Diffusion vacuum pump manufacturers    Diffusion pump heaters     Europe, Middle East and Africa     North and South America     Asia Pacific      Germany     Italy     United Kingdom     Varian Vacuum Technologies (Europe) - www.varianinc.com - via F.lli Varian 54, 10040 Leini (TO), Italy E-Mail: vtt.technical.support@varianinc.com, Tel: 00 (800) 234.234.00 (toll-free), Fax: +39 (011) 997.9350 products: Varian has earned its position as the leading Diffusion Pump manufacturer in the world by listening to customer needs and by continuously improving the performance and reliability of our benchmark designs. Feature and Benefits Typical Applications Pump Models Fluids Baffles Technical Notes company profile: Varian, Inc. is a leading worldwide supplier of scientific instruments and vacuum technologies for life science and industrial applications. The company provides complete solutions, including instruments, vacuum components, laboratory consumable supplies, software, training and support through its global distribution and support systems. Varian, Inc. employs approximately 3,700 people and operates manufacturing facilities in 13 locations in North America, Europe and Australia.   related pages:   cryopumps,   diffusion pumps,   getter ion pumps,   turbomolecular pumps,   vacuum oil and sealants   Keywords   www.vacuum-guide.com  Diffusion pumps are a type of vacuum pump designed to achieve higher vacuum (lower pressure) than possible by use of mechanical pumps alone. They use a high speed jet of vapor to direct residual gas molecules in the pump throat down into the bottom of the pump and out the exhaust. The high speed jet is generated by boiling the fluid (typically a low vapor pressure oil) and directing the vapor through a multistage jet assembly. Often several jets are used in series to enhance the pumping action. The outside of the diffusion pump is cooled using either air flow or a water line. As the vapor jet impacts the outer cooled shell of the diffusion pump, the working fluid condenses, is recovered, and directed back to the boiler. The pumped gases continue flowing to the base of the pump at increased pressure, flowing out through the diffusion pump outlet, where the pressure is increased to ambient, and exhausted by the secondary mechanical "rough pump". Note that the oil is gaseous when entering the nozzles. Within the nozzles, the flow changes from laminar, to supersonic and molecular. Unlike mechanical pumps, diffusion pumps have no moving parts and as a result are quite durable and reliable. They can function over pressures ranges of 10-8 to 1 pascals. They are driven only by convection and thus have a very low efficiency. Diffusion pumps cannot discharge directly into the atmosphere, so a mechanical forepump is typically used to maintain an outlet pressure around 10 pascals. One major disadvantage of diffusion pumps is the tendency to backstream oil into the vacuum chamber. This oil can contaminate surfaces inside the chamber or upon contact with hot filaments or electrical discharges may result in carbonaceous or siliceous deposits. Due to backstreaming, diffusion pumps are not suitable for use with highly sensitive analytical equipment or other applications which require an extremely clean vacuum environment. Often cold traps and baffles are used to minimize backstreaming, although this results in some loss of pumping ability. more about diffusion pumps (Wikipedia)