Ion pump
- "Ion pump" redirects here. For a protein that moves ions across a plasma membrane, see Ion transporter.
An ion pump (also referred to as a sputter ion pump) is a type of vacuum pump capable of reaching up to 10−11 mbar under ideal conditions.[1] An ion pump ionizes gases and employs a strong electrical potential, typically 3kV to 7kV, to accelerate them into a solid electrode. A swirling cloud of electrons produced in hollow Penning cells ionizes incoming gas atoms and molecules while they are trapped in a strong magnetic field. The swirling ions strike the chemically active cathode inducing sputter and are then pumped by chemisorption which effectively removes them from the vacuum chamber, resulting in a net pumping action. Inert and lighter gases, such as He and H2 do not effectively induce sputter and are absorbed by physisorption. Some fraction of the energetic gas ions (including gas that is not chemically active with the cathode material) that strike the metal cathode steal an electron from the surface and rebound as a neutral atom. These energetic neutrals are reflected back from the cathodes and buried as neutrals in exposed pump surfaces.[2]
The pumping rate and capacity of such capture methods is dependent on the specific gas species being collected and the cathode material absorbing it. Some species, such as carbon monoxide, will chemically bind to the surface of a cathode material. Others, such as hydrogen, will diffuse into the metallic structure. In the former example, pump rate can drop as the cathode material becomes coated. And, in the latter, the rate remains fixed by the rate at which the hydrogen diffuses.
There are three main types, the conventional or standard diode pump, the noble diode pump and the triode pump.[3]
Ion pumps are commonly used in ultra high vacuum (UHV) systems, as they can attain ultimate pressures less than 10−11 mbar.[4] In contrast to other common vacuum pumps such as turbomolecular pumps and diffusion pumps, ion pumps have no moving parts and use no oil, and are therefore clean and low-maintenance, and produce no vibration, which is an important factor when working scanning probe microscopy.
Recent work has suggested that species escaping from ion pumps can influence the results of some experiments.[5]
Not to be confused with the ionic liquid piston pump or the ionic liquid ring vacuum pump.
See also
References
- ^ http://www.varianinc.com/image/vimage/docs/products/vacuum/pumps/ion/shared/ion-catalog.pdf
- ^ Moore, J.H. (2003). Building Scientific Apparatus. Westview Press. ISBN 0-8133-4006-3.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ The pumping of helium and hydrogen by sputter- ion pumps part II
- ^ "Ion Pumps" (PDF). Varian, Inc.
- ^ J. Zikovsky, S. A. Dogel, A. J. Dickie, J. L. Pitters, R. A. Wolkow (2009). "Reaction of a hydrogen-terminated Si(100) surface in UHV with ion-pump generated radicals". J. Vac. Sci. Technol. A. 27 (2): 248. doi:10.1116/1.3071944.
{{cite journal}}: CS1 maint: multiple names: authors list (link)
Sources
- Hablanian, Marsbed. "Gettering and Ion Pumping". High-Vacuum Technology: A Practical Guide (ISBN 082478197X).
- "Sputter Ion Pumps" (PDF). Paul Scherrer Institute.