he helium mass spectrometer leak detector is a gas tightness detection instrument made using helium gas as the exploration gas based on the principles of mass spectrometry The mass spectrometry principle is shown in the figure.

The mass spectrometry principle of helium mass spectrometer leak detector

The electrons emitted by the filament oscillate back and forth in the ionization chamber, colliding with the gas inside the chamber and the helium gas that enters the chamber through the leakage hole of the tested object, causing it to ionize into positive ions. These ions enter the magnetic field under the action of an accelerating electric field, and are deflected by the Lorentz force, forming a circular arc orbit with a radius of

In the formula, R&dash& mdash; Distance from the deflection orbit radius (cm)

B&dash& mdash; Magnetic field strength (T)

&--& mdash; Ion mass/charge ratio (positive integer)

U&dash& mdash; Ion acceleration voltage (V)

As can be seen from the above equation, when R and B are constant values, changing the acceleration voltage can cause ions of different masses to pass through the magnetic field and the receiving slit to reach the receiving electrode and be detected.

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