Characterisation of sputter-ion pumps to be used in combination with non-evaporable getters

• The characterisation of NEG + SIP combination pumps requires a specific approach.
• Pumping of Ar and CH4 by SIPs acquires a particular relevance.
• Standard SIP characterisation techniques may lead to misleading results.
• A new way to characterise a SIP in view of the combination pump is proposed.
• The method is based on the use of QMS and on procedure for getter characterisation.

The pumping behaviour of sputter-ion pumps (SIPs), as a direct result of their underlying pumping mechanisms, is heavily influenced by several factors, including operation pressure and composition of the residual gas being pumped. Depending on their pumping history, SIPs can be thus characterised by transient phases in which some gases are released prior to the attainment of equilibrium between pumped and re-emitted species.In recent years, the feasibility of innovative vacuum pumps, based on the combination of SIPs with non-evaporable getter (NEG) technology, has been demonstrated; the optimisation of this coupling requires in-depth characterisations of SIPs, thus entailing the fine tuning of new specific testing procedures, which should flank and integrate the consolidated practice for SIP performance assessment. In this paper, some examples of the characterization of small SIPs are reported, in particular showing how the performances for Ar and CH4 can be evaluated in view of the synergic coupling with NEGs.