A helium mass spectrometer works by using a combination of electromagnetism and gas ionization techniques.
It involves the following steps:
The sample is placed in a vacuum chamber, and the chamber is evacuated to create a low-pressure environment.
Helium gas is introduced into the chamber, and any existing air molecules are removed, as helium is the primary gas used in the process.
An electron beam is emitted, colliding with helium atoms in the chamber and ionizing them by removing an electron. This creates a stream of positive helium ions.
The ions are accelerated by an electric field, causing them to move towards a detector.
The ions pass through a magnetic field created by an electromagnet. The magnetic field causes the ions to follow a curved path due to the Lorentz force.
The curvature of the ion path is determined by their mass-to-charge ratio. Lighter ions with higher charge-to-mass ratios will curve more, while heavier ions with lower charge-to-mass ratios will curve less.
The detector at the end of the ion path records the ions, measuring their arrival time and intensity.
By analyzing the arrival times and intensities of the ions, the mass and concentration of helium in the sample can be determined.
In summary, a helium mass spectrometer uses ionization, acceleration, magnetic deflection, and detection techniques to measure the mass and concentration of helium, making it useful for various applications such as leak detection and gas analysis.