 The orbiting of the electrons is achieved without the use of a magnetic field, even though a weak axial magnetic field may be employed.A "noble diode pump" is a type of ion pump used in high-vacuum applications that employs both a chemically reactive cathode, such as titanium, and an additional cathode composed of tantalum.The tantalum cathode serves as a high-inertia crystal lattice structure for the reflection and burial of neutrals, increasing pumping effectiveness of inert gas ions.