Ion pump (physics)

The ion pump, also known as sputter ion pump is a type of vacuum pump. In this special form of the sorption of residual gas particles (atoms or molecules), are ionized by electron bombardment and are accelerated by an electric field onto a surface. There they can be chemically attached or implanted and are thus removed from the residual gas. The impingement of the ions on the surface, electrons are released, they can further ionize residual gas particles. Chemically reactive molecules (usually titanium) bound without prior ionization on impact with a getter material. The pump is not conveying the residual gas consequently from the vacuum chamber, but keeps the atoms pumped only by their internal pump surfaces or " bury " it in the metal. Therefore, the ion pump has no gas outlet port.

Upon impact of the ions on the titanium surface atoms are ejected from the surface ( " sputtering ", hence the name " sputter ion pump "). This fresh titanium is deposited on the opposite electrodes and over again, so the getter layer renewed permanently.

In order to achieve a more efficient ionization of the residual gas atoms or molecules, the electrons have to travel a great distance as possible. This is achieved by a magnetic field in which the electrons are deflected by the Lorentz force and is therefore similar to follow a path of a helix.

This type of pump will work only if a high vacuum has already been reached, that is, when the vacuum chamber was previously pumped by another pump to a pressure below about 10-3 mbar. With ion getter pumps can be achieved a much lower pressure, it could be about 10-11 mbar under optimal conditions. Ion getter pumps are not very well suited for noble gases, because abgepumptes chemically inert gas can not be bound and is released again under certain circumstances.

Ion getter pumps have no moving parts, therefore no maintenance and only need to operate a high voltage supply ( DC voltage, depending on the pump type 3000-7000 V).

Special designs

The ion pump is an ion pump evaporator, wherein the highly reactive getter layer is not produced by sputtering, but evaporation of the getter material (for example, by electron bombardment ).

A variant of the ion pump is the Orbitronpumpe. To ionize the largest possible number of residual gas particles, the electrons rotate a centrally disposed, rod-like anode surrounded by a cylindrical cathode.

• Pump by effects
• Vacuum pump