VACUUM SCIENCE BLOG

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.

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.

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.

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).

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.

In the world of vacuum systems, scroll pumps hold a valuable place as one of the few pumps that are traditionally employed in low (i.e. 1000 mbar to 1 mbar) and medium (i.e. 1 mbar to 10^-3 mbar) systems, and yet are now also frequently being employed as fore (or backing) pumps in high and ultra-high (i.e. 10^-3 to 10^-12 mbar) vacuum systems.

Vacuum simulation (or modelling) is an essential part of vacuum system design. It is now a well-established practice and is primarily concerned with the prediction and calculation of how vacuum pumps and systems will perform in specific scenarios.

These simulations enable engineers to identify anomalies in the design stage and acquire the right components, rather than building a vacuum system that later needs to be redesigned.

Sharing knowledge and expertise on all things vacuum science and technology is our foundation. We are delighted to share this opportunity to learn from international researchers and innovators in the Renewable Energy and Vacuum Insulation community at the International Conference on Renewable Energy and Vacuum Insulation for Nearly Zero Energy Buildings.

Vacuum science has been integral to major scientific advancements. One of the most prominent of these is gravitational wave detectors. Gravitational waves are ripples in space-time that are caused by violent processes such as exploding stars, collisions between neutron stars or the merging of black holes – a concept predicted by Einstein’s theory of General Relativity in 1915.

One of the most discussed concepts amongst the astrophysics community is black holes. A black hole is a volume of space where the presence of gravity is so extreme that fast moving particles or light cannot escape.