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Alcatel Vacuum Technology France - ASM 180 TD/TD+ - ASM 181 TD+ User’s Manual
Testing methods
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Edition 03 - May 97
He
Part
He
Part
Chamber 1
Chamber 2
Detector
Bombing method
This method is used for sealed objects that cannot be
connected directly to the detector (semiconductors,
waterproof watches, etc.).
The part is placed in a vessel containing pressurised helium.
The helium penetrates the part if it has a leak.
The part is then removed from the vessel and placed in
another vacuum vessel which is connected to the detector.
The helium escapes from the part through the leak and
produces a signal.
This signal is not a direct measurement of the leak
as the
helium pressure inside the part is difficult to determine. It
depends on the pressurisation time, pressurisation pressure,
internal volume of the part, dwell time before vacuum test
and size of the leak.