It was initially developed in the Manhattan Project during World War II to find extremely small leaks in the gas diffusion process of uranium enrichment plants.
If the part is small the vacuum system included in the leak testing instrument will be able to reach low enough pressure to allow for mass spectrometer operation.
If the size of the part is too large, an additional vacuum pumping system may be required to reach low enough pressure in a reasonable length of time.
The vacuum system will carry any tracer gas molecule into the analyzer cell of the magnetic sector mass spectrometer.
If the part is small the vacuum system included in the instrument will be able to reach low enough pressure to allow for mass spectrometer operation.
If the size of the part is too large, an additional pumping system may be required to reach low enough pressure in a reasonable length of time.
The vacuum system will carry any tracer gas molecule into the analyzer cell of the magnetic sector mass spectrometer.
Thus correlation between maximum leakage signal and location of helium spray head will allow the operator to pinpoint the leaky area.
This test method applies to a lot of components that will operate under pressure: airbag canisters, evaporators, condensers, high-voltage SF6 filled switchgear.
The tiny amount of gas that entered the device under pressure will be released in the vacuum chamber and sent to the mass spectrometer where the leak rate will be measured.
Modern machines can digitally remove the helium two decades below the background level and thus it is now possible detect leaks as small as 5·10−10 Pa·m3·s−1 in sniffing mode.