Oil diffusion pump is a jet pump is used to obtain high vacuum or ultra-high vacuum main equipment. Oil diffusion pump working pressure of 10-4 ~ 10-6Torr (1 Torr = 1mmHg = 133.32Pa, the same below), the pumping speed, pumping speed range (several liters per second to tens of thousands of liters), each No gas selectivity, simple structure, no mechanical parts. It is mainly composed of pump body, cooling cap, nozzle, steam conduit and heater. Diffusion pump commonly used oil is 2 # or 3 # oil, 274 or 275 silicone oil, etc .; In addition, with mercury as the working fluid mercury diffusion pump, mercury vapor through the front stage pump to the surrounding environment on the human body is toxic, it is not commonly used . Diffusion pump at work, you must first access the appropriate cooling water, and then heating the pan; work at the end of the heater should be cut off until the pump cooled to near room temperature and then turn off the cooling water.