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A cryopump or a "cryogenic pump" is a vacuum pump that traps gases and vapours by condensing them on a cold surface, but are only effective on some gases. The effectiveness depends on the freezing and boiling points of the gas relative to the cryopump's temperature.
The working fluid is 3 He, which is circulated by vacuum pumps at room temperature. The 3 He enters the cryostat at a pressure of a few hundred millibar . In the classic dilution refrigerator (known as a wet dilution refrigerator ), the 3 He is precooled and purified by liquid nitrogen at 77 K and a 4 He bath at 4.2 K.
Nitrogen is a liquid under −195.8 °C (77.3 K).. In physics, cryogenics is the production and behaviour of materials at very low temperatures.. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of "cryogenics" and "cryogenic" by accepting a threshold of 120 K (−153 °C) to ...
The term is most often used for smaller systems, typically table-top size, with input powers less than about 20 kW. Some can have input powers as low as 2–3 W. Large systems, such as those used for cooling the superconducting magnets in particle accelerators are more often called cryogenic refrigerators. Their input powers can be as high as 1 MW.
A cryogenic gas plant is an industrial facility that creates molecular oxygen, molecular nitrogen, argon, krypton, helium, and xenon at relatively high purity. [1] As air is made up of nitrogen, the most common gas in the atmosphere, at 78%, with oxygen at 19%, and argon at 1%, with trace gasses making up the rest, cryogenic gas plants separate air inside a distillation column at cryogenic ...
Pumps that use oil either as their working fluid (diffusion pumps), or as their lubricant (mechanical rotary pumps), are often the sources of contamination in vacuum systems. Placing a cold trap at the mouth of such a pump greatly lowers the risk that oil vapours will backstream into the cavity.
Ion pumps; Titanium sublimation pumps; Non-evaporable getter (NEG) pumps; Cryopumps; Diffusion pumps, especially when used with a cryogenic trap designed to minimize backstreaming of pump oil into the systems. Turbo pumps and diffusion pumps rely on supersonic attack upon system molecules by the blades and high speed vapor stream, respectively.
Figure 1: Schematic drawing of a Stirling-type single-orifice PTR. From left to right: a compressor, a heat exchanger (X 1), a regenerator, a heat exchanger (X 2), a tube (often called the pulse tube), a heat exchanger (X 3), a flow resistance (orifice), and a buffer volume.