ion pump — An ion getter pump is a vacuum pump that works by ionizing the residual gases in vacuum so that they can be adsorbed to special material on the walls of the pump, a process known as gettering. Thus, it is very different from a rotary pump or a turbomolecular pump because it does not have any moving parts. Ion pumps can operate in the range of 10?3 to 10?12 torr.

References: Wikipedia, the free encyclopedia – http://en.wikipedia.org/wiki/Ion_pump_%28physics%29