Anhui Bowei is a company specializing in the design of helium mass spectrometer leak detector and helium leak detection system using helium as a tracer gas for leak detection In addition to high sensitivity, this instrument also has the advantages of wide range of adaptation, accurate positioning and quantification, non-toxic, safe and fast reaction speed. Helium is usually selected as the tracer gas in the mass spectrometer leak detection system for the following reasons:
- The content of helium in the air and the residual gas of the vacuum system is very small (about 5.2ppm in the air), and it is also very small in the output gas of the material, so the background pressure is small and the output background current is small. Because the background is small, the fluctuation of the background is caused by some reasons, that is, the background noise is small, so the small leakage rate can be reflected and the sensitivity is high.
- Helium has a small mass (relative molecular mass is 4) and is easy to pass through leakage holes. In this way, helium has a larger leakage rate than other gases except hydrogen through the same leak hole, which is easy to find and has high sensitivity.
3, helium is an inert gas, does not react with the wall of the inspected part, will not pollute the inspected part, safe to use. - On either side of helium are hydrogen (mass-to-charge ratio of 2) and double-charged atom carbon (mass-to-charge ratio of 6), both of which differ greatly from helium. In this way, their deflection radius in the analyzer is also large, easy to separate, calibration to find helium peak, not easily affected by other ions, so it reduces the requirements for the analyzer manufacturing accuracy, easy to process. At the same time, the gap between the outlet electrode of the analyzer and the accelerator pole of the ion source can also be enlarged to allow more helium ions to pass through and improve the sensitivity of the instrument.
5, helium is not easy to be adsorbed in the test and vacuum system. In this way, the detection of a leak hole can make the helium signal disappear quickly so that the leak detection can continue, and improve the leak detection efficiency of the instrument. - Some properties of hydrogen (such as small mass and easy to pass through leakage holes) are better than helium, however, because hydrogen has an explosive risk on the one hand, on the other hand, in the oil diffusion pump, due to the thermal cracking of oil will produce a large amount of carbon and hydrogen, so that the hydrogen background is extremely high and fluctuations are large, so that the sensitivity is greatly reduced, so it is rarely used.
