Design and characterization of high capacity nonevaporable getter pumps embedded inside the interaction regions of DA$Φ$NE

The DA$Φ$NE $Φ$-factory is a twin-ring 510 MeV $e+e-$ collider facility under commissioning at INFN-LNF in Frascati. With a stored beam current of 5.3 A, a mean pressure of 1.3$×10−9$ mbar is required in each ring. For the KLOE interaction region, where a mean pressure of the order of $1.3×10−10$ mbar is required, an embedded nonevaporable getter (NEG) pump with a CapaciTorr®-type structure was chosen mainly because of the unavailability of room for the installation of lumped pumps and to take maximum advantage of the sorption capability of the NEG pump for CO in the UHV operating conditions of the machine. A NEG pumping system of the kind discussed in this article seemed to be particularly suitable for the KLOE experiment, where limited servicing and high reliability is required. In this article we report on the design and characterization of both the first pump prototype, fitted with St-172 NEG alloy and the final pump version, where St-185 NEG alloy was used.