The #cryopump is a high vacuum pump that is based on the adsorption of gas on cold surfaces. The cooler the surface – the better the pumping! For that purpose liquid helium is often used for cooling the system parts as it is extremely cold, having a temperature only four degrees above absolute zero. The pumping is done in multiple stages, where each stage has a different temperature. The „warmest“ part is the first stage, that has a temperature of 100 degrees Kelvin (or lower) and that causes water to condensate on it. During the #condensation of water also some other gases may also be trapped under the water and that process is called #cryotrapping. However, in order to effectively pump gases such as nitrogen, even colder surfaces (less than 17 degrees Kelvin) are required. In this stage the metal may also be coated with porous activated charcoal and that allows to adsorb even smaller gas molecules such as helium and even hydrogen (this is called #cryosorption ). So basically the pumping of gases with this #vacuumpump is based on three processes: condensation, cryotrapping and cryosorption.
The titanium sublimation pump is a vacuum pump used as a part of vacuum systems in order to briefly improve the level of #vacuum. The working principle is relatively simple. A pulsing current passes through a titanium filament, causing it to sublimate (goes directly from solid phase to gas phase). The fresh titanium chemically reacts with gas in the vacuum chamber, creating a solid product that deposits on the chamber walls. As the walls are also coated with highly reactive freshly deposited titanium, they may also chemically bind gas molecules that interact with them. Some gases may not chemically bind with titanium but can still be physically trapped under the titanium atoms on the chambers walls.
The ion pump is a high vacuum pump that is based on ionizing the gas. When the gas that enters the #ionpump it always has some ions in it and those are pulled towards the titanium cathode. These ions are then trapped between the titanium atoms and they may also chemically react with titanium forming solid titanium nitride or titanium oxide, depending on the gas. In addition electrons and titanium atoms are emitted from the cathode when bombarded by the ionized gas molecules. These electrons are then accelerated towards the steel anode as the potential between the anode and cathode is thousands of volts. A magnetic field caused by the magnets makes the electrons move spirally so they spend more time in the open and more likely hit gas molecules to ionize them. The generated gas ions move again towards the cathode and kick out even more electrons and titanium atoms. Some of the kicked out titanium atoms also deposit on the anode and in this process bury gas molecules under them. The pump may work for several years if used in high vacuum environment and if the amount of pumped gas is not large. At some point however the cathodes need to be replaced.
Turbomolecular pump ( #TMP ) is a popular high vacuum pump, that is widely used in many vacuum systems (electron microscopes for example) as it is clean, fast and efficient for maintaining high vacuum over a long period of time. Inside the pump there are rotor blades that rotate with a speed up to 90 000 rotations per minute and stator blades that are stationary. If a gas molecule enters the pump then it is hit by the rotor blades that are tilted at a certain angle. The kinetic energy from the blade is transfered to the gas molecule and causes it to move down and hit a stator blade that is also tilted at a certain angle, causing the molecule to „bounce“ down, where it meets the next rotor blade. Eventually the gas molecules reach the bottom of the turbomolecular pump where they are removed with a backing pump (prevacuum pump). The turbomolecular pump usually also needs a pre-vacuum before it can work efficiently and this can be done with a pre-vacuum pump (for example a scroll compressor pump). Once the pressure is low enough, the #turbomolecularpump starts working and the rotation speed of the rotor blades is gradually increased.
The diffusion pump is an oil-based vacuum pump, that is used for obtaining different levels of vacuum – even high vacuum of 10 powered -9 Pascal. In this system the oil is boiled by a heating with a heater. Next, the jets of vaporized oil grab the gas molecules in the chamber and transport them to the colder chambers walls where oil condensates and moves down. At this stage the captured gas molecules are released and removed from the system with a pre-vacuum pump. The #diffusionpump has very high pumping speeds and it can even be used for the pumping of corrosive gases. The downside however, is the possibility of contaminating the vacuum system with oil and therefore oil traps are highly recommended.