Diffuuspumput

Diffuuspumput, or diffusion pumps, are a type of vacuum pump used to achieve high vacuum in scientific and industrial systems. They rely on a heated oil vapor that is expelled through a network of diffusers, creating a stream of vapor jets inside the pump. Gas molecules entering the pump are entrained in the oil vapor and carried downward to the exhaust, where the oil condenses and the gas is pumped away by a separate backing pump.

Operation requires a forepump or backing pump to establish the initial vacuum and to remove the oil vapor exhaust. Diffusion pumps cannot start from atmospheric pressure and cannot provide strong suction on their own, so they are paired with a rotary or turbomolecular forepump. To prevent oil backstreaming into the processed chamber, diffusion pumps are equipped with baffles and are often used in conjunction with a cold trap or cold finger.

Construction typically includes a heated oil reservoir, a diffuser section with jet nozzles, a series of baffles, and an exhaust that leads to the forepump. Oils used are chosen for vacuum stability and low vapor pressure, such as mineral oils, silicones, or polyalphaolefins. Regular oil changes and filtration are required to maintain performance and minimize contamination of the system.

Applications of diffuuspumput include semiconductor fabrication, surface coating, mass spectrometry, and electron microscopy, where high pumping speeds for light gases are valuable. Limitations include oil backstreaming risk, limited effectiveness for heavy gases, and greater maintenance compared with dry or turbomolecular pumps.