NEG coating deposition and characterisation of narrow-gap insertion devices and small-diameter chambers for light sources and particle accelerators

Abstract

NEG-coating technology is becoming very popular in the particle accelerator community, as it provides a very effective mean to reduce the surface outgassing while significantly increasing the pumping efficiency of the beam pipes.An extensive use of NEG coatings is especially suitable in view of next-generation machines, for which long and small-aperture tubes (i.e., down to 4 mm) are envisaged in order to reach even higher luminosities and lower emittances. Such stringent requirements should be carefully addressed, as a number of technical issues arise—both in terms of coating deposition and characterisation—when dealing with narrow-gap beam pipes of this kind.The use of NEG coating for narrow-gap insertion devices has steadily grown over the past ten years; a review of both current R&D activities and future perspectives in this field is presented, together with an overview of the analytical techniques employed for the characterisation of the film deposited on small-section chambers. These include SEM morphological inspections, chemical composition analyses and thickness profiling made by EDS and measurements of the getter film's sorption capacity for CO.