Diffusion pumps use a high speed jet of vapor to direct gas molecules in the pump throat down into the bottom of the pump and out the exhaust. They were the first type of high vacuum pumps operating in the regime of free molecular flow, where the movement of the gas molecules can be better understood as diffusion than by conventional fluid dynamics. Invented in 1915 by Wolfgang Gaede, he named it a diffusion pump since his design was based on the finding that gas cannot diffuse against the vapor stream, but will be carried with it to the exhaust. However, the principle of operation might be more precisely described as gas-jet pump, since diffusion plays a role also in other high vacuum pumps. In modern textbooks, the diffusion pump is categorized as a momentum transfer pump.
The main manufacturers of Diffusion pumps would include Edwards Leybold Varian and CVC. The Edwards Diffusion pumps having held the best pump speeds for a number of years. The Diffusion pump is still used widely in industrial applications where large gas loads can be found, such as vacuum furnaces , large web area roll to roll coaters.
The pumps usually run on a high grade silicon oil or even santovac. Poor oil quality will reduce pumping speeds and result in oxidisation build up within the pump.
We can provide help and advice on all types of Diff pump, including heater elements oil and seals.