Vacuum unit classification
The ultra-high vacuum unit with the work above 10-5pa has the diffusion pump, the ultra-high vacuum unit of the molecular pump and the non-oil ultra-high vacuum unit. The unit has the following characteristics:
1. The ultimate vacuum degree of the main pump is high, which is above 10-7~10-8pa;
2. Can withstand the high temperature of 200 ~ 450 ℃ baking;
3. The partial pressure of main pump reflux gas is very low;
4. For the main pump that is selected by the exhaust gas, it should be equipped with enough auxiliary pump;
5. Vacuum chamber, pipe, valve and other components are required to have low gas discharge rate and low air leakage rate.
一. diffusion pump ultra-high vacuum unit:
The ultimate vacuum of the ultra high vacuum unit with diffusion pump as the main pump is 10-7~ 10-8pa.
To reduce the level from diffusion pump the gas diffusion and block mechanical pump oil anti diffusion effect on the ultimate vacuum, but in front of the diffusion pump level type a small pumping speed of diffusion pump, in order to reduce the compression ratio, reduce the diffusion. If a titanium sublimation well is added to the air inlet of the diffusion pump, the nitrogen partial pressure from the diffusion pump can be further reduced, and the ultra-high vacuum of 10-11pa can be obtained.
二. Ultra-high vacuum unit of molecular pump:
The ultra-high vacuum unit with molecular pump as the main pump has a limit vacuum of 10-8pa, characterized by fast start and low pollution of oil.
Increasing the liquid nitrogen cold trap in the unit can increase the pumping speed. A water cooling trap is provided at the outlet of the mechanical pump to prevent oil vapor from entering the system.
三. No-oil ultra-high vacuum unit:
The vacuum unit that does not use oil for working fluid and does not have organic material seal is called an oil-free ultra-high vacuum unit. The commonly used main pump has low temperature pump, titanium pump, sputtering ion pump and so on, which can get the ultimate vacuum degree 10-7~ 10-8pa. Compared with an oil vacuum unit, it has the following advantages:
1.Clean vacuum and no pollution source;
2. When the oil-free vacuum pump is started, the pre-pump can be isolated;
3. If the exhaust gas stops suddenly, the system will not be polluted;
4. No oil, no sound, no vibration, improve the working environment;
5. High vacuum degree, large pumping speed and short exhaust time.