Residual gas analyzers vs leak detectors when to use an RGA

September 23, 2020


Spacecrafts can spring leaks for any number of reasons. Unmonitored leaks can lead to rapid temperature changes and threaten the safety of personnel. For these reasons, it is vital for space research teams to employ the correct tools when conducting testing in a simulated space atmosphere.  

The space industry is not the only trade in which leak detection is critical. Here's a quick overview of leak detectors and Residual Gas Analyzers' (RGAs) functions, and some signs that say it's time to employ RGA technology. 

How leak detectors work

Leak detectors identify, analyze, and measure any gases or fluids either entering or escaping an enclosed space or pressurized system. Leak detectors search for the source of a leak, how fast the substance may be coming in or going out and evaluating if the rate of entry or escape is increasing or decreasing. Most leak detectors measure the presence of helium gas and have vacuum technology already built into their construction. 

Most leak detectors use a 180° mass spec, capable of bonding ions around a magnetic field. Leak detectors, in general, are fine-tuned to detect the presence of helium. Particles become ionized in the vacuum and accelerated with added voltage, separating them within the magnetic field and turning the ions into an electric current. 

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Understanding residual gas analyzers (RGAs)

Residual Gas Analyzers (RGAs) look beyond the presence of helium. They evaluate all the gases present within a space.

Effective use of RGAs relies on pressures in a high vacuum range. RGAs, like our LEYSPEC range, can be used as an enhancement for companies who already have vacuum technology.  

Three basic components of RGAs

Ion source

The ion source is used to turn the gas located within a space into ions. The measurement cell is a hot cathode ionization vacuum gauge. The electrons emitted from the hot filament accelerate toward the source using an electrical bias. The rapidly moving electrons collide with the gas molecules, dislodging and ionizing the electrons. 

Mass filter 

The mass filter is a quadrupole array comprised of four stainless-steel rods. The quadrupole flushes away and varies voltages to favor certain ions when their presence is detected.  


Ions exiting within the filter collide with a metal plate called a detector, or Faraday cup. The ions become neutralized as the electrons transform into an electrical signal. The resulting current matches the current of the incoming ion. An election multiplier amplifies the signal and alerts researchers to their presence. The boost becomes extremely helpful when gases present at low levels in a vacuum might otherwise go undetected.

RGAs and leak detectors: similarities and differences

RGAs and leak detectors are both mass spectrometers.

The biggest difference is that RGAs do not come with their own vacuum technology: they must be supported within a vacuum system. The advantage RGAs give you over leak detectors is their ability to detect different gas types besides helium. 

The ability to distinguish between different vapors becomes helpful when dealing with gases that disperse over a wide space, making it harder to get to the source of a leak. RGAs also detect other elements like acetone or methanol that may be present in a space. 

When RGAs can make a difference

RGAs can help testers, researchers, and engineers understand the specifics of what is going in and out of their systems. That knowledge allows them to judge if they have the correct ratios present to achieve the ideal conditions for their project. 

Examples of RGA usefulness

The textile industry often relies on using physical vapor deposition (PVD) using argon gas to create plasmas to create coatings. Having an RGA present helps engineers know if they are bringing in the right mix of elements for the required processes. 

RGAs can also help evaluate chambers which may be outgassing. That can be beneficial in industrial industries to check for leaks in water jackets. The technology can even be adapted to perform emissions testing. RGAs can be a worthwhile investment for companies willing to put in the time and support structures needed for optimal performance.

Use experienced RGA developers

Leybold specializes in RGAs designed to meet the needs of various industries. Take a look through our current selection of RGAs or request a customized RGA built to your specifications.

Our engineers are always ready to provide innovative solutions that protect the safety and integrity of your systems and processes.  
If you'd like to explore your options for customized RGAs or have a question for us — get in touch!

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