Ion Pumps are electro physical vacuum pumps which serve to remove gases from their environments by converting them into solid materials. The vacuum process is one which removes certain elements from a sample field, for example gases. This allows a material to be tested and examined without the presence of said gases – as well as a great deal other applications.
Each industry uses ion pumps and the concepts for a great number of applications and processes. these applications can be as varied and as varied as medical usage (in x-ray machines, as well as varying treatment and diagnosis machinery), scientific application (electron microscopes, focused ion beams, scanning prove microscopes, mass spectrometry, molecular beam epitaxy – just to name a few dedicated machines that utilise ion pump technology), military application in radars, and so much more.
Whatever the application, and however ion pumps are incorporated into other machinery, the process of extracting oxygen from the environment remains exactly the same. There are four steps involved in the operation of an ion pump, and the eventual aim of the extraction of gases from an environment, known as a vacuum chamber.
The first of the steps which are required to operate an ion pump is to generate a high magnetic field. This has to be created in order to strip the environment of gases. An ion pump may look like a metal cube on the outside, but on the inside it is filled with anodes, assembled in an isolated manner from the system and the vacuum chamber.
The corresponding cathodes are at ground potential along with the rest of the system. Outside the vacuum are a series of magnets, and a flux pole which work to generate a 1200 gauss magnetic field in order to guide electrons in the environment through the anode rings inside. Magnetic steel is added to the outside of the ion pump, which works to concentrate the field as well as keep it all inside the ion pump.
The ion pump is then “roughed” to 1×10-4 torr or lower in order to remove most of the gas in the sealed environment – with free electrons getting pulled toward the anodes, but the magnetic field catches them. The free electrons are forced to orbit around the anode. This magnetron motion forces the electrons to move in this manner until they are forced to hit something – which is more than likely going to be a gas molecule.
As the free electron hits the gas molecule, they react together – creating a new positively charged gas molecule within the anode tube. This gas molecule, of course, carries with it the energy of both molecules as well as the reaction, and is capable of breaking free of the magnetic field, hurtling toward the cathode. This positively charged molecule accelerates toward the cathodes within the ion pump at high speed and velocity, and impacts against the titanium cathode. Titanium is sputtered onto the anode walls.
Oxygen then chemically combines with the titanium, oxidising it into titanium oxide. (TiO) Of course, this is not a process that may continue on and on. In time, the titanium cathode will wear to the point of not having any more titanium on it, and therefore will have to be replaced. There are a number of suppliers such as Scanwel in North Wales, who work closely with well-respected manufacturers of ion pumps such as Agilent, in order to ensure a good stock is always maintained.
