high-sensitivity helium mass spectrometry leak detection for noise sources

The sensitivity of a high-sensitivity helium mass spectrometer leak detector is mainly limited by the background and noise of the instrument. Let’s take a look at the noise source of high-sensitivity helium mass spectrometry leak detection this time.

The noise sources of high-sensitivity helium mass spectrometer leak detectors can be roughly divided into two types: one is the noise of the ion current receiving amplifier output circuit, and the other is the background noise. In fact, through the improvement of electronic circuits, the noise caused by ion current reception amplification and output circuits in instruments has been reduced to a very low level. Therefore, it is no longer the main factor limiting device sensitivity. If it is still the main factor limiting sensitivity in special circumstances, the signal-to-noise ratio can be improved by amplifying the signal to improve sensitivity.

The background noise is caused by the instability of the background peak, which is related to the size of the background and the stability of the electromagnetic field parameters, including:
1. The instability of electron flow emitted by ion sources, the instability of acceleration voltage, and the electromagnetic parameters of analyzers; 2. The adsorption and re release of helium gas in vacuum systems (such as vacuum grease, synthetic rubber, and organic insulation materials can all adsorb and re release helium gas), and the memory effect of ionization vacuum gauges, especially magnetic discharge vacuum gauges, on helium gas (which is more severe when contaminated);
3. The anti diffusion of helium in the pumping system and the instability of helium pumping speed;
4. The helium mass spectrometer leak detector itself leaks gas and the permeation of helium gas;
5. Scattering of helium ions by residual gas molecules, etc.
The above factors have a significant impact on the background noise and sensitivity.