Pumping of heavy noble gases by ion burial. Diffusion of hydrogen and helium into titanium. Dissociation of complex molecules into simple ones for pumping ease, e.g., CH 4 breaks down into C and 2H 2 . Hydrogen is pumped separately. Carbon is no longer part of the residual gas and resides in solid form.
Burial is the basic means of pumping heavy noble gases.
Argon ions neutralized via glancing collisions with a sputter cathode impact the pump wall and are coated with sputtered titanium. Triode pumps are specially designed to maximize the kind of collisions that produce energetic neutrals. Argon is permanently pumped on the wall behind the cathode in these pumps. The wall area receives titanium for inert gas burial but, because of a retarding electrical field between the cathode and the wall, it is not subjected to ion bombardment and thus gases are not resputtered. The main elements of a standard diode pump are a vacuum tight envelope, external magnets, and an element consisting of multiple anode cells and two cathodes.