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A vacuum flange is a flange at the end of a tube used to connect vacuum chambers, tubing and vacuum pumps to each other. Vacuum flanges are used for scientific and industrial applications to allow various pieces of equipment to interact via physical connections and for vacuum maintenance, monitoring, and manipulation from outside a vacuum's chamber.
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.
Ultra-high vacuum systems are usually made of stainless steel with metal-gasketed vacuum flanges. The system is usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials in the system and boil them off.
Austenitic stainless steels are the most common choice for high vacuum and ultra-high vacuum systems. Not all alloys are suitable; e.g. the free-machining 303 steel contains sulfur, which tends to outgas. Alloys with good weldability under argon arc welding are usually chosen. 304 stainless steel is a common choice of a stainless steel.
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]
High to ultra-high vacuum removes the obstruction of air, allowing particle beams to deposit or remove materials without contamination. This is the principle behind chemical vapor deposition , physical vapor deposition , and dry etching which are essential to the fabrication of semiconductors and optical coatings , and to surface science .
Vacuum systems usually consist of gauges, vapor jet and pumps, vapor traps and valves along with other extensional piping. A vessel that is operating under vacuum system may be any of these types such as processing tank, steam simulator, particle accelerator, or any other type of space that has an enclosed chamber to maintain the system in less than atmospheric gas pressure.
A roughing pump is any vacuum pump (typically mechanical) used to initially evacuate a vacuum system, as a first stage towards achieving high vacuum or ultra high vacuum.The term "roughing pump" derives from the vacuum range it works in, "rough vacuum", above 1x10 −3 torr (0.1 Pa).
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