Mass spectrometer inside the leak detector
Helium leak detection has established itself for many years as a method for testing the tightness in various fields of application. Its high degree of sensitivity, the reliability of its measurements as well as its easy reproducibility are the most convincing advantages compared to other tightness test methods. For detecting test gases, Pfeiffer Vacuum offers leak detectors based on mass spectrometers.
Fig.1: Function of a sector field mass spectrometer
Mass spectrometers ionize a gas mixture and isolate the desired tracer gas on the basis of their mass-to-charge ratio. Due to the low detection limit of the mass spectrometer, the high degree of sensitivity for the Pfeiffer Vacuum leak detector is guaranteed. The so-called “spectrometer cell “is the centerpiece of the helium leak detector. From the inlet of the leak detector, the gases are guided into the spectrometer cell. Here, the electrically loaded gas particles are bombarded with an electron beam at high energies (figure 1, violet). This beam is generated by a filament at high temperatures. If an electron is hit in the shell of a neutral gas particle, it emerges from the electron shell. Consequently, a positively loaded gas particle – an ion – remains. A large part of the introduced gas particles is ionized by these collisions between electrons. The positively loaded gas particles which are still present in the mixture are now accelerated in an electrical field.