VACUUM SCIENCE BLOG

47th Conference on the Physics & Chemistry of Surfaces & Interfaces

The 47th Conference on the Physics and Chemistry of Surfaces and Interfaces (PCSI-47) will be held from January 19-23, 2020 at Millennium Harvest House in Boulder, Colorado, USA. The annual PCSI conference is devoted to achieve a fundamental understanding of the physical, chemical, biological, structural, optical, magnetic and electrical properties of surfaces and interfaces.

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10th Vacuum Symposium 2019 Report

Over the years, vacuum pumps have evolved to dry versions (no oil in the swept volume), robust, process specific, low power consumption and reduced footprint. With this shift in the industry, it was great to hear a range of discussions around this during the 10th Vacuum Symposium UK.

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Everything you need to know about screw pumps

Screw pumps belong to the family of dry compressing gas transfer pumps. (Learn more about the origins of dry pumps here) They are positive-displacement pumps that use two screw shaped intermeshing rotors to move gas along the screw’s axis. They are frequently used in industrial vacuum applications, often in combination with roots blowers and as oil-free roughing pumps in high and ultrahigh vacuum systems.

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Nearly Zero Energy Buildings conference summary

On 28 August 2019, Vacuum Science World contributor Dr Saim Memon hosted an international, one-day conference on Renewable Energy and Vacuum Insulation for Nearly Zero Energy Buildings (NZEBs) at London South Bank University.

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Seven factors affecting the sensitivity of vacuum gauges

In terms of engineering and science, it is hard to over emphasise the importance of measurements. They are the very essence of these two disciplines, which we use to explain the otherwise unexplainable with equations, tables, graphs and figures. In turn, this allows us to compare, contrast, repeat and define the apparent chaos which defines our world.

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Residual Gas Analysers (RGA) explained

What is a residual gas analyser?

A residual gas analyser (RGA) is a small and usually rugged quadrupole mass spectrometer, typically designed for environment analysis, process control and contamination monitoring in vacuum systems. RGAs can monitor the quality of the vacuum by detecting (and measuring) minute traces of impurities in a low-pressure gaseous environment. RGAs can also be used as sensitive in-situ leak detectors, usually using helium.

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Vacuum bake out: its importance and implementation

The presence of gaseous molecules, whether slow or fast moving, is what gives rise to pressure. A vacuum is created by reducing the number of molecules that exist within, for example, a chamber or a flask. However, by reducing the number of molecules that exert a pressure on the internal surface of such a chamber, one reduces the pressure. Unfortunately, this causes “additional” molecules to enter into play.

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The importance of gas ballast for vacuum pumps

When atmospheric air (or a gas) is used as a source for a vacuum system, it will however “pure” it may appear to be invariably contain some vapour. As the pressure drops this vapour will condense out and unless vented from the system form a contaminant which will prevent the pump from achieving its optimum vacuum pressure. In addition, this condensate can enter the pump’s oil-seal where as a contaminant, it can have a further detrimental effect.

In simple terms, a gas ballast valve incorporated into the system will allow a small portion of the compressed gas (containing this detrimental condensate) to be expelled without impacting upon the overall performance of the pump.

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The limitations of achieving UHV with turbomolecular vacuum pumps

There are several types of pumps that can deliver high and ultra-high vacuum pressures; diffusion pumps, cryo pumps; ion getter pumps (IGP); titanium sublimation pumps (TSP); non-evaporable getter (NEG) pumps; and turbomolecular pumps (TMP).

The methods whereby these pumps are capable of producing high and ultra-high vacuum pressures (between 10-3 and 10-11 mbar) are either by momentum transfer of gas molecules or by capturing them (either physically or chemically).

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The Working Principle of Multistage Roots Vacuum Pumps

Multistage roots pumps are dry vacuum pumps used in low, medium, high and ultra-high vacuum systems to produce “dry” conditions.

The simple (single-stage) roots pump is most commonly employed as a booster pump for several types of fore-pumps (such as rotary vane pumps, screw and liquid ring pumps) to improve ultimate pressure and pumping speeds. When multistage roots pumps are employed, no fore pump is required and they can operate from atmospheric pressure. Roots pumps are suitable where a dry and clean atmosphere is important or more likely essential. Consequently, they are frequently used in the manufacture of semiconductors and solar panels, as well as for coatings and other industrial applications.

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