Interior view of a turbomolecular pump

Turbomolecular pumps is a form of turbopump used to obtain and maintain high vacuum. These pumps work on the principe that gas molecules can be given momentum in a desired direction by repeated collision with a rapidly moving solid surface.They use a rapidly spinning turbine rotor to transport gas from the inlet of the pump towards the exhaust in order to create or maintain a vacuum. Image File history File links Cut_through_turbomolecular_pump. ... Image File history File links Cut_through_turbomolecular_pump. ... A turbopump can refer to either of two types of pump. ... For other uses, see vacuum cleaner and Vacuum (musical group). ... In physics, momentum is the product of the mass and velocity of an object. ... WWII era steam turbine used for ship propulsion. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... Manual pump used to obtain water A pump is a mechanical device used to move liquids or gases. ... For other uses, see vacuum cleaner and Vacuum (musical group). ...

Working

Most turbomolecular pumps employ multiple stages consisting of rotor,stator pairs mounted in series. Gas captured by the upper stages is pushed into the lower stages and successively compressed to the level of the fore-vacuum pressure. As the gas molecules enter through the inlet, the rotor,which has a number of angled blades, impacts on the molecules. Thus the mechanical energy of the blades is transferred to the gas molecules. With this newly acquired momentum, the gas molecules enter into the gas transfer holes in the stator. This leads them to the next stage where they again collide with the rotor surface, and this process is continued, finally leading them outwards through the exhaust. The exhaust is generally connected to a backing pump, which produces a pressure low enough for the turbomolecular pump to work efficiently. In general, this pressure must be below 100 millitorr with 10-20 millitorr as common averages. The turbomolecular pump can be a very versatile pump. It can generate many degrees of vacuum from intermediate vacuum (~10^-4) up to ultra-high vacuum levels (~10^-10 Torr). R0t0r is from efnet ... The stator is the fixed part of a rotating machine. ... The torr (symbol: Torr) or millimetre of mercury (mmHg) is a non-SI unit of pressure. ... Ultra high vacuum is that regime of vacuum characterised by pressures lower than about 10-9 torr (0. ...

Practical Considerations

Laws of fluid dynamics do not apply in high vacuum environments. The maximum compression varies linearly with circumferential rotor speed. In order to obtain extremely low pressures down to 1 micropascal, rotation rates of 20,000 to 90,000 revolutions per minute are often necessary. Unfortunately, the compression ratio varies exponentially with the square root of the molecular weight of the gas. Thus, heavy molecules are pumped much more efficiently than light molecules. Most gases are heavy enough to be well pumped but it is difficult to pump hydrogen and helium efficiently. Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ... -1... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... The pascal (symbol Pa) is the SI unit of pressure. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ...

An additional drawback stems from the high rotor speed of this type of pump: very high grade bearings are required, which increase the cost. A bearing is a component used to reduce friction in a machine. ...

External links

• Turbomolecular pumps manufacturer directory
• Some practical guidelines