High Vacuum Obtaining 

Mechanical pump is often used to obtain low vacuum. 

Mechanical pump is a device that uses mechanical methods to continuously change the volume 

of suction chamber in the pump and expand the volume of gas in the pumped container to obtain 

vacuum. 

It can work directly under atmospheric pressure. 

The ultimate vacuum degree is generally 1.33-1.33x10-2pa. 

The pumping rate is related to the rotating speed and the chamber volume V, 

which is generally between a few liters per second and dozens of liters per second. 

High Vacuum Obtaining

Now, the widely used pump to obtain high vacuum is the diffusion pump. 

Diffusion pump is to use the phenomenon of gas diffusion to pump gas, it can not work directly under atmospheric pressure, 

but needs a certain amount of preparatory vacuum (1.33-0.133 Pa). 

The ultimate vacuum degree of oil diffusion pump mainly depends on the vapor pressure of oil and the 

anti-diffusion of gas molecules, 

which can reach 1.33 x10-5---1.33x10-7pa. 

Generally the pumping rate is related to the structure, ranging from several liters to hundreds of liters 

per second.