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www.thinkSRS.com Choosing a Quadrupole Gas Analyzer Application Note #9 Modern-day contamination control requirements for gas phase Residual Gas Analyzers processes are constantly pushing the limits of performance of quadrupole gas analyzers. The quadrupole technology is The prototypical residual gas analyzer (RGA) has an open ion rapidly evolving and adapting to lower contamination level source (OIS) and is mounted directly on a vacuum chamber so specifications. A good understanding of the various factors that the entire sensor is at the same pressure as the rest of the affecting the detection capabilities of the different gas analysis vacuum system. Small physical dimensions make it possible systems currently available is an essential tool when selecting to attach an RGA to virtually any vacuum system, including a sensor for a specific application. As is usually the case, most both research and process setups. The maximum operating choices involve compromises, and a good understanding of pressure is 10-4 Torr. Minimum detectable partial pressures the basic tradeoffs associated with different detector (typically measured for N2 at 28 amu) are as low as 10-14 Torr configurations will minimize mistakes and maximize for units equipped with an electron multiplier. productivity. In high vacuum applications such as research chambers, All gas phase processing setups can benefit from the addition surface science setups, accelerators, aerospace chambers, of a quadrupole gas analyzer. The information delivered by a scanning microscopes, outgassing chambers, etc., RGAs are well-matched detector rapidly becomes an integral part of the effectively used to monitor the quality of the vacuum, and process, dramatically reducing the amount of guesswork that they can easily detect even the most minute impurities in the has traditionally been part of most vacuum troubleshooting low pressure gas environment. Trace impurities can be procedures. As quadrupole gas analyzers become more measured down to 10-14 Torr levels, and sub-ppm detectability affordable, they are rapidly becoming commonplace in all is possible in the absence of background interferences. During industries that require strict control of contamination levels in system troubleshooting, RGAs are also used as very sensitive, process gases. A smart software interface, lower detection in-situ, helium leak detectors. limits and reduced cost of ownership are some of the features to look for in modern instruments. In the semiconductor industry,