolecular pump is a type of vacuum pump, superficially similar to a turbopump, used to obtain and maintain high vacuum. [ 1 ] [ 2 ] These pumps work on the principle that gas molecules can be given momentum in a desired direction by repeated collision with a moving solid surface.
The turbomolecular pump overcame many of these disadvantages. Many modern turbomolecular pumps contain built-in molecular drag stages, which allows them to operate at higher foreline pressures. As a stage in turbo molecular pumps, the most widely used design is the Holweck type, due to a significantly higher pumping speed than the Gaede design.
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Ultra-high vacuum (often spelled ultrahigh in American English, UHV) is the vacuum regime characterised by pressures lower than about 1 × 10 −6 pascals (1.0 × 10 −8 mbar; 7.5 × 10 −9 Torr). UHV conditions are created by pumping the gas out of a UHV chamber.
This is also called the regime of high vacuum, or even ultra-high vacuum. This is opposed to viscous flow encountered at higher pressures. [1] The presence of free molecular flow can be calculated, at least in estimation, with the Knudsen number (Kn). [2] If Kn > 10, the system is in free molecular flow, [3] also known as Knudsen flow. [4]
The article Edwards' IPUP2 Vacuum Pump Sets New Standards for Load Lock and Transfer Chamber Applications originally appeared on Fool.com. Try any of our Foolish newsletter services free for 30 days .
To achieve a higher vacuum, other techniques must then be used, typically in series (usually following an initial fast pump down with a positive displacement pump). Some examples might be use of an oil sealed rotary vane pump (the most common positive displacement pump) backing a diffusion pump, or a dry scroll pump backing a turbomolecular pump.
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