Requirements of vacuum degree in vacuum system for electronic energy spectrometer
The requirement of vacuum degree in vacuum pump of electron energy spectrometer is that of all large analytical instruments, which is generally better than 10-7pa. On the one hand, it is because the photoelectron energy emitted by the sample is the lowest, in order to reduce the movement of electrons to the detector
The signal strength is lost due to collision with residual gas in the process, which requires all parts of the spectrometer to be in vacuum.
On the other hand, EDS is a kind of appearance analysis skill. Photoelectrons with sample information emitted from the sample usually come from dozens of atomic layer thickness of the outer layer. Therefore, it is required to provide a clear surface with atomic number and address level, and can maintain this cleanliness within the required time. Any contamination on the surface will have an adverse effect on the analysis.
It is obvious that the degree of contamination on the surface of the sample is related to the vacuum degree of the environment. When the vacuum degree is 10-5pa, a layer of gas molecules will be adsorbed on the surface of the sample within 3S. When the vacuum degree is 10-7pa, it takes about 1h to adsorb a single molecular layer. At this time, the analysis requirements can be satisfied. A good vacuum system should be able to meet the requirements of high vacuum degree (10-7pa), high pumping rate and low noise during operation No oscillation, baking and other requirements. At present, the vacuum pumps used more include oil diffusion pump, vortex energy molecular pump, rotary vane vacuum pump, titanium pump, etc.